Channeling 2018

23 Sept 2018, 00:00 → 28 Sept 2018, 19:40 Europe/Rome

Sultan Dabagov, Frank Zimmermann (CERN), Luigi Palumbo (ROMA1)

The 8^th International Conference "Charged & Neutral Particles Channeling Phenomena Channeling 2018" organized by the Italian National Institute for Nuclear Physics (INFN), the European Organization for Nuclear Research (CERN) and the National Research Nuclear University MEPhI will be held in ISCHIA (NAPLES-Italy) on September 23-28, 2018.

Sunday, 23 September ¶

12:00 → 14:00 Registration¶

Registration at Hotel Continental Ischia
Francesca Casarin & Cecilia D'Ambrosio & Daniela Napoleoni

14:00 → 17:25 Channeling Primer¶

Channeling Primer

14:00 Opening¶

Speakers: Prof. Aldo Spallone (Embassy of Italy in Russian Federation), Dr Claudio Cigliano, Danilo Giulietti (PI), Prof. Sultan Dabagov (LNF)

14:30 Geology Activities and Radon in Ischia Island¶

Since 2006, the Liceo Statale Ischia has joined the Envirad and Radiolab Projects, promoted by the INFN (Naples section) on the study of radon. Radon is a natural radioactive gas that can get high concentrations in indoor environments, with consequent risk to health. The Lyceum students promoted in the first years a measurement campaign of radon concentrations in public buildings, especially in schools of Ischia. Later the monitoring extended to the homes of the students who attended the project. Experimental results indicated a great variability in radon concentrations: many measures reported values below 400 Bq/cm (as limited by the Italian law), others, not rare, have detected up to 800 Bq/cm, highlighting risk situations. In the last two years, the project has focused more on the dissemination of radon-risk culture and on the statistic compilation of the perception of radon-risk in the island population.

Speakers: Mrs A. Ulianova (Liceo Statale Ischia), Mrs Anna Coppa (Liceo Statale Ischia), Mrs Chiara Di Leva (Liceo Statale Ischia)

Slides 14.30_ch2018_liceo_ischia.pdf

14:45 Alternative Methods for Light Dark Matter Detection¶

I will present some new ideas for detecting sub-GeV light dark matter, from 2D materials, like graphene and carbon nanotubes, to superfluid helium.

Speaker: Antonio Davide Polosa (ROMA1)

15:15 Soliton-like Regime of Neutron Transport in a Multiplying Medium. Physical Ground of Traveling Wave Reactor¶

An essentially nonlinear process of neutron transport in a multiplying medium, such as fuel of a nuclear reactor, under certain conditions leads to the realization of a self-sustaining regime of a propagating chain nuclear reaction in the form of a traveling wave. This phenomenon is called nuclear deflagration or slow nuclear burning. The possibility, as well as the criterion for the appearance of such a regime in a fast reactor-breeder, was first demonstrated by Lev Feoktistov in 1988 [1] by means of analytical solving the diffusion equation for neutron transport together with a set of burn-up equations for nuclear transformations, that make this problem nonlinear. The most important distinctive feature of the self-sustaining regime of a nuclear burning wave (NBW) is the lack of the need for operational criticality control of such a reactor, since its critical state is maintained automatically. This practically eliminates a role of so called "human factor" in reactor control and, therefore, the risk of this type of accident. Moreover, a special mechanism of the negative feedback inherent in this reactor ensures its automatic return to a critical state, even with external intervention, bringing the reactor out of the stationary mode in one or the other direction. In addition, either natural (or even depleted) uranium and thorium or spent fuel from conventional reactors can be used as a fuel in such reactor that solves the problem of providing mankind with energy resources for thousands of years. Significant contribution to the development of this concept was made also E. Teller [2], H. Sekimoto [3], and others. The ambitious plan for the practical realization of the Traveling Wave Reactor in the close future has announced by the firm TerraPower created with financial support from Bill Gates [4]. A brief review of the progress in development of the NBW reactor concept obtained over the past 10 years, including the original results of the authors, is presented in this paper. The main attention in our studies [5-7] was concentrated on studying the stability of the NBW regime, especially at transient processes in the reactor during its start-up, forced shutdown and subsequent restart. The impressive reactor stability against different types of external actions demonstrates its intrinsic safety property.

Speaker: Dr Sergii Fomin (NSC "Kharkov Institute of Physics and Technology")

Slides 15.15_ch2018-ChP_FominS.pdf

15:45 From Galileo to Abbe: the Contribution of Lenses to the Foundation of Modern Sciences. What is the Role of Lens in the Coming Quantum Era?¶

The invention of the compound microscope dates back to 1590 and, while visiting Venice in 1609, Galileo first heard of the spyglass invented by Dutch. He realized that a device based on lenses could be modified to made distant objects appearing closer with obvious military and potential financial value. By combining concave and convex lenses he was able to improve the original design by increasing the magnification. Galileo presented his improved telescope to the senate of Venice and demonstrated how ships at sea could be identified as friend or foe many hours. Actually, improving his telescope with higher magnifying power, improved lens shaping and polishing techniques, he started the observations of the heavens making incredible discoveries on the moon, Jupiter and many other stellar objects. He is certainly the father of the observational astronomy and Stephen Hawking, described him as the single individual most responsible for the birth of modern science.The lens-based microscope became increasingly popular in the mid-17th century giving rise also to the modern biology. It was used by Hooke that in the Micrographia volume, showed a wide range of microscopic views of organic systems. In this book appeared for the first time the term cell. The physics of lens construction was studied by the physicist Ernst Abbe. In 1868 he invented an apochromatic system of lenses, and in 1873 he published a comprehensive analysis of lens theory. The magnifying power of lens-based instruments always fascinated men and women, but the users of optical microscopes know that the lens power is limited by diffraction. As explained by Abbe: any object, no matter how small, will be imaged by a conventional optical system as a finite-sized spot, with a minimum dimension obtained for point-like objects approximately equal to the wavelength of light multiplied by the optical magnification and divided by the numerical aperture. Light microscopes produced in the closing quarter of the 19th century reached the effective limits of optical microscopy. Subsequent instruments such as phase-contrast microscopes, interference microscopes, and confocal microscopes solved specific problems allowing the study of important objects such as living cells. The 19th century is certainly the age of microscopy. In 1903 Richard Zsigmondy develops the ultramicroscope showing objects with size below the wavelength of light (Nobel Prize in Chemistry in 1925). In 1932 Frits Zernike invents the phase-contrast microscope that allows the study of colorless and transparent biological materials (Nobel Prize in Physics in 1953). Later in 1938 Ernst Ruska develops the electron microscope greatly improving the resolution and expanding the use of this instrument. Gerd Binnig and Heinrich Rohrer introduced in 1981 the scanning tunneling microscope that gives three-dimensional images of objects down to the atomic level. They won the Nobel Prize in Physics in 1986 together with Ruska. But the story is not ended with the century and Eric Betzig, Stefan W. Hell and William E. Moerner were awarded with the Nobel Prize in Chemistry in 2014 for having taken optical microscopy into a new dimension using fluorescent molecules, bringing microscopy to nanoscopy. Finally in 2017, the Nobel chemistry prize has been awarded for a revolution in biochemistry. Jacques Dubochet, Joachim Frank, and Richard Henderson were recognized for their work that led to the “cryo-electron microscopy”. This technique allows to see individual atoms within biological molecules and can be used to generate 3D images of extremely small objects such as the Zika virus. All these advancements in science are due to the technology and to the production of better and better lenses thanks to new ideas and technologies, but also, in particular in the last decades, to the advent of synchrotron sources, powerful and brilliant sources of radiation from THz to hard x-rays. The size of the SR community, and the potential applications experienced an exponential growth continuously triggering the design, manufacture and test of new optical systems at all wavelengths. The SR sources with lower emittance and higher coherence now appearing and also the continuous developments of conventional sources such as lasers, QCL, Continuum, etc. represent the real engine for the next generation of optics.

Speaker: Augusto Marcelli (LNF)

Slides chp_ch2018_marcelli.pdf

16:15 Science Communication: a New Frontier of Researcher’s Job¶

In the world of communication, nobody can be out of the fray! Since many years the science communication and more in general the ability of a researcher to communicate his work to founding agency, policy makers, entrepreneurs and public at large, starts to be a fundamental skill of the researcher’s job. This skill is needed and requested to access funds and successfully disseminate the research outcome, as well as to engage society in understanding science and its benefits. Moreover, due to the large decrease of research funds and of people starting scientific carrier, researchers have to be in the front line to promote the scientific culture in order to invert the dreadful trend of last years. Where we are and where we are going? We will make the point on that introducing successful models that everybody can apply without huge overloads for our job.

Speaker: Giovanni Mazzitelli (LNF)

Slides https://www.slideshare.net/giovannimazzitelli/science-communication-a-new-frontier-of-researchers-job-120570848

16:45 The International Radiation Physics Society¶

The International Radiation Physics Society (ISRP) has been in existence for over thirty years, having been founded at the Third International Symposium on Radiation Physics (ISRP-3), which was held in Ferrara, Italy, in 1985. The primary objective of IRPS is “to promote the global exchange and integration of scientific information pertaining to the interdisciplinary subject of radiation physics, including the promotion of 1. theoretical and experimental research in radiation physics, 2. investigation of physical aspects of interactions of radiations with living systems, 3. education in radiation physics, 4. utilization of radiations for peaceful purposes.” The Society hosts symposia every three years and recently has begun sponsoring the Industrial Radiation and Radioisotope Measurement Applications (IRRMA) conferences, which are also held on a three-year cycle, and—even more recently—the International Conferences on Dosimetry and its Applications (ICDA). The recent meetings sponsored by IRPS have been ISRP-14 (Córdoba, Argentina, October 2018), IRRMA-10 (Chicago, Illinois, July 2017), ICDA-2 (Guildford, UK, July 2016), ISRP-13 (Beijing, China, September 2015), IRRMA-9 (Valencia, Spain, July 2014), ICDA-1 (Prague, the Czech Republic, June 2013), ISRP-12 (Rio de Janeiro, Brazil, October 2012), IRRMA-8 (Kansas City, Missouri, June 2011). The Society’s Constitution, recently updated, defines Radiation Physics as “the branch of science which deals with the physical aspects of interactions of radiations (both electromagnetic and particulate) with matter.” Officers are elected for three-year terms and modest three-year dues for full voting membership are $75(developedcountries)or$25 (developing countries) or for student membership are $30(developedcountries)or$10 (developing countries). It is my hope that some of you attending Channeling 2018 who are not now members of IRPS will consider joining.

Speaker: Prof. William Dunn (Kansas State University)

Slides dunn_IRPS.pdf

Monday, 24 September ¶

09:00 → 11:00 S1.1 Channeling & Radiations in Crystals¶

Chair Dabagov

Convener: Prof. Sultan Dabagov (LNF)

09:00 Advances in Coherent Radiation and Channeling¶

At motion of fast charged particles in crystal at small angle to one of its axes or planes different coherent and interference effects are possible in interaction of particles with the lattice atoms. Thanks to these effects, the interaction cross-sections of particles with atoms may differ substantially from the corresponding cross-sections of particle interactions with the amorphous medium atoms. Firstly the possibility of such effects was noted in the works by Ferretti [1], Ter-Mikaelian [2] and Überall [3] at study of the Bremsstrahlung process by relativistic electrons in crystal. The results obtained in these works were based upon the consideration of the radiation process in first Born approximation of quantum electrodynamics. The applicability conditions of this approximation are quickly broken with the increase of the particle energy and crystal thickness, with the decrease of the incidence angles of particles relatively crystal axes or planes and also in several other situations. In this case new possibilities are opened in the particle interaction with crystal atoms that are connected, in particular, with the channeling phenomenon, dynamical chaos phenomenon at the particles motion in crystal, a number of phenomena at particles motion in bent crystals, etc. Some results in this field obtained earlier were presented in the works [4, 5]. In the present report a short review is given of the last results obtained in this field. The main attention is paid to the scattering and radiation processes in the transition region of crystal thicknesses, from those at which the channeling process is absent up to those at which it is developed, and to the comparative analysis of quantum and classical effects in interaction of fast particles with the lattice atoms in this thickness range. References 1. B. Ferretti, Nuovo Cimento 7 (1950) 118. 2. M.L. Ter-Mikaelian, Zh. Eksp. Theor. Fiz. 25 (1953) 296. 3. H. Überall Phys. Rev. 103 (1956) 1055. 4. A.I. Akhiezer, N.F. Shul’ga, High energy Electrodynamics in Matter, Gordon and Breach Pub., Amsterdam (1996). 5. N.F. Shul’ga. Advances in coherent Bremsstrahlung and LPM-effect studies. In proceedings of the 51st workshop of the INFN Eloisation Project, Charged and Neutral Particles Channeling Phenomena, Channeling 2008, Editors S. Dabagov, L. Palumbo, A. Zichichi, World Scientific, 2010, pp. 11-35.

Speaker: Prof. Nikolai Shul'ga (Akhiezer Institute for Theoretical Physics of NSC KIPT, Karazin Kharkiv National University)

Slides 9.00_ch2018_ShulgaN.pdf

09:30 Analysis of Channeling Experiments in Diamond and Silicon Single Crystals with the Aid of the Fokker-Planck Equation¶

The formula of Baier et al. for the de-channeling length of electrons in single crystals Lee = 2U_0 pvX_0/E_s^2 [1] was frequently used for a comparison with various calculations, including simulation calculations. It will be pointed out in this contribution, that the fundamental parameter E_s^2 = (2π/α) (m_ec^2)^2 = (15 MeV)^2 must be replaced by E_s = 10.6 MeV if thin crystals are used. The same parameter Lde appears also as a scaling length in the Fokker-Planck equation if written in a dimensionless form. This fact has the consequence that both, the formula of Baier et al. as well as the solution of the Fokker-Planck equation, overestimate the de-channeling length by more than a factor of two in comparison with recent simulation calculations, e.g. [2]. It is well known that in the photon spectra of diamond at electron beam energies below 110.2 MeV pronounced line structures appear. Such structures were recently also observed at a beam energy of 195 MeV at the Mainz Microtron MAMI [3]. Since it is an open question whether quantum state phenomena may enhance the de-channeling length even at such high beam energies, we performed de-channeling length measurements for plane diamond single crystals. The analysis requires model assumptions. We rely on the solution of the Fokker-Planck equation for plane crystals. In addition, results obtained for silicon [4] have been reanalysed. The Fokker-Planck equation has been modified also for bent crystals [5]. Measurements at the National Accelerator Laboratory SLAC, USA, at electron beam energies in the multi-GeV range for a bent (111) silicon single crystal (bending radius 0.15 m) [6] can be reproduced. This result provides confidence to apply solutions also for a typical bending radius of 6.6 mm for our Si_1-xGe_x undulator crystal in (110) orientation (four periods with 9.9 µm each) resulting in small de-channeling lengths at MAMI beam energies in accord with observations [7]. References 1. V.N. Baier, V.M. Katkov and V.M. Strakhovenko, Electromagnetic Processes at High Energies in Oriented Single Crystals, World Scientific Publishing, Singapore (1998), p. 250 2. A.V. Korol, V.G. Bezchastnov, and A.V. Solov’yov, Eur. Phys. J. D 71 (2017) 174 3. H. Backe, W. Lauth, and Thu Nhi TRAN THI, JINST 13 (2018) C04022 4. H. Backe and W. Lauth, Channeling experiments with sub-GeV electrons in flat silicon single crystals, Nucl. Instrum. Meth. B 355 (2015) 24 5. H. Backe, JINST 13 (2018) C02046 6. T.N. Wistisen, U.I. Uggerhøj, U. Wienands, T.W. Markiewicz, R.J. Noble, B.C. Benson et al., Phys. Rev. Accel. Beams 19 (2016) 071001 7. H. Backe et al., Nucl. Inst. Meth. Phys. Res. B 309 (2013) 37, and Journal of Physics: Conference Series 438 (2013) 012017

Speaker: Prof. Hartmut Backe (Institute for Nuclear Physics)

Slides BackeChanneling2018_online-version.pdf

09:45 CRYSTALRAD Simulation Code for Modeling of Coherent Effects of Radiation in Crystals¶

In this work we present the CRYSTALRAD simulation code, including all the features of the CRYSTAL simulation code for calculation of charged particles trajectories in a bent crystal and RADCHARM++ routine for calculation of radiation. The CRYSTALRAD code is based on Monte Carlo simulations of trajectories in interplanar and interaxial electric field either in a straight or bent crystal with simulation on each step of multiple and single Coulomb scattering on nuclei and electrons, ionization energy losses etc. The simulated trajectories are used for calculation of radiation spectra through the direct integration of the Baier Katkov formula.

Speaker: Dr Alexei Sytov (FE)

10:00 X-ray Emission by a High-Energy “Half-Bare” Electron in Ultra-Thin Crystals¶

The process of coherent X-ray emission by a high-energy electron successively crossing two parallel targets – thick upstream amorphous and ultra-thin downstream crystalline ones, separated by a certain distance – is considered. Inside the thick target the electron’s field becomes partially screened by the target polarization [1]. After crossing this target the electron still has suppressed electromagnetic field around itself, which lacks considerable part of virtual photons comparing to the Coulomb field in vacuum (which makes such electron “half-bare” [2,3]). It is shown that the process of the electron’s field regeneration in the space between the targets dramatically modifies characteristics of radiation in the crystalline target. The discussed radiation is a superposition of parametric X-ray and diffracted transition radiations, which interfere with each other. It is demonstrated that in the considered case such characteristics of the radiation reflex as angular distribution and total yield significantly differ from the corresponding characteristics typical for thick (see, e.g. [4]) and for ultra-thin [5] crystals and depend on distance L between the targets. At sufficiently high energies of the electron (exceeding 10 GeV) such dependence takes place within macroscopically large values of L. Special attention is drawn to the study of the influence of the crystalline target finite size upon radiation characteristics, which turns out to be noticeable in the considered process. It is shown that it leads to the change of the total radiation yield with the increase of L for macroscopically large values of this distance even for the electron energies lower than 1 GeV. References 1. E. Fermi, Phys. Rev. 57 (1940) 485. 2. E.L. Feinberg, Sov. Phys. JETP 23 (1966) 132. 3. A.I. Akhiezer, N.F. Shul’ga, High-energy electrodynamics in matter, Gordon and Breach Publ., Amsterdam, 1996. 4. P. Rullhusen, X. Artru, P. Dhez, Novel radiation sources using relativistic electrons: from infrared to x rays, World Scientific Publ., Singapore, 1998. 5. N.N. Nasonov, Phys. Lett. A 246 (1998) 148.

Speaker: Mr Sergii Trofymenko (Akhiezer Institute for Theoretical Physics of NSC KIPT)

Slides 10.00_ch2018_Trofymenko.pdf

10:15 Orbital Angular Momentum of Channeling Radiation from Relativistic Electrons in Thin Crystals¶

The radiation from relativistic electrons moving along a helical trajectory is known to possess the orbital angular momentum (OAM) [1]. An example of the trajectories of such a type is the trajectory of a charged particle in a helical undulator. Twisted photons with energy of 99 eV and OAM ± ħ are observed experimentally in the undulator radiation from 917 MeV electrons [2]. However, the interaction of sub-GeV relativistic particles with a crystalline target allows one to generate radiation in the above-MeV region. The radiation of relativistic particles at axial channeling moving along rosette trajectories also carries the OAM. Here, using the developed code BCM-2 [3] and the general formula for the probability of radiation of a twisted photon by a classical current derived in [4], we calculate the distribution of photons of channeling radiation over its orbital angular momentum projection and the density of the average number of twisted photons against the photon energy. The calculations are carried out for the initial electron beam energies ranging from 155 to 855 MeV. These are the typical energies of modern accelerators (INFN-LNF and SAGA-LS). It is shown that the radiation from electrons at planar channeling also carry the OAM. The comparison of the results with the ones obtained using the semi-classical approach [5,6] is performed. The proposed scheme for production of radiation carrying the OAM allows one to generate the twisted photons with much higher energies as compared with the scheme based on using the undulator radiation [3,7]. References 1. M. Katoh, M. Fujimoto, N. S. Mirian, et al., Sci. Rep. 7 (6130) (2017) 1. 2. J. Bahrdt, K. Holldack, P. Kuske et al, Phys. Rev. Lett. 111 (2013) 034801. 3. S. V. Abdrashitov, O. V. Bogdanov, K. B. Korotchenko, et al., Nucl. Instrum. Meth. B 402 (2017) 106. 4. O. V. Bogdanov, P. O. Kazinski, and G. Yu. Lazarenko, Phys. Rev. A 97 (2018) 033837. 5. D. Ivanenko, A. Sokolov, Classical Field Theory. (Russian),Gostehizdat, Moscow, 1951. 6. C. Teitelboim, D. Villarroel, C. van Weert, Nuovo Cim. 3 (1980) 1. 7. S. Sasaki, I. McNulty, Phys. Rev. Lett. 100 (2008) 124801.

Speaker: Mr Sergei Abdrashitov (National Research Tomsk Polytechnic University)

10:30 Measurement of Phase and Topological Properties of OAM Channeling Radiation through Asymmetric Lateral Coherence¶

Even though the generation of radiation carrying Orbital Angular Momentum (OAM) has been made both with visible light [1] and with millimeter-waves [2], the practical realization of high brilliance X-ray vortices is an open problem. The main limitation is related to the damage threshold of the optical elements. Novel approaches to generate OAM X-ray by using relativistic beams interacting with ultra-high power lasers [3] brought absolutely new challenges for the development of measuring methods. The real part of the coherence factor of an OAM radiation provides a direct measurement of the phase properties and topological charge of X-ray vortices, in fact the number of azimuthal lobes of the coherence factor increases as the topological charge is increased, thus providing a suitable method to diagnose X-ray beams with orbital angular momentum produced by ultra-relativistic beams in channeling phenomena. We show a novel diagnostic technique based on scanning interferometry called Asymmetric Lateral Coherence [4][5] to accurately measure the real part of the complex degree of coherent of X-ray OAM radiation.

Speaker: Dr Bruno Paroli (Dipartimento di Fisica, Università degli Studi di Milano)

10:45 Beam Steering and Radiation in Ultrashort Silicon and Germanium Bent Crystals at the MAinzer MIkrotron¶

In this work we report the observation of 855 MeV electrons deflection and radiation by ultrathin silicon and germanium crystals, bent along (111) planes, at the MAinzer Mikrotron MAMI. The crystal length of 15 μm of length was chosen to be comparable with the dechanneling length of electrons. In order to make the measurements for different values of bending radius of the same crystal we used a piezo-actuated dynamical holder, allowing one a remote change of the crystal curvature. The channeling efficiency, the dechanneling length, the volume reflection angle as well as the radiation spectra were measured in dependence on the crystal curvature and its orientation for both silicon and germanium bent crystal. All the results were critically compared with our simulations by CRYSTAL and RADCHARM++ simulation codes. For silicon the measured channeling efficiency exceeded 35 %, being a new record for negatively charged particles. On the other hand, for germanium the efficiency turned out slightly below 10% due to the stronger contribution of multiple scattering. However, this is the first evidence of negative beam steering by planar channeling in a Ge crystal at sub-GeV energies. These results are relevant for crystal-based beam steering as well as for the propagation of e.m. radiation in bent and periodically bent crystals.

Speaker: Andrea Mazzolari (FE)

11:00 → 11:20 Coffee break

11:20 → 13:05 S1.2 Channeling & Radiations in Crystals¶

Convener: Augusto Marcelli (LNF)

11:20 Electromagnetic Dipole Moments of Charged Baryons with Bent Crystals at the LHC¶

We propose a unique program of measurements of electric and magnetic dipole moments of charm, beauty and strange charged baryons at the LHC, based on the phenomenon of spin precession of channeled particles in bent crystals. Studies of crystal channeling and spin precession of positively- and negatively-charged particles based also on GEANT4 simulations are presented, along with feasibility studies and expected sensitivities for the proposed experiment using a layout based on the LHCb detector.

Speaker: Dr Nicola Neri (MI)

Slides Neri_Channeling18.pdf

11:50 Electromagnetic Dipole Moment and Time Reversal Invariance Violating Interactions for High Energy Baryons in Bent and Straight Crystals at LHC¶

Spin rotation of channelled particles at the LHC enables measuring constants, which determine Todd, Podd (CP) violating interactions and Podd, Teven interactions of baryons with electrons and nucleus, similarly to possibility of measuring electric and magnetic moments of charm, beauty and strange baryons. For a particle moving in a bent crystal a new effect, which is caused by nonelastic processes, arises: the spin hyperbolic rotation to the direction of the effective magnetic field (bend axis), the direction of the electric field and the direction of the particle momentum also appears.

Speaker: Prof. Vladimir Baryshevsky (Belarusian state University, Institute for Nuclear Problems)

Slides 11.50_ch2018_BARYSHEVSKY.pdf

12:05 Dechanneling Population at Extreme Crystal Bending with 6.5 TeV Proton Beam¶

The Crystal Collimation layout present in LHC provides, since 2015, a unique test stand for hadron beam manipulation at TeV energy. The two crystals installed in 2014 were used to investigate the performance of the crystal collimation system in LHC. The data collected were used to probe the channeling, and the other coherent effect related, of hadrons with bent crystal in this specific framework. In particular, the dechanneling population at low deflection angles is observed to be enhanced when the bending radius of one of the crystals is close to the critical radius at the LHC top energy. The interpretation of the data, also using simulations code, is presented. The conclusions are used to understand the observations in collimation cleaning measurements.

Speaker: Mr Roberto Rossi (CERN)

Slides 12.05_ch2018_Rossi.pdf

12:20 Total Yield and Spectra of Positrons Produced by Coherent Bremsstrahlung from 10 – 70 MeV Electrons¶

As known the radiation of high-energy electrons in aligned crystalline target (radiator) and subsequent electron-positron pair production in downstream amorphous target (convertor), so called a “hybrid” solution [1, 2], might be an effective positron source. Here we investigate the dependence of total positron yield and positron energy spectra on incident electron beam energy by means of computer simulation based on the method proposed in [3]. The hybrid scheme of positron source via photoconversion of coherent bremsstrahlung (CB) [4] from 10 – 70 MeV electrons into electron-positron pairs is considered. Computer simulations are carried out taking into account positron stopping in a thick convertor. For the initial electron beam with energy of 70 MeV the comparison of the total yield and the energy spectra of positrons obtained from photoconversion of CB with the ones from photoconversion of bremsstrahlung and channeling radiation [5] is carried out. References 1. R. Chehab, et al. Physics Letters B 525 (2002) 41. 2. X. Artru, et al., Nucl. Instr. Meth. B 266 (2008) 3868. 3. V.A. Dolgikh, Yu.P. Kunashenko, and Yu.L. Pivovarov, Nucl. Instr. Meth. B 201 (2003) 253. 4. M. L. Ter-Mikhaelyan, Physics-Uspekhi 44(6) (2001) 571 5. S. V. Abdrashitov, et al., Nucl. Instrum. Meth. B 402 (2017) 106.

Speaker: Mr Sergei Abdrashitov (National Research Tomsk Polytechnic University)

12:35 The Hybrid Positron Source Using Channeling: a Promising Device for Future Colliders¶

The important enhancement in photon generation due to channeling radiation in oriented crystals, with respect to ordinary bremsstrahlung, was observed experimentally at CERN and KEK. Positron sources using crystals have been extensively studied . Devices associating crystal-radiators and amorphous converters with a sweeping magnet between them, the so-called hybrid source, have been adopted by the CLIC linear collider as the baseline source and studied for ILC also. The interest of such sources is also evident for circular machines –colliders or storage rings- as illustrated by the studies on FCC-ee and SLEM (muon collider) which are presently under consideration. A large collaboration has been progressively built to develop such sources; it is associating French, Japanese, Russian and Italian laboratories as well as CERN. This presentation is showing the main features of this source as the state of the art and the R&D progresses for the different projects.

Speaker: Dr Robert CHEHAB (IPNL/IN2P3)

Slides 12.35_ch2018_chehab.pdf

12:50 Comparison of Parametric X-ray Radiation and Diffracted Transition Radiation¶

Comparison of parametric X-ray radiation and diffracted transition radiation A.V. Shchagin Belgorod National Research University, Belgorod, 308015, Russia Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine Ultra-relativistic charged particle incident a crystal emits both diffracted transition radiation (DTR) and parametric X-ray radiation [1]. Both kinds of radiation can be used for beam diagnostics. Recently, comparison of differential yields of the DTR and PXR in maxima of the reflections was performed in [2]. In the present paper, the yields of the DTR and PXR integrated over reflections angular sizes are compared. References 1. Adischev, Y.N., Arishev, S.N., Vnukov, A.V., Vukolov, A.V., Potylitsyn, A.P., Kuznetsov, S.I., Zabaev, V.N., Kalinin, B.N., Kaplin, V.V., Uglov, S.R., Kubankin, A.S., Nasonov, N.N. Angular distribution of X-ray radiation by 500 MeV electrons in a tungsten crystal. NIM B 201(1) (2003) 114-122. 2. I. Chaikovska, R. Chehab, X. Artru, A.V. Shchagin. Characteristic, parametric, and diffracted transition X-ray radiation for observation of accelerated particle beam profile. Nucl. Instrum. Meth. Phys. Res. B 402 (2017) 75–78.

Speaker: Dr Alexander Shchagin (Kharkov Institute of Physics and Tecknology)

13:05 → 14:30 Lunch

14:30 → 16:30 S2.1 Channeling & Radiations in Various Fields¶

Convener: Dr Pavel Karataev (Royal Holloway, Unviersity of London)

14:30 Quantum Versus Classical Approach of Dechanneling and Other Incoherent Processes at High Energy in Aligned Crystals¶

Particles travelling in aligned crystals at small angle w.r.t. crystallographic axes or planes are essentially steered by the continuous Lindhard potential. This interaction conserves the energy E, the parallel momentum p_||, the transverse energy of the particle E_T and is elastic concerning the crystal wave function. At high enough energy the resulting transverse motion can be described by classical mechanics. The temporal fluctuations of the positions of the atoms or of the electrons of the crystal create a residual potential on which the particle can scatter. This interaction does not conserve the previous quantities and is inelastic for the crystal. We discuss whether it can be treated classically, like in the binary collision model, or if it should be treated quantum-mechanically. We give arguments for the latter opinion. We show that the quantum approach predicts a slower dechanneling than the classical one.

Speaker: Mr Xavier Artru (Institut de Physique Nucléaire de Lyon)

Slides artru_ch2018.pdf

15:00 Statistics of the Radiating Relativistic Electrons¶

We report the statistical consideration of the radiating electrons. At the statistical stage, the spectrum of radiating electrons moves toward a stable distribution. The stability parameter gradually increases when the average number of recoils increase, from unity (the Landau distribution) asymptotically approaching two (the Gaussian distribution). A concrete dependence of the stability parameter upon the average number of the recoils is determined by the profile of the recoil spectrum. The results of this consideration reveal that the width of the electron spectrum is increasing with the number of recoils according to the power law, with the power being inverse to the stability parameter. Increase of the spectrum width limits the ability of the beam to generate coherent radiation in hard x-ray and gamma-ray region. A heavy tail in the electrons spectrum, inherent in the stable distributions with the parameter less than two, causes an increase in the quantum losses of the beam in the Compton sources based on storage rings, and reduces the recovering efficiency of the ERL based ones.

Speaker: Dr Eugene Bulyak (NSC KIPT)

Slides 15.00_ch2018_Bulyak.pdf

15:15 Physical Interpretation and Asymptotic Analysis of Particle’s Energy Losses on the Polarization Radiation Process¶

Dynamic polarization is a complex process of the rapid interchange of energy between the alternating electromagnetic fields and medium's atoms/molecules. In result of this process a part of the electromagnetic field free energy is expended in the moving of “free” electrons (the conduction current) and displacement of the latent electricity (the displacement current). The first component of the electromagnetic field energy losses brings about the well characterized effect - Joule heating of the target material. At the same time, the last part of the energy losses, which induces the electromagnetic radiation also known as polarization radiation, is not adequately investigated. In this report, the energy losses of a particle electromagnetic field on the polarization radiation process will be asymptotically analyzed for the non-polar mediums with the arbitrary conductivity and the flat shape. The asymptotical behavior of the energy losses dependence on the medium dielectric properties, particle's energy and task's geometric pattern will be deemed in the frame of the classical electrodynamics and the solid state physics. Since the dynamic polarization is part and parcel of the particle-medium interaction process, the presented results will be of especial interest for the electromagnetic radiation sources development, the wakefield acceleration and the particle beam diagnostics. This work was supposed by the Russian Foundation for Basic Research within the Grant No. 18-32-00385_mol_a.

Speaker: Dr Anatoly Konkov (Tomsk Polytechnic University)

Report_Konkov_Channeling_2018.pdf

15:30 Coherent Radiation from Modulated Electron Beams in a Сompton Laser¶

The brightest sources of X-ray radiation are known to be realized on the basis of radiation from the beams of charged particles. Depending on the required range of the X-ray part of the spectrum, various radiation generation schemes are used. For example, synchrotron radiation exhibits extremely high spectral brightness in a wide frequency range. The absolute leaders in vacuum UV and soft X-ray range are the free-electron lasers (FEL), such as European XFEL, SwissFEL, FLASH (DESY), etc. The maximum intensity in hard X-ray region is presented by the coherent bremsstrahlung and channeling radiation in crystals. The most promising source of X-ray radiation in a wide range, however, is one based on the Compton backscattering. From the beginning, this phenomenon was proposed as the source of gamma rays for the nuclear physics applications. The idea belongs to E. Feenberg who published it in 1948 [1], and afterwards it was developed in the works of R. Milburn [2], O. Kulikov [3], F. Arutyunyan and V. Tumanyan [4]. Starting from the 90-s, the Compton sources have been working out over the world, but for a variety of reasons, the radiation registered experimentally is much weaker than that predicted theoretically. That is why the researches of this mechanism of X-ray radiation generation are still on the front burner. The coherence effect plays a crucial role in all mechanisms listed above. For the radiation to be coherent, the length should be smaller or at least comparable with the radiation wavelength, or, for modulated electron beams, with the period of modulation. This effect is clearly marked at present accelerators, where the number of the bunch particles amounts up 10^12 and higher. Such short electron bunches can be produced by FEL facilities that are rather large and expensive and need GeV electron energy. But it is not the only opportunity: for example, in [5] it was shown that MeV electron beams with the nanometer modulation period are achievable. In this work we suggest using the relativistic beams modulated with very short period for realization of effective Compton laser. Using the method developed before for the form-factors of modulated beams to be obtained [6], we develop the consistent theoretical approach of Thomson scattering of the electromagnetic waves in frames of classical electrodynamics, and analyze the characteristics of the generated radiation. References 1. E. Feenberg, H. Primakoff, Applications for Nuclear Phenomena Generated by Ultra-Intense Lasers, Phys. Rev. 73, 449 (1948). 2. R. Milburn, Electron Scattering by an Intense Polarized Photon Field, Phys. Rev. Lett. 10, 75 (1963). 3. O.F. Kulikov, Yu.Y. Tel’nov, E.I. Filippov, M.N. Yakimenko, Compton effect on moving electrons, Physics Letters 13, 344 (1964). 4. F.P. Arutyunyan, V.A. Tumanyan, The Compton Effect on Relativistic Electrons and the Possibility of Producing Beams of Hard γ-Rays, Sov. Phys. JETP 17, 1412 (1963). 5. E.A. Nanni, W.S. Graves, D.E. Moncton, Nanomodulated electron beams via electron diffraction and emittance exchange for coherent X-ray generation, Phys. Rev. AB 21, 014401 (2018). 6. D.Y. Sergeeva, A.P. Potylitsyn, A.A. Tishchenko, M.N. Strikhanov, Smith-Purcell radiation from periodic beams, Optics Express 25, 26310 (2017).

Speaker: Ms Anastasiia Feshchenko (NRNU MEPhI)

Slides Feshchenko_Channeling18.pdf

15:45 Coherent Unipolar Cherenkov and Diffraction Radiation Generated by Relativistic Electrons¶

For usual (bipolar) radiation the integral of the electric field strength over the time is zero. First time the possibility of unipolar radiation (strange electromagnetic waves) generation has been considered theoretically in 1990 [1]. According to this work the unipolar radiation is radiation for which the integral of the electric field strength over the time differs significantly from zero. Futher a number of theoretical articles (for example [2,3]) have been devoted to this problem mainly in respect to a synchrotron radiation. However up to now there are no experimental investigations of this phenomenon except the work [4]. In this report we present the results of experimental observation of the unipolar Cherenkov and diffraction radiation generated by relativistic electrons. For this purpose the detector sensitive to the selected direction of the electric field strength has been ellaborated. We observed the coherent Cherenkov radiation and backward diffraction radiation of bunched electron beam when the electrons moving near the targets. The partial unipolarity effect has been registered for the Cherenkov radiation and almost full unipolarity has been observed for the backward diffraction radiation. This work was supported by the program ``Nauka'' of the Russian Ministry of Education and Science and the Competitiveness Enhancement Program of Tomsk Polytechnic University. [1] Preprint No 76 of the Lebedev Physical Institute of the Academy of Science of the USSR, Moscow, 1990. [2] M. Schwarz, P. Basler, M. v. Borstel, and A.S. Müller. Analytic calculation of the electric field of a coherent THz pulse Phys. Rev. st AB 17 050701 (2014) [3] V.L. Bratmana, D.A. Jaroszynskib, S.V. Samsonova, A.V. Savilova. Generation of ultra-short quasi-unipolar electromagnetic pulses from quasi-planar electron bunches. NIM A 475 (2001) 436-440 [4] G. Naumenko and M. Shevelev. First indication of the coherent unipolar diffraction radiation generated by relativistic electrons. Journal of Instrumentation, Volume 13, 2018

Speaker: Dr Gennady Naumenko (Tomsk Polytechnic University)

Slides 15.45_ch2018_Naumenko.pdf

16:00 Partially Coherent Short-Wave Radiation of an Electron Bunch with Natural Asymmetric Distribution¶

The possibility of generating coherent THz radiation from an electron bunch with a weak asymmetry in the distribution as a result of grouping of electrons is considered. It is shown that the partially coherent THz radiation is generated in a wiggler from such electron bunch with energy of 50 MeV.

Speaker: Prof. Lekdar Gevorgian (A)

16:15 Parametric X-ray Radiation from Powders¶

Parametric X-ray Radiation (PXR) from a tungsten powder was registered during the interaction of the target with a 7 MeV electron beam. The tungsten powder presents a purity of 99,987 % and is constituted of crystallites which average size is between 0.8 and 1.7 µm. The radiation was registered by silicon drift detectors under observation angles of 150˚ and 180˚ regarding the velocity of the incident electrons. PXR peaks from the crystallographic planes (110), (200), (211), (220), (310) и (222) were clearly observed simultaneously. The experimental results show a good agreement with the theory [1] in both geometries for all the PXR peaks for the first time. In previous works, the influence of texture [2,3] and composition of the target [4] caused a disagreement of the observed relative intensity of the PXR peaks with the theory. The work was supported by the grant of the President of Russia for young doctors of sciences MD-5748.2018.2, a Program of the Ministry of Education and Science of the Russian Federation for higher education establishments, Project No. 3.1631.2017/4.6 and by the project No. PIJ-16-03 of the Escuela Politécnica Nacional. References [1] V. Astapenko, N. Nasonov, P. Zhukova. Anomalous peak in the spectrum of polarizational bremsstrahlung from relativistic electrons moving through a solid target, Journal of Physics B: Atomic, Molecular and Optical Physics. 40 (2007) 1337-1346. [2] V.I. Alekseev, A.N. Eliseev, E.F. Irribarra, I.A. Kishin, A.S. Kubankin, R.M. Nazh-mudinov, et al., Research of the polarization bremsstrahlung of relativistic elec-trons in polycrystalline targets, Nucl. Instrum. Methods Phys. Res., Sect. B, Beam Interact. Mater. Atoms 342 (2015) 47–51. [3] Y. Takabayashi, I. Endo, K. Ueda, C. Moriyoshi, A.V. Shchagin, Nucl. Instr. Meth. Phys. Res. B 195 (2006) 453. [4] V.I. Alekseev, A.N. Eliseev, E.F. Irribarra, I.A. Kishin, A.S. Kubankin, R.M. Nazh-mudinov, et al., Parametric X-ray radiation from powders, Radiation from Relativistic Electrons in Periodic Structures RREPS 2017.

Speakers: Dr Alexander Kubankin (Belgorod National Research University), Esteban Irribarra (Escuela Politécnica Nacional, Quito, Ecuador), Mr Ivan Kishin (Belgorod National Research University), Mr Ramazan Nazhmudinov (Belgorod National Research University)

16:30 → 16:50 Coffee break

16:50 → 18:35 S2.2 Channeling & Radiations in Various Fields¶

Convener: Giovanni Mazzitelli (LNF)

16:50 Guiding of Charged Particle Beams in Curved Capillary-Discharge Waveguides¶

A new method able to transport charged particle beams along a curved path is presented. It is based on curved capillary-discharge waveguides where the induced azimuthal magnetic field is used to focus the beam and, at the same time, keep it close to the capillary axis. We show that such a solution is highly tunable, it allows to develop compact structures providing large deflecting angles and, unlike conventional solutions based on bending magnets, preserves the beam longitudinal phase space. Such a feature, in particular, is very promising when dealing with ultra-short bunches for which non-trivial manipulations on the longitudinal phase spaces are usually required when employing conventional deflecting devices.

Speaker: Dr Riccardo Pompili (LNF)

Slides 16.50_PlasmaBending_Channeling18.pdf

17:20 Generation of Surface Polaritons in Dielectric Cylindrical Waveguides¶

We investigate the radiation of surface polaritons by a charged particle rotating around a dielectric waveguide. General case is considered when the waveguide is immersed in a homogeneous medium. For the evaluation of the corresponding electromagnetic fields the electromagnetic Green tensor is used. A formula is derived for the spectral distribution of the radiation intensity for surface waves. It is shown that these waves are radiated on the eigenmodes of the dielectric cylinder. The geometry under consideration is of interest from the point of view of generation and transmitting of waves in waveguides, a subject which is of considerable practical importance in microwave engineering and optical fiber communications.

Speaker: Ms Anna Kotanjyan (Yerevan State University)

Slides 17.20_Ischia2018SurfPol.pdf

17:35 Local Field Effect in Smith-Purcell Radiation from Dotted Grating¶

In this report we theoretically investigate the effect of interaction between separated elements of 2D dotted grating and its influence on SPR characteristics. The developed approach allows us to calculate the macroscopic radiation properties proceeding from the microscopic properties of the grating [M.I. Ryazanov, A.A. Tishchenko, JETP (2006)]. We show that the local field effects can change significantly the spectral-angular distribution of SPR. In particular, the described near-field resonances, which are responsible for such a change, lead to significant increasing in radiation intensity.

Speaker: Ms Darya Sergeeva (National Research Nuclear University "MEPhI")

Slides 17.35_Sergeeva.pdf

17:50 The Influence of Medium Polarization Inhomogeneity on the Channeling Radiation from a Positron Bunch¶

Channeling positrons of a bunch oscillate with equal frequencies, but with different amplitudes in a harmonic potential of a planar channel. That is, the positron bunch radiation generates in a medium with polarization inhomogeneity. Within the framework of the Thomas-Fermi statistical model, the electron density distribution, depending on the transverse coordinate of a channel, is obtained. An analytic expression for the spectral distribution of the total radiation of a positron bunch is deduced. It essentially depends on both the bunch energy and the medium polarization inhomogeneity, especially in the soft frequency range. A comparison with the experimental data is made.

Speaker: Mr Hayk Gevorgyan (Student)

Slides 17.50_ch2018_h-gevorgyan.pdf

18:05 Influence of Technical and Material Uncertainties on Optimized Parameters in X-ray Differential Phase Contrast Imaging System Based on Talbot Effect¶

Seems to be small any technical parameter deviations or uncertainties in the systems forming the scanning radiation (for example, diffraction gratings) may produce significant distortions of the wave phase that can lead to the wrong interpretation of the results of scanning (such as the incorrect location of the patient tumor). Due to this reason, the tomography systems based on Talbot effect are of high need to be considered in the view of the stability regarding to the small fluctuations of input parameters. The parameters of geometrical and material characteristics of interferometers’ components are assumed to be Gaussian-like distributed over the corresponding range of values that results in the change of the design working flow to reach the high-performance grating-based interferometer [1]. In particular, the optimal values of geometrical parameters determined in [1, 2] are shifted by more than 10% as compared to the deterministic approach. This study was partially supported by the Federal Targeted Program of the Russian Federation agreement no. 14.578.21.0198 (RFMEFI57816X0198) and by the Competitiveness enhancement program of Tomsk polytechnic university in part of providing simulation software. [1] P Modregger, BR Pinzer, T Thüring, S Rutishauser, C David, and M Stampanoni. Sensitivity of X-ray grating interferometry. Optics Express, 19(19):18324–18338, 2011. [2] W Yashiro, Y Takeda, and A Momose. Efficiency of capturing a phase image using cone-beam x-ray Talbot interferometry. Journal of the Optical Society of America. A, Optics, image science, and vision, 25(8):2025–2039, 2008

Speakers: Dr Alexey Gogolev (Tomsk polytechnic university), Dr Roman Rezaev (Tomsk polytechnic university)

Slides 18.05_ch2018_rezaev.pdf

18:20 X-ray Hybrid Radiation¶

Transition and Cherenkov radiation generated by a charge are well known phenom- ena and find a broad application for different scientific communities. Frank was the first to point out the possibility of interference between transition and Cherenkov radi- ation [1]. This interference is understandable, since both radiation mechanisms may be described as a secondary electromagnetic field produced by polarization currents that emerge from the interaction of an electromagnetic field of a charge with atomic electrons of the medium. In 1979 Zrevol and Ruzicka conducted theoretical investigations of this interference effect in the visible wavelength range [2]. They showed that the emitted radiation possessed both transition and Cherenkov radiation properties, i.e., that it is a hybrid radiation. However, despite the critical interest for development of new x-ray monochromatic sources, the theoretical investigations ignored this effect in x-ray range. In this report we present results of the theoretical investigation for x-ray hybrid ra- diation. Using the polarization current approach [3,4] and the atomic scattering factor formalism [5] to account anomalous dispersion of the complex permittivity we study spectral and angular distributions and polarization properties of x-ray hybrid radiation when a charge passes over a screen. This work was supposed by the Russian Foundation for Basic Research within the Grant No. 18-32-00385_mol_a and the Competitiveness Enhancement Program of Tomsk Polytechnic University. References [1] I.M. Frank, Sov. Phys. Usp. 5 (1962) 740. [2] V.P. Zrelov and Ruˇziˇcka, Nucl. Instrum. Methods. 160 (1979) 327. [3] D.V. Karlovets, J. Exp. Theor. Phys. 113 (2011) 27. [4] M. Shevelev, A. Konkov and A. Aryshev, Phys. Rev. A. 95 (2015) 053851. [5] B.L. Henke et al., A. Data Nucl. Data Tables, 27 (1982) 1.

Speakers: Mr Anatoly Konkov (Tomsk Polytechnic University), Mr Mikhail Shevelev (Tomsk Polytechnic University)

Slides 18.20_ch2018_shevelev.pdf

18:40 → 19:40 PS1 - Poster session¶

Convener: Dariush Hampai (LNF)

18:40 Backward X-ray TR from a Multilayered Structure¶

Backward transition radiation (BTR) is used at accelerators as a precise instrument for beam diagnostics. Being conventionally used in optical range, BTR based monitors are promising for submicron diagnostics, provided EUV and soft X-ray range is operated. Despite the theory of TR is very well developed, however, to the best of our knowledge the theory of backward TR from multilayered structures for arbitrary angles of incidence does not exist so far. We suggest a new and comparatively simple theoretical description of X-ray and EUV BTR from multilayered targets. For this aim we use Weizsäcker-Williams method of pseudophotons combined with the methods of X-ray optics in multilayered structures. Also, we compare the results with those obtained in well-known limiting cases, like and BTR for a normal incidence and X-ray BTR from a single plate.

Speaker: Mr Aleksandr Savchenko (NRNU MEPhI, Russia, Moscow)

18:40 Channeling Radiation of Twisted Phonons from Axially Channeled Polarized Electrons¶

In the present report on the base of solution Dirac equation [1] for axially channeled electron with fixed spin direction we find CR cross – section of twisted phonons (photons with fixed projection of angular momentum).

Speaker: Prof. Yuri Kunashenko (National Research Tomsk Polytechnic University; Tomsk State Pedagogical University)

18:40 Charged Particle Bunch Radiation in Cherenkov Concentrator¶

We continue investigation of radiation produced by a charged particle bunch moving through the concentrator for Cherenkov radiation. We take into account a series of issues affecting the dimensions of the focal spot and distribution of the field across this area. It is reasonable to take into account finite length of the bunch and a small shift of the bunch from the axis. Moreover, it is useful to consider target geometry without sharp “nose” to reduce parasitic multiple reflections in this area. In the second place, we consider interaction between the bunch and radiation pulse within the focal spot.

Speaker: Dr Sergey Galyamin (Saint Petersburg State University)

18:40 Coherent Bremsstrahlung from Axially Channeled Electrons¶

The solution of the Dirac equation for the electron (positron) in a continuous potential of the crystal axis taking into account the periodicity of the crystal in the direction of the axis was found in [1]. In a present report using those wave functions, we theoretical study the coherent bremsstrahlung from axially channeled electrons. Calculation shows that channeling of created particles result in a splitting of the coherent peak and changes its positions.

Speaker: Prof. Yuri Kunashenko (National Research Tomsk Polytechnic University; Tomsk State Pedagogical University)

18:40 Coherent Radiation Characteristics of Modulated Positron Bunch, Formed in Crystalline Undulator¶

The coherent X-ray radiation at a zero angle and at a resonant frequency, formed in crystalline undulator (CU) by the modulated positron bunch, is investigated. Taking into account the medium polarization, CU parameter and bunch energy are determined for both the conservation of channeling phenomenon and the photon beam with optimal characteristics. The spectrum of a coherent radiation has Gaussian distribution around a resonant frequency, unlike the spectrum of a spontaneous radiation, having the form of diffraction sine. Besides that the radiation intensity increases and the spectrum is narrowed. These changes are essential, if the modulation depth is not too small. Experiment is suggested, the results of which can determine this important parameter of modulation too. The case, when a positron bunch with LCLS parameters is modulated in the process SASE FEL, is considered.

18:40 Enhancement of Neutrons Yield in dd Reactions within a TiD2 Crystalline under Irradiation by a Deuterium Ion Beam¶

At ion accelerators, the neutron yield is investigated in dd reactions within a TiD2 crystalline under irradiation by a deuterium ion beam with the energy of less than 30 keV [1-8]. To study such reaction with an ultralow collision energy, there is a need in the information on the yield of neutrons in the reaction d(d,n)3He versus the angular and spatial distribution of particles during the channeling process in thin crystals. The authors of [9] performed the computer simulation of the dd reaction in TiD2 crystals and presented the results of computer simulations but they ignored the distribution of deuterons inside TiD2 crystal. They presented trajectories and spatial distribution of the deuterium ions channeled in the (200) Ti crystal instate of the TiD2 crystal. In our work we calculated the continuum potential of TiD2 for two different structures of TiD2. The probability of increasing the yield of neutrons is studied depending on the energy, the angular and spatial distribution of the incident deuterons during the dd reaction in TiD2 crystals, using computational modeling. The trajectories of deuterons in the crystal were modeled using our developed computer code with Mathematica. The results of the theoretical study concerning the effect of planar channeling of ultralow energy deuterons on the relative probability of dd-synthesis are in good agreement with the experimental data. [1] J. Kasagi, H. Yuki, T. Baba, T. Noda, T. Ohtsuki, A.G. Lipson, J. Phys. Soc. Japan 71 (2002) 2881. [2] A. Huke, K. Czerski, P. Heide, Nucl. Instr. Meth. B 256 (2007) 599. [3] K. Czerski, A. Huke, L. Martin, N. Targosz, D. Blauth, A. Górska, P. Heide, H. Winter, J. Phys. G: Nucl. Part. Phys. 35 (2008) 014012. [4] G. Ruprect, K. Czerski, D. Bemmerer, P. Heide, Phys. Rev. C 70 (2004) 025803. [5] A. Huke, K. Czerski, P. Heide, G. Ruprecht, N. Targosz, W. Zebrowski, Phys. Rev.C 78 (2008) 015803. [6] V.M. Bystritsky, Vit. M. Bystritskii, G.N. Dudkin, M. Filipowicz, S. Gazi, J. Huran, A.P. Kobzev, G.A. Mesyats, B.A. Nechaev, V.N. Padalko, S.S. Parzhitskii, F.M. Pen’kov, et al., Phys. At. Nucl. 75 (2012) 5. [7] V.M. Bystritsky, Vit.M. Bystritskii, G.N. Dudkin, M. Filipowicz, S. Gazi, J. Huran, A.P. Kobzev, G.A. Mesyats, B.A. Nechaev, V.N. Padalko, S.S. Parzhitskii, F.M. Pen’kov, et al., Phys. At. Nucl. 75 (2012) 913. [8] V.M. Bystritsky, Vit.M. Bystritskii, G.N. Dudkin, M. Filipowicz, S. Gazi, J. Huran,A.P. Kobzev, G.A. Mesyats, B.A. Nechaev, V.N. Padalko, S.S. Parzhitskii, F.M. Pen’kov, et al., Nucl. Phys. A 889 (2012) 93. [9] T.A. Tukhfatullin, Yu.L. Pivovarov, G.N. Dudkin, Y.L. Eikhorn, S.I. Kuznetsov, Nucl. Instr. Meth. B 402 (2017) 236.

Speaker: Dr Behnam Azadegan (Hakim Sabzevari University, Physics department)

18:40 Experimental and Theoretical Investigations of Generation and Transmission Mechanisms of Cherenkov Radiation in an Optical Fiber¶

This report demonstrates the results of experimental and theoretical studies of generation and transmission mechanisms of Cherenkov radiation in an optical fiber when an electron beam hits (or interacts with) a fiber. Measured dependence of a signal level of Cherenkov radiation transmitted through the fiber on value of incidence angle is presented. The experimental study has been carried out in Tomsk Polytechnic University using a 6 MeV electron beam extracted from microtron [1]. The divergence of an electron beam was 5 degree. Employed fiber was the flexible and transparent fiber made by dielectric with refraction index n=1.4 [2]. Energy of used electrons satisfies the Cherenkov criterion for radiation emergence in the fiber. In the current experiment the edge of the fiber with length of 5 mm interacts with an electron beam and the rest part of fiber covered by a lead foil. Produced radiation is transmitted through the fiber and then detected by photomultiplier tube (PMT). Fiber is placed parallel to center of the beam trajectory axis and during the scan crosses the center of an electron beam. The level of signal detected by PMT depends on several factors. First, the Cherenkov radiation intensity is directly proportional to the intensity of an electron beam which is function of the electrons propagation angle. Thereby, the fiber shift from the electron beam center causes the decrease of Cherenkov radiation intensity in the case of the divergence electron beam where most electrons travel along the center of the beam trajectory axis. Second, for the case of large value of the fiber shift, the mean free path of electrons in the fiber decreases due to variation of angle between electrons and the fiber and the Cherenkov radiation intensity drops. Important factor that determines the signal level is the beam pattern of generated radiation. As is generally known [3], the most Cherenkov photons are emitted in the forward direction at an angle relative to the electron trajectory theta θ by cosθ=c/(nv), where c is the speed of light and v is the electron velocity. There is another factor which can influence the beam pattern. This is the fiber transparency. To decrease of noise level the used optical fiber will transmit light if the light deviation from the fiber center axis is less the 5 degree. Light which does not fulfill this condition will be extinguished and can not spread in fiber. Therefore, a maximum signal of detected radiation corresponds to angle between electrons and fiber for condition where the angle of a maximum of angular distribution of Cherenkov radiation is equal to direction of the fiber center axis. Theoretical investigation and experimental test of influence these factors on a detected signal level are very significant for development and improvement of transverse beam size diagnostics using optical fiber. References 1. Stuchebrov S.G., Miloichikova I.A., Krasnykh A.A. Journal of Physics: Conference Series. 732 (2016) 012033. 2. Bolin, Frank P., et al. Applied optics 28.12 (1989): 2297-2303. 3. Jackson, John David. Classical electrodynamics. Wiley, 1999.

Speaker: Mr Sergei Stuchebrov (Tomsk Polytechnic University)

18:40 GEANT4 Simulation of Electromagnetic Shower Development in Oriented Crystals¶

We present the details of the modification of GEANT4 cross-sections for bremsstrahlung and electron-positron pair production in case of particle moving along the strongest PWO crystal axes. The scaling coefficients for cross-section modification depend on particle energy and have been previously calculated through the direct integration of Baier-Katkov formula. We used the modified GEANT4 to build up simulations of electromagnetic shower propagation in oriented PWO crystals, demonstrating the strong electromagnetic shower length reduction in comparison with standard GEANT4 simulation in amorphous PWO. This GEANT4 package can be the base for modeling of e.m. shower in oriented crystals.

Speaker: Ms Alesia Leukovich (INP BSU)

18:40 GEANT4 Simulation of Energy Deposition in Lead Fluoride Calorimeter for g-2 Experiment¶

We continue our investigation of the calorimeter system for the muon g-2 experiment. In our previous work we have shown the excellent spatial distribution of photons at the calorimeter crystals back surface, which is of a certain importance for the precise measurement of primary positron energy. We have also evaluated both photon energy and angular distributions as well as the time distribution, which has shown a nanoscale time resolution. In this work we report on Geant4 simulations of charged particles, such as 3 GeV muons, protons, electrons and positrons, passage through the calorimeter module. The module consists of a Delrin front panel for installation of the laser calibration system, 54 PbF2 Cherenkov crystals wrapped by the black paper, and silicon photo-multiplier sensors. Aluminum exit of the storage ring is also taken into account during the simulation. The main goal of our simulations is to evaluate the energy deposition of various particles in different parts of described system.

Speaker: Mr Aleksandr Savchenko (NRNU MEPhI, Russia, Moscow)

18:40 Generation of Twisted Photons by Bent Crystals¶

At the present moment, the bent crystals are employed as an effective tool for deflection of particle beams. There are also promising prospects for their use as alternative inexpensive sources of x-ray photons [1]. We develop this idea to apply the bent crystals for production of the so-called twisted photons, i.e., the photons with definite the energy, the longitudinal projection of momentum, the projection of the total angular momentum, and the helicity. Such photons are used in fundamental science and technology for the high-density information transfer, for the manipula-tion of rotational degrees of freedom of irradiated objects, for the high-contrast microscopy, and in radio-astronomy (see, for review, [2-5]). The detectors of twisted photons are also elaborated [6,7]. Employing the recently developed general formalism [8], we study the production of twisted photons by bent Si crystals. We find that the bent crystals can be used as an efficient and sufficiently pure source of twisted photons in the x-ray spectrum domain. Several schemes of how to realize such sources are proposed. References 1. A. Kostyuk, A. Korol, A. Solov’yov, W. Greiner, Channeling and Radiation in Periodically Bent Crystals, Springer, Heidelberg, 2013. 2. M.J. Padgett, Opt. Express 25 (2017) 11265. 3. D.L. Andrews, M. Babiker (Eds.), The Angular Momentum of Light, Cambridge University Press, New York, 2013. 4. J.P. Torres, L. Torner (Eds.), Twisted Photons, Wiley-VCH, Weinheim, 2011. 5. D.L. Andrews (Ed.), Structured Light and Its Applications, Academic Press, Amsterdam, 2008. 6. J. Leach et al., Phys. Rev. Lett. 88 (2002) 257901. 7. G.C.G. Berkhout et al., Phys. Rev. Lett. 105 (2010) 153601. 8. O.V. Bogdanov, P.O. Kazinski, G.Yu. Lazarenko, Phys. Rev. A 97 (2018) 033837.

Speakers: Dr Oleg Bogdanov (LNF&TPU), Dr Peter Kazinski (Tomsk State University)

18:40 Influence of Channeling Effect on Enhancement Factor for Reaction D(3He,p)4He in Astrophysical Energy Region 16÷34 keV in ZrD Target¶

The measurements of cross-sections of fusion reactions with ‘bare nuclei’ D(d, p)3H, D(d, n)3He, T(d, n)3He, 3He(d, p)4He, and D(3He, p)4He at astrophysical energies is of interest both for basic and applied physics [1]. These reactions participate in primordial nucleosynthesis. Information on the number of the D, T, 3He, and 4He nuclei formed in the early universe is used to characterize baryon density in today’s Universe. In addition, these studies provide information on electron screening of nuclear reactions. Electron screening potentials provide important information on the role of electrons in reactions induced by deuterons, tritons, and nuclei of helium isotopes that proceed in thermonuclear reactors in the energy range typical of nuclear astrophysics studies (kT ≈ 10÷100 keV), which in turn is of applied importance. The D(3He, p)4He reaction was investigated at the pulsed plasma Hall accelerator (Tomsk) in the 3He+ ion energy range EHe = 16–34 keV (E = 6.41÷13.61 keV in the center-of-mass system) with a step of 2 keV [2]. The enhancement factor of the D(3He,p)4He reaction and the electronic screening potential Ue using ZrD targets with the Miller indices [111] and [100] was determined. The measured electron screening potential is seven times higher than in gaseous targets. In addition, the channeling effect contributes due to so-called “flux-peaking” of initial beam. Recently we investigated similar effects in reaction D(D,n)3He in TiO2 crystal [3]. The combined effects of electronic screening and channeling on D(3He, p)4He reaction in ZrD lattice have not been studied either theoretically or experimentally so far. The goal of the present paper is the studies by means of computer simulations of proton yield enhancement in reaction D(3He,p)4He in deuterium saturated ZrD targets at (100) and (111) alignments. For simulations of 3He trajectories at channeling in a ZrD target the computer code BCM-2 [4] is used, which allows calculations of angular and spatial distributions of relativistic charged particles at channeling in the thin crystals [5]. Here, this code is adapted for heavy non-relativistic ions and the model to obtain the enhancement factor of reaction D(3He,p)4He is presented. The comparison with very recent experiment [2] on determination of enhancement factor in reaction D(3He,p)4He in aligned ZrD target is done. References 1. P. Navrátil and S. Quaglioni. Physical Review Letters, 108 (2012) 042503. 2. V.M.Bystritsky, G.N.Dudkin, B.A.Nechaev et al. Pis’ma v ZhETF, 107(11) (2018)705. 3. T.A.Tukhfatullin, Yu.L.Pivovarov, G.N.Dudkin, Y.L.Eikhorn, S.I.Kuznetsov, Nucl. Instrum. Methods B 402 (2017) 236. 4. S.V. Abdrashitov et al. Nucl. Instrum. Methods B 402 (2017) 106. 5. Y.Takabayashi, Yu.L. Pivovarov, T.A. Tukhfatullin. Phys. Lett. B751 (2015) 453.

Speaker: Dr Timur Tukhfatullin (National Research Tomsk Polytechnic University)

18:40 Investigation of the Wake Potentials in the Orientational Motion of Charged Particles in Ionic Crystals¶

This paper is a continuation of [1, 2]. In [1] at investigation of the channeling of relativistic electrons in ionic crystals it was shown that its electromagnetic field induces non-stationary dipole moments in a crystalline medium. This effect is the result of the inverse action of the field of channeled particle to crystal environment. From the other hand the arising non-stationary dipoles in a self-consistent manner generate non-stationary scalar and vector potentials, leading, first, to a certain contribution to the initial interaction potential of the channeled particle with the crystal, and, secondly, to the appearance of the so-called “wake potential” that influence only on the velocity of the electrons. Similar calculations were performed in [2] for non-relativistic protons. It was shown that the calculations of the wake potentials for all investigated ionic crystals are in good agreement with the calculations performed in accordance with the theory of the wake effect in nonmetallic foils proposed in [3]. In addition, under certain conditions the expressions obtained for the wake potentials reduce to the classical formula contained in [4]. This fact is a one of the stimulus for further studies of wake potentials in ionic crystals. Calculation of the wake potential should be carried out in the following sequence: 1) first, the usual problems of planar and axial channeling are solved, i.e. there are levels of transverse energy and corresponding wave functions, the probabilities of population of these levels are calculated (see, for example, [5]); 2) after that are calculated the electric and magnetic field strengths of a charged particle moving at a certain velocity and channeled in a certain quantum state [6]; 3) then the induced dipole moments of the crystalline medium are calculated as a result of solving the equation of the oscillator type (using the forward and inverse Fourier transform); 4) finally, on the basis of the use of the principles of superposition and causality, wake potentials influencing the longitudinal motion of particles (together with corrections to the initial interaction potentials) are calculated. References 1. N.V. Maksyuta, V.I. Vysotskii, Ye.V. Martysh // Problems of atomic science and technology, 2015, No. 1, P. 33 – 36 (In Ukraine). 2. N.V. Maksyuta, V.I. Vysotskii, Ye.V. Martysh // Problems of atomic science and technology, 2017, No. 1, P. 28 – 31 (In Ukraine). 3 Y.-H. Ohtsuki, Charged Beam Interaction with Solids, 1983, Taylor & Francis Ltd, Lonlon and New York. 4. J. Neufeld, R.H. Ritchie // Phys. Rev., 1955, V. 98, No. 6, P. 1632. 5. V.A. Bazylev, N.K. Zhevago, Radiation of Fast Particles in a Matter and External Fields, Nauka, Moscow, 1987 (in Russian). 6 L.D. Landau, E.M. Lifshitz, The Classical Theory of Fields, 1971, Pergamon Press, Oxford New York Toronto Sydney Braunschweig.

Speaker: Dr Nikolai Maksyuta (Taras Shevchenko National University of Kiev, Ukraine)

18:40 Large-Angle Channeling Radiation by Relativistic Muons¶

Speaker: Ms Xiatong Li (Tomsk Polytechnic University)

18:40 Longitudinal Beam Profile Diagnostics Using Coherent Cherenkov Diffraction Radiation at CLARA Facility¶

Producing and diagnostic of short bunches in modern particle accelerators are forefront issues. For example in modern high-gain free-electron lasers the electron bunches are longitudinally compressed down to 100 fs to achieve high peak currents which is crucial to drive FEL process. Such a short bunch duration opens the possibility to use effect of coherent radiation for longitudinal beam profile diagnostics. In compartments with other mechanisms the use of coherent Cherenkov diffraction radiation (ChDR) has a several significant advantages. First of all, it is non-destructive unlike a deflection cavity and less expensive than electro-optical methods. Moreover, in compartment with other polarisation radiation methods ChDR is highly directional, enabling us to separate useful signal from any background such as diffraction radiation generated from an input surface and synchrotron radiation generated upstream our target. In current work we shall describe the methodology we propose for longitudinal diagnostics using Cherenkov diffraction radiation at CLARA (beam area 1) facility. ChDR induced by charged particle beam (~50 MeV beam energy at up to 10 Hz pulse repetition rate with sub-ps bunch length) will be detected by Martin-Pupplet interferometer with use of pyroelectric detectors with 0.1-30 THz spectral range. We shall also investigate the possibility of using mathematical approach [1] for single electron spectrum prediction and further longitudinal charge distribution reconstruction by Kramers-Kronig analysis. Preliminary results will be demonstrated and analysed.

Speaker: Mr Kirill Fedorov (Royal Holloway, University of London)

18:40 On Coherency of Gamma Photons¶

We report estimations on production of coherent photons in gamma region by relativistic electrons in periodic structures. Two aspects of coherency were considered: coherency of photons emitted by a single electron over the system, and coherency of the photons emitting by a bunch of electrons at a given position. The first aspect provides density of radiation in proportion to squared number of photons per electron; the second one -- proportional to squared number of electrons in a coherent bunch. As is shown, degree of the coherency in both processes decreases with increase of the energy of gammas, due to stochastic process of energy losses. The degree of coherency for both processes is estimated analytically, and thus the overall coherency. Recommendations on increase the limit of coherency are expressed in the report.

Speaker: Dr Eugene Bulyak (NSC KIPT)

Slides ps1-26_ch2018_Bulyak.pdf

18:40 On Fast Charged Particles Scattering in a Thin Crystal Undulator¶

When fast charged particles move in crystal at small angle to one of the crystalline planes their motion in the crystal can have both finite (planar channeling) and infinite (above-barrier) character relatively the crystalline planes. The problem of the motion of such particles in a crystalline undulator in which the crystalline planes are periodically deformed is of special interest. It is bound up with the possibility of multiple reflection of particle from such atomic crystal planes in this case. The present report is devoted to an analysis of the particle scattering in a crystalline undulator. This process is considered on the basis of a numerical simulation of the particle passage through a crystal. It is shown that the angular distributions of scattered particles in this case have a significant asymmetry. In this case, the average value of the particle scattering angles in the direction of crystalline planes bending can significantly exceed the values of the critical angle of planar channeling. The effect can be used to change the shape of the beam at small lengths of a crystal. The work was carried out with the partial financial support by the project of National Academy of Sciences of Ukraine No. F56-2018.

Speaker: Prof. Nikolai Shul'ga (Akhiezer Institute for Theoretical Physics of NSC KIPT)

18:40 On the Restructuring of the Radiation Spectrum at Three-Frequency Parametric Interaction during Plane Electron Channeling in the Crystals with the Structure of a Zinc Blende¶

This paper is a continuation of the work [1], in which was considered the possibility of generation of a short-wave radiation due to the pseudophotons fields use based on three-frequency parametric interaction on channeled electrons system in certain crystallographic directions of some crystals in which there are non-unimodal potential wells. For example, crystals with the structure of a zinc blende, investigated in [2], can be chosen as such ones. To realize this idea, it is necessary to fulfill a number of resonant conditions. a). Lorentz factor of channeled electron should have such a value that in a potential well arise only three energy transverse energy level (calculation of the energy levels and corresponding wave functions in this study, in contrast to [1] is based on the numerical solutions Sturm-Liouville problem) . b) The electron velocity must be such that the bounce-frequency of the pump wave in the comoving coordinate system coincides with the frequency of the transition between the upper and lower levels (we note that this coincidence has the Okorokov effect [3]). c) The so-called synchronism condition, which includes the wave vectors of the pump wave, the signal wave, and the idler wave (it follows from the momentum conservation law) must be satisfied. Due to the nonlinearity that takes place in the interaction of electrons with real electromagnetic fields and the field of pseudophotons in a system of three energy levels of channeling, we can expect a substantial rearrangement of the spontaneous emission spectrum. The calculation is made by analogy with calculations for nonlinear systems considered in nonlinear optics (see, for example, it is carried out on the basis of a numerical solution of the Sturm-Liouville problem) [4, 5]). . References 1. V.I. Vysotskii, N.V. Maksyuta // Surface, 2005, No. 4, P. 77. 2. N.V. Maksyuta, V.I. Vysotskii, S.V. Efimenko, Y.A. Slinchenko // JINST, 2018, V. 13, P. C04010. 3. Y.-H. Ohtsuki, Charged Beam Interaction with Solids, Taylor & Francis Ltd, Lonlon and New York, 1983. 4. V.G. Dmitriyev, L.V. Tarasov, Applied nonlinear optics. Moscow: Radio i svyaz, 1982 (in Russian). 5. S.A. Achmanov, R.V. Chochlov, Problems of nonlinear optics (electromagnetic waves in nonlinear dispersive media). Moscow: VINITI, 1965 (in Russian).

Speaker: Dr Nikolai Maksyuta (Taras Shevchenko National University of Kiev)

18:40 Orbital Angular Momentum of Radiation at Axial Channeling¶

The angular momentum of electromagnetic radiation has been widely studied in recent years. The first theoretical and experimental research have been made by use of laser radiation. Radiation in the x-ray range carrying the angular momentum was recently obtained by using a helical undulator at BESSY II storage ring. Some authors proposed the methods for generation radiation with angular momentum in the free electron lasers based on helical undulators. The twisted beam of high-energy photons can provide new methods in the solid-state physics and enable the design of novel imaging systems of microscopic scale. In this talk, we propose a method for generation of such radiation in the x-ray and gamma-range energies by means of relativistic particles at axial channeling in a crystal. Electrons in the axial channeling are known to trace a rosette-like trajectory in the transverse direction. We use a simplified model of the averaged crystal axes potential in order to solve analytically the equations of motion. The obtained solution is used for calculation of the angular momentum of radiation in order to explore the basic characteristics of the angular momentum of emitted radiation. We show that the presence of angular momentum in radiation could manifest itself via a left-right asymmetry of the radiation and the asymmetry magnitude can be well detectable. Despite the fact that part of the channeling electrons are revolving around the axis of the crystal in the opposite directions, radiation of the electron beam can carry significant orbital momentum under certain initial conditions. The prerequisite to the formation of radiation with maximum value of orbital angular momentum are explored. Research of J.J. was supported by the Russian Science Foundation, project No 17-19-01217.

Speaker: Dr Julia Janz (Tomsk polytechnic university)

18:40 Peculiarities of Channeling and Generated Radiation of Relativistic Electrons in the Charged Axes of Lithium Hydride Crystals¶

Crystal LiH is one of the best objects for creation of effective sources of hard radiation, generated by electron channeling. We have calculated the interaction potential of electrons with the main charged axes [110] of LiH and also found the radiation spectrum in this potentialal. These calculations were based on one-particle potentials for Li+ and Н– ions in a lithium hydride (LiH) crystal (see [1]) in accordance with standard averaging procedures along the axes and by thermal vibrations (see, for example, [2]), and in accordance with the method proposed in [3] and applied in [4, 5]. In the process of this calculation, it was shown that the structures of potential wells in charged axes are formed to a large extent due to unscreened Coulomb interaction, respectively, with negative and positive ions of hydrogen and lithium. It should be noted that similar constructions were carried out in [6], but for charged planes. The report also noted that in connection with the difference in the amplitudes of the thermal vibrations of hydrogen and lithium ions, a significant correction to the structure of potential wells is necessary in the case of electrically neutral axes. The effect of the temperature factor in the range up to the melting point of the crystal at which the lithium hydride crystal can be considered a low-temperature crystalline plasma is also investigated. It is shown that in this case, in the axes constructed from negatively charged hydrogen ions, there is a so-called inversion effect, i.e. Instead of a potential well, a potential barrier appears. For relativistic electrons with different Lorentz-factors, the transverse energy levels and the corresponding wave functions are found as a result of a numerical solution of the Schrödinger equation when reducing it to the corresponding Sturm-Liouville problem. Using the quantum theory of dechanneling (see, for example, [2]), partial dechanneling lengths are calculated that allow us to estimate the widths of transverse energy levels. Based on these data, short-wave radiation spectra are calculated for electron bunches with different angular dispersions. It is shown that for relatively low electron energies it is possible to obtain sufficiently intense short-wave spontaneous emission in a wide spectral range. References 1. V.I. Vysotskii, N.V. Maksyuta // BRAS Physics / Supplement Physics of Vibrations, 1994, V. 58, No. 3, P. 147. 2. V.A. Bazylev, N.K. Zhevago, Radiation of Fast Particles in a Matter and External Fields, Nauka, Moscow, 1987 (in Russian). 3. N.V. Maksyuta / Thesis of the Reports of XLIV International Conference on Physics of Charged Particles Interaction with Crystals, Moscow, 2014, P. 19. 4. N.V. Maksyuta, V.I. Vysotskii, S.V. Efimenko, Nucl. Instr. Methods, 2015, V. B 355, P. 90. 5. N.V. Maksyuta, V.I. Vysotskii, S.V. Efimenko, J. Phys.: Conf. Series., 2016, V. 732, P. 012023. 6. V.I. Vysotskii, R.N. Kuz’min, and N.V. Maksyuta // Sov. Phys. JETP, 1987, V. 66(6), P. 1150.

Speaker: Dr Nikolai Maksyuta (Taras Shevchenko National University of Kiev)

18:40 Photonic Crystal-Based Compact High-Power Vacuum Electronic Devices¶

Combining the photonic crystal-based structures with vacuum electronic devices opens the way for creation of a family of radiation sources: photonic BWOs, volume FELs (VFEL), etc. Some beneficial options of such structures, which enable tunability and increasing the radiation source efficiency, are discussed. The VFEL instability law declares start current for generator with the interaction length L to be determined by L^-5 rather than L^-3, thus enabling miniaturization of radiation source. Conditions enabling achievement of generation threshold and observation of THz single-frequency generation in a photonic BWO for electron beam parameters available at existing accelerators are discussed.

Speaker: Prof. Vladimir Baryshevsky (Belarusian state University, Institute for Nuclear Problems)

18:40 Processes of Coherent and Incoherent Scattering of Charged High-Energy Particles in Ultra Thin Targets¶

In the present paper there was investigated on the base of the quantum electrodynamics eikonal approximation the process of charged high-energy particles scattering in ultrathin targets. There was suggested a unified approach that allows one to consider the scattering of particles in this case in both amorphous and crystalline targets from a single point of view. Particular attention was paid to the analysis of particles coherent and incoherent scattering processes in a crystal. There were considered different variants of the crystal axes and planes orientation with respect to the incident beam. It was shown that in the Born approximation the suggested method for describing the scattering process agrees with the analogous Ter-Mikaelian's results [1] for the interaction cross section of particles with a crystal. It was shown that particles scattering on the crystalline atoms planes is significantly asymmetric process. In this case, there are possible conditions when scattering characteristics as in an amorphous medium occur in the particles scattering along the plane, while in the transverse direction the scattering process has a coherent character. [1] M.L. Ter-Mikaelian. High-energy electromagnetic processes in condensed media. New York, Wiley-Interscience, 1972

Speaker: Prof. Nikolai Shul'ga (Akhiezer Institute for Theoretical Physics of NSC KIPT)

18:40 Radiation from a Dielectrically Loaded Waveguide with Open End¶

In this report, we study electromagnetic field produced by a charged particle bunch exiting an open-ended circular waveguide with dielectric filling placed inside collinear vacuum waveguide of a larger radius. We suppose that the bunch is prolonged along its trajectory and negligibly thin in the orthogonal direction. Based on the previously developed theory, we mainly investigate Cherenkov radiation generated in dielectric section and penetrated vacuum regions of the structure due to the diffraction mechanism. We pay the main attention to the case of a train of short bunches resulting in high-order Cherenkov modes excitation. We also develop analytical procedure allowing performing the limiting process to the case of infinite radius of the outer waveguide.

Speaker: Dr Sergey Galyamin (Saint Petersburg State University)

18:40 Radiation of a Bunch in a Waveguide with a Semibounded Anisotropic Dielectric¶

Investigation of the field of a particle bunch in a waveguide loaded with dielectric is important for the wakefield acceleration technique and for other problems in the accelerator physics. Problems of producing high acceleration fields bring to study more effective methods, for example, with using anisotropic materials. Here we study the dielectric anisotropy influence on radiation of a bunch in a dielectric loaded waveguide with a transversal border. We investigate two instances: the bunch flies from a vacuum into the dielectric and, inversely, from the dielectric into a vacuum. We make a comparison with the analogous problems with isotropic dielectric.

Speaker: Dr Tatiana Alekhina (SPbSU, Saint-Petersburg, Russia)

18:40 Spin Rotation of Planar Channeled Muons and Anti-Muons in Bent Crystal¶

In the present report, we study the spin rotation of muons and anti – muons moving in a bent crystal in planar channeling regime. For this purpose, we find particle’s trajectory in the crystal. Using calculated trajectory we find exact solution of the BMT equation and calculated the angel of muon (anti - muons) spin rotation. The result of calculation is compared with one for spin rotation of muons and anti – muons in the rectilinear crystal.

Speaker: Ms Xiatong Li (Tomsk Polytechnic University)

18:40 The Channeling Radiation from Positron Bunch in Nanotubes with Polarization Inhomogeneity¶

The problem of channeling radiation of positron bunch in the system of packed nanotubes is investigated. An expression is obtained for the spectral distribution of the total radiation of a positron bunch. The spectral distribution, taking into account the inhomogeneity of the polarization of the medium, differs significantly from the case when the averaged homogeneous polarization of the medium is taken into account. We also note that the spectral distribution depends on the energy of the bunch.

Speaker: Mr Koryun Gevorgyan (Yerevan State University (student))

18:40 The Electrons Capture into the Axial Channeling State as the Radiative Recombination Effect¶

The capture process of the high energy particle into the axial channeling state in single crystal if considered in the laboratory reference system is a sufficiently relativistic process. The cross-section calculation of this process, especially in case when the electrons capture is accompanied by the emission of a high energy photon in ultra-relativistic case is not trivial and not very clear. Authors propose to use for considering of this and similar quantum electrodynamics relativistic processes in the so called accompanying reference system (ARS), moving parallel to the channeling axis with the velocity, equal to the longitudinal component of the fast particle velocity. In such an accompanying reference system the transversal motion of a particle, entering the single crystal at the angles, not exceeding the critical Lindhard angle [1], can be considered as non-relativistic up to the really very high total energies of entering particles. Considering of the electron transversal motion with the non-relativistic energies allows employ the familiar standard results from the atomic physics [2]. In particular the cross-section calculation of the radiative recombination of electron with atom, which accompanied by the photon emission is presented.

Speaker: Ms Dina Badreeva (National Research Nuclear University MEPhI)

18:40 The Polarization Characteristics of Radiation from Electrons Channeled in a Half-Wave Crystal¶

The concept of channeling in a Half-Wave Crystal (HWC) was proposed in [1-3] for a proton beam. In our previous works [4,5], the processes of scattering and radiation of relativistic electrons channeled in a Si HWC according the beam parameters of the SAGA LS accelerator (Japan) were studied in detail. It is known, that the radiation from channeled electrons in a straight crystal has a linear polarization [6]. A distinctive feature of electrons motion under channeling in a HWC is that the part of electrons moves along arc-shaped trajectories. It can be expected that in this case the channeling radiation from HWC- channeled electrons will have interesting polarization properties. In this study, we present the numerical calculations of the polarization features ( namely, the Stokes parameters) of radiation from 255 MeV electrons channeled in a HWC Si crystal. Every trajectory is simulated using BCM-2.0 code [7], and the averaging over electrons trajectories is performed. In contrary to ordinary planar channeling radiation, there appears some circular polarization, the degree of which is estimated. References 1. Tsyganov E. N., Taratin A. Nucl. Instr. and Meth A 363 (1995), 511. 2. Guidi V., Mazzolari A., De Salvador D., Bacci L. Phys. Rev. Lett. 108 (2012) 014801. 3. Scandale W., Arduini G., Butcher M. et al Phys. Lett. B 734 (2014) 1. 4. Takabayashi Y., Pivovarov Yu.L., Tukhfatullin T.A. Phys. Lett. B 751 (2015) 453. 5. Takabayashi Y., Bagrov V. G., Bogdanov O. V., Pivovarov Yu. L., Tukhfatullin T. A. Nucl. Instrum. Methods B 355 (2015) 188. 6. Baier V. N., Katkov V. M., Strakhovenko V. M. 1998 Electromagnetic Processes at High Energies in Oriented Single Crystals (Singapoure: World Scientific Publishing) 7. Abdrashitov S. V. , Bogdanov O. V. , Korotchenko K. B. , Pivovarov Y. L. , Rozhkova E. I. , Tukhfatullin T. A. , Eykhorn Y. L. BCM-2.0 – The new version of computer code “Basic Channeling with Mathematica©” // Nuclear Instruments and Methods in Physics Research B. - 2017 - Vol. 402. - p. 106

Speaker: Dr Oleg Bogdanov (TSU&TPU)

18:40 Tunable Optical Radiation Formed in Crystalline Undulator¶

The problem of optical radiation produced by a bunch of relativistic positrons channeled to a crystalline undulator (CU) is considered. Taking into account the polarization of the crystal medium, an energy threshold takes place to form the radiation. If the energy of the bunch is above the threshold, the radiation is created in a limited frequency range. Both soft and hard boundary photons exist and are emitted at a zero angle due to the polarization of the medium. In the case where the ratio between bunch's and threshold energies is much greater than unity, the energy of the boundary soft photons depends only on the characteristic parameters (spatial period, amplitude) of the crystalline sinusoidal undulator and can be tuned to the optical range. It is shown that it is possible to obtain a directed optical beam in the "water window" range. Such photon beams have important applications in medicine and biological research.

Speaker: Mr Hayk Gevorgyan (Student)

18:40 Ultraviolet Channeling Radiation by Protons Accelerated at Medical Units¶

CR in both optical and ultraviolet regions occurs under the condition n > 1 for the crystal refractive index (see [2]), i.e. at the large angles to the direction of motion for channeled particles - near Cherenkov angle. This radiation can be used, for example, in biomedical research. In modern medical clinics the proton accelerators are in active use. By supplementing at such medical accelerator a relatively inexpensive device (optimized for channeling conditions), one can obtain a source of monochromatic ultraviolet radiation.

Speaker: Mr Yury Eikhorn (National Research Tomsk Polytechnic University)

Tuesday, 25 September ¶

09:00 → 11:00 S2.3 Channeling & Radiations in Various Fields¶

Convener: Gianluca Cavoto (ROMA1)

09:00 Surface Plasmon Slowing Down and Cherenkov-Type THz Emission in Graphene Based Structure¶

We demonstrate that surface plasmon-polariton waves with low phase velocity in carbon nanostructures can be utilized for the generation of coherent terahertz radiation through the Cherenkov mechanism, the effect being expected to be observable in carbon nanotubes and being especially pronounced in spatially expanded double- and multi-layer graphene structures owing to the suppression of the inter-layer tunneling. Generation frequency tuning is proposed by varying the graphene doping, the number of graphene sheets, the distance between sheets, etc. Significant slowing down of plasmon-polariton in carbon nanotubes and multi-layered graphene structures allows proposing them for nano-scale realization of traveling wave tube.

Speaker: Prof. Sergey Maksimenko (Institute for Nuclear Problems, Belarusian State University)

Slides 9.00_ch2018_Maksimenko.pdf

09:30 Observation of the X-ray Cherenkov Effect Near 100 eV Photons Energy¶

Recently [1] we have reported about the observation of the Cherenkov effect on the L-edge of the absorption of the aluminium. In the present report new results are provided in experimental study of the X-ray Cherenkov effect with photons energy about hundred eV. Using an electron beam with energy of 5.7 MeV, we observed the Cherenkov effect on Si and Be target with a photon energy of about 99.8 eV and 111 eV, respectively. The experimental result on the observation of the Cherenkov effect with Si on the jump of the susceptibility of the L-edge agrees well with an earlier observation of this phenomenon in [2, 3]. The result with Be foil was observed for the first time. In this case the Cherenkov effect was observed at about 111 eV of the photon energy, which corresponds to K-edge absorption of the radiation in the Be. All measurements were carried out using the electron beam of Tomsk microtron [4]. The intensity of the angular distributions of the radiation was investigated using a multilayer mirror {Mo / B4C}100 with a period d = 7.65 nm. In this report the experimental results are compared with calculation. Also the observation possibility of the Cherenkov effect with other kind materials, for example, S, Ba, La, Ce are discussed. This work was partially supported by the Federal Targeted Program of the Russian Federation agreement no. 14.578.21.0198 (RFMEFI57816X0198). References [1] Uglov S., Vukolov A., Kaplin V., Sukhikh L. and Karataev P., EPL,118 (2017) 34002. [2] Moran M. J., Chang B., Schneider M. B. and Maruyama X. K., NIM B, 48 (1990) 287. [3] Knulst W., PhD Thesis, Thechnische Universit, Eindhoven (2004). [4] Uglov S. R., Kaplin V. V. et al., J. Phys.: Conf. Ser., 517 (2014) 012009.

Speaker: Dr Sergey Uglov (Tomsk Polytechnic University)

Slides 9.30_ch2018_uglov.pdf

09:45 Charge Radiation in the Presence of Conical and Prismatic Dielectric Objects: Far-Field Area¶

We analyze radiation of charges moving in presence of some dielectric targets. The first of them is a cone with vacuum channel where the charge moves. The second is a prism (the charge moves along one of its borders). We use the “aperture method” developed in our previous works. Here the main attention is given to the far-field area. Analytical and numerical results are shown and main physical effects are described (in particular, the phenomenon of “Cherenkov spotlight” for the cone target). Prospects of use of aperture technique for other objects are discussed as well.

Speaker: Prof. Andrey Tyukhtin (Saint Petersburg State University)

Slides 9.45_ch2018_Tyukhtin.pdf

10:00 Radiation of a Charge Moving in a Wire Structure¶

In the X-ray frequency region, interaction of relativistic electrons with crystals results in parametric X-ray radiation (PXR), with its frequency being determined by distance between crystallographic planes and direction of electron motion. If instead of crystal one considers an artificial periodic structure with periods of the order of mm, one can expect emission of radiation of a similar nature at terahertz (THz) frequencies. This frequency range is of significant interest during last decade due to its prospective applications [1]. Moreover, artificial wire-like structures are considered as a promising alternative to conventional dielectric structures for wakefield acceleration [2]. Here we consider electromagnetic (EM) field produced by a charged particle bunch moving through a lattice of parallel conducting wires. The portion of the EM radiation related to wavelengths comparable with the periods of the structure (``short-wave response'') can be described similarly to PXR in real crystals [3]. The wire structure should be referred to as a ``wire crystal'' in this case. Moreover, since the bunch spectrum contains relatively low frequencies, a ``long-wave response'' will also occur with wavelengths much larger then structure periods. The portion of EM radiation related to this low frequency part of spectrum should be described using the ``effective medium'' formalism, where the discussed wire assembly is usually referred to as ``wire medium''. This ``long-wave response'' is also of essential interest due to, for example, its non-divergent properties [4]. In this report we present several approaches for analysis of EM field in the described wire structure. First, conventional two-wave approximation for describing the ``short-wave response'' is developed. The main attention here is paid to investigation of EM field near the trajectory of the bunch. Second, we use the effective medium approach and describe the ``long-wave'' part of the spectrum. Third, we develop a method based on vibrator antenna theory which can be useful for finite length wire structure. Moreover, a series of numerical simulation is performed and obtained results are compared and discussed. This work is supported by the grant from Russian Foundation for Basic Research (No. 17-52-04107). [1] G.P. Williams, Rep. Prog. Phys., V. 69(2), P. 201, (2006). [2] P.D. Hoang, et al., Phys. Rev. Lett., V. 120, P. 164801, (2018). [3] V. Baryshevsky and E. Gurnevich, Nuclear Inst. Meth. Phys. Res. B, V. 402, P. 30, (2017). [4] V.V. Vorobev, A.V. Tyukhtin, Phys. Rev. Lett., Vol. 108, P. 184801, (2012).

Speaker: Dr Sergey Galyamin (Saint Petersburg State University)

Slides 10.00_ch2018_Galyamin.pdf

10:15 On Amplification of Radiation from a Charged Particle Circulating around a Cylinder¶

The radiation from a charged particle uniformly rotating around an infinitely long cylinder made of composite material is investigated. For the dielectric function of the cylinder we use the generalized Drude-Lorentz-Sommerfeld formula. The study is based on the exact solutions of the Maxwell equations. The dispersion of electromagnetic waves inside a cylinder is taken into account. It is shown that the charged particle can generate powerful radiation if rotates around a cylinder at a specific resonant frequency, which is determined by the parameters of the cylinder.

Speaker: Prof. Aram Saharian (Yerevan State University, Yerevan, Armenia)

Slides 10.15_ch2018_saharian.pdf

10:30 Radiation on Conducting Sphere and Hemispherical Bulge in Conducting Plane: Further Development¶

The description of diffraction and transition radiation (DR and TR) on a metal sphere based on the method of images known in electrostatics (see, e.g., [1]) has been developed in [2]. In the method of images the boundary conditions for the field of the incident particle on the perfect conductor surface are satisfied via introduction of one or more fictitious charges (the “images” of the real one). The uniform motion of the incident charge near the conducting sphere leads to the accelerated motion of its image that produces the radiation. This approach had been expanded in the paper [3] to the problem of DR by the particle moving parallel to the conducting plane with the hemispherical bulge on it. This problem requires introduction of three fictitious charges two of which move with acceleration. The present report contains the further consideration of the problem including: (i) Exact formulae for the polarization of DR both on the spehere and hemisphere in the long-wavelength limit ($\lambda \gg R$). The possibility of the projectile's trajectory monitoring via the polarization of DR on the sphere is demonstrated. (ii) Computation of TR intensity on the hemispheric bulge. The complex character of the interference leads to a large variety in TR directional diagram shapes. (iii) Numerical computation of the radiation from the bunch of charged particles on the sphere as well as on the hemispheric bulge. References [1] J.D. Jackson, Classical Electrodynamics, Wiley, New York, 1999. [2] N.F. Shul’ga, V.V. Syshchenko and E.A. Larikova, Nucl. Instrum. Methods B 402 (2017) 167. [3] V.V. Syshchenko, E.A. Larikova and Yu.P. Gladkih, JINST 12 (2017) C12057.

Speaker: Prof. Vladislav Syshchenko (Belgorod State University)

Slides 10.30_ch2018_syshchenko.pdf

10:45 Features of Radiation Generated by Bunches of Charged Particles Passing Through the Centre of a Ball¶

The radiation generated by a rectilinearly and uniformly moving train of fine bunches of charged particles is investigated. It is assumed that the particles cross a ball made of conductive, dielectric or composite material passing through its center. The obtained numerical results are based on the corresponding exact analytical solutions of Maxwell equations [1,2]. It is shown that there may be peaks in the emission spectrum of particles at some “specific frequencies” with the wavelengths of the order of ball radius. The values of the spectral density of radiated energy at these specific frequencies may be many times larger than the values of that quantity at adjacent frequencies. The peaks in the spectrum of radiation generated by the particles disappear if one replaces the ball by a plane-parallel plate made of the same materials, with a thickness equal to the diameter of the ball. A visual explanation of this phenomenon is given. References 1. S.R. Arzumanyan, L.Sh. Grigoryan and A.A. Saharian, Izv. Nats. Akad. Nauk Arm., Fiz. (Engl. Transl.: J. Contemp. Phys.) 30 (1995) 99. 2. S.R. Arzumanyan, J. Phys.: Conf. Ser. 357 (2012) 012008.

Speaker: Prof. Alpik Mkrtchyan (Institute of Applied Problems of Physics NAS RA)

Slides 10.45_ch2018_mkrtchyan.pdf

11:00 → 11:20 Coffee break

11:20 → 13:05 S4.1 Charged Beams Shaping & Diagnostics¶

Convener: Prof. Alexander Potylitsyn (Tomsk Polytechnic University)

11:20 Optical Cherenkov Diffraction Radiation as a Tool for Non-invasive Charged Particle Beam Diagnostics¶

Transverse beam diagnostics is a key sub-system in any accelerator facility enabling to evaluate its performance. Invasive techniques such as optical transition radiation (OTR) or wire scanners are not good enough because high power beam can destroy the OTR target or a thin wire so quickly that the diagnostics equipment will become useless for a long period of time required to repair it. Moreover, a solid target can distort beam parameters such that the distorted beam can damage expensive accelerator components. Recent years have witnessed an intense development of non-invasive techniques for charged particle beam diagnostics. Physicists and engineers together were searching for physics phenomena which can give information about the beam without direct interaction with matter. The state-of-the-art in non-destructive transverse beam diagnostics is a so-called laser-wire [1], when a thin laser beam is scanned across a particle beam and the secondary particles are detected downstream. This technique has micron scale resolution and is recognised as a primary equipment for future linear colliders. However, this method is not a turn-key device. It is expensive and requires a team of experts looking after it. Optical diffraction radiation [2] appearing when a charged particle moves through a slit in a conducting screen has been rigorously investigated as an alternative to the laser-wire technique. However, contribution of synchrotron radiation (SR) background into ODR [3] significantly complicates its use for beam diagnostics, because it requires special settings of the beam parameters. Recently we have proposed to use Cherenkov Diffraction Radiation (ChDR) as a promising technique for transverse beam diagnostics. ChDR appears when a fast charged particles moves in the vicinity of and parallel to a dielectric interface. The polarized interface emits radiation along the direction defined by Cherenkov radiation propagation angle (cosθ = 1/βn, where β is the speed of particles in units of the speed of light and n is the refractive index of the medium) away from the particle trajectory. Due to very high directionality ChDR can be separated from SR generated upstream and ODR generated from the any accelerator components or incoming edge of the target itself. On the other hand the ChDR parameters can be used to diagnose the beam size, emittance, position, and direction. Due to very short wavefront along the Cherenkov direction, a fast detector can give information about the beam arrival time. In this report we shall present the first observation of ChDR in optical wavelength range in Cornell University, its basic experimentally observed characteristics and their comparison with simulations performed by polarization current approach, and demonstration of ChDR feasibility for charged particle beam diagnostics. Our future plans for experimental work at KEK-ATF (Japan) and Diamond LS (UK) facilities. References 1. L. J. Nevay, et al., Physical Review Special Topics – Accelerators and Beams 17, 072802 (2014). 2. P. Karataev, et al., Physical Review Letters 93 (2004) 244802. 3. L. Bobb, et al., Physical Review – Accelerators and Beams 12, 032801 (2018)

Speaker: Dr Pavel Karataev (Royal Holloway, Unviersity of London)

Slides 11.20_ch2018_Karataev.pdf

11:50 A Simple Model to Describe Smoke Ring Shaped Beam Profile Measurements with Scintillating Screens at the European XFEL¶

Standard beam profile measurements of high-brightness electron beams based on optical transition radiation (OTR) may be hampered by coherence effects induced by the micro-bunching instability which render a direct beam imaging impossible. For the European XFEL it was decided to measure transverse beam profiles based on scintillating screen monitors using LYSO:Ce as scintillator material. While it is possible to resolve beam sizes down to a few micrometers with this kind of scintillator, the experience during the commissioning of the XFEL showed that the measured emittance values were significantly larger than the expected ones. In addition, beam profiles measured at bunch charges of a few hundreds of pico-Coulomb show a ‘smoke ring’ shaped structure. While coherent OTR emission and beam dynamical influence can be excluded to explain this observation, it is assumed that the beam profile distortions are caused by effects from the scintillator material. Following the experience of calorimetry in high energy physics, a simple model was developed which takes into account quenching effects of excitonic carriers inside a scintillator in a heuristic way. Based on this model, the observed beam profiles can be understood qualitatively. Together with the model description, first comparisons with experimental results will be presented, and possible new scintillator materials suitable for beam profile diagnostics at the XFEL are proposed.

Speaker: Dr Gero Kube (Deutsches Elektronen-Synchrotron (DESY))

Slides 11.50_Ch2018_Kube.pdf

12:05 Diffraction Radiation for 2D Transverse Beam Size Diagnostics¶

In this report, we suggest a new type of target capable of advanced beam diagnostics. The target is a screen with 5 holes in it: one in the centre and 4 are at the corners of a rectangle. As the rectangle’s sides differ, the radiation will contain information about two beam sizes, which opens the possibility to detect two transversal beam sizes simultaneously. To describe the radiation we developed a DR theory for the case of off-axis passage of electrons through central hole in the screen with. In the limiting case the expressions coincide with those obtained by M.L. Ter-Mikaelian.

Speaker: Dr Alexey Tishchenko (National Research Nuclear University "MEPhI")

Slides 12.05_ch2018_Tishchenko.pdf

12:20 Evolution of the Landau Spectral Peak Produced by 50 GeV Protons and 7 GeV Electrons in Si Detector at Rotation of the Detector¶

The spectra of ionization loss of 50 GeV protons and 7 GeV electrons in 131 and 300 μm thick silicon detector [1,2] at different alignments of the detector are presented. The thickness of the depleted zone of the semiconductor detector Hamamatsu S3590-18 was 131 μm at 10 V and 300 μm at 100 V power supply. Spectra of ionization loss were measured at different angles of the detector rotation relative to the alignment when the plane of the detector is parallel to the beam axis for both thicknesses. The experiment was performed at accelerator U70 in Protvino (Russia). Possibilities for applications of the effect are discussed. [1] Shchagin A.V., Shul’ga N.F., Trofymenko S.V., Nazhmudinov R.M., Kubankin A.S. Semiconductor detector with smoothly tunable effective thickness for the study of ionization loss by moderately relativistic electrons. Nuclear Instruments and Methods in Physics Research B 387 (2016) 29–33. [2] Nazhmudinov R.M., Kubankin A.S., Shchagin A.V., Shul’ga N.F., Trofymenko S.V., Britvich G.I., Durum A.A., Kostin M.Y., Maisheev V.A., Chesnokov Y.A., Yanovich A.A. Study of 50 GeV proton ionization loss by semiconductor detector with smoothly tunable thickness. Nuclear Instruments and Methods in Physics Research B 391 (2017) 69–72.

Speaker: Mr Ramazan Nazhmudinov (Belgorod National Research University)

Slides 12.20_ch2018_Nazhmudinov.pdf

12:35 Orientation Effect in the Neutron Yield in Deuterated Pd Target Bombarded by Deuterium Ion Beam¶

O.D. Dalkarov a, M.A. Negodaev a, A.S. Rusetskii a, A.P. Chubenko a, Yu.L.Pivovarov b, T.A.Tukhfatullin b a P.N. Lebedev Physical Institute Russian Academy of Sciences (LPI), Moscow, Russia b National Research Tomsk Polytechnic University, Tomsk, Russia At the ion accelerator HELIS at the LPI, the neutron yield is investigated in DD reactions in deuterated Pd target, during an irradiation of its surface by a deuterium ion beam with the energy 20 keV. The measurements of the neutron flux in the beam direction are performed in dependence on the target angle, β, with respect to the beam axis. These measurements are performed using a multichannel detector based on He3 counters. A significant anisotropy in neutron yield is observed, it was higher by a factor of 2 at β=0 compared to that at β = ±30o. The possible reasons for the anisotropy, including ion channeling, are discussed. A similar effect was observed earlier when irradiated deuterated CVD diamond samples with a deuterium ion beam [1]. To explain the experimental results, we used the computer code earlier applied in [2] to interpret the orientation effect in the neutron yield from deuterated C(400) target irradiated by 20 keV deuteron beam. The code allows calculation of the deuterons flux under channeling condition. Now, the code is modified in order more exactly take into account the dependence of reaction probability on impact parameter. The dependence on impact parameter was “constructed” conjugating the classical definition of reaction cross-section (integral over impact parameters) from one side, and real yield of DD reaction from another side, which is the convolution of energy-dependent cross-section (includes astrophysical S-factor), effect of screening, and energy loss. Reference 1. A.V. Bagulya, O.D. Dalkarov, M.A. Negodaev, A.S. Rusetskii, A.P. Chubenko, V.G. Ralchenko, A.P. Bolshakov, Nucl. Instr. and Meth B 355 (2015) 340. 2. A.V. Bagulya, O.D. Dalkarov, M.A. Negodaev, Yu.L. Pivovarov, A.S. Rusetskii, T.A. Tukhfatullin. Nucl. Instr. and Meth. B 402 (2017) 243.

Speaker: Dr Alexey Rusetskii (P.N. Lebedev Physical Institute Russian Academy of Sciences)

Slides 12.35_ch2018_rusetsky.pdf

12:50 Crystal Optical Solution for Generation of High Energy Neutrino Beams¶

The problem of creation of high energy neutrino beams on the basis of modern and future circular proton accelerators with the help of traditional technology seems to be expensive and difficult. Because of this, we propose the solution of this problem based on the usage of focusing bend single crystals. In the report we demonstrate the possibilities of acceptance and focusing of a pion beam with the help of a crystal optical lens system. As an illustration of these features the calculated neutrino fluxes for energy of circulating proton beam equal to 6.5 TeV are presented. The work is supported by Russian Science Foundation (grant 17-12-01532).

Speaker: Dr Vladimir Maisheev (Institute for High Energy Physics)

Slides 12.50_ch2018_maisheev.pdf

13:05 → 14:30 Lunch

14:30 → 16:30 S1.3 Channeling & Radiations in Crystals¶

Convener: Prof. Hartmut Backe (Institute for Nuclear Physics)

14:30 Past and Future Channeling Experiments in the US¶

In recent years, several key experiments channeling high-energy electrons and positrons have been performed in the US at SLAC. using the FACET and the ESTB beam facilities. The results include measurements of channeling parameters in a little-explored energy range and the first experimental demonstration at high energy of quasi-channeling oscillations predicted by Sytov et al. Quantitative measurements provide data suitable to benchmark simulations and, e.g., design crystal-based beam collimation systems. Since these measurements the experiments have shifted towards studying the gamma-ray emission by high-energy electrons passing through crystals with tantalizing albeit preliminary results. Crystalline undulator devices have been proposed and are being investigated; some of these suitable for electron beams as well as positron beams. There is renewed interest in channeling radiation as a means to increase the efficiency of positron targets for high-energy linear colliders. SLAC FACET-II and ESTB are prime facilities for experimental investigation and quantifying the enhancement over amorphous targets that can be expected. The presentation will review the work done by our group and provide an outlook of planned investigations.

Speaker: Dr H.-Ulrich (Uli) Wienands (Argonne National Laboratory)

Slides 14.30_ch2018_wienands.pdf

15:00 Quantum Features of Relativistic Particle Scattering and Radiation in Crystals¶

Classical trajectory simulations, widely used in crystals at high energies, have never been supported by a rigorous quantum treatment. To do this, both the notion of optic curved ray eiconal and Wigner function proved to be necessary. We reveal that, being essentially quantum in nature, incoherent scattering of relativistic elementary particles in crystal is correctly described by both the modified Mott cross-section at the large momentum transfers and r.m.s. scattering angle at the the small ones. We also address both the inclusion of incoherent radiation to the algorithm of Baier-Katkov formula numerical integration and suppression of the same by coherent scattering.

Speaker: Prof. Victor Tikhomirov (Research Institute for Nuclear Problems)

Slides 15.00_ch2018_Tikhomirov.pdf

15:15 Periodical Dependence of Radiation Intensity on Crystal Thickness and Incidence Angle at Motion of Fast Charged Particles in the Planar Field of a Thin Crystal¶

At motion of a fast charged particle in crystal near the direction of one of main crystallographic planes, a periodical deviation of the trajectory from the initial direction is observed (channeling, over-barrier motion), that is accompanied by irradiation of the electromagnetic field quanta. If the target thickness is small compared to the radiation formation length, the spectral density of radiation is equal over entire range of photons energy. At the target thickness increase, the effect of radiation suppression takes place [1]. Here we study the possibility of experimental observation of the effect of radiation suppression and predict new accompanying effects in radiation at motion of charged GeV particles (electrons and positrons) in thin crystals. We considered the radiation of the particles moving in the field of (110) Si planes at channeling and over-barrier motion. For such conditions we obtained the dependences of the spectral density of radiation on crystal thickness, incidence angle and particle energy, being averaged over all impact parameters. The obtained results show that, if the radiation formation length is large compared to the target thickness, an observation is possible, besides the effect of radiation suppression, of the effect of periodical dependence of radiation intensity on the above-stated parameters of motion. We show that the conditions of observation of described effects are reachable on modern instrumentation and indicate approximate ranges of particles’ and photons’ energies to deal with. [1] N.F. Shul’ga, S.P. Fomin, JETP Letters 27(2), 126-128, 1978.

Speaker: Dr Sergiy Shulga (aNational Science Center “Kharkiv Institute of Physics and Technology)

Slides 15.15_ch2018_ShulgaS.pdf

15:30 The Thin Structure of the Transversal Energy Spectrum of Electrons at Axial Channeling due to the Spin-Orbit Interaction¶

The ultra-relativistic electron with energy E up to 10^11 eV moving along the crystallographic axis in an axial channeling mode, can be considered as a non-relativistic 2D-atom, possessing the discrete spectrum of energies and orbital momentum, if the electron motion is considered in the so called accompanying reference system (ARS), moving parallel to the channeling axis with the velocity, equal to the longitudinal component of the electron velocity. In the ARS the electron in axial channeling (the 2D-atom) may go through all the same effects as electrons in regular atoms. In particular – the energy levels of its transversal motion may be split due to the spin-orbit interaction. In this report we try to estimate the magnitude of this splitting effect as well as to estimate the influence of the magnetic field generated by the ionic rows in crystal, which in ARS will be looking moving and thus producing the strong axial current. The transitions between split levels may be resonantly provoked by the optical laser beam, directed also at some small angle to the crystal axis. The radiation transitions between the split levels of transversal motion shall result with emission of rather high energy X-ray photons (due to the relativistic Doppler effect) with certain discrete energies in straight forward direction.

Speaker: Prof. Nikolay Kalashnikov (National Research Nuclear University Mephi)

Slides 15.30_ch2018_kalashnikov.pdf

15:45 Non-Dipolarity of Axial Channeling Radiation at GeV Beam Energies¶

We continued our investigation of the non-dipolarity of channeling radiation (CR) at GeV beam energies [1] which remarkably change the CR spectrum and its intensity [2]. The experimental proof that CR and coherent bremsstrahlung (CB) substantially influence the output of positrons at conversion of γ-radiation into e+e- pairs in crystalline targets has been given at the KEK B facility [3]. An advanced concept to create a non-conventional intense positron source, the so-called hybrid setup, has been suggested long time ago [4]. Motivated by the pending CLIC and ILC projects, active discussions of this concept did not drop and stay actual up to now [5,6,7]. Besides de-channeling [8,9], the non-dipolarity of CR at GeV beam energies cannot be neglected in realistic simulations of CR spectra [10] being the initial point for any evaluation of positron production via conversion of γ-radiation into e+e- pairs [5]. We for the first time consider the non-dipolarity of axial CR at electron beam energy of several GeV carrying out simulations based on realistic axial continuous potentials. References 1. B. Azadegan and W. Wagner, “Non-dipolarity of channeling radiation at GeV beam energies”, 7th Int. Conf. “Channeling 2016”, Sirmione, Italy, Nucl. Instrum. Methods B 402 (2017) 63. 2. N. F. Shul’ga, L. É. Gendenshteĭn, I. I. Miroshnichenko et al., Sov. Phys. JETP 55(1) (1982) 30 (and Refs. therein) 3. T. Suwada, M. Satoh, K. Furukawa et al., Phys. Rev. Spec. Topics – Accelerators and Beams 10 (2007) 073501 (and Refs. therein) 4. R. Chehab, F. Couchot, A. R. Nyaiesh et al., Proc. IEEE PAC’89, Chicago, IL, USA, 1989, p. 283. 5. B. Azadegan, S. A. Mahdipour and W. Wagner, “Simulation of positron energy spectra generated by channeling radiation of GeV electrons in a tungsten single crystal”, Journal of Physics: Conf. Series 517 (2014) 012039. 6. A. Potylitsyn et al., “Undulator-based and crystal-based gamma radiation sources for positron generation”, Journal of Physics: Conf. Series 517 (2014) 012041. 7. I. Chaikovska, R. Chehab et al., „Optimization of a hybrid positron source using channeling“, Nucl. Instrum. Methods B 402 (2017) 58 (and Refs. therein) 8. H. Backe et al., Nucl. Instrum. Methods B 266 (2008) 3835. 9. O. V. Bogdanov and S. B. Dabagov, Journal of Physics: Conf. Series 357 (2012) 012029. 10. B. Azadegan and W. Wagner, Nucl. Instrum. Methods B 342 (2015) 144.

Speaker: Mr Aleksandr Savchenko (NRNU MEPhI Moscow)

Slides 15.45_ch2018_savchenko.pdf

16:00 Volume Reflection Dependence on the Interplanar Potential¶

The analytic theory of volume reflection of fast charged particles in a bent crystal [1] is generalized to the case of an arbitrary interplanar potential shape. The mean deflection angle and the angular distributions for positively and negatively charged volume reflected particles are derived, with simplifications occurring under condition R>>R_c. Cases of crystal orientation (110) and (111) are compared. An interpretation for the effect of deflection to the side opposite to that of the crystal bending is offered, from the viewpoint of the non-inertial reference frame related with the bent crystal. [1] M.V. Bondarenco, Phys. Rev. A 82 (2010) 042902.

Speaker: Dr Micola Bondarenco (Kharkov Institute of Physics and Technology)

Slides 16.00_ch2018_Bondarenco.pdf

16:15 Deflection of High-Energy Negatively Charged Particles by Means of a Bent Crystal¶

When a high-energy charged particle moves in a crystal having a small angle between its momentum and one of the main atomic axes or planes, correlations between successive collisions of the particle with neighboring atoms occur. These correlations give the possibility to deflect the direction of motion of the particle to the angles, which significantly exceed the critical angle of channeling. There are three mechanisms of high-energy charged particles deflection by a bent crystal: planar channeling, volume reflection and stochastic deflection. All these mechanisms are well studied in the case of positively charged particles. However, in the case of negatively charged particles, an important contribution to the dynamics of particles in the crystal is made by incoherent scattering. The effect of incoherent scattering complicates the consideration of the problem of particles deflection and leads to a decrease in the angles of deflection of negatively charged particles in comparison with positively charged particles. In recent years, a number of experiments have been carried out to study the motion of negatively charged particles in bent crystals. In this work we analyze the possibility of deflection of high-energy negatively charged particles by a bent crystal using theoretical calculations and numerical simulation. This study makes it possible to compare the efficiency of the three mechanisms of deflection of negatively charged particles with the help of bent crystals.

Speaker: Dr Igor Kyryllin (Akhiezer Institute for Theoretical Physics of National Science Center Kharkov Institute of Physics and Technology)

Slides 16.15_ch2018_kyryllin.pdf

16:30 → 16:50 Coffee break

16:50 → 18:35 S5.1 Novel Sources: FEL/Laser/Plasma¶

Convener: Prof. Sultan Dabagov (LNF)

16:50 Free Electron Laser and CARM Devices: A Unified Point of View¶

Review of undulator based Free Electron laser (U-FEL) theory Review of CARM (Coherent Auto Resonance Maser) theory Analysis of analogies and differences Development of a common theoretical framework Presentation of the ENEA Frascati CARM experiment

Speaker: Prof. Giuseppe Dattoli (ENEA)

Slides 16.50_ch2018_dattoli.pdf

17:20 Radiation of Twisted Photons in Periodical Structures in the Classical Regime¶

It is known [1,2] that the radiation produced by classical sources may possess a well-defined projection of the angular momentum. Such a radiation is convenient to represent as a collection of the so-called twisted photons, i.e., the photons with definite the energy, the longitudinal projection of momentum, the projection of the total angular momentum, and the helicity. At present, the twisted photons find an application for fundamental science and technology (see, for review, [3-5]). There are sources and detectors of twisted photons [1-6]. However, the general formula for the probability of radiation of a twisted photon by a classical current was unknown. We derive such a formula and employ it for description of the undulator radiation. In this way, we develop the general theory of generation of twisted photons by undula-tors. Due to universality of the undulator radiation, this theory can be applied to the radiation of free electron lasers and to the channeling radiation. We find the symmetry property of the average number of twisted photons produced by a charged particle moving along a planar trajectory. We obtain the explicit formulas for the average number of twisted photons generated by undulators both in the dipole and wiggler regimes. In particular, for the forward radiation of the ideal right-handed helical undulator, the harmonic number n of the twisted photon coincides with its projection of the total angular momentum m. As for the ideal left-handed helical undulator, we obtain that m=-n. It is found that the forward rad-iation of twisted photons by a planar undulator obeys the selection rule that n+m is an even number. We establish that the average number of twisted photons produced by the undulator and detected off the undulator axis is a periodic function of m in a certain spectral band of the quantum numbers m. References 1. S. Sasaki, I. McNulty, Phys. Rev. Lett. 100 (2008) 124801. 2. M. Katoh et al., Phys. Rev. Lett. 118 (2017) 094801. 3. M.J. Padgett, Opt. Express 25 (2017) 11265. 4. D.L. Andrews, M. Babiker (Eds.), The Angular Momentum of Light, Cambridge University Press, New York, 2013. 5. J.P. Torres, L. Torner (Eds.), Twisted Photons, Wiley-VCH, Weinheim, 2011. 6. G.C.G. Berkhout et al., Phys. Rev. Lett. 105 (2010) 153601.

Speaker: Dr Peter Kazinski (Tomsk State University)

Slides 17.20_ch2018_kazinsky.pdf

17:35 Dual Color X-Rays Production from Thomson or Compton Sources at THU¶

Recently, the dual color X-rays production from Thomson/Compton sources has been demonstrated on the high brightness linac at Accelerator Laboratory of Tsinghua University (THU). We present two simple schemes for producing two-color Thomson/Compton radiation with the possibility of controlling time separation of the two different colors, respectively based on the interaction of one single electron beam with two light pulses that one is generated by second harmonic generation (SHG) of another, and the interaction of two different-energy electron bunches with two light pulses centered at the same wavelength. The X-rays were spectrally measured by the distribution images obtained by HOPG crystal diffraction, and the experimental results were consistent with the theoretical simulations. there are widely applications of the dual-color X-rays. One of the most promising applications is the pump-probe experiment which can open the door for scientists to study the structural dynamics on the atomic and molecular scale. This work was supported by the National Natural Science Foundation of China (NSFC Grants No. 11475097, 11375097 and 11435015) and the National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504).

Speaker: Dr Lixin YAN (Accelerator Lab, Tsinghua University, Beijing)

Slides 17.35_ch2018_lixinyan.pdf

17:50 Compton Scattering in Delayed Counter-Propagating Laser Beams Irradiating Solid Target¶

In the realm of quantum dynamics, electrons can absorb one or several photons and emit a photon with higher energy through Compton scattering. A novel scheme, i.e. using electrons accelerated by laser-plasma interaction to collide head-on with laser to create ultra-bright γ-rays has already attracted lots of attention in the past decades. However, the number of accelerated electrons is limited in this scheme. In order to increase the number of electrons participated in the Compton scattering, we propose to a new regime by using the delayed counter-propagating laser beams. After the first laser deposits energy into the target and heats the electrons, a dense electron zone will be formed in the rear side of the target. When the second laser irradiates this zone, nonlinear Compton scattering will occur and a large number of γ-rays will thus be generated. Such γ-ray emissions are continuous in the period from the time when laser starting interaction with electron zone to the time when the reflected laser moving away from the electron zone. The simulation results show that in this regime, both the average density of electrons participated in the Compton scattering and the interaction area are increased significantly.

Speaker: Ms yuan zhao (Miss)

Slides channel.pdf

18:05 Timing Resolution in Aligned PWO Crystal Scintillators¶

Evaluation of crystal effects in the PWO scintillator of the CMS electromagnetic calorimeter showed that the peak of the electromagnetic shower shifts by 2-4 radiation lengths to its entry surface [1]. Shower development acceleration also affects timing resolution of a crystal calorimeter. In current study we used the similar approach like in [1], in order to get in-depth understanding of PWO timing performance. In contribution we will present timing evolution of the electromagnetic showers in “crystal” PWO in comparison with showers in the “amorphous” PWO. 1. V. Baryshevsky et al., Nucl. Instr. Meth. B 402 (2017) 35.

Speaker: Prof. Alexander Lobko (Institute for Nuclear Problems, Belarusian State University)

Slides 18.05_ch2018_Lobko.pdf

18:20 Towards Positron Acceleration and High Quality Preservation in Nonlinear Wakefields in Hollow Plasma¶

Unlike electrons, it is difficult to accelerate positrons in the blowout regime as the positive charges are quickly expelled away from the bubble by the background ions therein. To obtain an acceptable efficiency, it requires precisely placing the positrons in the narrow region of plasma electrons with a peak density. In addition, the transverse nonlinearity of the accelerating field results in an increase of energy spread inevitably. By introducing a hollow plasma channel, the defocusing ions in the acceleration region for positrons are removed. Furthermore, the steep and negative slope of the accelerating field reduces the resultant energy spread gained in the preceding acceleration dramatically. The emittance of positrons can be preserved as well. This hollow channel also facilitates the focusing of the multiple driving proton bunches. With the huge energies stored in the protons, the positrons can be accelerated to the energy frontier in a single stage.

Speaker: Ms Yangmei Li (University of Manchester, Cockcroft Institute)

Slides Channeling2018_YLi.pdf

18:40 → 19:40 PS2 - Poster session¶

Convener: Dr Sergey Galyamin (Saint Petersburg State University)

18:40 Azimuthal Asymmetry of Coherent Cherenkov Radiation From a Tilted Bunch¶

Femtosecond and sub-femtosecond electron pulses are used in different scientific fields (pump-probe experiments, laser-driven acceleration, ultrafast electron diffraction, etc.). Diagnostics tools for such ultrashort electron bunches have to be developed parallel to the progress of accelerator technologies. In the paper [1] the coherent transition radiation process is proposed to measure not only bunch duration but tilting angle of the ultrashort pancake-like bunch. In the present report, we have considered a coherent Cherenkov radiation (CChR) from a tilted bunch in a thin inclined dielectric plate and showed a possibility to use this process for bunch diagnostics. Simulation was performed using the polarization current model [2]. We have demonstrated that in this case the CChR azimuthal distribution is strongly distorted. Changing an inclination angle of the plate and measuring an azimuthal asymmetry of the resulting CChR one can reconstruct a bunch length and bunch tilting angle. The work was supported by the "Science" of the Ministry of education and science of the Russian Federation, grant No. 3.1903.2017, and the development program of the National Research Tomsk Polytechnic University in the project of the leading universities of the world. References [1] G. Kube, A.P. Potylitsyn, JINST 13, C02055 (2018). [2] D. V. Karlovets, JETP 113(1), 27-45 (2011).

Speaker: Prof. Alexander Potylitsyn (Tomsk Polytechnic University)

18:40 Electrostatic Cumulation of High-Current Electron Beams for Terahertz Sources¶

The electrostatic cumulation of current density in relativistic vacuum diodes with ring-type cathodes is described theoretically and confirmed experimentally. The distinctive feature of the suggested cumulation mechanism is a very low energy spread of electrons. As a result of electrostatic cumulation, a thin relativistic electron beam with a current density of 1 kA/mm2 can be formed. This quantity exceeds a typical current density in high-current Cherenkov sources for an order of magnitude. Such a beam can be used as an active medium in high-power terahertz sources.

Speaker: Prof. Vladimir Baryshevsky (Research Institute for Nuclear Problems)

18:40 Polarization Characteristics of the Grating Diffraction Radiation¶

The Grating Diffraction Radiation (GDR) mechanism can provide monochromatic beams in THz and sub-THz ranges with a possibility of the spectral line tuning [1]. Additional advantage of this mechanism is connected with its flexible polarization characteristics. In contrast with THz beams generated via the transition radiation (TR) mechanism [2], where polarization is radial, for the GDR case (as well as for the conventional diffraction radiation [3]) emitted photon’s polarization state may be chosen from pure linear to elliptical one by variation of experimental geometry. We have carried out investigations of the GDR polarization characteristics both experimentally and theoretically. Measurements were performed with 8 MeV electron beam and 4 mm period triangular profile grating. Simulations were conducted using the generalized surface current method for experimental conditions (real grating profile, finite size grating, near field and coherent effects, etc.). We confirmed a possibility to generate circularly polarized beams. Further investigations are foreseen to explore applicability of polarization selection for the high diffraction orders of emitted radiation.

Speaker: Dr Dmitry Shkitov (National Research Tomsk Polytechnic University)

18:40 Reaction Forces of Polarization Radiation¶

Some eight decades after the first experimental observation of the polarization radiation mechanism, new systems of particle acceleration, beam diagnostics and radiation sources are still being designed and implemented, illustrating the continued and dynamic interest in this unique physical phenomenon. Polarization radiation, like many other processes of the particle-medium interaction, brings about the reaction forces which effect on the particle dynamics, on the one hand, and target's material, on the other. In this report, we will consider only the reaction forces from the electromagnetic fields of polarization radiation affected on a charged particle, which interacts with the non-polar mediums with the arbitrary conductivity and the flat shape. Relying upon the polarization currents approach [1, 2], the direction of reaction forces will be analyzed depending on target's parameters and particle’s overflight conditions. The obtained results will be essential to compile the equation of particle's motion in the particle-medium interaction process. This work was supposed by the Russian Foundation for Basic Research within the Grant No. 18-32-00385_mol_a and the Competitiveness Enhancement Program of Tomsk Polytechnic University. References [1] D.V. Karlovets, J. Exp. Theor. Phys. 113 (2011) 27. [2] M. Shevelev, A. Konkov and A. Aryshev, Phys. Rev. A. 92 (2015) 053851.

Speaker: Dr Anatoly Konkov (Tomsk Polytechnic University)

18:40 Surface Radiation from Charge Moving along Corrugated Metal Structure with Small Period¶

We study a "longwave" radiation of a charge moving along a corrugated structure perpendicularly to its grooves. The wavelengths under consideration are assumed to be much more than the period and the depth of corrugations. The real surface is replaced with the plane on which equivalent boundary conditions are set. It is shown that relativistic charge can generate surface waves. The detailed analysis is performed for the case of ultra-relativistic charge. We obtain the field components and the spectral density of surface radiation. The results obtained are of interest for development of new methods of generation of microwave radiation.

Speaker: Prof. Andrey Tyukhtin (Saint Petersburg State University)

18:40 The Mechanism of Induced-Dispersive Channeling of Neutral Atoms and Molecules in Zeolite Channels, Natural Asbestos Fibers and Structured Cylindrical Superlattices¶

Controlled long-distance transportation of neutral particle beams is one of the most interesting problems of atomic physics. Some features of the interaction of moving neutral atoms, molecules and clusters with a superlattice field (e.g., crystal lattice and system of magnetic or electric domains) were considered in [1]. In our new paper we consider the possibility of using the induction-dispersion method of interaction of particles for the realization of long distance channeling in natural channels of zeolites , asbestos fibers and similar cylindrical structured nanotubes . 1. V. I.Vysotskii, M.V.Vysotskyy, N.V.Maksyuta. Journal of Surface Investigation, 2010, V.4, No.4, 696

Speaker: Prof. Vladimir Vysotskii (Kiev National Shevchenko Univ, Kiev, Ukraine)

18:40 Capillary Optics. Modeling of Numerous Transformations of X-rays¶

Capillary optics is one of the best tools for controlling X-ray radiation. It allows handling the X-ray beams, which pass through many materials practically without breaking and much loss of intensity, with the correct selection of the parameters of the optics and the source of radiation. In order to proper calculate the experiment as well as to define optimized optics it is necessary to build mathematical models that reproduce these processes. Presented research is devoted to computer modeling of X-ray transmission through and shaping capillary optical systems (single capillary and multi capillary, polycapillary, ones). These studies make it possible to obtain a qualitative picture of the transformations that the radiation experiences during the passage through various capillary lenses.

Speaker: Mr Aleksandr Baryshnikov (NRNU MEPhI)

18:40 Cherenkov Radiation from Relativistic Heavy Ions in Liquid Radiator¶

Properties of spectral and angular distributions of Cherenkov radiation (ChR) from relativistic heavy ions (RHI) in solid radiators taking account of their slowing-down have been recently investigated [1-3]. The obtained new peculiarities such as the bright diffraction like structure showed that not all features of ChR are well studied yet while they might be attractive for modern detector physics [4-7]. Here we present calculations of ChR spectral and angular distributions from RHI (Ag, Pb, U) with initial energies starting from 600 MeV/u in Iodine-Naphthalene (C10H7I) liquid radiator. Such type of radiator has good resistance to a high radiation rate of RHI – the reason why it was chosen for new Time of flight Cherenkov detector [5-7] that is currently being developed at GSI for the FAIR Super FRS facility. A precision down to about 50 ps in time is also a key parameter for new detector. Consequently, correct simulations of RHI penetration through a liquid radiator are required in order to quickly estimate detector capabilities during the design stage. References: 1. O.V. Bogdanov, E.I. Fiks, Yu.L. Pivovarov, JETP 115(3) (2012) 392. 2. E. Fiks, et al., Nucl. Instrum. Methods B 309 (2013) 146. 3. O. Bogdanov et. al., 2018 JINST 13 CO2015. 4. E. Fiks, et al., Nucl. Instrum. Methods B 314 (2013) 51. 5. N. Kuzminchuk-Feuerstein et. al. Nucl. Instrum. Methods A 866 (2017) 207. 6. O.V. Bogdanov, E.I. Rozhkova, Yu.L. Pivovarov and N. Kuzminchuk-Feuerstein and the Super-FRS Experiment collaboration et.al. Cherenkov radiation and half-wave crystal channeling as possible new mass/charge/velocity detectors of relativistic heavy ions // GSI Scientific report 2018. 7. E.I. Rozhkova, N. Kuzminchuk-Feuerstein et. al. A new modular detector design as a possible TOF detector for the Super-FRS // GSI Scientific report 2018, contribution ID 140.

Speaker: Dr Rozhkova Elena (National Research Tomsk Polytechnic University)

18:40 Compact Thomson Parabola Spectrometer for Fast Diagnostics of Different Intensity Laser-Generated Plasmas¶

A compact Thomson parabola spectrometer for diagnostics of laser-generated plasma was built in Messina University to be employed in different experiments. It allows to detect the charge particles emitted from hot and fast plasma separating them per charge state, energy and mass-to-charge ratio. Moreover, it is possible to detect electrons emitted from plasma. It uses a double pin-hole input for alignment direction, a permanent magnet (0.004 - 4 kG) and an electric field (0.05 - 5 kV/cm) both orthogonal to the direction of the incident particles, and different type of planar detectors (multi-channel plates, phosphorous screen, gaf-chromix, CR39 and PM 355 track detectors). Measurements were acquired at MIFT in Messina observing electrons up to 10 keV kinetic energy, at INFN-LNS of Catania using ions emitted from plasma submitted to a post acceleration up to 30 kV per charge state and at PALS laboratory in Prague detecting energetic ions above 1 MeV per charge state. The particle recognition was obtained comparing experimental parabola curves with theoretical simulations obtained using COMSOL software. Results will be presented and discussed.

Speaker: Prof. Lorenzo Torrisi (Dipartimento MIFT, Università di Messina, Italy)

18:40 Comparison of Electron Beam Attenuation in Samples of ABS and HIPS Plastics by Fused Deposition Modeling¶

In this paper, the numerical simulation and the experimental study of the electron beams propagation in polymer materials suitable for the sample production by rapid prototyping technique were carried out [1]. To conduct experimental studies the sets of plates with various thicknesses were made of ABS and HIPS plastics by fused deposition modeling [1]. The combination of these plates allows measurements to be made in 1 mm increments. Experiments were carried out for electron beams of linear accelerators TrueBeam 2.0 (Varian) for the energy range 6 – 20 MeV and ONCOR Impression Plus (Simens) for the energy range 6 – 18 MeV [2, 3]. Pre-calibrated GafChromic EBT3 polymer films were used as the detector [4]. The numerical model was created in accordance with experimental set-up. Since the manufacturing process of the sample by fused deposition modeling is the formation of an objects from a thermoplastic mass by layer-by-layer volume alignment [1]. A distinctive feature of the printed samples is the lower actual density of the objects, in comparison with the density of the material (filament) of which they are made [5]. Taking into account this fact, the real density of the polymer plates was calculated and an additional correction of the numerical model was carried out. On the concluding stage of the research the calculated and experimental data of the electron beam attenuation in samples made of ABS and HIPS plastics by fused deposition modeling were compared. This work is supported by the grant of Russian Science Foundation (18-79-10052). References 1. F.Bähr, E. Westkämper, Procedia CIRP. 72 (2018) 1214-1219. 2. The TrueBeam system. Information on https://www.varian.com/sites/default/files/resource_attachments/ TrueBeamBrochure_RAD10119D_September2013.pdf. 3. ONCOR Impression Plus Linear Accelerator. Information on http://www.siemens.com.tr/i/assets/saglik/ onkoloji/oncor.pdf. 4. P. Sipilä et al., J. Appl. Clin. Med. Phys. 17(1) (2016) 360-373. 5. A. K. France Make: 3D printing: The essential guide to 3D printers. – Maker Media, Inc., 2013. – 222 p.

Speaker: Mr Yury Cherepennikov (Tomsk Polytechnic University)

18:40 Development of XRFA-SR Method with the Hard X-Ray (65 keV) Range for Paleoclimate Reconstruction (Selena River of Lake Baikal Region) at the Storage Ring VEPP-4M¶

The analysis of bottom settlings by the scanning X-ray fluorescence spectrometry method (SR-XRF scan) is carried out in the context of paleoclimate research. Comparison of these reconstructed Siberian records with the annual record of air temperature for the Northern Hemisphere shows similar trends in climatic variability over the past 800 yr. Estimated harmonic oscillations of temperature and precipitation values for both historical and reconstructed periods reveal subdecadal cyclicity. The Selenga River is the main inflow of Lake Baikal and its suspended material penetrates away into the lake. The catchment of the Selenga River is 447000 km2 and water content of the river is a proxy of moisture of the south part of East Siberia and the Northern Mongolia. In this reason, studing of geochemical pattern of bottom sediments of Lake Baikal we can reconstruct water content of the Selenga River in the past. All measurements were carried out on the station of XRFA-SR on the storage ring VEPP-4M. The work is supported by the Ministry of Education and Science of the RF (project RFMEFI62117X0012). The conditions of VEPP-4M were the following: Ee = 4.5 GeV, SR beam from 9-pole wiggler with B = 1.9 T, and Ie= 20 mA. The excitation energy for the determination of concentrations in practically all bottom sediments was 65 keV. The new XRFA-SR station on the storage ring VEPP-4M allowed to move to a new level of research on paleoecological reconstructions, by increasing the number of detectable concentrations of 35 chemical elements. Elements determined at the new station of XRFA-SR on the storage ring VEPP-4M -I, Cs, Ba, La, Ce, Pr, Nd, Sm are unique markers of specific rocks occurring only in local places. Scanning analysis with a spatial resolution of 1-0.1 mm made it possible to reconstruct the dynamics of bottom settlings of the Baikal region with a time resolution "year-season" in the range from 100 to 1000 years.

Speaker: Dr Valentina Trunova (Nikolaev Institute of Inorganic Chemistry Siberian Branch of the Russian Academy of Sciences)

18:40 Experimental Cave Design for Neutron Diffraction at a High Brilliance Source¶

The objective of the presented cave is to shield users from radiation of a series of macromolecular neutron diffraction experiments planned at European Spallation Source being constructed in Lund Sweden. The design process was iterative considering physical (radiological) and engineering constraints. The vicinity of the cave is considered as supervised area and a factor two was considered as conservatism of the numerical modelling the dose consequence by MCNP code. The architectural design concept has changed multiple times; the final layout contains a labyrinth and a steel door behind. The structure is constructed of reinforced, prefabricated blocks. This solution was chosen to be able to disassemble and reassemble the full cave without dust generation. This resulted in many, previously unseen engineering challenges.

Speaker: Prof. Szabina Torok (HAS Centre for Energy Research)

18:40 Features of Scattering of a Plane Electromagnetic Wave on a Conductive Ball¶

The phenomenon of scattering of a plane electromagnetic wave on a conductive ball is studied taking into account the dispersion of electromagnetic waves inside the ball material. The analysis is based on the corresponding exact analytical solutions of Maxwell equations. These solutions are obtained by the method of Green function presented in [1,2]. A visual explanation is given about why the resonant scattering may appear when plane waves of certain frequencies scatter on the ball. The operation of spaser [3] is based on the special case of the phenomenon under consideration, when the ball radius is much smaller than the wavelength of scattered wave. This phenomenon may have a wide spectrum of important practical applications. References 1. Y. Avishai and Y. B. Band, Phys. Rev. A 40 (1989) 5500. 2. A. Boum, Quantum Mechanics: Fundamentals and Applications. Mir, Moscow (1990) (in Russian). 3. D. J. Bergman and M. I. Stockman, Phys. Rev. Lett. 90 (2003) 027402.

Speaker: Ms Anush Sargsyan (Institute of Applied Problems of Physics NAS RA, 25 Hr. Nersessian St.,Yerevan, Armenia)

18:40 Hybrid Graphene Based Material Promising Target in Laser Matter Interaction¶

Graphene oxide foils implanted by copper ions at low energy and high dose, have been proposed as hybrid graphene based materials suitable to be laser irradiated in vacuum to produce hot plasmas. The special lattice structure of the graphene oxide foil can improve the propagation of the laser accelerated electrons inside the foil and enhance the electron density emerging from the rear foil surface. In such conditions increases the electric field developed in the non-equilibrium plasma and the consequent forward ion acceleration. The foils have been optimized in thickness and they were irradiated with optimized laser parameters in order to produce high energy and quasi-monoenergetic proton beams by the femtosecond laser at the Institute of Plasma Physics and Laser Microfusion in Warsaw, Poland. Silicon carbide and ion collector detectors were used in time-of-flight configuration to monitor the plasma properties and to measure the velocity of the emitted protons and carbon ions from plasma.

Speaker: Dr Alfio TORRISI (Nuclear Physics Institute, AS CR)

18:40 Investigation of the Iridescence Scattering of Hydrogen Atoms in Non-Chiral Carbon Nanotubes¶

As shown in [1], the radial profile function of the probability density of localization of channeled hydrogen atoms in a carbon nanotube (CNT) has two clearly fixed maxima. One of them (the greater) is in the center of the CNT. The second maximum (smaller) is located in the region of the minimum of the averaged interaction potential of hydrogen atoms with the inner wall of a CNT. It was shown in [1] that the relationship between these maxima depends on the angular dispersion of the beam of hydrogen atoms: the central narrow maximum essentially decreases in magnitude with increase of angular dispersion and the second wide maximum increases by a small value at the same condition. The so-called focusing effect of channeled particles in a CNT is associated with the first maximum (see, for example, [2, 3]). With the second maximum, apparently, the so-called iris-scattering effect should be associated [4]. In this paper, the position and magnitude of this maximum are analyzed in detail. Based on the one-particle Lennard-Jones potential we have calculated an exact potential for the interaction of a hydrogen atom with all CNT atoms, after which its expansion into a two-dimensional Fourier series was performed: one-dimensional reciprocal-lattice vectors and azimuthal harmonics. Taking into account only two terms in this expansion (one term corresponds to the so-called averaged interaction potential, and the second is a perturbation potential depending on the azimuth angle), the two-dimensional Schrödinger equation is numerically solved within the framework of the stationary perturbation theory and the levels of the transverse energy and the system of wave functions are found. Further, the probabilities of populating these levels by a beam of hydrogen atoms incident on the entrance of a nanotube with a certain angular dispersion are calculated. Finally, the probability density of localization the hydrogen atom in the CNT channel is calculated as a function of two variables: the radial coordinate and the azimuth angle. As a result, it is shown that this function is periodic in the azimuth variable with maxima between the longitudinal axes of the CNT. Thus, in this paper it is shown on the basis of the quantum mechanical calculation that the system of periodically located maxima of the distribution function of the hydrogen atom in the CNT channel is associated with iridescence scattering studied within the framework of the classical approach, for example, in [5]. References 1. M. Maksyuta, V. Vysotskii, S. Efimenko / Abstract of the XXIX International Conference on Photonic, Electronic and Atomic Collisions, 22 – 28 Jule, Toledo (Spain), 2015, ICPEAC – Abstracts Available Online, TU – 152. 2. V.A. Aleksandrov, I.V. Lysova, A.S. Sabirov at al // Journal of Surface Investigation, 2012, V. 6, No. 1, P. 172 – 175. 3. I.V. Lysova // Journal of Surface Investigation, 2013, V. 7, No. 1, P. 130 – 132. 4. H. Winter, A. Schüller // Progress in Surface Science, 2011, V. 86, P. 169 – 221. 5. V.S. Malyshevsky, G.V. Fomin, E.V. Dergacheva, N.I. Jylina // Theses of the Reports of XLVIII International Conference on Physics of Charged Particles Interaction with Crystals, Moscow, 2018, P. 48.

Speaker: Dr Nikolai Maksyuta (Taras Shevchenko National University of Kiev)

18:40 Light Guiding By Defects Into Frustrated Cholesteric Liquid Crystals¶

We study the light scattering by localized quasi planar excitations of a Cholesteric Liquid Crystal known as spherulites. We quantitatively evaluate the cross section of the axis-rotation for polarized light, by taking into account the anisotropic optical properties of the medium and the peculiar shape of the excitations. Because of the complexity of the system under consideration, first we give a simplified analytical description of the spherulite. We evaluate the above mentioned scattering cross-sections in the Born approximation, by using both the analytical results and, for comparison, the numerical exact skyrmion solution for several paramenters. The effects of changing values of the driving external static electric (or magnetic) field is also considered. Possible applications of the phenomenon are envisaged.

Speaker: Mr Vito Turco (Università del Salento - Dipartimento di Matematica e Fisica)

18:40 Measurement of Gamma Radiation Beam Profile in the Cross Section by Analyzing of Cherenkov Radiation Generated in the Fiber during Multi-Angle Scanning¶

The report presents result of experimental measurement of gamma radiation beam profile in the cross section. The measurement done using radioactive gamma source Со60. Dielectric fiber located under different angles in the scanned plane is used as sensitive detector. The interaction between gamma radiation and dielectric material causes creation of electrons with energy sufficient to generate Cherenkov radiation [1], which is further registered by photomultiplier [2]. The definition of the beam profile in the cross section is provided by the reconstruction of the gamma radiation intensity dependence on the spatial coordinates in the measured plane Iɣ(y,z) from generated in the fiber Cherenkov radiation intensity dependence on fiber location ICh(s,φ). To obtain such dependencies, an installation that allows to move the fiber in the measured plane has been created. The movement of the fiber is made translationally in the measured plane perpendicular to the gamma-ray beam in the s direction. After that, the scanning angle φ is changed to the predetermined value and the measurement is repeated. The intensity of generation of Cherenkov radiation depends on the total intensity of gamma radiation that has fallen on the fiber. Generated Cherenkov radiation is guided by the fiber to silicon photomultiplier. The recording device records The dependence of the signal intensity on the photomultiplier ICh on the fiber location s and on the angle of fiber orientation φ is recording by the PC. After that, using the inverse Radon transformation the gamma radiation intensity distribution in the primary beam cross-section Iɣ is reconstructed from the set of recorded data. The advantaged of the used in the experiment device is that scanning element and the detector is essentially the same. The latter provides rather simple construction of the device and increases reliability [3]. References 1. J.V. Jelley, Cherenkov radiation and its applications, Pergamon, London, U.K., (1958). 2. Sensl MicroSB silicon photomultiplier technical user manual, http://sensl.com/downloads/ds/DS-MicroJseries.pdf. 3. A.V. Vukolov et al., Russ. Phys. J. 59 (2017) 1681.

Speaker: Mr Sergei Stuchebrov (Tomsk Polytechnic University)

18:40 Multi-Particle Time-Domain Analysis of Coherent Synchrotron Radiation¶

A Coherent Synchrotron Radiation source is under construction at Inter University Accelerator Centre, New Delhi. In this project, a train of super-radiant electron microbunches will be created inside a 2.6 cell normal conducting photo-injector and injected in to a compact undulator to produce coherent radiation in the frequency range of 0.18 - 3.0 THz. The synchrotron radiation emitted by an ensemble of electrons traversing through an insertion device is well understood in the frequency-domain. In this paper, the detailed time-domain analysis of the emission of radiation in the case of a single electron extended up to an electron bunch has been performed. The exact formula to calculate the phase-difference between the electro-magnetic waves emitted by different electrons occupying different spatial coordinates inside the electron bunch has been derived. The calculation is aimed at understanding the super-radiant emission of coherent synchrotron radiation in time domain and to explicitly understand the effect of the longitudinal and the transverse beam size on the emitted radiation. It is shown that the transverse electron beam size has only a second order effect on the radiation emitted along the axis of the trajectory but in the case of off-axis radiation, its intensity is dependent on the transverse and longitudinal distribution of the electron beam.

Speaker: Dr Subhendu Ghosh (Inter University Accelerator Centre)

18:40 New Linear Microfocus Bremsstrahlung Source Based on Compact Betatron With Light and Heavy Narrow Targets inside¶

The paper presents the results obtained in the study of the properties of bremsstrahlung generated at the grazing incidence of 18-MeV betatron electrons with narrow targets, 50 μm and 8 μm thick Si crystals and 13 μm thick Ta foil with a length of 4 mm along the electron beam, mounted in an internal goniometer inside the betatron chamber. The results show strong changes in the angular distribution of radiation at the variation of the target orientation that is not observed in the case of normal incidence of electrons on the surface of a thin target. It is also shown that a light or heavy target enables generation of radiation with its predominant contribution to the x-ray or γ-ray spectral regions, respectively. The 18-MeV betatron-based linear microfocus source generates bremsstrahlung with a spectrum up to the electron energy, while microfocus X-ray tubes widely used for various purposes have so far attained the photon energy of 750 keV. Radiation beams generated in the targets were used to obtain magnified images of a microstructure of 50 Pt and 8 W wires and of an object that consisted of four steel bars with 10 μm gaps between them mounted in an external goniometer. The images indicate high absorption and edge-phase contrasts of their components due to a small horizontal size of the radiation source, the width of which in the cases of Si crystals and Ta foil was 30-, 187- and 115-fold smaller than the diameter of the electron beam, respectively. The obtained results attest to high quality of the radiation generated by the new microfocus source that can also be used in a laboratory physical experiment, for example, in materials science and x- and γ-optics. This work is supported by the Russian Science Foundation, project #17-19–01217.

Speaker: Mr Vladimir Smolyanskiy (Tomsk Polytechnic University)

18:40 New Targets for Laser Proton Production¶

We present a new method for the hydrogen enrichment of targets for high-power laser-matter interaction. Transition metals (Ta, Ti, Nb, Pd) are known as good H2 adsorbers. After a laser cleaning process (by KrF excimer laser) of thin samples (thickness ~ 10 µm) a constant flow of H2 (6.0 pure) was maintained inside the vessel. Next, we exposed the metal foils to excimer laser irradiation (1500 pulses) in order to promote adhesion of the hydrogen. We tested the targets at Lecce and Frascati laboratories. Measurements performed on Ti targets showed an increase (a factor ~ 4, up to 5×109 protons/shot) of proton yield with respect to reference targets not enriched in Hydrogen.

Speaker: Dr Luciano Velardi (Università del Salento, Dipartimento di Matematica e Fisica, LEAS Laboratory, Lecce)

18:40 Particles Deflection, Focusing and Collimation in Optical Lattices¶

Charged particles interaction with high-intensity optical lattice is often referred to as channeling. Indeed, as was shown previously, charged particles could be trapped, guided, focused or collimated with channels of effective potential, formed in non-uniform laser field [1]. On the one hand, beams shaping and control techniques, based on charged particles channeling in optical lattice, requires high power lasers to deal with tasks easily performed by nowadays tools of accelerator physics, e.g. to turn a sub-GeV electron on a mrad angle one needs a laser of power more than 1e16 W/cm^2! So there is no foreseeable perspective of replacing all the beam optics with laser formed optical lattices. On the other hand, using field to turn, guide and shape charged particle beams involves no beam-matter interaction, purging most of inelastic components from the process. Moreover, a number of distinctive features of optical lattice makes it a promising tool for particles colliders. For example, the fact that unlike crystal channels, channels in optical equally affect both positively and negatively charged particles [2, 3, 4], which could be used to increase luminosity for electon-positron colliders of the future. In this report those possible applications will be discussed and illustrated by numerical simulations with the newly created code. The main focus of current report are examples close to real conditions found in experiments. For that reason non-uniform (e.g. Gaussian profile) finite laser beams are considered to form optical lattice. Feasible laser intensities and electron beam energies have been chosen to exemplify the phenomena of interest. [1] A. Andreev, S. Akhmanov, Channeling, collimation, and radiation of relativistic electrons in ultrastrong nonuniform optical fields, Zh. Eksp. Teor. Fiz. (Pis'ma), 1991, 53, 18-21 [2] S.B. Dabagov, A.V. Dik, E.N. Frolov, Channeling of electrons in a crossed laser field Physical Review Special Topics - Accelerators and Beams, American Physical Society (APS), 2015, 18 [3] P.W. Smorenburg, J.H.M. Kanters, A.Lassise et al., Polarization-dependent ponderomotive gradient force in a standing wave, Phys. Rev. A, 2011, 83 063810. [4] A.L. Pokrovsky, A.E. Kaplan, Relativistic reversal of the ponderomotive force in a standing laser wave, Phys. Rev. A, 2005, 72, 043401.

Speaker: Mr Evgenii Frolov (LPI RAS and NR TPU)

18:40 Peculiarities of Electron Beam Propagation through Polymer Samples Manufactured by Layer-by-Layer Fusing Method with Different Printing Parameters¶

In this work, we study the features of the passage of an electron beam through polymer samples manufactured using additive technologies with different printing parameters. The technology of layer-by-layer fusing makes it possible to produce samples with different filling factor by plastic in the volume of the product [1]. For the experimental studies, ten polymer test samples with different filling factors from 10 to 100% have been made. Peculiarities of the electron beam interaction with these objects are revealed. Measurements were made for 6 MeV small-sized electron beam of betatron MIB-6E [2]. Pre-calibrated polymer films of GafChromic EBT3 [3] were used as a detector. In the work the profiles of electron beams after passing through the polymer test samples are measured. This work is supported by the grant of Russian Science Foundation (18-79-10052). References 1. A. K. France Make: 3D printing: The essential guide to 3D printers. – Maker Media, Inc., 2013. – 222 p. 2. V. A. Novikov et al., AIP Conf. Proc. 1882 (2017) 020054. 3. P. Sipilä et al., J. Appl. Clin. Med. Phys. 17(1) (2016) 360-373.

Speaker: Mr Sergei Stuchebrov (Tomsk Polytechnic University)

18:40 Plasma Electron Density Control in TNSA Regime Using fs Laser¶

Advanced targets based on thin films of graphene oxide covered by metallic layers have been irradiated at high laser intensity (1018 - 1019 W/cm2) with 40 fs laser pulses to investigate the forward ion acceleration in the TNSA regime. Time-of-flight technique was employed with silicon-carbide detectors and ion collectors as on-line plasma diagnostics. At the optimized laser focus position with respect to the target surface was measured the maximum proton energy using metallic films of Al, Cu and Au. A maximum proton energy of 3 MeV was measured using the Au metallization. This energy decreases decreasing the atomic number of the metallic film, i.e. the electron density injected in the thin foil and in the forward plasma. The acceleration energy seems acquired also by the detected carbon ions proportionally to their charge state. The effect of plasma electron density control using the graphene oxide is presented and discussed.

Speaker: Prof. Lorenzo Torrisi (Dipartimento MIFT, Università di Messina, Italy)

18:40 Polycapillary-Based X‐Ray Tomography of Complex Samples with Porous Matrix¶

X-ray computed tomography (CT) is one of the most advanced methods for the non-destructive investigation of the internal structures of various objects. Researchers have been developing instrumentations for the CT research over several decades. As a result, some modern units can provide a spatial resolution of about several microns but their contrast resolution is often not high enough for CT analysis. The problem becomes even more evident for the studies on the imaging of low-absorbing and consequently low-contrast objects at conventional X-ray tube based table-top facilities. Indeed, organic porous objects are extremely hard to investigate at laboratory facilities, and the corresponding X-ray images obtained are characterized by low quality. Moreover, CT imaging of the objects composed by both low and high absorbing parts is even more problematic due to the mistakes occurring during mathematical reconstruction [1]. These mistakes may result in various “artefacts” in final reconstructed images. One of the ways to increase the image quality for such objects is to utilize a more intense X-ray flux going through the investigated sample. High radiation flux on a sample can be obtained by either the X-ray source current or the longer exposition time. Both these options have an obvious drawback: they require either greater maximum X-ray source power or longer measurement time. An alternative approach is based on the application of X-ray concentrating optical elements, for instance, polycapillary lenses or semilenses, in experimental setups in order to collect photons from the primary divergent beam and guide them to the sample [2, 3]. On the other hand, controlling the geometry of the primary beam provides us with an additional option necessary for a new approach in 3D tomography. In this work, a test sample consisting of low absorbing porous matrix and high absorbing central part is studied at the Xlab Frascati laboratory tomography stages using two approaches based on polycapillary optics. The first approach is based on the use of a conventional CT scheme modified by the presence of a polycapillary semilens between the X-ray source and the object. The second one relies on a confocal scheme [4, 5] enabling us to scan the object under study point by point while recording the intensity of secondary (fluorescent and scattered) X-rays.

Speaker: Mr Yury Cherepennikov (Tomsk Polytechnic University)

18:40 Synchrotron Radiation in a Homogeneous Medium for a Rotating Observer¶

The electromagnetic fields and the energy-momentum tensor are considered for a charged particle rotating in a homogeneous medium from the point of view of a rotating observer. In the corresponding coordinate system there is a horizon and the latter can serve as a simple model for horizons in more complicated problems with gravitational fields.

Speaker: Mr Vardazar Kotanjyan (erevan State University)

18:40 The Transparency Effect in Two Wall Acoustic Tubes at the Presence of Standing and Running Acoustic Fields Exited There¶

The transparency effect in two wall acoustic tubes at the presence of standing and running acoustic fields excited there which allows to manage all working parameters of transparency. It has been investigated experimentally and theoretically the dependence of X-ray absorption on the parameters of external acoustic waves [1]. Sharp decrease of the X-ray absorption coefficients has been observed for quartz crystals in Laue-geometry diffraction under full pumping conditions [2-4], depending on diffraction geometry parameters and amplitude of acoustic waves. Under certain conditions the linear coefficient of absorption decreases to zero. The phenomenon mentioned above may be interpreted as X-rays coherent scattering. Under certain conditions the acoustic waves lead to the formation of strong bounded electron system or to the formation of double-wall acoustic nanotubes. The state of the formed walls of the acoustic nanotubes can be described by means of the same wave functions. The photons interact with the walls as with collective scattering unit, and the wave function before and after interaction are the same. 1. A.R. Mkrtchyan, A.H. Mkrtchyan at all, Charged and neutral particles channeling phenomena Channeling 2008, Copyright 2010 by world Scientific publication Co. Pte. Ltd, ISBN-13 978- 981-4307-00-0, pp. 306-308. 2. A.R. Mkrtchyan, M.A. Navasardyan, V.K. Mirzoyan, Technical Physics Letters, 1982, vol.8, B.11, pp.677-680. 3. A.R. Mkrtchyan, M.A. Navasardyan, R.G. Gabrielian at all. Technical Physics Letters, 1983, v.9, B.11, p.1181. 4. R.G. Gabrielyan, H.A. Aslanyan, Phys. Stat. sol.(b), 1984, V123, pp. K97-K99.

Speaker: Prof. Alpik Mkrtchyan (Institute of Applied Problems of Physics NAS RA)

18:40 Transition Radiation on Surface Waves¶

We investigate the electromagnetic fields and the radiation from a charged particle intersecting the boundary between two dielectric media on which surface waves are excited. A formula is derived for the spectral-angular density of the radiation intensity assuming that the amplitude of the surface wave is small compared with the corresponding wavelength. The dependence of the peaks in the angular distribution of the radiation intensity on the characteristics of the surface wave is discussed. In addition we consider the possibility for the determination of the surface profile by using the properties of the radiation.

Speaker: Prof. Aram Saharian (Institute of Applied Problems in Physics NAS RA)

18:40 Ultrashort Optical Parametric Amplifier and Oscillator up to the Near-Infrared¶

Coherent light sources in spectral regions which are inaccessible to lasers has been an important issue for more than five decades. Despite tremendous progress in laser technology over the last five decades, substantial portions of the optical spectrum from the ultraviolet (UV) to the infrared (IR) still remain inaccessible to conventional laser sources, at time scales ranging from continuous to almost single-cycle pulses. This limitation arises from the limited gain bandwidth of the active medium, which defined the operating spectral region of the laser. This directly limits the application of such devices, while also placing a boundary on ultrashort pulse generation, which requires very broad bandwidths. In this context, coherent optical sources based on nonlinear conversion, with femtosecond pulse duration and wide tunability, are rapidly emerging. They are extremely versatile and of considerable interest for a wide range of scientific and technological applications in different areas. Our goal is to investigate the generation of ultrashort laser pulses in the near infrared region between 900 and 1000 nm, which is of interest for current large-scale laser projects based on optical parametric chirped pulse amplification. For this, we will design and develop an innovative sub-20 fs tunable optical parametric oscillators (OPO) optimized at a chosen central wavelength and a uJ level double stage optical parametric amplification (OPA) within the new beamline project in Vulcan for betatron imaging. The OPO systems will be implemented at two existing laser systems: the Laboratory for Intense Lasers (L2I, IST), with the goal of generating a seed pulse for a new ultrashort amplifier; and the Vulcan laser system (CLF, RAL), with the goal of generating an off-harmonic femtosecond probe line to upgrade the system. Their requirements are similar ensuring that the same technology can be applied, with suitable modification to the spectral parameters.

Speaker: Mr Mario Galletti (Instituto Superior Tecnico, Universidade de Lisboa)

18:40 X-ray Sampling Calorimeter for Bunch Length Measurement¶

The challenge of reliable measurement and diagnostics of extremely short electron bunches is of crucial importance for commissioning and operation of the accelerators like a FELs and colliders. A method widely applied for bunch length diagnostics is Coherent Radiation Diagnostics (CRD). Radiation is emitted coherently if the wavelength is in the order of the bunch length, i.e. information about bunch length and shape is encoded in the emission spectrum which is exploited in CRD. For bunch lengths in the order of hundreds of femtoseconds, the Far-Infrared wavelength region is of interest. It is propose to extend the range of CRD up to attoseconds by using radiation in X-ray region, but for this our will need to register of high intensity X-ray pulses. The goal of this work is developed of technic and setup for bunch length measuring based on registration of high intensity X-ray pulses by sampling calorimeter. This study was partially supported by the Federal Targeted Program of the Russian Federation agreement no. 14.578.21.0198 (RFMEFI57816X0198) and by the Competitiveness enhancement program of Tomsk polytechnic university in part of providing simulation software.

Speakers: Dr Alexey Gogolev (Tomsk polytechnic university), Dr Roman Rezaev (Tomsk polytechnic university)

Wednesday, 26 September ¶

09:00 → 11:00 W1.1 Channeling in Plasma Physics by Laser and Applications¶

Convener: Prof. Lorenzo Torrisi (Dipartimento MIFT, Università di Messina, Italy)

09:00 Challenges of High Repetition Petawatt Lasers¶

The basic principles of laser acceleration using a short pulse Petawatt laser are well established, and now is probably the right time to consider them as an interesting alternative to conventional accelerators, with some restrictions on one side and some advantages in other side. There are now a few Petawatt lasers at one shot per second operative around the world (Berkeley, Dresden and Salamanca). There are also a few ones with higher repetition rate under construction. Those lasers with a convenient beam delivery and new-generations of multi-shot targets are a quite interesting alternative. One of the main point to discuss is that laser based experiments have to be designed from the very beginning as so. In many cases laser community is trying to mimic too much the conventional accelerators community and this is a waste of resources. High repetition rate laser accelerators have different characteristics and have to be used having this in mind. Of course, among those lasers is our VEGA Petawatt laser, 30 J / 30 fs at one shot per second. Our experience is going to be presented. Moreover VEGA is open to the international community through competitive access.

Speaker: Prof. Luis Roso (Director of the Spanish Center for Pulsed Lasers, CLPU. and Professor of Applied Physics at the University of Salamanca)

Slides 9.00_ch2018-ChP_roso.pdf

09:30 New Ultrashort OPCPA PetaWatt Class Beamline for Vulcan Laser Facility¶

The Vulcan Petawatt Laser Facility is operational from different years, delivering high quality support for the laser plasma community. To keep the facility at world leading level, continuous development is necessary. For that reason, to allow better understanding of the laser plasma interaction at petawatt level, a new laser beamline was proposed to allow betatron radiation probing of the plasma. The design specification for the new beamline are: • Pulse length: < 30fs • Energy: ~30J • Repetition rate: 1 shot every 5min. There are different laser technology that can provide laser pulses within the requested parameters. Using the expertise in the Central Laser Facility, we decided to use the Optical Chirped Pulse Amplification (OPCPA) for the new beamline. In this way, a short pulse length could be generated, supporting in principle large bandwidth. While this is not important for betatron radiation, it will open a new set of experiment for QED. The overall project is aiming to deliver first pulses of 7J in 30fs in the next three years. In the second phase, the addition of a 108mm disk amplifier and an amplification stage will increase the energy up to 30J, with a limited repetition rate of 1 shot every 20min. Finally, in the third phase a new design of gas cooled disk amplifier, under development, will increase the repetition rate to 1 shot every 5min. In this contribution, we present the new beamline project in the Vulcan laser system. The overall project is quickly discussed, followed by a more in depth presentation on the work on the Front End and the CPA design.

Speaker: Dr Marco Galimberti (Science and Technology Facilities Council)

Slides 9.30_ch2018_Galimberti.pdf

10:00 High Power Laser Irradiation of Low-Z Porous Media: Numerical Simulations and Experiments¶

The internal structure of porous materials determines the features of laser absorption and the characteristics of relaxation and transport processes in laser-produced plasma. Many experiments have been carried on in the last decades, producing a large dataset, which can be the base for improving theoretical models and numerical codes. The microscopic structure of these materials cannot be reproduced in detail in hydrodynamic codes for laser-plasma interactions and for long time the laser-produced plasma behavior has not been correctly reproduced in numerical simulations. For this reason, foam targets have been numerically modeled as constituted by equivalent homogeneous media with the same average density. However, this approach cannot reproduce the peculiar characteristics of plasma evolution and transport phenomena expected for these materials. After an introduction about the recent progress of the research on porous media, the numerical code MULTI-FM [1] will be presented. MULTI-FM is a modification of the original one-dimensional MULTI [2] code improving its simulation capabilities for porous low-Z targets. Recent experimental results performed at ABC laboratory will be discussed and compared with numerical calculations, along with the results of other experiments reported in the recent literature.

Speaker: Dr Mattia Cipriani (ENEA - CR Frascati)

Slides 10.00_ch2018_Cipriani.pdf

10:30 Monitoring of the Plasma Generated by a Gas-Puff Target Source Dedicated for SXR/EUV Microscopy¶

A 10-Hz repetition rate, Nd:YAG pulsed laser (λ=1064 nm, pulse energy of 700 mJ, pulse duration of 3 ns) was used to irradiate different double stream gas-puff targets (DSGPTs). The interaction gives rise to the formation of plasma and the emission of SXR/EUV radiation. The DSGPTs are produced by a 0.4 mm in diameter nozzle, which injects the working gas (N2, Ar or Xe) at different pressures, and by a concentric ring-shaped nozzle with diameter from 0.7 to 1.5 mm for the He injection, which is the outer gas. The SXR/EUV emission from the plasma was optimized at 90° with respect to the incident laser radiation and nozzle axis. Silicon carbide (SiC) and AXUV-HS1 Si detectors were employed to characterize the produced plasma. Some aspects, related to monitoring, stability, and characterization of the plasma source, important from a standpoint of modern compact SXR/EUV microscopy systems, such as the overall evaluation of the signal and pulse time duration, will be presented and discussed.

Speaker: Dr Alfio TORRISI (Nuclear Physics Institute, AS CR)

Slides 10.30_ch2018_Torrisi_A.pdf

10:45 KrF Laser Irradiation of Highly Efficient Photocathodes Based on NanoDiamond Layers¶

In this work we report the investigation of two different photocathodes (PCs) based on nanodiamonds (NDs) irradiated by a nanosecond excimer laser (KrF) operating at 248 nm (5eV). The ND layers of cathodes were deposited by means of pulsed spray technique. Specifically, the active ND layer of each PC consists of untreated or hydrogenated particles, 250 nm in size, sprayed on p-doped silicon substrate. The ND-based photocathodes were tested in a vacuum chamber at 10−5 Pa and compared to a conventional Cu one. They were irradiated at normal incidence, and the anode–cathode distance was set at 3 mm. The maximum applied accelerating voltage was 7 kV, while the laser energy ranged from 10-3 to 10-2 J/cm2, limited by the electrical breakdown of the photodiode gap and by the plasma formation. The quantum efficiency of the photocathodes was assessed in the saturation regime. We also calculated the target temperature and the contribution of multiphoton processes to the photoemission mechanism. The obtained results showed QE values for the ND-based photocathodes higher than that of a conventional Cu target. In particular, the hydrogenated ND-based PC exhibited the highest QE value due to the negative electron affinity of its surface terminated by hydrogen.

Speaker: Prof. Vincenzo Nassisi (Dip. di Matematica e Fisica, Università del Salento, Lecce, Italia)

Slides 12.35_ch2018_nassisi.pdf

11:00 → 11:20 Coffee break

11:20 → 13:05 W1.2 Channeling in Plasma Physics by Laser and Applications¶

Convener: Danilo Giulietti (PI)

11:20 Advanced Instrumentation for Laser-Driven Acceleration Experiments¶

In laser-driven ion-acceleration experiments the interaction of the ultra-intense laser beam (in the order of 1020 W/cm2) with the solid target produces an extremely intense emission of radiation with a broad spectrum. The occurrence of such an emission, sometimes named EMP-electromagnetic pulse-, traditionally prevents the implementation of active devices for ion beam diagnostics in the interaction chamber or even in the close proximity. The presentation reports on the progress in the advanced instrumentation developed for the L3IA experiment.

Speaker: Prof. Alberto Fazzi (Politecnico di Milano and INFN-MI)

Slides 11.20_ch2018_fazzi.pdf

11:50 Laser Impulse Transfer and Real-Time Target (Re-) Alignment Systems¶

Laser irradiation with various materials has plenty of technical and technological applications, from CD players and material processing (cutting drilling and so on) to medical applications. There are special cases when the laser beam needs to target a precisely determined zone or the target needs to be in a rather narrow laser focus zone, and laser driven particle acceleration it is just one of the examples when the beam alignment becomes a critical issue. If the target is not rigidly fixed or moves (oscillate or ‘shakes’ ), then the difficulty of the targeting and respectively focusing operation further increases. Based on impulse transfer measurements on thin metallic targets and respectively target (predictable) movement, the aim of this paper is to present an implementation of multidimensional laser targeting system for a moving target along with the laser triggering system based on the trajectory prediction. The current experimental setup involves 1 basic movement in polar coordinates (respectively 1 oscillation) while target position data acquisition is based on an alignment laser and a fast CCD camera for the movement detection in 3D coordinates. Computer modelling software is based on a template matching algorithm and a predictive algorithm for target motion based on Prony’s Method. The experimental setup and results are presented for 1D (polar coordinates) case and further extended for the a generic 3D case. The ‘targeting’ performances are shown with respect on the main spatial and temporal performances, while some applications in high-power laser interactions are also discussed.

Speaker: Dr Aurelian Marcu (NILPRP)

12:05 Fusion Reactions in Solid and Plasma Targets¶

In recent years there has been a renewed interest in nuclear fusion processes, induced in laser produced plasmas. The consequences of these studies, both experimental and theoretical, concern the production of nuclear energy for civil purposes, the development of mono-energetic high brillance neutron sources, up to the models of nucleosynthesis within the stars. In particular we want to understand if the p- 11 B fusion process is more favored when the proton is directed on a solid Boron sample or a Boron plasma. Similar questions arise for the D + D fusion process. To answer these questions it is necessary to consider at the roots the process of nuclear fusion (intimately linked to the tunnel effect) and the role played by the electronic screen of the nuclei when the target is in the solid or gaseous state, or the Debye length in the case the target is a plasma. In this last case the most favorable conditions for the nuclear fusion could be realized inside very dense and relatively cold plasmas, so called Fermi degenerate plasmas. Clearly in such a complex scenario the length of penetration of the colliding nuclei within the fusion target will also be considered.

Speaker: Dr Alessandro Curcio (CERN)

Slides 12.05_ch2018_curcio.pdf

12:20 Cherenkov-Transition Radiation in a Waveguide with a Semibounded Strongly Magnetized Plasma¶

The plasma filled waveguides was of great interest since it was shown that such devises could be useful for the purpose of particle acceleration and development of high power electromagnetic radiation sources. One of problems consists in analysis of the effect of the transverse boundary on the wave field. Here we consider the case of waveguide loaded with semi-infinite magnetized plasma using a strong magnetic field approximation when the gyration parameter is neglected. We analyze the electromagnetic field of the waveguide mode components analytically and numerically. We give the detailed description of so-called Cherenkov-transition radiation generated in the vacuum area.

Speaker: Dr Tatiana Alekhina (SPbSU, Saint-Petersburg, Russia)

Slides 12.20_ch2018_alekhina.pdf

12:35 Investigation of Stimulated Action of Distant Undamped (Self-Channeled) Temperature Waves on Nuclear Fusion in Remote Targets¶

In the paper the results of the investigation of the effect of undamped (self-channeled) thermal waves on low energy nuclear fusion in a remote TiD target are presented. These waves are formed on the reverse side of the metal (cavitation) target, which is affected by the jet of water in a state of cavitation, and are characterized by strictly defined frequencies (in air under normal conditions and different humidity, the minimum frequency of such a wave is equal to ω=75…85 MHz [1,2]. These waves can propagate in air for a long distance without absorption (in the laboratory - more than 2 meters and this distance was limited only by the size of Lab). It is shown for the first time that the action of such waves on a remote "nuclear" target (made of deuterated polycrystalline titanium) generates intensive flow of alpha particles, the axial direction of emission of which corresponds to the geometry and orientation of the "nuclear" target. The possible mechanism of low energy nuclear fusion optimization is associated with the formation of coherent correlated states of deuterons [3,4] in non-stationary potential nano-wells in a volume of loaded titanium under action of these waves. The features of this mechanism are also discussed in the report. 1. Vysotskii V.I., Kornilova A.A., Krit T.B., Vysotskyy M.V. Surface, 2017, v.11(4), 749-755. 2. Kornilova A.A., Vysotskii V.I. et al. Engineering Physics, 2018, №5, 13-22 (in Russian). 3. Vysotskii V.I., Vysotskyy M.V. European Phys. Journal A, 2013, 49, 99. 4. Vysotskii V.I., Vysotskyy M.V. Journal of Experimental and Theoretical Physics, 2017, 152(8), 234.

Speaker: Prof. Vladimir Vysotskii (Kiev National Shevchenko Univ, Kiev, Ukraine)

12:50 On a Zone Structure for Channeled Particles in Optical Lattices¶

Recent theoretical studies have shown the possibility of charged particles channeling at their interaction with inhomogeneous laser field, particularly with so-called optical lattices, similar to crystal channeling. Till present we have not yet been related to careful experimental investigations in this field, however, the results on electron diffraction by the light standing wave [1] have demonstrated the feasibility of such a process. As known due to the periodicity of the effective interaction potential [2] for charged particles in a crystal at channeling, the energy spectrum of channeled particles might reveal a zone structure at well defined conditions. One may expect similar feature at particles channeling in optical lattices but with one very strong difference, i.e., optical lattices are characterized by much wider channel sizes. It results in the use of a single potential approximation without taking into account the potential periodicity [3] and of a classical approximation for a channeled particle as well [4,5]. On the contrary to crystals where the bandwidths of quantum levels are mainly defined by inelastic scattering processes, in optical lattices for light particles the broadening of energy levels takes place because of the life time limit defined by spontaneous radiation. The same is valid for muons in much strong laser fields. In this report we are going to present our results on zone structure of energy levels for channeled particles in optical lattices, in general. [1] Kapitza P.L., Dirac P.A.M., "The reflection of electrons from standing light waves", Math. Proc. Cambridge, V. 29, 1933. [2] Donald S. Gemmell, "Channeling and related effects in the motion of charged particles through crystals", Reviews of Modern Physics, V. 46, 1974. [3] Dik A.V., Frolov E.N., Dabagov S.B., "On a quantum particle in laser channels", Journal of Instrumentation, V. 13, 2018. [4] Andreev A.V., Akhmanov S.A., "Interaction of relativistic particles with intense interference optical fields", Zh. Eksp. Teor. Fiz., V. 72, 1991. [5] Dabagov S.B., Dik A.V., Frolov E.N., "Channeling of electrons in a crossed laser field", Phys. Rev. ST, V. 18, 2015.

Speaker: Mr Alexey Dik (Lebedev Physical Institute of Russian Academy of Science)

Slides 12.50_ch2018_Dik.pdf

Thursday, 27 September ¶

09:00 → 11:00 S4.2 Charged Beams Shaping & Diagnostics¶

Convener: LAURA BANDIERA (FE)

09:00 The CRYSBEAM Project¶

The parasitic non-resonant beam extraction aided with bent crystals is an interesting solution to direct the LHC high energy particles to external targets. This would open new opportunities in the study of hadronic interactions in a kinematic range not easily accessible before. I will review the status of the ERC funded CRYSBEAM project. The aims of CRYSBEAM were to develop high quality crystals to manipulate the several TeV LHC particles, detectors to monitor an extracted beam based on the Cherenkov effect and an instrumented absorber made of low Z materials to study the hadronic shower evolution as in the Ultra High Energy cosmic ray interaction in the Earth’s atmosphere.

Speaker: Gianluca Cavoto (ROMA1)

09:30 Crystal-Assisted Beam Manipulation at CERN SPS¶

The UA9 experiment is installed in the CERN SPS since 2009 with the aim of investigating the coherent interaction of high energy particle beams with crystalline materials, and ultimately of demonstrating the feasibility of crystal-aided beam halo collimation in high energy particle colliders such as the LHC. Recently the scope of the UA9 experiment has been extended to new investigations implying even more challenging methods to manipulate beams by means of bent crystals. In view of the proposed Beam Dump Facility (BDF-SHiP) at the SPS, the reduction of the extraction-induced activation of the accelerator becomes of paramount importance. Among several options, the use of bent crystals in different configurations is being studied to minimize particle loss at the electrostatic septum. The first encouraging experimental results of a crystal-aided stochastic non-local slow extraction are shown here. In the framework of the “Physics Beyond Colliders” Study Group at CERN, experiments have been proposed that make use of two bent crystals in series. The first crystal should steer part of the beam halo towards an in-pipe target; whilst the second crystal, just after the target, should channel the produced short-lived baryons in order to make their spin precess, thus allowing the measurement of their polarization. In order to investigate the feasibility of this double-crystal scenario, the UA9 layout in the SPS has been modified and the number of detectors has been increased, with the aim of evaluating the efficiency of the double-channeling process and the relative background. A description of the modified apparatus is given and preliminary experimental results are presented.

Speaker: Dr Francesca Galluccio (INFN-NA)

Slides 9.30_ch2018_Galluccio.pdf

09:45 Future Transition Radiation Detectors: Theory and Experiment¶

X-ray transition radiation (XTR) is known to be the only precise instrument for identification of charged particles with a Lorentz factor more than 1000. With increasing of charged particle energies at modern and future colliders a separation of high energy collision products becomes a complicated task. A further development of the XTR detector techniques is required for many physics studies. In order to increase a particle identification capability of XTR detectors, all possible features of XTR should be exploited. For instance, along with the energy spectrum of XTR, the angular distribution of XTR can give additional important information about Lorentz factor of the particles. One of the examples for the application of this technique can be a forward physics experiment at LHC called Small Angle Spectrometer (SAS). The XTR detector will play a crucial role in this experiment making proton, kaon and pion separation in the 1 – 6 TeV particle energy range. In this work, recent experimental results of simultaneous measurements of the XTR photon energy and production angle are presented. They are compared with theoretical prediction (analytical expressions for both energy and angular distributions) and simulations (RADIATOR and GEANT4). Future plans of an improvement of the quality of the detector are discussed.

Speaker: Mr Aleksandr Savchenko (NRNU MEPhI, Russia, Moscow)

Slides 9.45_ch2018_Savchenko.pdf

10:00 High-Energy e−/e+ Spectrometer via Coherent Interaction in a Bent Crystal¶

The atomic order of a crystalline structure generates an electrostatic field capable of confining charged particle trajectories. Depending on the charge sign, points of equilibrium of the oscillatory motion under channeling lie between or on atomic planes for positive and negative particles, respectively. This forces positive particles to stably oscillate far from the planes, while negative ones repeatedly cross them, causing a tremendous discrepancy between the deflection efficiency of positive and negative particles under channeling. We suggest the use of charged-particles interactions in oriented bent crystals as a novel non-cryogenic passive charge spectrometer for the measurement of the positron to electron ratio to aid the search for dark matter in the Universe in satellite-borne experiment. The limited angular acceptance makes this technique particularly suited for directional local sources of energetic charged particles.

Speaker: Enrico Bagli (FE)

Slides 10.00_ch2018_bagli.pdf

10:15 Bent Crystals for Large Angle Deflection of TeV Particle Beams¶

Bent crystals can be efficiently employed to steer high energy particles via channeling. To achieve optimal performances several strict conditions must be satisfied, such as a homogeneous curvature and a high lattice quality. While for small bending angles up to few hundreds of microradians several solutions have already been deployed, for larger deflection angles in the range of 1-15 milliradians novel approaches must be devised. In this talk configurations exploiting the primary curvature will be reported, as well as new manufacturing processes for the holders and the crystal sample production. Also prototype samples and the curvature achieved will be presented

Speaker: Marco Romagnoni (F)

Slides 10.15_ch2018_Romagnoni.pdf

10:30 New Experimental Method to Measure Inelastic Nuclear Interactions of High Energy Positive Charged Particles with Bent Crystals¶

A new experimental method able to study inelastic nuclear interactions of high energy positive charged particles with bent crystals has been developed. This new approach permits precise measurements of this interaction rate for different crystal orientations, providing the interaction reduction factor both in planar and axial channeling, with respect to the amorphous case. Moreover, using a customized FLUKA user routine, used to simulate the experimental apparatus, it is also possible to estimate the absolute interaction probability. One of the most interesting result of this method is the measurements of the planar channeling reduction factor for bent silicon crystals developed for beam collimation in the Large Hadron Collider at CERN. These studies are helpful for better understanding of bent crystal physics, and can be applied for other kinds of beam manipulation, such as extraction, splitting, focusing, and defocusing.

Speaker: Dr Marco Garattini (CERN, Imperial College London)

Slides 10.30_ch2018_Garattini.pdf

10:45 Crystal Based Fusion Processes¶

Chemical energy sources (oil and gas) will run out in the next 30-50 years. In addition to the depletion of these sources, there is a so-called greenhouse effect, which imposes severe restrictions on the use of chemical fuels. Nuclear reactors use uranium and thorium reserves of fissile materials that will last for no more than 100–200 years. In addition, the problem to hide the radioactive nuclear waste for a period of several thousand years has no any reliable solution. During the last 25–30 years, the so-called cold fusion process in conductive crystals has being developed. This process is seen most in the case of implantation of deuterium atoms in heavy conductive crystals (palladium, platinum). The presence of conduction electrons in metals does not allow impurity atoms of deuterium in ground state to be localized in the deepest niches of the conductive crystal cell. However, this problem has overcome during the implantation of the deuterium atoms in conducting crystals with the excitation of these atoms by about ~10 eV, which is essentially a chemical process. Through this, the cold fusion of deuterium atoms in the conductive crystal cell in the p-states becomes possible. If two such excited deuterium atoms are placed in the same cell of a conducting crystal in a close proximity to each other in the “crisscross” configuration, the quantum fluctuations of the deuterium nuclei with a frequency of about 1017 per second provide a fast fusion process producing a 4He* nucleus. The residual Coulomb repulsion between deuterons that already in the potential well of a strong interaction prevents the rapid γ−decay of the excited 4He*, which is in the state of orbital angular momentum l = 0. The release of the binding energy of 4He* of about 24 MeV in this case is carried out through the energy exchange of the excited nucleus with the crystalline lattice by the virtual photons with their spin being directed along the time axis (Richard Feynman’s condition).

Speaker: edward tsyganov (cold fusion power int)

Slides 10.45_Ch2018_tsyganov.pdf

11:00 → 11:20 Coffee break

11:20 → 13:05 S3.1 X-Rays/Neutrons/Atoms Channeling¶

Convener: Dr Luigi Allocca (LNF)

11:20 Channeling X-Rays: Applied Polycapillary Optics¶

Polycapillary optics (polyCO) is a commonly utilized optical device for a wide variety of applications that operates by collecting X-rays and efficiently propagating them down to the channels by total external reflection in order to form both focused and parallel beams. The development of a compact source-detector system with characteristics to match the requirements of polyCO allows substantial reduction in a size, weight, and power of complete units. The latter becomes crucial for development of portable, remote and in-line sensors for applications in industry, material science, chemical/environmental and bio-medical applications. In this short overview presentation we are going to discuss X-ray optics, in general, and polyCO, in details, paying attention to important beam parameters such as its flux, focal spot-size and divergence. The work is dedicated to the state of the art for PolyCO-based researches and applications at different centres within international and national collaborations. Providing a comparative analysis for various polyCO-based techniques, future possible developments in PolyCO-like technologies will be presented.

Speaker: Dariush Hampai (LNF)

11:50 Understanding the X-ray Emission Spectrum after Excitation with a Source of X-rays: from Theory to Experiment¶

The modified Boltzmann-Chandrasekhar equation of transport for photons is the proper framework for describing the photon radiation field with a complete description of the polarization state. The characterization of the radiation field requires a detailed description of the interactions of photons with mater and comprises also the contribution of the secondary electrons to the photon field through mechanisms like inner impact ionization and bremsstrahlung without need of solving the coupled transport electrons-photons. The theoretical characterization of the x-ray spectrum of emission after excitation with a source of x-rays can be straightforwardly obtained from the albedo solution to this equation. However, this solution is still far from the experimental measurements modified by the detector and the measurement devices, comprised the pulse electronics. In this work we put together the theoretical framework, the interactions needed to get a detailed solution and the contributions to the detector and pulse handling modification in order to obtain a theoretical x-ray spectrum fitting well the real measurement.

Speaker: Prof. Jorge Fernandez (Alma Mater Studiorum University of Bologna)

Slides 11.50_Ch2018_fernandez.pdf

12:05 Performance of K-edge Subtraction Tomography as Application of the X-ray Source Based on Parametric X-ray Radiation¶

K-edge subtraction (KES) imaging is one of the advanced imaging techniques based on drastic change of X-ray absorption power at K-shell absorption edge of an attention element. The method can provide the information on the spatial distribution of the element. Since the monochromaticity and the energy tunability are required for X-rays in the imaging, it is substantially difficult to carry out utilizing a conventional X-ray source based on X-ray tubes. Almost researches on KES imaging, therefore, have been performed at major synchrotoron radiation (SR) facilities. An X-ray source based on parametric X-ray radiation (PXR) is also one of the advanced X-ray source which allow KES imaging. Actually, we achieved KES tomographic imaging for strontium element using the PXR source at the Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University. In addition to conventional temporal-KES imaging in which two data sets are separately acquired for image subtraction, simultaneous-KES imaging was possible using the PXR source. Since the PXR beam has a dispersive property in the spatial distribution, dual-energy crossing beams are formed when only the half of the PXR beam is reflected by an analyzer crystal. This configuration makes it possible to simultaneously acquire two tomographic images across the K-edge energy of interest. Computed tomography (CT) based on simultaneous-KES is a very unique methodology in the world including SR facilities and was demonstrated in our previous work using the LEBRA PXR source. As the next step, the quantitative performance of simultaneous-KES imaging have been investigated, especially with respect to the sensitivity to the concentration of the element to be measured. In the case of Sr K-shell edge, simultaneous-KES CT using the LEBRA-PXR source can detect the existence of Sr element of which concentration is higher than 0.5 weight percent at least.

Speaker: Prof. Yasushi Hayakawa (Laboratory for Electron Beam Research and Application (LEBRA), Nihon University)

Slides 12.05_ch2018_hayakawa.pdf

12:20 X-ray Tomography and 3D CFD Simulation of Fuel Mass Distribution in a GDI Spray¶

The spray formation plays a fundamental role for the optimization of combustion efficiency and exhaust emissions of Gasoline Direct Injection (GDI) engines, allowing the control of the combustion process through the local equivalence ratio of air-fuel mixing. Non-intrusive diagnostics and three-dimensional (3D) Computational Fluid Dynamics (CFD) models provide a deep insight of fuel-air interaction. However, conventional optical techniques allow getting experimental data only in the less dense regions of the spray, while they miss to provide information about fuel distribution in the near-nozzle region, where liquid break-up effectively occurs. X-ray tomography can overcome these limitations making available quantitative measurements of fuel mass concentration in the high dense spray regions. This paper reports the results of a numerical and experimental investigation of the inner structure of a high-pressure gasoline spray injected by a 6-hole GDI nozzle. A desktop facility based on polycapillary optics system, providing a high flux beam with low divergence, has been used to perform a spray micro-computed tomography (μCT) in the region immediately downstream of the nozzle. The operative conditions considered are reproduced through the development of a 3D CFD model in the AVL FireTM environment, where the spray development in the near-nozzle region is investigated through a Reynolds Averaged Navier-Stokes (RANS) approach. The spray evolution is described through a Lagrangian Discrete Droplet Method (DDM), while the continuous gaseous phase is described by the standard Eulerian conservation equations. This paper aims in comparing the results of x-ray based techniques with 3D CFD numerical model. The local mass distribution of a single jet at different distances from the nozzle was estimated through x-ray tomography and radiography. Experimental data were compared with numerical ones, enlightening the distribution of the liquid fuel concentration in a plane orthogonal to the axis of the spray injector. The comparison demonstrates the accuracy of x-ray tomography desktop facility as a reliable diagnostic tool to get quantitative information about the local mass distribution and fuel flow.

Speaker: Mr Luca Marchitto (Istituto Motori- Im)

Slides 12.20_Ch2018_Marchitto.pdf

12:35 Characterization of a High Resolution Von Hamos Spectrometer with HAPG Crystals for Extended Sources; a New Opportunity for High Precision Nuclear Physics Measurements¶

Bragg spectroscopy is one of the best established experimental methods for high energy resolution X-ray measurements; however, this technique is limited to the measurement of photons produced from well collimated or point-like sources (tens of microns) and becomes quite inefficient for photons coming from extended and diffused sources. The VOXES project’s goal is to realise a prototype of a high resolution and high precision X-ray spectrometer, using Highly Annealed Pyrolitic Graphite (HAPG) crystals in the Von Hamos configuration, working also with extended isotropic sources. The aim is to deliver a cost effective system having an energy resolution at the level of eV for X-ray energies from about 2 keV up to tens of keV, able to perform sub-eV precision measurements with non point-like sources. The proposed spectrometer has possible applications in several fields, going from fundamental physics to quantum mechanics tests, synchrotron radiation and X-FEL applications, astronomy, medicine and industry. In particular, these technique is fundamental for a series of nuclear physics measurements like, for example, the energy of the exotic atoms radiative transitions which would allow to extract fundamental parameters in the low energy QCD in the strangeness sector. Here, the working principle and the characterization of the spectrometer will be presented, together with the preliminary results on the pionic carbon 4f → 3d and 4d → 3p transition lines measurment performed at the Paul Scherrer Institute (PSI).

Speaker: Alessandro Scordo (LNF)

Slides 12.35_Ch2018_Scordo.pdf

12:50 Interaction of Channeled X rays, Coherent Excitation of Fluorescence and Interference Phenomena of Transmitted Radiation at the Exit of Microchannel Plates¶

We present here investigation on x-ray fluorescence excited inside hollow microcapillaries which propagates inside them and this phenomenon corresponds to the process of channeling of x-ray fluorescent radiation through a waveguide. The propagation of radiation through microcapillaries is a complex wave process depending by the energy of the radiation and the characteristics of the optical system. We have found experimentally and simulated theoretically that the coherently excited Si L-fluorescence mainly propagates in the direction close to the axis of the microchannels.

Speaker: Dr Mikhail Mazuritskiy (Southern Federal University)

Slides 12.50_ch2018_mazuritsky.pdf

13:05 → 14:30 Lunch

14:30 → 16:30 S4.3 Charged Beams Shaping & Diagnostics¶

Convener: Dr Wolfgang Wagner (HZDR Dresden)

14:30 Strong Reduction of the Effective Radiation Length in an Axially Oriented Scintillator Crystal¶

We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic eld. The data collected at the external lines of CERN SPS were critically compared to Monte Carlo simulations based on the Baier Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of ve in case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters/detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments as well as in satellite-borne gamma-telescopes. Reference L. Bandiera et al., arXiv:1803.10005, accepted to be published on Phys. Rev. Lett.

Speaker: LAURA BANDIERA (FE)

Slides 14.30_Ch2018_bandiera.pdf

15:00 Crystalline Target for Radioisotope Production via Anti-Channeling¶

The development of more efficient production techniques for radioisotopes is a field of special interest, especially for modern nuclear medicine, in order to overcome some possible limitations in the supply chain of Mo-99 with nuclear reactors [1]. In particular, the production of radioisotopes in cyclotrons is spreading worldwide, despite its higher cost with respect to the production in nuclear reactors. Oriented ordered structure can modify particle trajectories inside the medium, leading to a sensible variation of the interaction rate with atomic nuclei. Under specific orientations of the target with respect to the incident beam, a higher probability of inelastic interaction with nuclei can be obtained, compared to the standard rate into amorphous medium. This effect is called anti-channeling and leads to an increase of the radioisotope production yield. The INFN-TROPIC project aims to the characterization in laboratory- and production- environment of a crystalline target for the production of radioisotopes of interest for nuclear medicine. In particular, a dedicated study of the anti-channeling phaenomenon through Monte Carlo simulations is required. Alongside, the research of crystals with a chemical and isotopical composition suitable for the production of an isotope of interest, with at the same time a crystalline quality sufficiently high to observe the anti-channeling effect is mandatory. First crystals to be studied are Yttrium and Rhodium. They are supplied in crystalline form by some specialized manufacturers, and they have the advantage of naturally occurring in only one isotope. Y and Rh are used respectively for the production of Zirconium-89, useful as a Positron-Emission Tomography (PET) tracer, and Palladium-103, used for prostate cancer treatment. Both Y and Rh have a rather high cross section (hundreds of millibarns) for the reaction with protons at the typical energy obtained with commercial cyclotrons (10 to 15 MeV). The crystalline structure of the first samples was characterized with a 140 keV photon beam at the European Synchrotron Radiation Facility (ESRF) of Grenoble (France). Preliminary simulations with the Monte Carlo N-Particle (MCNP6) code confirm the possibility of measuring online the radionuclide production rate via spectroscopy of the prompt γ-rays upon de-excitation of produced nuclei. [1] http://www.oecd-nea.org/ndd/reports/2010/nea6967-radioisotpes-full-report.pdf

Speaker: Dr Giacomo Germogli (INFN Ferrara)

Slides 15.00_ch2018_Germogli.pdf

15:15 Simulations of Beam Channeling in a Spherically Bent Crystal¶

In the report the next model is considered. The spherically bent crystal is the crystalline plate that has surfaces bent spherically, i.e surfaces represented by a fragment of sphere. Beam of charged particles enters (and then exits) the crystal through spherically bent surface. The planar channeling in the crystal was simulated for the case when planes providing the channeling are orthogonal to enter (and exit) surfaces. The re-distribution of beam flux behind the crystal was modeled. The possibility of the scheme advantage for beam focusing is investigated. The same task for the axial channeling was considered.

Speaker: Dr Anton Babaev (Tomsk Polytechnic University)

Slides 15.15_ch2018_Babaev.pdf

15:30 Low EMittance Muon Accelerator¶

A study of a new scheme to produce very low emittance muon beams using a positron beam of about 45 GeV interacting on electrons on target is presented. One of the innovative topics to be investigated is the behaviour of the positron beam stored in a low emittance ring with a thin target, that is directly inserted in the ring chamber to produce muons. Muons can be immediately collected at the exit of the target and transported to two μ+ and μ− accumulator rings and then accelerated and injected in muon collider rings. We focus in this paper on the simulation of the e+ beam interacting with the target, the effect of the target on the 6-D phase space and the optimization of the e+ ring design to maximize the energy acceptance. We will investigate the performances of this scheme, ring plus target system, comparing different multi-turn simulations. A preliminary review of the full scheme parameters is discussed in view of the results obtained on the ring plus target system.

Speaker: Mario Antonelli (LNF)

Slides 15.30_ch2018_antonelli.pdf

15:45 Measuring the Magnetic Dipole Moments of Short Living Particles Using Bent Crystals¶

We discuss a possibility of measuring the magnetic dipole moments (MDM) of short living particles by studying their spin precession induced by the strong effective magnetic field inside the channels of a bent crystal. This method was proposed by Baryshevsky in 1979 and its first and only experimental realisation was carried out in Fermilab at the 800GeV proton beam for measuring the MDM of the strange Sigma baryon. In the current study we consider various experimental setups, and find the optimal setup schemes and properties for measuring the MDM of short living particles, and present a detailed sensitivity study showing the feasibility of such experiments at the LHC in the coming years.

Speaker: Mr Oleksiy FOMIN (LAL, CNRS et Université Paris-Sud, Orsay, France)

Slides 15.45_ch2018_Fomin.pdf

16:00 Formation and Application of Coherent Correlated States of Charged Particles at Action of Weak Electromagnetic Field and During Orientation Motion of Particles in Periodic Structures¶

In the report the universal method of short-term and very significant suppression of the tunneling effect and very essential optimization of nuclear interaction of low-energy particles by the use of coherent correlated states [1-10] formed by weak controlled external action on these particles is discussed. The main factor of such process is connected with the self-similar synchronization of weak fluctuations in the quantum superposition state of a particle and the generation of giant synchronized fluctuations of momentum and kinetic energy, sufficient for the realization of effective nuclear processes. The action of this mechanism can increase the transparency of the potential barrier for low energy particles by 10^100…10^1000 and more times. The most important characteristics of such states is the possibility of the existence of a giant fluctuation of the kinetic energy of the particle for a long time, sufficient for the reaction to proceed. This mechanism explains practically all detected features of successful nuclear experiments conducted in numerous laboratories at low energy: a) anomalously high probability of these reactions at low energy of interacting particles; b) very significant suppression (as compared to similar reactions at high energy) of the accompanying gamma radiation; c) complete ban on "radioactive" channels of nuclear reactions and total absence of radioactive daughter isotopes, which may be formed in analogous reactions occurring without the use of coherent correlated states. The possibility of formation an effective coherent correlated states under the influence of a pulsed [1-5,8-11,12] or periodic [4-9,11,12] electromagnetic fields on particles (including action of damping and fluctuations [6]) is also considered in this work. The efficiency of this process during the motion of low-energy particles through periodic structures (including the motion of particles in the crystal lattice field in the channeling regime [11,12]) is considered in details. It is important to note that the method of coherent correlated states allows to explain, justify and numerically consider all known low energy nuclear reaction paradoxes without applying new radical hypotheses, basing only on the powerful foundations of modern quantum theory and nuclear physics. References 1. V.I.Vysotskii, S.V.Adamenko. Technical Physics, 2010, 55, 613. 2. V.I.Vysotskii, M.V. Vysotskyy, S.V. Adamenko. Journal of Experimental and Theoretical Physics, 2012, 114, 243. 3. V.I.Vysotskii, S.V.Adamenko, M.V.Vysotskyy. Journal of Experimental and Theoretical Physics, 2012, 115(4), 551. 4. V.I.Vysotskii, M.V. Vysotskyy. European Phys. Journal A, 2013, 49, 99.. 5. V.I.Vysotskii, S.V.Adamenko, M.V.Vysotskyy. Annals of Nuclear energy, 2013, 62, 618. 6. V.I.Vysotskii, M.V. Vysotskyy. Journal of Experimental and Theoretical Physics, 2014, 118(4), 534. 7. V.I.Vysotskii, M.V. Vysotskyy. Journal of Experimental and Theoretical Physics, 2015, 120(2), 246. 8. V.I.Vysotskii, M.V. Vysotskyy. Journal of Experimental and Theoretical Physics, 2015, 121(4), 559. 9. V.I.Vysotskii, M.V. Vysotskyy. Current Science, 2015, 108(4), 30. 10. V.I.Vysotskii, M.V. Vysotskyy. Journal of Experimental and Theoretical Physics, 2017, 152(8), 234. 11. V.I.Vysotskii, S.V.Adamenko, M.V.Vysotskyy. Journal of surface investigation, 2012, 6(2), 369. 12. V.I.Vysotskii, M.V. Vysotskyy, S. Bartalucci. 2018, 154 (2).

Speaker: Prof. Vladimir Vysotskii (Kiev National Shevchenko Univ, Kiev, Ukraine)

16:15 Correlated States and Nuclear Reactions: an Experimental Test with Low Energy Beams¶

An experimental programme is described in this paper, aiming at detecting the formation of correlated coherent states (CCS) in thin surface layers of crystals, when bombarded by a very low energy proton/deuteron beam. CCS are a generalization of “non-classical” states of light, such as the coherent and squeezed states, whose existence has been demonstrated long ago, giving rise to the remarkable development of Quantum Optics. In other fields, ranging from Condensed Matter physics to Cosmology, such states have been intensively studied, but a clear signature of their existence is still lacking. This may be a clue to various unexplained phenomena, including the strong enhancement of nuclear fusion reaction rates in metal environments, which have been reported on by several experiments, and cannot be accounted for by electron screening only.

Speaker: Sergio Bartalucci (LNF)

16:30 → 16:50 Coffee break

16:50 → 18:35 S5.2 Novel Sources: FEL/Laser/Plasma¶

Convener: Andrea Ghigo (LNF)

16:50 Advanced Accelerator Developments at EuPRAXIA@SPARC_LAB¶

On the wake of the results obtained so far at the SPARC_LAB test-facility at LNF, we are currently investigating the possibility to design and build a new multi-disciplinary user-facility, equipped with a soft X-ray Free Electron Laser (FEL) driven by a ~1 GeV high brightness linac based on plasma accelerator modules in the framework of the H2020 Design Study EuPRAXIA. EuPRAXIA@SPARC_LAB is conceived as an innovative and evolutionary tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. It could be progressively extended to be a high brightness “particle beams factory” able to produce electrons, photons (from THz to γ-rays), neutrons, protons and positrons, that will be available for a wide national and international scientific community interested to take profit of advanced particle and radiation sources. This fundamental goals will be integrated in the LNF facility by using a high gradient X-band RF linac and the high power laser FLAME to drive Plasma Oscillations in the accelerator module. This activity is performed in synergy with the EuPRAXIA and CompactLight design studies. In this talk we report about the recent progresses in the on going design study and about opportunities and perspectives for the high brightness beam physics scientific community.

Speaker: Massimo Ferrario (LNF)

Slides 16.50_ch2018_ferrario.pdf

17:20 Conception of Piezoelectric Accelerator¶

Conception of piezoelectric accelerator O. Ivashchuka, A. Shchagina,c, A. Kubankina,b, V. Miroshnikc, I. Nikulina, A. Oleinika,d, V. Volkovc a Laboratory of Radiation Physics, Belgorod National Research University, Belgorod, Russia b Lebedev Physical Institute, Moscow, Russia c J. Kharkov Institute of Physics and Technology, Kharkov, Ukraine d John Adams Institute at Royal Holloway, University of London, Egham, UK Here we propose the conception of small-size piezoelectric accelerator of charged particles that operates due to piezoelectric effect at varying mechanical force applied to piezoelectrics in vacuum. The accelerating voltage and the energy accelerated particles are estimated. In the proof-of-principle experiment we demonstrate the effect of the emission of X-ray radiation at the mechanical compression of piezoelectric ceramics in vacuum. The compression leads to the appearance of charges and potentials on the surfaces of the piezoelectrics and also to the arising of the electric field in vacuum. Electrons are accelerated in the electric field, strike the matter and produce the X-ray radiation. In the experiment, we have observed emission of the characteristic and bremsstrahlung X-ray radiation of energy up to 60 keV due to the compression of piezoelectric ceramics in vacuum. This means that electrons are accelerated in the piezoelectric accelerator up to the energy at least of 60 keV. The agreement of calculated and experimental data confirms the conception. Advantages of the piezoelectric accelerator and possibilities of its development and applications are discussed. Acknowledgments The work of co-authors from BNRU was supported by the grant from the Russian Science Foundation (project №16-19-10535).

Speaker: Mr Oleg Ivashchuk (Belgorod National State University)

Slides 17.20_ch2018_ivashchuk.pdf

17:35 Time-Resolved Measurements of Fast Electrons and Protons Emitted in Ultra-Intense Laser-Solid Matter Interactions at SPARC_LAB¶

The interaction between solid state matter and very intense lasers in the relativistic regime (IL>1018 W/cm2) has been widely investigated in the last two decades, mainly aiming to probe the feasibility of completely new, extremely compact proton accelerators thanks to the high electric fields generated (>TV/m). Nevertheless, the physical mechanism is still not completely clear, also due to the fast temporal evolution of this phenomenon, in the picosecond time scale. Therefore, time-resolved diagnostics tools are mandatory to probe this kind of interaction. At SPARC_LAB, the high power laser FLAME (25fs, 4J, 10Hz) is currently employed in pump-and-probe experiments, making it interact with solid state target. The main purpose concerns the temporal characterization of the charged particles emitted during the interaction. For this reason two main diagnostics have been set-up in our experimental chamber: an Electro Optic Sampling (EOS) line to measure, with sub-picosecond resolution, the temporal distribution of fast electrons leaving the target, and a time of flight (TOF) detector to measure the longitudinal profile of the emitted protons/ions. In this work, last results obtained with these two online temporal diagnostics will be presented.

Speaker: Fabrizio Giuseppe Bisesto (LNF)

Slides 17.35_ch2018_bisesto.pdf

17:50 Pyroelectric undulator¶

Pyroelectric Undulator A.V. Shchagin Belgorod National Research University, Belgorod, 308015, Russia Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine The electric undulator for production of radiation was first proposed in [1]. However, magnetic undulators were developed in further researches [2]. More recently, pyroelectric source of strong electric field was developed. The pyroelectric deflectors of non-relativistic [3] and relativistic [4] electron beams were studied experimentally. In the present paper, the electric undulator based on pyroelectric elements is proposed. The pyroelectric undulator operates in vacuum without any outer high voltage power supply due to heating or cooling of pyroelectric elements. The main properties of the pyroelectric undulator are considered in linear approximation. Acknowledgments The research was supported by a program of the ministry of education and science of The Russian Federation for higher education establishments, project №14.578.21.0192 (RFMEFI57816X0192). References 1. V.L. Ginzburg. On The Emission Of Microwaves And Their Absorption In The Air. The Preceding of Academy of Sciences of USSR 11.2 (1947) 165-182. 2. D.F. Alferov, Yu.A. Bashmakov, P.A. Cherenkov. Physics-Uspekhi, 32 (1989) 200-227. 3. A.N. Oleinik, A.S. Kubankin, R.M. Nazhmudinov, K.A. Vokhmyanina, A.V. Shchagin, P.V. Karataev. Pyroelectric deflector of charged particle beam. JINST 11 (2016) P08007. 4. O. Ivashchuk, I. Kishin, A. Kubankin, A. Oleinik, A. Shchagin, V.I. Alekseev, A.N. Eliseyev. Pyroelectric deflector of 7 MeV electron beam, the paper in present conference.

Speaker: Dr Alexander Shchagin (Kharkov Institute of Physics and Tecknology)

Slides 17.50_ch2018_shchagin.pdf

18:05 Experiments on Polarization Control of Thomson Scattering X/γ-ray Source¶

Thomson scattering of intense laser pulses from relativistic electrons can generate high-brightness and tunable-polarization X/γ-ray pulses. In this paper, we demonstrate an experiment about the polarization control of the Thomson scattering source. The polarization of X/γ-ray relates to the incident polarized laser beams, which is controlled by rotating a wave plate. In this experiment, the polarization of X-ray is determined by recording the spatial distribution of scattered photons, produced by antarget radiated by the X-ray pulse. According to modulation curves analyzed from experiment results, the conclusion is that the polarization of Thomson scattering source is tunable and controllable. This work was supported by the National Natural Science Foundation of China (NSFC Grants No. 11475097, 11375097 and 11435015).

Speaker: Dr Zhang Hongze (Tsinghua Center)

Slides 18.05_ch2018_Hongze_Zhang.pdf

18:20 Silicon Undulator Prototype: Manufacturing and X-ray Characterization¶

High-intensity and monochromatic X-ray sources are important tools for research in fundamental to applied science. Nowadays, intense and monochromatic soft X-ray beams are produced by means of Free-Electron Lasers (FELs). With currently available magnetic undulators, the minimum achievable oscillation period λu is of the order of the centimetres, thus limiting the generation of X-ray to a few tens/hundreds of keV at the highest synchrotron electron energies. In order to produce photon beams at higher energies, undulators with shorter λu are needed. A promising solution is the usage of a Crystalline Undulator (CU), i.e. a periodically bent crystal to drive the particles inside manipulated channels via channeling. Indeed, in a CU the charged particles (e.g. positrons) are forced to an oscillatory motion, in a similar way to that of magnetic undulators. By exploiting currently available techniques of crystal deformation, crystals with an undulated geometry with short period can be fabricated. Here, we show the manufacture and the characterization of three CU samples, obtained with the grooving method, which is a method to achieve controlled crystal deformation by manufacturing a controlled series of grooves on the sample surfaces by means of a diamond blade. Indeed, it was shown that a series of grooves may cause a permanent and reproducible deformation of the whole sample. In particular, an alternate and periodic pattern of 150 μm-wide parallel grooves was manufactured on the largest surfaces of the crystalline samples. The three CUs were tested at the line ID11 at ESRF (Grenoble, France) via a hard X-ray beam, showing a homogeneous and undulated deformation. The obtained λu were 334 μm, 120 μm, and 80 μm, depending on the geometry of the grooves. The substrates were (110) Si crystals.

Speaker: Riccardo Camattari (FE)

Slides 18.20_ch2018_camattari.pdf

18:40 → 19:40 PS3 - Poster session¶

Convener: Mr Luca Marchitto (Istituto Motori- Im)

18:40 A Study on Implementation of Multistripe Crystals to Protect the Septum-Magnets and to Generate the Gamma Radiation on the U-70 Accelerator¶

Recently started studies on the application of volume reflection of particles in crystals for the steering beams (for extraction and collimation of a circulating beam in accelerators). Volume reflection is more efficient than channeling, but requires amplification of the deflection angle by applying multicrystals. The report discusses two new applications of multicrystals made like multistripe structures: 1. The property of effective deflection of particle beam was used to protect the septum-magnets of the U-70 in the process of extraction of the proton beam with energy of 50 GeV. 2. The possibility of generation of gamma radiation was studied in the secondary electron beam with energy of 7 GeV. In both cases, promising preliminary data were obtained. The work is supported by Russian Science Foundation (grant 17-12-01532).

Speaker: Dr Vladimir Maisheev (IHEP, Protvino, Russia)

18:40 Advanced Experimental Setups for Investigation of Coherent Interactions of High-Energy Particle Beams with Crystals¶

The last decade has seen a growing interest in the study of the passage of high energy charged particles in oriented or bent crystals. An increasing number of experiments on high energy beam lines are performed to investigate all the involved physical processes. An experimental apparatus which includes different type of detectors run by a modular architecture data acquisition software is presented. It copes with all the requirements of a modern crystal/particle interaction experiment: high data acquisition rate, single particle tracking, emitted photon tagging and energy measurements, online monitoring and analysis tools and a full integration with motorized precision goniometers. The flexibility of the system makes it suitable for a wide spectrum of experiments. In particular, the AXIAL and KLEVER 2017 and 2018 setups at the CERN North Area will be described. AXIAL studies axial and quasi-axial phenomena in crystals for beam steering and generation of intense electromagnetic radiation, while KLEVER focuses on pair production and radiation enhancement in straight crystals. Despite being different experiments with a large degree of complexity, they share the above described experimental apparatus which should also grant a prompt versatility.

Speaker: Valerio Mascagna (MIB)

18:40 Application of Split-Ring Resonator Based Metamaterials in Accelerators¶

Development of non-invasive instrumentation for modern and future accelerator facilities including linear and circular colliders and X-ray free electron lasers has become a separate area of research in accelerator physics during the past two decades. The reason is that the usage of any invasive devices is excluded in high-energy particle accelerators because of safety reasons. Since the beginning of the race several techniques have been developed: beam position sensors, laser based beam diagnostics, diffraction radiation, residual gas luminescence, etc. Most of these techniques are based on the fact that an ultrarelativistic charged particle non-invasively interacts with surroundings via its electric field extended in transvers direction. A search for new methods and geometries is on because there are still some beam parameters which can not be monitored non-invasively. Moreover, some of available techniques have limitations on resolution, accuracy and flexibility. Metamaterials offer an exciting new avenue for particle accelerator applications. For example one can design material with a negative refractive index. We design, manufacture and test of such a metamaterial - Pendery’s split ring resonator with the wire array. The application under consideration is the use of a metamaterial target as non-invasive radiation generator via coherent Backward Cherenkov Diffraction Radiation process. In particular this material is intended to isolate a narrow band within a wide spectrum and send it in the direction available in an experimental facility. The design consists of metallic split ring resonators and bars, separated by a silicon wafer. For our frequency range of around 10 GHz the best manufacturing technique is to deposit thin metal films on Si wafers through a thin metallic mask and to assemble a stack of such wafers. The assembly is positioned with respect to the beam at the angle determined by the requirement of not having total internal reflection due to the Snell’s law. The material is compared to the simulation results using a VNA and horn antenna setup in open air. Finally, the Cherenkov radiation spectrum generated by the interaction of the target and a relativistic electron beam will be compared to a Teflon target of the same geometrical dimensions. In this report we shall present the radiator design, test results and future plans.

Speaker: Dr Pavel Karataev (Royal Holloway, Unviersity of London)

18:40 Characteristic X-Ray Wire-Scanner for Fast Charged and Neutral Particle Beams Diagnostics¶

Diagnostics of transverse phase space of charged particle beams is an important task for modern scientific research. Solid wire-scanners are still very popular due to their simplicity, robustness and sufficient resolution. In high energy linear accelerators bremsstrahlung photons are highly collimated, therefore a detector have to be placed very far downstream that implies difficulties with alignment and constructional constraints. We propose the method for measuring the transverse phase-space characteristics of particle beams which can ionize a medium. The method is based on the measurement of the Characteristic X-ray spectra generated during the monitored beam interaction with a wire-scanner. The electron beam diagnostics system of the experimental station developed to study mechanisms for electromagnetic radiation generation presented in [1] was modernized. The main part of the experimental station is a DC electron gun, which produces an electron beam with energy up to 100 keV. Five wires are located in different places along the beam axis. After the upgrade, wire scanners of different materials (Ti, W, Mo, Cu, Pt) are used. The different materials of the wires were chosen to generate Characteristic X-ray lines (CXR) at different energies. The X-rays are measured while scanning by the wires across the beam. The use of a semiconductor detector makes it possible to separate signals from different wires. The presented scanner allows measuring spatial profiles, dimensions, trajectory, divergence and emittance of beams of charged particles in a wide energy range from few of keV to tens of GeV, as well as the characteristics of atomic, X-ray and gamma-ray beams. Since CXR distribution is isotropic, there are no requirements and limitations on the location of the X-ray detector relative to the beam axis. The work was support by the grant of the President of Russia for young doctors of sciences MD-5748.2018.2. [1] Nazhmudinov R. M., Karataev P., Kubankin A., Lekomtsev K., Potylitsyn A., Vukolov A. Experimental station with continuous electron beam for investigation of various mechanisms of EM radiation generation. Journal of Instrumentation 13 (2018) C06007.

Speaker: Mr Ramazan Nazhmudinov (Belgorod National Research University)

18:40 Charged Particles Production by High-Energy Electron Beam in a Tungsten Target¶

Positrons are usually produced in tungsten (further W) single-crystalline and amorphous targets (see, e.g. [1]). However, in tungsten single-crystals dechanneling length of incident electrons is rather short, which restricts their applicability. The possibility of application of textured polycrystalline targets (in which the channeling of electrons was recently observed [2]) for increasing of positron production was proposed in [3]. This aim is supposed to be achieved due to channeling in the crystallites of the downstream textured W target of the electrons scattered in the upstream W single-crystal. In the present work, we report about the beginning of experimental research in this direction with the use of W targets acting as amorphous ones [4]. Presently charged particles production by 7 GeV electron beam in a W target was studied with the use of thin silicon surface-barrier detectors. The beam was supplied at accelerator U70 in Protvino. In the first experiments there was observed the production of charged particles in upstream W targets of different thicknesses (1.5–12 mm) placed on different distances (11–110 mm) from the downstream silicon detector. Determination of the number of created particles and their nature was performed by the analysis of ionization loss spectra (Landau peaks) formed by the particles in the detector. Comparison with corresponding theoretical estimations is presented. References 1. X. Artru, I. Chaikovska, R. Chehab, M. Chevallier, O. Dadoun, K. Furukawa., H. Guler, T. Kamitani, F. Miyahara, M. Satoh, P. Sievers., T. Suwada., K. Umemori, A. Variola, “Investigations on a hybrid positron source with a granular converter”, Nucl. Instr. Methods B 355 (2015) 60. 2. Y. Takabayashi, K. Ishiji, “Observation of channeling effects for relativistic electrons in a polycrystal”, Nucl. Instr. Methods B 355 (2015) 53. 3. A.V. Shchagin, “Textured polycrystal for increasing of positrons production”, 2016 in Book of Abstracts of 7th International Conference Charged & Neutral Particles Channeling Phenomenon - Channeling 2016, September 25-30, 2016, Sirmione-Desenzano del Garda, Italy, p. 112. 4. R.M. Nazhmudinov, A.S. Kubankin, A.V. Shchagin, O.O. Ivashchuk, N.F. Shul’ga, S.V. Trofymenko, A.G. Afonin, G.I. Britvich, A.A. Durum, M.Yu. Kostin, V.A. Maisheev, V.I. Pitalev, Yu.A. Chesnokov, A.A. Yanovich, “Observation of Positrons Production in W Target by 7 GeV Electrons”, XII International Symposium RREPS, September 18-22, 2017, Hamburg, Germany, Book of Abstracts, p. 136.

Speaker: Mr Sergii Trofymenko (Akhiezer Institute for Theoretical Physics of NSC KIPT)

18:40 Computer Simulations for Charged Particles Channeling in Capillaries¶

Charged particle beams are now widely used in various fields of science, from basic and applied research to technology, in biomedicine and other fields. In this regard, an important task is to transport the beam to the object of investigation or processing. At present, the main technique to form the beams of charged particles is to use magneto-optical systems that are quite complex and require additional and powerful sources of energy. Since the middle of the 80s of last century glass capillaries have been used to handle X-ray and thermal neutron beams. The research, both theoretical and experimental, has been developing rapidly in the world in recent years, extending the use of capillary systems for charged particle beams.Interest in controlling charged beams by means of capillary structures is growing due to the development of technologies for manufacturing micro- and nanostructures and their successful application to the problems of radiations shaping. The theory of the passage of neutral particles through capillary structures is well known and is based on the formalism of particle channeling in crystals. Following the formalism of channeling physics, in this work the approximation for continuous potential of the reflecting surface used for the computer simulation of the process of charged particles passage through aligned capillary structures is applied for the first time. The program (CapStruct) is implemented in its first version that allows simulating the motion of a beam down to capillary channels in dependence on both geometry of these structures and beam parameters. This program calculates and graphically depicts distributions of particles on the detector. Two computer models of particle-capillary interaction were constructed using approximation of continuous potential as well as approximation of elastic interaction of particles with a capillary inner surface. It is shown that for microcapillaries the simpler elastic scattering model is applicable with essentially good accuracy, and also for large database realized for large countable regions. It provides a significant performance gain in comparison with a more accurate continuous potential model. At first stage, all models are characterized by a significant simplification of the processes of beam interaction with a surface. The loss of energy at reflection, the influence of various fields induced by charged particles on a capillary surface will be taken into account in the next stage of the work.

Speaker: Egor Kurnikov (NRNU MEPhI)

18:40 Development of New Approaches to Increase the Intensity of X-ray Radiation in a Pyroelectric Source¶

Pyroelectric materials (for example, single crystals of lithium niobate and lithium tantalate or PZT ceramics) are used to generate high potential in vacuum, to accelerate electrons and positive ions, to produce X-rays and neutrons [1-4]. Portable X-ray and neutron sources are being developed, based on this phenomenon [5,6]. However, low intensity makes it difficult to use such sources for practical applications. Recently, various ways of improving pyroelectric sources (application of nanostructures, selection of the optimum rate of temperature change) have been discussed [7-9]. In this report, features and nature of charge generation on the side surfaces (parallel to the axis of spontaneous polarization) of a lithium niobate crystal are considered. It is shown that a large amount of charge on side surfaces is present that affects the process of an electric field generation. Advantages and disadvantages of this effect are considered and demonstrated in light of improving the pyroelectric sources. Acknowledgments The work of co-authors from Belgorod National Research University was financially supported by a Program of the Ministry of Education and Science of the Russian Federation for higher education establishments, (project No.3.1631.2017/ПЧ). References 1. J.D. Brownridge, Nature 358 (1992) 287 2. J.D. Brownridge and S. M. Shafroth, Appl. Phys. Lett., 79 (2001) 3364 3. B. Naranjo, J.K. Gimzewski and S. Putterman, Nature 434 (2005) 1115 4. A.V. Shchagin, V.S. Miroshnik, V.I. Volkov, and A.N. Oleinik, Appl. Phys. Lett. 107 (2015) 233505 5. Amptek Inc., Miniature X-ray generator with pyroelectric crystal www.amptek.com/coolx.html. 6. D. Gillich and et. al, Nucl. Instrum. Meth. A 602 (2009) 306 7. Y. Alivov, M. Klopfer and S. Mollo, , Appl. Phys. Lett. 102 (2013) 143106 8. A.S. Chepurnov and et al, JINST 12 (2017) 11002 9. A.S. Kubankin and et. al, AIP Advances 8 (2018) 035207

Speaker: Mr Andrey Oleinik (BelSU)

18:40 Enhancement of the Inelastic Nuclear Interaction Rate in Crystals via Anti-Channeling¶

The interaction rate of a charged particle beam with the atomic nuclei of a target varies significantly if the target has an ordered structure. In particular, under specific orientations of the target with respect to the incident beam, the probability of inelastic interaction with nuclei can be enhanced with respect to the standard rate. This effect can be advantageously used in the cases where the interaction between beam and target has to be maximised. A dedicated set of experimental measurements were carried out at the INFN Legnaro Laboratories with the AN2000 and CN accelerators to prove the existence of this effect. The variation of the interaction yield at hundreds of keV to MeV energies was proved by means of sapphire and indium phosphide crystals, achieving an enhancement of the interaction rate up to 73% and 25%, respectively. Such result may pave the way to the development of novel type of nozzle for the existing cyclotrons, which can exploit crystalline materials as targets for radioisotopes production, specially to enhance the production rate for expensive prime materials with minor upgrades of the current instrumentation.

Speaker: Enrico Bagli (FE)

18:40 FEL Gain Formed in Sectional Undulator¶

The problem of increasing the efficiency of free electron laser (FEL) during the passage of a relativistic electron bunch through an undulator with intervals is considered. A formula is obtained for the spectral distribution of spontaneous radiation. The dependence of FEL gain on the number of undulator sections is investigated. It is shown that a increase in the efficiency of FEL, when undulator is divided into two parts (an optical klystron), disappears with an increase in the number of undulator sections.

Speaker: Mr Hayk Gevorgyan (Student)

18:40 Half-Wave-Crystal Channeling of Relativistic Heavy Ions and Possible Applications¶

Half-wavelength crystal (HWC) is a thin crystal, when a channelled particle experiences only one collision with crystallographic plane during penetration through a HWC. Recent experiment [1] demonstrated 2 MeV protons mirroring by thin silicon HWC. More recently, the mirroring effect was observed for 400 GeV protons at CERN-SPS [2]. The existence of mirroring effect using HWC in the case of negative charged particles was recently demonstrated at the SAGA-LS Facility using 255-MeV electrons and thin (HWC) Si crystal [3]. The HWC effect is explained by computer simulations as a sequence of specific trajectories of planar channeled particles governed by one-dimensional periodic potential of crystallographic planes. The perspective atomic physics experiments (including crystal targets) with relativistic heavy ion (RHI) beams are the part of Super-FRS Experiment Collaboration program [4]. The critical channeling angle depends on three parameters of RHI beam: proton number Z, neutron number N and beam energy E (MeV/u), and one crystal parameter U0 – potential energy of a unit charge in the field of atomic plane (of order of 20 - 50 eV for planar channeling). Here, we present the results of computer simulations of RHI penetration through a HWC using computer code BCM-2.0 [5]. According the simulations, the RHI beam deflection angle through the HWC mirroring effect is of order of critical channeling angle θc. Moreover, simulations demonstrate the sensitivity of HWC-RHI channeling and mirroring effect to the isotope mass (N value). Based on simulations, we discuss possible applications of HWC-mirroring of RHI beams: as effective beam deflector similar to high-energy particle physics [2] and even more exotic ones, like Z filter, velocity (E) filter, isotope mass (Z+N) filter. References 1. V. Guidi, et al., Phys. Rev. Lett. (2012) 108 014801 2. W. Scandale et al., Phys. Lett. B (2014) 734 1 3. Y.Takabayashi, Yu.L.Pivovarov, T.A.Tukhfatullin Phys. Lett. B (2015) 751 453 4. H. Geissel, O.V. Bogdanov, C. Scheidenberger, Yu.L. Pivovarov, N. Kuzminchuk-Feuerstein, E.I. Rozhkova, T.A. Tukhfatullin, and the Super-FRS Experiment Collaboration. GSI SCIENTIFIC RE-PORT 2016 RESEARCH-NUSTAR-FRS-8, p. 179 DOI:10.15120/GR-2017-1 5. S.V. Abdrashitov, O.V. Bogdanov, B. Korotchenko et. al., Nucl. Instrum. and Meth. B 402 (2017) 106-111

Speaker: Dr Timur Tukhfatullin (National Research Tomsk Polytechnic University)

18:40 Influence of the Frequency Detuning to Electrodynamics Parameters of an Electron Linac¶

It is very important task to define the tolerances necessary for correct operation of electron linac. The detuning of linac main parameters as frequency, RF-field amplitude and phase can sufficiently influence to the beam parameters. It is highly sufficient for linacs with high brightness beams which are necessary for light sources and colliders. It is also sufficient for industrial linacs. Results of the numerical simulation of a linac electrodynamics parameters are presented in this paper. A section consists of regular and bunching parts. The influence of one cell detuning to electrodynamics parameters of the whole section was studied. The standing wave biperiodic accelerating structures (BAS) with coupling windows are one of the popular structures for research and industrial electron linacs. Such structures are used in the new industrial 10 MeV/ 20 kW accelerators developed by the joint team of NRNU MEPhI (Moscow) and Corad Ltd. (St. Petersburg) [1-3]. Optimized omega – shape accelerating cells provide the maximum RF-field on the structure axis and high shunt impedance are used in these linacs. New linac has high electrical efficiency, narrow beam energy spectrum within energy range of 5-10 MeV. The high coupling coefficient was obtained also to achieve the maximal efficiency of RF-pulse power usage. The gentle buncher was used to provide high capturing coefficient and narrow energy spectrum in wide energy band. The high-quality manufacturing of the buncher cells and its frequency tuning is one of the main problems for BAS. Investigation of the influence of one cell frequency detuning on the electrodynamics parameters of the whole structure is very sufficient for e-linac R&D. Results of such influence simulations effect on the whole structure frequency and RF-field amplitude distribution will be presented.

Speaker: Mr Alexey Pronikov (National Research Nuclear University MEPhI)

18:40 Injector Linac Prototype of the Russian 4th Generation Specialized Synchrotron Radiation Source SSRS-4 as a Possible Compact XFEL¶

In this report we present first results of the design of the compact XFEL based on prototype of new linac-injector. This linac develops for the one of the largest Russian scientific projects, 6 GeV 4-th generation light source SSRS4. Both synchrotron and XFEL based on top-up injection linac are proposed to construct in SSRS4 complex. Suggested prototype of the injector initially will include 10 MeV RF photo-gun and 50 MeV regular section. The report summarizes the results of preliminary research of SSRS4 linac injector prototype general layout and it's parameters. The possibility of future use of the prototype as a compact light-source will also discuss.

Speakers: Mr Iliya Ashanin (NRNU MEPHI), Dr Sergey Polozov (NRNU MEPhI)

18:40 Monochromatic Coherent Grating Transition Radiation of a Relativistic Electron Bunch Train¶

In Ref. [1,2] authors observed the monochromatic lines in the spectrum of the coherent transition and diffraction radiation generated by modulated electron beam with the frequency of the accelerating RF field and corresponding to the resonances for . In this report we present the results of coherent grating transition radiation (CGTR) and spectra measurements within the frequency range of 8 to 35 GHz when modulated electron beam hits the periodic target with inclined flat strips with vacuum gap between them. The monochromatic lines corresponding to the dispersion relations at the resonances were observed in the CGTR spectrum. For spectra measurements we used the Martin-Puplett interferometer with spectral resolution 800 MHz (FWMH). One of the main goals of this research is to prove the shadowing effect (see Ref.’s [ 3,4]) existence for such gratings. The spectra and orientation dependences (intensity dependence from grating tilt angle θ) were simulated for two gratings taking into account experimental conditions for two cases with shadowing effect and without. The discussion of the experimental results and comparison with the calculations has been done. This work was partially supported by the program ”Nauka" of the Russian Ministry of Science, by JSPS and RFBR under the Japan-Russia Research Cooperative Program (18-52-50002 YaF_a) and the Competitiveness enhancement program of Tomsk Polytechnic University. References 1. GA. Naumenko, AP. Potylitsyn, et. al. JETP Letters, 2017, Vol. 106, No. 2, pp. 115–118. 2. G. Naumenko, A. Aryshev et. al., NIM B 402 (2017) 153. 3. G. Naumenko, X. Artru et. al., Jour. of Phys.: Conf. Series 236 (2010) 012004. 4. R. Kieffer, M. Bergamaschi et. al., Phys. Rev. Lett. 120 (2018) 094802.

Speaker: Dr Gennady Naumenko (Tomsk Polytechnic University)

18:40 On the Use of Electron Diffracted Diffraction Radiation at X-ray Mirrors for Electron Beam Parameters Diagnostics¶

Projected International Linear Collider [1] and Compact Linear Collider [2] need new measurement methods of parameters of relativistic electron beam with size of some nm and divergence about 10-40 $\mu$rad. Using of fast electrons diffracted transition radiation (DTR) in thin crystals for beam divergence measurements [3] is really impossible because of the crystals destroying [4]. Using of diffracted diffraction radiation (DDR) of electrons in crystals [5] is practically unrealized also because of small wavelength $\lambda$ and necessity of $b<0.1\gamma \lambda$ condition fulfilment, where $\gamma$ and $b$ are relativistic factor and the distance between the crystal and the electron beam, respectively. Decision of the problem may be the wavelength increasing by means of using of multilayer X-ray mirror providing a rather high selectivity $\mathrm{\Delta }\lambda /\lambda \sim$ 0.04 and reflectivity up to 30-40\% [6]. Analysis of known methods of X-ray mirrors parameters calculation such as reflectivity and angular resolution and their dependence from the mirrors composition and observation angle are performed. Calculation of the DDR angular distributions was made for the selected method and measurement condition. The proof-of-principle experiment may be performed on already existing electron accelerators. Desirable X-ray mirror parameters and needful experimental equipment for the experiment at Mainz microtron and KEK-ATF accelerator are discussed. References [1] ILC Technical Design Report, 12 June 2013 www.linearcollider.org/ILC/TDR [2] A Multi-TeV Linear Collider Based on CLIC Technology: CLIC Conceptual Design Report, 2012. http://clic-study.web.cern.ch/content/conceptual-design-report [3] Goponov Yu.A. et al. NIM, 2016, A808, P. 71 [4] Babaev A.A., Gogolev A.S. J. Phys. Conf. Ser. 732 (2016) 012030. [5] Goponov Yu.A. et al. NIM, 2018, A885, P. 134 [6] Barysheva M.M. et al. Physics-Uspekhi. 2012. V. 55. P. 681.

Speaker: Prof. Igor Vnukov (Belgorod sate university, Belgorod, Russia)

18:40 Optimal RF-Photogun Parameters for the Compact XFEL Based on the New Linac-Injector Prototype¶

The beam dynamics analysis of the RF-photogun as the LUCX facility at KEK, Japan, and new photo injector for the Russian 4th generation light source SSRS4 was done to chose the optimal length of the section and cell’s number and also to define optimal accelerating gradient and injection phase. The simulation of electrodynamics characteristics and fields distribution in the RF-gun based on 3.5-, 5.5- and 7.5-cell π-mode standing wave accelerating structure was done. The influence of the beam loading effect on the field amplitude and beam dynamics was the main purposes of study also. The beam dynamics simulation results will present in the report and optimal RF-gun parameters will discus.

Speaker: Mrs Yulia Kluchevskaia (NRNU MEPHI)

18:40 Passage of 10 keV Electrons through Ceramic Macrochannels¶

Possibility of charged particles beam manipulation by means of dielectric surfaces has been demonstrated earlier. This effect is caused by formation of a self-consistent charge distribution on the dielectric channel walls. The distribution provides the passage of a part of the charged particle beam without direct contact with the surface of the channel. Efficiency of controlling a beam passing through a dielectric channel is characterized by the magnitude of the transmitted beam current, the energy state of charged particles transmitted through the channel, and the angular characteristics of the transmitted beam. The transmission of electron beam through ceramic cylindrical channels and plane channels made of two plates was studied. Method of estimation of transmitted electrons energy was suggested. The method is based on an analysis of X-ray spectrum generated by electrons in a copper plate placed in vicinity of the channel outlet. The results of experiments indicate the possibility of effective use of ceramic channels as autonomous elements of beam optics. The work was financially supported by a program of the ministry of education and science of The Russian Federation for higher education establishments, project №14.578.21.0192 (RFMEFI57816X0192).

Speakers: Dr Kristina Vokhmyanina (International Scientific and Educational Laboratory of Radiation Physics, Belgorod National Research University), Dr Ramazan Nazhmudinov (Belgorod National Research University)

18:40 Pyroelectric Deflector of 7 MeV Electron Beam¶

Pyroelectric deflector of 7 MeV electron beam O. Ivashchuka, I. Kishina,b, A. Kubankina,b, A. Oleinika,c, A. Shchagina,d, V.I. Alekseev a,b, A.N. Eliseyeva,b a Laboratory of Radiation Physics, Belgorod National Research University, Belgorod, Russia b Lebedev Physical Institute, Moscow, Russia c John Adams Institute at Royal Holloway, University of London, Egham, UK. d Kharkov Institute of Physics and Technology, Kharkov, Ukraine We have observed a deflection of relativistic electrons beam with an energy of 7 MeV in a transverse electric field, which is created by means of a pyroelectric deflector [1]. The experiment was performed on the microtron of the "Pakhra" accelerator complex in Lebedev Physical Institute. The deflection of the beam for angle of 1.43⁰ was observed on a fluorescent screen installed at a distance of 70 cm from the deflector. The transverse electric field strength generated by the pyroelectric deflector was 75 kV / cm when the crystals were heated from room temperature to 50 ⁰C. Experimental data are compared to calculations. The perspectives of creating a pyroelectric undulator are discussed. Acknowledgments The work was financially supported by a program of the ministry of education and science of The Russian Federation for higher education establishments, project №14.578.21.0192 (RFMEFI57816X0192). References 1. A.N. Oleinik, A.S. Kubankin, R.M. Nazhmudinov, K.A. Vokhmyanina, A.V. Shchagin and P.V. Karataev, Pyroelectric deflector of charged particle beam. // JINST (2016) 11, P08007.

Speaker: Mr Oleg Ivashchuk (Belgorod National State University)

18:40 Simulation of High-Energy Particles Channeling Using Mathematica©¶

Experiments with high-energy particle beams using straight and bent crystals is a popular recent trend in high-energy accelerator physics. The strong electrical field of the crystal planes allows steering of particle trajectories. Recently, experiments on the bent crystal channelling of 6.5-TeV protons were performed at the Large Hadron Collider in CERN toward the future beam collimation [1,2]. The studies on bent crystal channelling have also been carried out using sub-GeV and several GeV electrons at MAMI (855 MeV) [2] and SLAC [3]. Besides studies of basic properties of high-energy electron channelling, several applications of bent crystal channelling of electrons have been discussed: beam splitters, beam collimation [4] and so-called crystalline undulators as powerful γ-ray sources [5]. Here we present a computer code which allows calculating the trajectories of relativistic charged particles channelled in aligned crystals using Mathematica© code. It is a specific separate part of the BCM-2.0 code [6]. The simulation procedure takes into account multiple scattering and angular spread of the particle beam. The computer code allows calculate the flux dynamics and angular and spatial distributions of relativistic particles passing through straight and bent crystals, including mirroring. Simulations were validated against experimental data obtained at SAGA LS Linac for 255 MeV electrons channelled in the thin Si crystals [7,8]. We present also the results of simulations for another energies and another crystals than in [7,8] both for electrons and positrons, and make a comparative analysis and suggest further perspectives. References 1. W.Scandale et al., Phys. Lett. B 758 (2016) 129. 2. A.Mazzolari, et al., Phys. Rev. Lett. 112 (2014) 135503. 3. U.Wienands, et al., Phys. Rev. Lett. 114 (2015) 074801. 4. S.Strokov, et al., J. Phys. Soc. Jpn. 76 (2007) 064007. 5. T.N.Wistisen, et al., Phys. Rev. Lett. 112 (2014) 254801. 6. S.V. Abdrashitov, et al., Nucl. Instr. and Meth. B 402 (2017) 106. 7. Y. Takabayashi, Yu.L. Pivovarov, T.A. Tukhfatullin, Phys. Lett. A 378 (2014) 1520. 8. Y. Takabayashi, Yu.L. Pivovarov, T.A. Tukhfatullin, Phys. Lett. A 382 (2018) 153.

Speaker: Dr Timur Tukhfatullin (National Research Tomsk Polytechnic University)

18:40 Status of Diagnostic and Control System Development for Russian New Light Source Project SSRS-4*¶

The project of the new light source of 4th geberation is under development in Russia under Kurchatov institute leadership. In framework of this project the test bench for timing system as well for diagnostic system is under development. The approach to the control and diagnostic systems for this light sosurce are discussed. Also the first results obtained at the test-bench are presented and discussed.

Speaker: Dr Timur Kulevoy (ITEP)

18:40 Studies of Beam-Channel Misalignment in the Hollow Channel Plasma Accelerator in Nonlinear Regime¶

Hollow plasma has been demonstrated in favor of beam quality preservation in the proton-driven plasma wakefield accelerators, where the transverse wakefields acting on the accelerated beam vary in radius and time in uniform plasma even in the nonlinear regime. With hollow plasma, there is completely no transverse plasma wakefields. However, this scheme requires prefect beam-channel alignment. Otherwise asymmetric and non-zero transverse wakefields along the axis are induced, which could distort the driving bunch and ruin the witness beam quality. In this paper, by means of particle-in-cell simulations, we examine the transverse wakefields and potential detrimental effects on the witness bunch induced by the driving beam-channel offset and initial driver tilt. By analyzing the beam dynamics, we propose and assess corresponding solutions to such misalignment issues.

Speaker: Ms Yangmei Li (University of Manchester, Cockcroft Institute)

18:40 Studies on mm-Waves at CLEAR¶

We report on preliminary experimental studies on mm-waves at CLEAR electron LINAC (CERN). The production of coherent radiation in the (sub-)THz region by using ps-long electron bunches is the first step towards the realization of an intense source for both users and applications in accelerator physics. Some of different mechanisms like coherent transition, diffraction, Cherenkov and Smith Purcell radiation have been already explored and the others will be investigated in the next future. Coherent radiation has also been exploited for longitudinal bunch diagnostics. Finally, first results on electromagnetic shadowing are shown.

Speaker: Dr Alessandro Curcio (CERN)

18:40 The Crystal Surface Optimal Geometry to Reflect of a Charged Particles Beam¶

The aim of our investigations is to create the physical model for effective reflection of charged particle beam by the crystal surface to take into account relativistic effects. Particularly, calculation of the optimal structure and reflecting surface geometry, at which the reflection coefficient of incident beam will be maximum.

Speaker: Mr Yury Eikhorn (National Research Tomsk Polytechnic University)

18:40 The Features of Propagation and the Remote Collapse of the Correlated Wave Packet¶

In atomic and nuclear physics the state of moving particles is usually described by idealized plane waves. Such model is approximate and characterizes the features of such particles with some inaccuracies. A real alternative is to describe the particle as a moving localized wave packet. The main disadvantage of this description is the instability and continuous "spreading" and delocalization of the package, which does not allow using it for the analysis of real physical processes. Such packet corresponds to an uncorrelated superposition of spectral components, which form this packet. We consider the method of formation and features of the propagation of a correlated wave packet, which has the same initial form as an uncorrelated packet, but fundamentally different properties. It is shown that, in contrast to the "standard" uncorrelated packet, for a correlated packet at the initial stage a self-simulated self-compression process proceeds to the collapse state at a given (controlled) removed distance. The spatial width of the correlated packet for a time of collapse decreases from the initial value to the controlled minimum value (the state of collapse of the wave packet) and then increases monotonically. Simultaneously with the decrease of the width of the packet, up to the region of collapse, the amplitude of the packet sharply increases in time from the initial small value by many orders of magnitude to the maximum value, after which the accelerated "spreading" takes place. The evolution of the correlated packet leads to a very sharp increase of the fluctuations of kinetic energy of the particle in the region of collapse to a value, which can exceed its average kinetic energy by many orders of magnitude at large value of correlation coefficient of [1]. The considered features of correlated wave packet evolution make it possible to predict the possibility of using it for a number of applied and fundamental problems. In particular, it is possible to control area of collapse of this packet in such a way that it would release of the maximum energy in a specific remote area of some target. These features of the correlated packet can also be used to realize nuclear fusion at a low mean energy of a particle. The methods of formation of such correlated wave packet are also discussed. 1. V.I.Vysotskii, M.V. Vysotskyy, European Phys. Journal. 2013, A49, 99.

Speaker: Dr Mykhaylo Vysotskyy (Kiev National Shevchenko Univ)

18:40 The Mechanism of Effective Nuclear Reactions under the Action of Optimal Pulsed Magnetic Fields in Natural Lightning and Discharge Channels¶

In the report, the problem of realization and optimization of nuclear fusion reactions in electric discharge channel (for example, in a natural lightning channel) is considered. The main mechanism for optimization of such processes is connected with the self-similar formation of coherent correlated states under action of a pulsed magnetic field accompanying such a discharge. It is shown for the first time that the process of formation of such states and the corresponding tunneling probability for the subsequent nuclear interaction are characterized by a resonant dependence on parameters of the forming magnetic field pulse. The strict critical condition for possible combinations of optimal duration and amplitude of the magnetic pulse for each type of nuclear reaction, at which the efficiency of such reaction reaches its maximum value, have been obtained. It was shown that even slight deviation from this condition makes the reaction impossible. This result shows the incorrectness of the intuitive idea that the probability of tunneling always increases with the increase of the amplitude of the impact. This result, in particular, can be used to explain the random (unpredictable) results of experiments on the optimization of energy release due to the nuclear reactions carried out using pulse action with uncontrolled fluctuations in amplitude and duration. The results of theoretical analysis [1] are compared with the data of numerous successful experiments on observation of neutrons and alpha particles during both controlled and natural (lightning) electric discharge in air and gaseous deuterium. 1. V.I.Vysotskii, M.V. Vysotskyy. Journal of Experimental and Theoretical Physics, 2017, 152(8), 234.

Speaker: Dr Mykhaylo Vysotskyy (Kiev National Shevchenko Univ)

Friday, 28 September ¶

09:00 → 11:00 S5.3 Novel Sources: FEL/Laser/Plasma¶

Convener: Prof. Sultan Dabagov (LNF)

09:00 Radiotheraphy and Neurosurgery for the Treatment of Brain Lesions. An Uneasy but Necessary Joint Collaboration¶

Modern Neurosurgery is directed towards mini invasive for the reduction of post-operative complications. A common strategy between mini invasive neurosurgery and other parasurgical  modalities , between  which radiotherapy is the main tool, may represent the best available  option, and the strategic treatment modality in the future.    I present shortly here my view based on my personal experience with the treatment of demanding tumoral lesions of the brain.

Speaker: Prof. Aldo Spallone (Embassy of Italy in Russian Federation)

09:30 Current status of Russian 4th generation Specialized Synchrotron Radiation Source SSRS-4¶

In this report we present new information about one of the largest Russian scientific projects, a new and advanced 6 GeV 4-th generation radiation facility based on both synchrotron and FEL radiation. The report summarizes the results of preliminary research of SSRS4 general layout and accelerator complex parameters.

Speaker: Dr Sergey Polozov (NRNU MEPhI)

Slides 9.30_Ch2018_polozov.pdf

10:00 MariX/BriXS Design Study: a Combined Ultra-High Flux X-ray FEL and Compton Source¶

We developed a Design Study for a combined X-ray source system spanning the 0.3-150 keV photon energy range with un-precedented characteristics of brilliance, flux and coherence. The machine is based on an innovative scheme combining a compact 100 MeV energy recovery Super-Conducting Linac and a 1.5 GeV two-pass CW-SC Linac that can boost the electron beam energy up to 3.8 GeV via a newly conceived bubble-shape arc compressor. The radiation beam lines under design will generate mono-chromatic X-rays in the 20-150 keV range via Compton back-scattering, with fluxes up to 1013 photons/sec in 100 MHz rep rate pulses (ps-long), and Free Electron Laser photon beams in the 300 eV – 12 keV (1 Angstrom) range with coherent femto-second pulses at 1 MHz rep rate and up to 1017 photons/sec. MariX (Multi-disciplinary advanced research infra-structure with X-rays) is conceived to be developed in the context of the new Scientific Campus of Universita’ degli Studi di Milano in the Milan Expo area. We will illustrate the main rationale of the MariX design study and its Conceptual Design Report recently completed, as well as the main guide lines of the FEL scientific case and the Compton source clinical and scientific case (see also http://www.fisica.unimi.it/ecm/home/ricerca/marix).

Speaker: Luca Serafini (MI)

Slides 10.00_ch2018_serafini.pdf

10:30 Prospects of a THz/IR FEL at TRIUMF Laboratory¶

The TRIUMF Laboratory, located in Vancouver, Canada, presently undergoes the final stage of construction of an Advanced Radioactive Isotope production facility that will substantially enlarge its Nuclear Physics program [1]. One of the key component of the facility is a 50MeV 10mA CW linear electron accelerator. The construction of the linac has been completed and it is now in the commissioning mode. The linac exploits superconducting technology and is capable of delivering up to 0.3MW of beam power. Only a fraction of this power can presently be handled by isotope production targets. Much of the available capacity can be used for other applications. From the very beginning the linac was also considered as a test bench for an IR FEL in the ERL configuration, but that option has never been funded. The parameters of the machine are particularly suited for a powerful source of THz radiation. Recently, the FEL proposal has received a new impulse. The design studies are about to start targeting both coherent spontaneous emission and FEL process in THz and Infrared regions.

Speaker: Dr Victor Verzilov (TRIUMF)

Slides 10.30_ch2018_verzilov.pdf

10:45 Beam Dynamics Studies for the X-Band Linac of the EUPRAXIA@SPARC_LAB Project¶

An advanced accelerator facility EUPRAXIA@SPARC_LAB has been proposed to be realized at Frascati (Italy) Laboratories of INFN in the framework of the Eupraxia Design Study. Two advanced acceleration schemes will be applied: an ultimate high gradient 1 GeV X-band linac together with a plasma acceleration stage to provide accelerating gradients of the GeV/m order. A FEL scheme is foreseen to produce X-ray beams within 3-10 nm range. A Compton backscattering Interaction is also planned together with extraction beamlines at intermediate electron beam energy for neutron beams and THz radiation production. The electron beam dynamics studies in the linac are here presented together with the preliminary machine layout.

Speaker: Cristina Vaccarezza (LNF)

Slides 10.45_Ch2018_Vaccarezza.pdf

11:00 → 11:20 Coffee break

11:20 → 12:20 W2.1 Advanced Generation of THz and X-ray beams¶

Convener: Dr Alexander Aryshev (KEK)

11:20 Dispersion Relations for Different Types of Radiation from Periodic Structures: Similarities and Differences¶

In this report we discuss the similarities and differences of dispersion relations for different types of radiation in periodic structures – resonant transition radiation from multilayered stack of films, Smith-Purcell radiation, parametric X-ray radiation in crystals, undulator radiation. We show that the key factor here is the existence of frequency dependent dielectric permittivity leads to a new roots when the integrals with delta-functions are taken, which in their turn lead to the arising of new addend in the total expressions for spectral or angular distributions. The phenomenon of the so-called “end transition radiation” is discussed as well.

Speaker: Dr Alexey Tishchenko (National Research Nuclear University "MEPhI")

Slides 11.20_ch2018_Tishchenko.pdf

11:50 Delhi Light Source: a compact FEL-THz facility¶

A compact pre-bunched Free Electron Laser facility named as Delhi Light Source is under construction at IUAC [1]. A low emittance electron beam (~ 4 - 8 MeV) will be produced by a photocathode based normal conducting RF gun and will be injected into a compact undulator magnet to produce intense THz radiation (0.18 to 2.85 THz). The gun, electron beam transport, undulator and experimental stations for THz will be accommodated inside the newly built class 10000 clean room. The electron gun, already built and tested, is waiting to be installed in the beam line. The Klystron and Modulator will be delivered and installed during the autumn of 2018. The beam optics calculation was initially performed using ASTRA and finally fine-tuned with GPT code. GICOSY code is also being used to perform the transverse beam optics calculation including the achromatic bends. Another code, developed in-house, based on Lienard-Wiechert potential, is used to calculate the parameters of the THz radiation emitted from the wiggling electrons inside the undulator. The design of the laser system is finalized and is being developed in collaboration with KEK, Japan. The design of the photocathode deposition mechanism has been completed and currently is being developed in collaboration with BNL, USA. The design of the undulator magnet is frozen and its development/procurement process has been started. The development and the testing of the undulator magnet is being executed in collaboration with DESY, Germany. The design calculation or parameter finalization of various electromagnets, steering devices, beam optics and beam diagnostic devices are underway. Electron beam and THz radiation are expected to be produced by the beginning and end of 2019, respectively. References 1. S. Ghosh et al. NIMB vol. 402, p. 358-363, 2017.

Speaker: Dr Subhendu Ghosh (Inter University Accelerator Centre)

Slides 9.00_ch2018_SGhosh.pdf

12:20 → 13:05 Channeling 2018 - Closing¶

13:05 → 14:30 Lunch

14:30 → 16:30 W2.2 Advanced Generation of THz and X-ray beams¶

Convener: Dr Alexey Tishchenko (National Research Nuclear University "MEPhI")

14:30 Self-Similar Electron Beam: Prospects, Demands, and Applications¶

Advanced types of particle accelerator systems that could achieve multi-THz repetition rate of accelerated beams [1 and Refs therein] are of utmost importance to reduce the size and cost of future high brilliance radiation sources as well as to provide a widespread availability of a compact accelerator technology to applied labs around the world. Repetitions of the order of a few hundreds of MHz have been achieved by conventional RF guns and are limited by the availability of commercial laser systems in use. The novel laser pulse splitting technique [2] applied to commercially available near-infrared sub-terawatt femtosecond laser technology (Ti:Sa laser) can achieve folded GHz-THz repetition rates. However, it has an inadmissible technical limitation of kHz maximum pulse-sequence repetition. That is why the application of the same pulse splitting technique to a novel fiber-based laser system can potentially deliver MHz-GHz-THz sequence of femtosecond pulses which repeats every machine cycle (typically Hz rate) to RF gun photocathode and generates low emittance electron beam of the same time structure. It is important to emphasize that in the proposed approach THz bunches are accelerated on the same RF cycle, GHz sequences on neighboring RF buckets and MHz repeats are occupying every few thousands RF buckets. All frequencies are the phase-locked harmonics of the lowest frequency. Moreover, THz sequence can be remotely fine-tuned to provide so-called ``multi-color'' generation of coherent radiation spectra. In the specific case, it is possible to achieve self-similar bunch frequency patterns which in more general case can be named as a ``fractal beam'' [3]. Application of such beam condition for generation of coherent radiation opens a wide possibility for development of THz radiation generation mechanisms with the predetermined spectral characteristics.

Speaker: Dr Alexander Aryshev (KEK)

Slides 14.30_ch2018_Aryshev.pdf

15:00 Novel Responses of Solids by Terahertz Free Electron Laser¶

The free electron laser (FEL) is a tunable monochromatic light source using an electron linear accelerator. Its high power, coherence, pulse, polarized characters yield many aspects of utilization in basic and applied fields. Terahertz (THz) and/or far-infrared (FIR) is just located in the middle region between the light and the radio wave in the electromagnetic wave. This region is so-called “terahertz-gap” where technological development still exists even now for both in light source and detector. From the point of view, THz-FEL is expected as a light source that creates new scientific fields through interaction with materials. The ISIR THz-FEL is based on the stimulated radiation from a compressed high-energy electron pulses [1, 2]. The obtained THz beam is brought to the end station as a multiple pulsed lights. In the case when the beam is adjusted to a condition with micro-pulse length of about 20 ps, the electromagnetic wave is oscillated for ~108 cycles in the micro-pulse at a wavelength of 100 μm (3 THz), which is quasi-monochromatic light with a bandwidth of about 3%. The frequency can be changed between 2.5 and 7.5 THz, and the maximum electric field reaches up to 3 MV/cm at a focal point in this condition. Recently, nonlinear interactions between semiconductors and the THz-FEL have been investigated. Semiconductors showed nonlinear absorptions corresponding to their band structures under high photon flux irradiation. Furthermore, a laser induced periodic surface structure (LIPSS) as an irreversible phenomenon was found under the higher photon flux [3]. LIPSS in NIR region has been known in the mid-19th century soon after the invention of the ruby laser, but the LIPSS generation mechanism is still under hot discussions even today. Due to the scaling law found between the LIPSS periodicity and the pulse number in this study, a LIPSS investigation can possibly be understood as a self-organizing phenomenon in a nonequilibrium open system. References 1. The heading “References” follows one double space below the body text in Times New Roman 10 bold. 2. L.J. Marshall and G. Talleni, Phys. Rev. A 43 (2001) 5897. 1. S. Okuda et al., “Free-electron laser oscillation with a multibunch electron beam of the 38 MeV L-band linear accelerator at ISIR”, Nucl. Instr. Meth. A 358 (1995) 244. 2. R. Kato et al., “High Power Terahertz FEL at ISIR, Osaka University”, Proc. 1st International Particle Accelerator Conference (IPAC'10). (2010) 2209-2211. 3. A. Irizawa et al., “Laser-induced fine structures on silicon exposed to THz-FEL”, Appl. Phys. Lett. 111 (2017) 251602.

Speaker: Dr Irizawa Akinori (The Institute of Scientific and Industrial Research, Osaka University, Japan)

Slides 15.00_Ch2018_irizawa.pdf

15:15 Longitudinal Motion Stability of Electrons inside the Plasma Channel of LPWA¶

The acceleration of electrons in laser plasma channels is one of the contemporary ideas on energy frontier of accelerators. Many simulations and experimental studies are provided before now but all results shows that low fraction of electrons are capturing into acceleration and accelerated electrons have very broad energy-band. New results of beam dynamics simulations in laser plasma channel having pre-bunching stage are discussed in report. Main simulations were focused to the study of the longitudinal motion stability. It was shown that plasma potential well form is sufficiently depends of laser pulse amplitude and plasma density gradient and the electron beam dynamics is defined by the form and velocity of the plasma potential well. Electrons loosed from the synchronous motions with the plasma wave are defocusing fast after fall out from the potential well.

Speaker: Dr Sergey Polozov (NRNU MEPhI)

Slides 15.15_ch2018_Polozov.pdf

15:30 The THz Radiation Development Based on High Brightness Linac at THU¶

Recently, the high brightness linac at Accelerator Laboratory of Tsinghua University (THU) has been focused on the production of tunable high-peak-current electron bunch trains with picosecond or sub-picosecond spacing. In this talk, we will report on recent research activities with this kind of widely tunable high intensity bunch trains in our laboratory. The production and diagnostics of the bunch trains have been successfully demonstrated. Experiments on coherent undulator radiation, coherent transition radiation, coherent Smith-Purcell radiation, dielectric wakefield radiation were performed with high peak-current electron bunch and bunch trains for THz production. Novel schemes based on laser-beam interactions to generate bunch trains with more flexibility will also be presented. The results indicate that such bunch trains are quite promising for the development of tunable high power THz source by different radiation schemes.

Speaker: Prof. Lixin YAN (Accelerator Lab, Tsinghua University, Beijing)

Slides 15.30_Ch2018_Lixin_Yan.pdf

15:45 First Observation of the Grating Diffraction Radiation¶

Development of the linac-based narrow-band THz sources with sub-picosecond, $\mu J$-level radiation pulses is of the great demand among wide scientific community [1 and Refs therein]. The interest appears due to the fact that THz radiation is nonionizing, which prevents destruction of a test sample and enables investigation of living cells without radiation damage. Intrinsically monochromatic emitters like coherent Smith-Purcell radiation (SPR) [2] seem to become a natural selection. SPR appearing when a charged particle moves above and parallel to a grating. However, the lack of a broad spectral tunability still stimulates an active research in this direction [3, 4]. Presented here, first experimental investigation of the coherent Grating Diffraction Radiation (GDR) process for which an initial electron beam passes above(below) the grating at oblique incidence with respect to the grating surface, and shows comparable radiation intensity with central frequencies fine-tuning in a much wider spectral range. Additionally, it allows for a bandwidth selection at the same central frequency. Experimental confirmation includes the basic spectral and spatial properties. The discussion on GDR intensity in comparison with other coherent radiation sources is also presented. The result further widens the potential of designing a tabletop wide-range tunable quasi-monochromatic or multi-color radiation source in GHz-THz frequency ranges.

Speaker: Prof. Alexander Potylitsyn (Tomsk Polytechnic University)

Slides 15.45_ch2018_potylitsyn.pdf

16:00 Wakefield Acceleration Based on Smith-Purcell Effect in Corrugated Dielectric Capillary¶

The accelerating gradient in conventional radio-frequency accelerators is limited to 100 MeV/m. A promising solution is to use wakefield effects either in dielectrics or plasma, where breakdown limit is higher. Cherenkov radiation (CR) is considered to be the main mechanism in dielectric wakefield acceleration (DWA). Our preliminary study with corrugated capillaries show some modification to the CR-generated wakefields [K.V. Lekomtsev et al., Phys. Rev. AB 21, 051301 (2018)], but the possibility of using Smith-Purcell radiation (SPR) in DWA is still under consideration. Here we propose to apply SPR in DWA instead of CR. Theoretical results are compared with computer simulation.

Speaker: Mr Alexsandr Ponomarenko (Russia)

Slides 16.00_Ch2018_Ponomarenko.pdf

16:15 Parametric X-ray Radiation in Crystals with Locally Disturbed Characteristics¶

Electron moving through a crystal target can affect the crystal cell by its Coulomb field. Within the first approximation, it leads to arising parametric X-ray radiation (PXR). In the case of consequent short and intense bunches the witness-bunches come to the crystal cells disturbed by the driver-bunches. It can cause the change in the radiation characteristics. To date, such short and extremely intense beams are available in modern FELs. In this work we consider the influence of electron wake-field on the electrons of a target. We obtain the electron densities in crystal after the electron passage and calculate the locally disturbed dielectric properties. So, the dielectric constant of the crystal changes locally, and, as a result, the intensity of PXR changes as well. We compare the spectral-angular density of PXR from conventional, undisturbed crystal with that from a one locally disturbed by intense electron beam.

Speaker: Ms Daria Danilova (National Research Nuclear University "MEPhI")

Slides 16.15_ch2018_Danilova.pdf

16:30 → 16:50 Coffee break

16:50 → 18:35 Discussion Table¶