Welcome / admin & logistics

• Carsten Peter Welsch
• Hannah Acton (University of Liverpool/Cockcroft Institute)

Room: CNR-INO, Building A, Room 27

Laser Technology

• Leonida Antonio Gizzi (CNR - INO, and INFN - Sez. di Pisa)

Room: CNR-INO, Building A, Room 27 The talk will provide an overview of high power lasers and short pulse ultraintense lasers, also discussing key properties of amplifying lasing media for short-pulse amplification. An overview of ultraintense laser systems will be given, discussing main issues, from amplification to plasma, including focal spot quality, temporal contrast etc. Scaling of laser technology to drive future large accelerator systems will be discussed, highlighting potential and limits of existing Ti:Sa technology and reviewing other approaches for high rep-rate and high wall-plug efficiency. An overview of ongoing research projects related to laser development for EuPRAXIA and other user infrastructures will also be given.

Laser Manipulation

• Marta Fajardo (Instituto Superior Técnico)

Room: CNR-INO, Building A, Room 27

Laser beams under tight focusing conditions and electron charge diagnostics in a laser-plasma environment

• David Gregocki (Consiglio Nazionale delle Ricerche - Istituto Nazionale di Ottica)

Room: CNR-INO, Building A, Room 27 **Part I: Laser beams under tight focusing conditions** Off-axis parabolic mirrors are commonly used in high-power laser facilities for a variety of purposes, as they are able to focus laser pulses to relativistic intensities. Particularly, in the laser interaction with plasma or solids, it is highly desirable to have precise knowledge of the spatial and temporal structures of the incident laser pulse. Therefore, field distortion effects related to the use of an OAP mirror under tight focusing conditions by employing the full Stratton-Chu vector diffraction theory are presented. **Part II: Electron charge diagnostics in a laser-plasma environment** Laser-plasma accelerators are gradually gaining importance in various fields, such as medicine, due to their ability to produce very high electron beams. Because of the strict conditions put on the quality of generated electron beams, precise diagnostic tools are required. Regarding the electron charge, integrating current transformers (ICTs) are commonly used for their non-invasive nature. However, due to the transient electromagnetic waves created in the laser-plasma interaction, any electronic device in close proximity can be compromised. Therefore, an experimental investigation on the ICT capabilities in a harsh laser-plasma environment was conducted, and the results are presented.

Design and Optimization

• Sören Jalas

Room: CNR-INO, Building A, Room 27 Particle accelerators based on plasma waves promise revolutionary advancements in compact accelerator technology. To design and reliably operate these advanced accelerators, rapid yet accurate simulations and efficient optimization tools are essential. In this talk, I will provide a concise overview of the state-of-the-art in plasma accelerator modeling, highlighting fundamental simulation techniques and novel computational strategies that enable efficient exploration of vast design parameter spaces. I will discuss modern optimization and exploration techniques, particularly Bayesian optimization and surrogate modeling, and their application to accelerator design. Finally, I will demonstrate how these computational tools and optimization strategies can be effectively integrated with experimental efforts, facilitating improved experimental design, control, and efficient utilization of experimental resources.

Plasma Mirror-Enabled Non Linear Compton Scattering: An Approach to GeV scale Photon Generation

• Flanish Dsouza (Lund University)

Room: CNR-INO, Building A, Room 27

Latest trends in Laser Wakefield Acceleration

• Andrea Macchi (CNR, Istituto Nazionale di Ottica, u.o.s Adriano Gozzini, Pisa, Italy)

Room: CNR-INO, Building A, Room 27 Twenty years after the celebrated "dream beam" experiments, laser wakefield acceleration has reached new milestones. For instance in 2024 electron energies up 10 GeV were reached in two different experiments, while other parameters of beam and source quality has been improved. Such progress has been achieved by either exploiting novel ideas or putting together already known concepts for key elements such as e.g. laser pulse guiding and electron injection. Support from laser driver development and from computational advances for laser-plasma simulation and data-driven optimization was also pivotal. This talk will briefly review recent experiments in the field with an outlook towards different applications.

Discharge Plasma Source for Laser Plasma Accelerator at ELI Beamlines

• Alex Johannes Whitehead

Room: CNR-INO, Building A, Room 27 **A. Whitehead** 1,2, M. Miceski1,2, R. Demitra3,4, P. Zimmermann1, S. Niekrasz1, A. Jancarek1,2, S. Maity1, P. Sasorov1, J. T. Green1 and A. Molodozhentsev1 *1 ELI Beamlines Facility, The Extreme Light Infrastructure ERIC, Za Radnicí 835, 25241 Dolní Břežany, Czech Republic 2 Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 115 19 Prague 1, Czech Republic 3 INFN-LNF, Via Enrico Fermi 40, 00044 Frascati, Rome, Italy 4 Sapienza University of Rome, 00161 Rome, Italy* Laser-plasma accelerators have demonstrated the ability to accelerate high-energy electrons but require improved beam stability and repeatability for practical applications. Pre-formed plasma channels enhance the stability in Laser-Wakefield Accelerators by overcoming diffraction effects and maintaining laser focus over longer distances, increasing energy transfer efficiency. The characteristics of such channels are highly dependent on capillary geometry, gas parameters, discharge setup, and repetition rate. This study investigates the electron density profiles in plasma from gas-filled capillary discharges. Using Stark broadening, we measured profiles under varying conditions, achieving densities of (2−3)×1018 𝑐𝑚−3. In this presentation, we showcase the stability and uniformity of the plasma, and the necessity to use long capillaries with limited apertures to preserve beam quality in high-energy, high-repetition-rate applications. This type of plasma source is a crucial technology for the 100 Hz plasma accelerator based Free Electron Laser developed at ELI-ERIC as well as for the EuPRAXIA project.

Laser-Plasma Accelerators as Compact Radiation Sources

• Daniele Francescone (Istituto Nazionale di Fisica Nucleare)

Room: CNR-INO, Building A, Room 27 Since the invention of Chirped Pulse Amplification (CPA), laser-driven plasma acceleration (LWFA) has experienced an exponential increase in performance, leading to a growing number of applications. These extend beyond particle acceleration, positioning LWFA as a promising source of radiation across a broad spectral range, from terahertz to gamma rays, potentially serving as a viable alternative to conventional light sources. Several plasma-based emission mechanisms involved in these sources, such as bremsstrahlung, Compton scattering, and Transition Radiation, are already well-established in other fields. Among these, betatron radiation stands out as a unique feature of plasma accelerators, offering novel opportunities for compact, high-brilliance X-ray generation.

Beam Driven Plasma Sources

• Romain Demitra (Istituto Nazionale di Fisica Nucleare)

Room: CNR-INO, Building A, Room 27 This talk provides an overview of recent progress and future directions in the development of plasma sources for beam-driven acceleration. I will review key achievements in designing and testing plasma discharge systems capable of generating long, uniform plasma channels for efficient acceleration. Emphasis is placed on high repetition rate operation, where experimental studies have demonstrated promising advances in managing heat loads, optimizing vacuum integration, and mitigating material degradation. The presentation will also address the remaining challenges, including enhancing plasma stability, improving system reliability, and refining diagnostic techniques to better control plasma parameters under continuous operation. This roadmap outlines the essential steps required to advance plasma source technology toward practical implementation in next-generation accelerator facilities.

Diagnostics for beam and plasma

• Alessandro Cianchi (Tor Vergata University and INFN)

Room: CNR-INO, Building A, Room 27 Plasma-based acceleration is a promising technology for next-generation particle accelerators, enabling high-gradient acceleration over compact distances. However, accurate diagnostics are crucial to fully exploit its potential. In this talk, we will explore the diagnostics of both particle beams used to drive plasma acceleration and those accelerated within plasma structures. We will present practical examples and discuss the key characteristics required for effective diagnostics in these extreme conditions. A particular focus will be given to plasma density measurement, as it represents a fundamental parameter for the control and optimization of plasma acceleration experiments.

Solid-state plasma-based wakefield accelerators

• Bifeng Lei (University of Liverpool)

Room: CNR-INO, Building A, Room 27 The development of ultra-compact plasma-based particle accelerators is primarily beneficial from the ultra-high acceleration gradient, which is achieved through coherent plasma wave excitation driven by high-intensity beams, such as photon or charged particle beams. The acceleration field in plasma wave is dependent upon the plasma density. The current state-of-the-art gaseous plasma-based accelerators, for example, laser-driven wakefield accelerator (LWFA) or beam-driven wakefield accelerator (PWFA), practically work with the low-density classical plasma in the range from 1014 to 1018 cm-3. This density can, in principle, support an acceleration gradient of 1-100GV/m. To achieve a higher acceleration gradient, denser solid-state plasma is required, which, for example, naturally exists in metallic crystals. The density of charge carriers (conduction electrons) in these crystals ranges from 1020 to 1024 cm-3, which can support acceleration gradient in TV/m-level. In this talk, we will discuss recent scientific progress in generating extremely strong wakefields in solid-state plasmas, as well as the new opportunities and challenges presented by high-intensity lasers, high-energy beams, and novel crystal materials.

Generating VHEE Beams from a Laser-Plasma Accelerator and Characterizing their Stability for Medical Applications

• Chaitanya Varma (Laboratoire d'Optique Appliquée)

Room: CNR-INO, Building A, Room 27 Laser-driven Plasma Accelerators (LPAs) have emerged as compact (sub-)picosecond sources of Very High Energy Electron (VHEE, energy ≥ 50 MeV) beams. VHEE beams are of great interest to the medical physics community for their applications in radiotherapy in the Ultra-High Dose-Rate (UHDR) domain. Our experiments focus on optimizing VHEE beam stability and reproducibility from an LPA. Using different gas mixtures with varying N₂ concentrations (1%, 2%, and 5% N₂ in He), experimental results show stable electron beams consistently peaking around 50 MeV, with high charge-per-shot (~450 pC/shot) and minimal charge fluctuations (≤10%). Such beam stability and consistent peak energy directly contribute to improved dose accuracy and reliability, essential for clinical radiotherapy applications. Real-time diagnostics, including online spectrometry, beam profiling, and charge measurements, were developed and enabled precise control & monitoring, significantly advancing our capability to optimize beam parameters. Plasma density profiles and laser focus measurements provided necessary inputs for complementary Particle-in-Cell (PIC) simulations to investigate the underlying physical mechanisms. These advancements establish a solid foundation for active-feedback stabilization strategies and higher repetition-rate operations, essential steps toward practical medical applications. Moving forward, integrating these beam stability improvements into clinical setups and exploring robust feedback control methods remain exciting challenges.

Advances in sCVD Diamond Detectors: Quality Control, Energy Resolution, and Statistical Fluctuations

• Divya Divya (TU Wien & CIVIDEC Instrumentation GmbH)

Room: CNR-INO, Building A, Room 27 Radiation detectors based on wide-bandgap semiconductors, such as single-crystal chemical vapor deposition (sCVD) diamond, have gained significant attention due to their versatility and potential for beam monitoring in demanding environments. sCVD diamond detectors, in particular, are promising candidates for high-energy particle physics experiments, beam diagnostics in accelerator facilities, and plasma diagnostics in fusion facilities. These detectors are known for their high radiation hardness and excellent performance at elevated temperatures, making them suitable for a wide range of applications. Quality control of diamond sensors involves optical assessment of defects via microscopy, Transient Current Technique (TCT) for electron and hole movement,and IV-It measurements for dark current profiles. The energy resolution of sCVD diamond detectors, evaluated using alpha spectroscopy, is a reliable method for calibrating newly developed diamond detectors. Furthermore, we experimentally derived the statistical fluctuations in diamond and compared it to the theoretical value.

Single-shot spectrometer with pointing angle correction for laser-driven electron beams featuring moderate pointing instability and transverse inhomogeneity

• Simon Vlachos (CNR-INO)

Room: CNR-INO, Building A, Room 27 Electron beams produced via Laser WakeField Acceleration, which relies upon several nonlinear processes, can be notoriously affected by a non-negligible pointing instability, which makes the retrieval of the energy spectrum via magnetic dipole-based spectrometers particularly prone to energy miscalculations. For this reason, various spectrometer configurations have already been suggested to correct spectra for the pointing angle. Here, we experimentally demonstrate an improved scheme of a previously published concept employing two scintillating screens and a magnetic dipole in between. The first screen, providing the pointing angle, is placed upstream of the dipole, at the exit of the vacuum chamber, and the second one behind the dipole. A collimator is placed right in front of the dipole, allowing a portion of the beam to be detected, resulting in an improved energy resolution. For the electrons entering the collimator, a numerical procedure is laid out to retrieve the exact entrance angle of each transverse beamlet on the dipole, which in turn allows a weighted sum procedure to be carried out to retrieve the final spectrum. Since the first scintillator screen used in our setup results in the impinging electrons being scattered, thus ultimately acting as an energy dependent attenuator, we performed Monte Carlo simulations to account for this effect and finally corrected the observed spectrum to retrieve the actual one. The effect of such a procedure on the lower energy detection threshold for the proposed scheme is discussed.

Designing a femtosecond-resolution longitudinal profile monitor using simulated and experimental coherent transition radiation images

• Ana Maria Guisao Betancur (University of Liverpool)

Room: CNR-INO, Building A, Room 27 Ultra-short bunch length measurements with femtosecond (fs) resolution are essential for characterizing electron beams in novel accelerator experiments like EuPRAXIA and any other short pulse accelerators, such as Free Electron Lasers (FELs). This contribution shows the progress towards a non-invasive and single-shot longitudinal profile monitor by showcasing a prototype of a broadband imaging system for Coherent Transition Radiation (CTR) recently installed at the MAX IV Short Pulse Facility. A THz-based imaging system was designed and tested using optical system simulation software, and preliminary CTR images were captured experimentally. This talk will cover the processes behind conceptualizing the bunch length monitor, the current experimental setup, supporting simulation work, and the system's installation. It will also provide an early preview of the data acquired experimentally and a discussion on the considerations for future iterations of the prototype aimed at the monitor being less invasive, achieving higher resolution, and exploring alternative design options.

Measurement of femtosecond incoherent XUV pulses using shot-noise-driven fluctuations in plasma betatron sources

• Alessandro Curcio (Istituto Nazionale di Fisica Nucleare)

Room: CNR-INO, Building A, Room 27 The duration of incoherent XUV pulses down to the femtoseconds (fs) can be retrieved through a statistical analysis of the modulations on the observed radiation spectrum. Uncorrelated shot-noise fluctuations in the pulse temporal profile result in incoherent radiation showing a multispike spectrum where the spike width is inversely proportional to the pulse length. In this Letter, single-shot temporal characterization of the betatron radiation pulses emitted by fs-long, 100’s MeV electron bunches undergoing acceleration, and propagating through a plasma wiggler was performed in the XUV domain. The retrieved pulse lengths agree with independent measurements performed in the THz spectral range and with theoretical predictions.

Synchronization in plasma accelerators

• Luca Piersanti (Istituto Nazionale di Fisica Nucleare)

Room: CNR-INO, Building A, Room 27 This presentation provides an overview of synchronization systems for plasma accelerators, focusing on the critical role of phase stability in ensuring the successful operation of these advanced facilities. We begin with an introduction to the fundamentals of phase noise in oscillators, including its sources and methods of measurement, which are essential for understanding the challenges faced in advanced accelerator facilities. The core of the presentation describes the main building blocks of synchronization systems, with examples drawn from current state-of-the-art, highlighting the latest advancements and their practical implementations. Finally, we review accelerator facilities worldwide, showcasing those with the highest performance in terms of synchronization, while also discussing the challenges that future plasma accelerators will pose to synchronization systems. This presentation aims to offer insights into the evolving landscape of synchronization technologies and their pivotal role in the development of next-generation plasma accelerators.

Status of X-Band LLRF Prototype Development

• Phani Deep Meruga

Room: CNR-INO, Building A, Room 27 EuPRAXIA@SPARC_LAB is the next generation free-electron laser (FEL) aimed at developing a compact, cost-effective particle accelerator based on the wake-field accelerator technology. High-energy physics demands higher acceleration voltages and advancing accelerator technology to higher frequencies enables the achievement of high gradients within shorter accelerating structures. The LINAC injector at EuPRAXIA@SPARC_LAB includes a dedicated X-band section, which contributes to achieving a maximum beam energy of 1 GeV. Low-Level Radio Frequency (LLRF) systems are essential for RF station synchronization and ensuring machine stability with femtosecond precision. This project, in context of the EuPRAXIA-DN, focuses on developing an X-band LLRF prototype tailored to meet the requirements of the EuPRAXIA@SPARC_LAB LINAC. This talk will present the development approach and implementation of the X-band LLRF prototype, covering the prototype requirements, detailed architecture and RF signal distribution. Additionally, a detailed analysis of laboratory results obtained at Instrumentation Technologies will be presented and discussed.

Development of a Gas-Jet based Ionization Profile Monitor for Proton FLASH Therapy

• Farhana Thesni Mada Parambil (University of Liverpool/ Cockcroft Institute)

Room: CNR-INO, Building A, Room 27 The global acceptance of proton therapy for cancer treatment due to the conformal dose delivery to the tumour and effective sparing of normal tissue, by the benefit of Bragg peak, has been significantly increased recently. This further lead into the development of advanced treatment delivery techniques such as proton FLASH therapy utilising instantaneous Ultra High Dose Rates. With the FLASH effect, a better Tumour Control Probability (TCP) to Normal Tissue Complication Probability (NTCP) ratio can be achieved, which indicates the improved Organ at Risk (OAR) sparing than the conventional proton therapy. One of the technical challenges to establish FLASH protons are the limited dosimetry of the high intense proton beams with short pulse width, especially for laser-driven protons. Most of the dosimetry methods are either saturates or erroneous for these proton beams. In this study, a gas-jet based minimally invasive beam profile monitor is introduced with the end goal of real-time monitoring. The working principle of gas-jet based IPM monitor is detecting the ionization of gascurtain caused by the incident ion beam, while preserving the profile information of the ions. The produced ions are further drifted towards the detector mounted at the top of the drift region with the help of an external electric field. The Micro-Channel Plate (MCP)- phosphor screen assembly amplifies the signal and produce the beam profile, which can be then captured by CMOS camera mounted on the detector system. The beam-profile measurement done at the University of Birmingham ensures the suitability of the system for proton beams at energies 10.8, 16, 20 and 28 MeVs. The existing Detection part of the system modified to generate a compact extraction system, vacuum chamber and a high gain MCP-phosphor screen assembly. The modified design will be assessed to check the feasibility of easy integration with the medical accelerators and will address the space limitation. The CST simulations were performed for the previous and upgraded designs with a target to reduce the size by 25% and to have the similar uniform electric field distribution along the drift region. The energy gained by the ions at the MCP is kept as 2 keV, which will ensure the detection efficiency of 85%. A significant inhomogeneity in energy distribution at the MCP around ±7% or more was found for the beam sizes from 10 mm. This will be addressed in the future design by adjusting the geometry and bias potential for the plates in order to focus the beam to obtain less uncertainty in the energy distribution. The shift in trajectory due to the directional velocity of the gas-jet was reflected in the profile. It is not affecting the measurement of beam profile. But need to quantify the shift to get the precise beam position. The effect of beam fluctuations, ion states, space charge effect of the beam and the realistic density distribution of gas curtain will be accounted for future studies.

Putting it all together / Discussion

• Carsten Peter Welsch

Room: CNR-INO, Building A, Room 27