NUSPIN 2016 Workshop of the Nuclear Spectroscopy Instrumentation Network and AGATA Physics Workshop

27 Jun 2016, 13:00 → 1 Jul 2016, 13:00 Europe/Rome

San Servolo, Venice

S.M. Lenzi (PD)

The Nuclear Spectroscopy Instrumentation Network (NuSpIn), in the framework of ENSAR2 (HORIZON2020), promotes the mutual coordination between the research groups involved in high-resolution gamma-ray spectroscopy. The objective is to strengthen the nuclear structure community by the exchange and transfer of knowledge and the enhancement of synergies between the different collaborations active in the European Infrastructure Facilities. The aim of the NUSPIN 2016 Workshop is to present the status of nuclear structure research in Europe and to discuss its perspectives. Sessions will be dedicated to the presentation of recent theoretical studies, the latest results obtained at the gamma-ray facilities in Europe, and the discussion of the challenges of future research, the development of new instrumentation and technical developments with gamma-ray techniques and particle detectors. The main topics to be discussed at the workshop are: • shell structure far from stability • isospin degrees of freedom • collective excitations • nuclear moments • spectroscopy with radioactive ion beams • superheavy nuclei • nuclear astrophysics • gamma-ray detectors technology • complementary instrumentation Review talks are planned with ample time scheduled for discussion. These reviews will be followed by shorter contributions selected from the submitted abstracts. The deadline for abstract submission is 6th May 2016. Information regarding the abstract selection will be notified to the contributors by 13th May 2016. AGATA Physics Workshop and Annual Meeting of the AGATA Collaboration. The afternoon of Thursday 30th June and the morning of July 1st will be dedicated to an AGATA Physics Workshop, followed by the Annual Meeting of the AGATA Collaboration, and the meeting of the AGATA Collaboration Council. Meetings of the NUSPIN Scientific Committee and the Working Groups. The afternoon of Tuesday 28th June will be devoted to the meetings of the NUSPIN Scientific Committee and of the Working Groups coordinating the instrumentation developments.

Slides accommodation_NUSPIN_2016.pdf

Monday, 27 June

Registration

Physics of neutron-rich nuclei

Convener: Giacomo De Angelis (LNL)

1 Welcome

Speaker: Prof. Silvia M. Lenzi (PD)

Slides Lenzi.pdf

2 The Inversion Archipelago at The Neutron Rich Shores

I will discuss the physical origin of the Islands if Inversion/Deformation which occur at different neutron magic numbers for very neutron rich isotopes and its connection with shape coexistence in doubly magic nuclei. I will present our predictions for a new IoI at N=50 which should add to the well known ones at N=8, 20, 28 and 40.

Speaker: Prof. Alfredo Poves (Universidad Autonoma de Madrid)

Slides APoves.pdf

3 ISOLDE physics in the HIE-ISOLDE era

The HIE-ISOLDE upgrade of the post-accelator LINAC complex at ISOLDE aimed to increase the intensity and energy of post-accelerated beams at the ISOLDE facility, CERN. With a projected energy of 12 MeV/U for beams of A/q up to 4.5 the HIE-ISOLDE facility will allow users to study entirety of the species available at ISOLDE. After the two year Long Shutdown 1 at CERN the first HIE-ISOLDE superconducting cavity was manufactured, tested and installed after the REX-ISOLDE linac. Fall of 2015 saw the final commissioning and first post accelerated radioactive beams for users. The structure of neutron rich nickel isotopes was studied using Coulomb excitation. A very successful program with low energy beams was run at ISOLDE parallel with the construction and commissioning of the HIE-ISOLDE linac. Highlights of the study of ground state properties using mass and laser spectrometry, as well as nuclear structure studies from beta-decay will be presented.

Speaker: Dr Miguel Madurga (CERN)

Slides Madurga.pdf

4 Shape coexistence in neutron-rich Strontium isotopes at N=60

Neutron-rich A~100 nuclei are among the best examples of interplay of microscopic and macroscopic effects in nuclear matter. A dramatic onset of quadrupole deformation is observed in the neutron-rich Zr and Sr isotopes at N=60, making this region an active area of experimental and theoretical studies. This rapid shape transition is accompanied by the appearance of low-lying 0+2 states that, for N<60, can be interpreted as a deformed configuration that becomes the ground state at N=60, while the spherical ground-state configuration of the isotopes with N<60 becomes non-yrast for those with N≥60. Low-energy Coulomb excitation experiments were to study properties of coexisting structures in 96,98Sr (N=58,60) using post-accelerated exotic Sr beams from REX-ISOLDE. The experiments were carried out in the particle-gamma coincidence mode using the MINIBALL HPGe array coupled to an annular Double Sided Silicon Detector. Several different targets were used in order to make use of the dependence of the Coulomb excitation cross section on the atomic numbers of collision partners: 109Ag and 120Sn in the case of 96Sr, 60Ni and 208Pb for 98Sr. For 96Sr, the 2+1→0+1 transition was observed together with excitation of target nuclei and a weak transition corresponding to the 0+2 deexcitation. For 98Sr, the rotational ground-state band was populated up to spin 8+, and the decay of the 2+2 state was also observed. Reduced transition probabilities and spectroscopic quadrupole moments were extracted from the measured differential Coulomb excitation cross sections. The results support the scenario of shape transition at N=60 giving rise to coexistence of two very different configurations in 96,98Sr. In 96Sr, the spectroscopic quadrupole moment of the first 2+ state was found to be small and negative, corresponding to a weak prolate deformation. In 98Sr, the large and negative spectroscopic quadrupole moments in the ground state band prove its well-deformed prolate character, while the value close to zero obtained for the 2+2 state confirms that a spherical configuration coexists with the deformed configuration of the ground state. The comparison of the B(E2) values and the spectroscopic quadrupole moments between the 2+1 state in 96Sr and the 2+2 state in 98Sr underlines their similarity and further supports the shape inversion when crossing the N=60 line. Furthermore, a very small mixing between the coexisting structures was determined from measured intra-band transition probabilities in 98Sr. This effect has been attributed to the rapidity of the shape change at N=60: a larger mixing would give rise to a more gradual transition from spherical to deformed ground state in Sr isotopes, like what is observed in other areas of shape coexistence, for example neutron-deficient Kr and Hg isotopes. The experimental results, together with a detailed comparison with new beyond-mean-field calculations, will be presented. The present work will be also highlighted in a larger framework of the shape change in the mass region.

Speaker: Dr Emmanuel Clement (GANIL)

Slides clement.pdf

5 Collectivity of 4+ states in heavy Zn isotopes and the first HIE-ISOLDE experiment

Shell evolution in the vicinity of 68Ni has recently attracted many theoretical and experimental investigations. By now it has been clearly established that the presumed subshell closure at N=40 is not very pronounced. While the intruder character of the 1g9/2 and 2d5/2 neutron orbital induces collectivity by pair excitations from the fp shell into the g9/2 orbital, the parity change hinders quadrupole excitations and therefore mimics the properties of a doubly magic nucleus in 68Ni, i.e., a high 2+1 energy and a low B(E2; 2+ → 0+) value. Adding valence nucleons to the N=40 open shell leads to a rapid increase of collectivity, with an interplay of both collective and single-particle degrees of freedom. Such rapid changes indicate underlying complex effects and make this region ideal for testing theoretical calculations. While measurements of B(E2; 2+→ 0+) values are useful to investigate the evolution of collectivity along isotopic chains, even more insight into the collective behavior can be gained by measuring lifetimes of higher-lying states. Almost all stable Zn isotopes present an anomalously low B(E2; 4+ → 2+)/ B(E2; 2+ → 0+) ratio of 1 or less, which is normally observed only around closed shells. Coulomb excitation studies at ISOLDE (74,76Zn [1]) as well as a DSAM lifetime measurement in 70Zn [2] suggested an important increase of collectivity of the 4+ state for heavy Zn isotopes with a maximum at N=40. However, a recent RDDS lifetime measurement performed with AGATA Demonstrator in Legnaro [3] yielded lifetimes of the 4+ states in 70-74Zn that are considerably longer and correspond again to B(E2; 4+ → 2+)/ B(E2; 2+ → 0+) ratio lower than 1. This has been confirmed by the results of another RDDS measurement performed at GANIL [4] for 70,72Zn. The observed discrepancy between lifetime and Coulex data triggered further measurements of transition probabilities in heavy Zn isotopes. In order to decide between the two experimental values of B(E2; 4+ → 2+) in the heaviest stable zinc isotope 70Zn, a dedicated Coulomb excitation measurement was carried out at HIL Warsaw. Very recently, Coulomb excitation studies of neutron-rich 74,76Zn nuclei were performed at HIE-ISOLDE as the very first experiment at this facility. Preliminary results from Coulex analysis and future perspectives will be discussed. [1] J. Van de Walle et al., Phys. Rev. C79 (2009) 014309 [2] D. Muecher et al., Phys. Rev. C79 (2009) 054310 [3] C. Louchart et al, Phys. Rev. C87 (2013) 054302 [4] I. Celikovic et al, Acta Phys.Pol. B44, 375 (2013)

Speaker: Dr Magda Zielinska (CEA Saclay)

Slides Zielinska.pdf

16:00 Coffee break

Nuclear Structure with Radioactive beams

Convener: Prof. Jan Jolie (Institut für Kernphysik, Universität zu Köln)

6 Recent Results and Perspectives of Gamma-ray Spectroscopy at the RIBF

At the Radioactive Isotope Beam Factory (RIBF), in-beam spectroscopy is employed since 2008 with the NaI(Tl)-based DALI2 array and decay spectroscopy with the Ge-based EURICA array since 2012. Since then, a variety of experiments has been performed at maximum isospin across the nuclear chart. In the talk, the two setups will be introduced and recent highlights presented. Furthermore, the perspectives of the two methods, in-beam and Ge-spectroscopy will be discussed based on the expected beam intensity and energy developments at the RIBF and future detector developments.

Speaker: Dr Pieter Doornenbal (RIKEN)

Slides Doornenbal.pdf

7 New developments of the Recoil Distance Doppler-Shift method

In this presentation we give an overview of recent developments for measurements with the recoil distance Doppler-shift method (RDDS) by our group. We will present a new plunger device for RDDS experiments at the GALILEO spectrometer at LNL and its performance in a recent commissioning experiment. We will report on RDDS measurements on exotic nuclei in the latest campaigns at GANIL with AGATA coupled to the magnetic spectrograph VAMOS where the Cologne plunger for deep inelastic reactions was successfully used. Within this context special respect will be paid to a very recent experiment of our group on neutron rich nuclei around 54Ti. We will also discuss target problems that appeared during this experiment. Further, new plunger devices will be reviewed that are developed by our group for future experimental campaigns with stable and radioactive beams in different energy regimes, for example, a plunger for HIE-ISOLDE. Supported by the BMBF, Grant No. 05P15PKFNA and 05P15PKCIA and the DFG, Grant No. DE 1516/3-1.

Speaker: Dr Christoph Fransen (Institut für Kernphysik, Universität zu Köln, Cologne, Germany)

Slides Fransen.pdf

8 Coulomb excitation of superdeformed states in 42Ca

A Coulomb excitation experiment to study electromagnetic properties of the strongly-deformed band in 42Ca and its coupling to yrast states was performed at the Laboratori Nazionali di Legnaro in Italy using the gamma-ray spectrometer AGATA Demonstrator and the DANTE charged particle detector array. Gamma rays from Coulomb excited 42Ca nuclei were measured in coincidence with calcium projectiles back-scattered on 208Pb and 197Au targets and detected by three position-sensitive MCP detectors forming the DANTE array. For this study, the AGATA Demonstrator spectrometer consisting of three clusters was used for the first time in a nuclear physics experiment. The motivation for this measurement was the observation of a rotational structure in 42Ca, which is similar to previously identified super-deformed bands in several A~40 nuclei, such as 40Ca, 36,38Ar, 44Ti. Lifetime measurements in 42Ca using the Doppler-shift attenuation method suggest a smaller deformation of the band built on the second 0+ state (1837 keV) than in the case of 40Ca. On the other hand, the moment of inertia of this band was found to be very similar to the one of the super-deformed band in 40Ca. Another argument for the highly-deformed character of this band was the observation of its preferential feeding by the low energy component of the highly split GDR decaying from 46Ti. In the present experiment, Coulomb excitation was used for the first time to populate the highly-deformed band and to study its decay. Shape parameters of a weakly-deformed ground-state band and highly-deformed slightly triaxial side band in 42Ca were determined from E2 matrix elements measured in the first low-energy Coulomb excitation experiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell model and beyond-mean-field calculations. In this talk the experimental evidence for superdeformed and slightly triaxial character of the band built on the excited 0+ state will be discussed.

Speaker: Dr Katarzyna Hadynska-Klek (INFN LNL, Italy)

Slides Hadynska.pdf

9 Nuclear Spectroscopy with Stable and Radioactive Beams at ALTO

ALTO is a facility that provides a variety of stable and radioactive beams for studies in the domain of nuclear structure, astrophysics, astrochemistry, atomic physics, biology, nano-technology, etc. Stable light- and heavy-ion beams as well as clusters are produced using a 15MV Tandem accelerator. The low-energy radioactive beams are produced using the photo-fission of uranium, induced by the bremsstrahlung of a 50 MeV impinging on an UCx target. The gamma-ray spectroscopy has always been one of the main driving horses of the facility with a number of Ge-detectors arrays utilized. Results from the ORGAM and MINORCA campaigns will be presented and the plans for the use of the PARIS and the nu-ball spectrometers in near future will be discussed. Presently a number of developments at ALTO are being pursued in the direction of nuclear-moment and transition-probability investigations. The ideas and the possibilities for these studies with both stable and radioactive beams at ALTO or at other RIB facilities will be presented.

Speaker: Dr Georgi Georgiev (CSNSM)

Slides Georgiev.pdf

Tuesday, 28 June

Radioactive Beam Facilities

Convener: Prof. Berta Rubio (CSIC Valencia)

10 Shell-model applications to gamma-ray strength function and level density

The nuclear shell model is a very powerful tool to study low-lying level structure in nuclei including very unstable ones, whereas its application to higher excited energy region has been rather limited. This is primarily because a very large model space is required to describe such highly excited levels. Recently, one of my colleagues has developed a large-scale shell-model code named KSHELL which is suited for running on a massively parallel computer such as the K supercomputer in Japan. In the present talk, I will show some of its recent applications to gamma-ray strength function and level density for pf-shell nuclei, adopting the full 1-hbar-omega model space or beyond. One of the advantages of the shell-model approach is that one can obtain most of the energy levels including non-collective ones. Indeed, it is demonstrated that nuclear level density is very well described with large-scale shell-model calculations combined with a new stochastic method. As a result, the low-energy tail of the giant resonance, which is composed of the coupling to non-collective levels, is well described. Another advantage of the shell model is that one can easily calculate transition probabilities between excited states. Taking this advantage, we will also discuss some decay properties and giant resonances on top of excited states.

Speaker: Dr Yutaka Utsuno (Japan Atomic Energy Agency)

Slides 28m01_Utsuno.pdf

11 Status and future plans of GANIL- SPIRAL2

Recent results related to study of nuclei far from stability obtained at the GANIL facility [1] will be presented. A short and middle-term scientific program of the current facility and, in particular, the AGATA campaign at GANIL will be put in the perspective of the present and futures research program of the GANIL-SPIRAL2 facility. An ambitious scientific program at GANIL/SPIRAL2 imposes a use of the most efficient and innovative detection systems as a new separator/spectrometer S3, the upgraded magnetic spectrometer VAMOS, the 4π gamma-array EXOGAM2 and the European gamma-ray tracking array AGATA as well as charged particle detectors like ACTAR-TPC, FAZIA and GASPARD/MUGAST. A status of the construction of the SPIRAL2 facility and future operation modes of the GANIL/SPIRAL2 complex as a multi-user facility will be shortly presented. [1] http://pro.ganil-spiral2.eu/

Speaker: Dr Gilles de FRANCE (GANIL)

Slides 28m02_DeFrance.pdf

12 The SPES radioactive ion beam project. Status and perspectives

Speaker: Giacomo De Angelis (LNL)

Slides

• 28m03a_de_Angelis.pdf
• 28m03b_de_Angelis.pdf
• 28m03c_de_Angelis.pdf
• 28m03d_de_Angelis.pdf

13 Perspectives for gamma-ray spectroscopy at FAIR

Nuclear structure studies at FAIR will be pursued within the NUSTAR scientific pillar. Gamma-ray spectroscopy in particular is dealt with in the HISPEC/DESPEC project. The HISPEC experiment aims for in-beam investigations, employing exotic heavy-ion beams both at relativistic and at Coulomb barrier energies. The high-energy programme at the Super-FRS of FAIR will employ the AGATA gamma tracking detector array and the LYCCA particle detection array combined with a large acceptance dipole magnet for the unique determination of projectile-like particles to distinguish Coulomb excitation, knock-out and secondary fragmentation reactions. In addition a slowed-down beam set-up with ultrathin particle detectors will enable studies using classical reaction types, i.e. transfer, multiple Coulomb excitation, deep inelastic reactions. DESPEC decay spectroscopy, in particular following beta- and alpha-decay will be possible with the active implantation set-up AIDA in combination with the compact DEGAS gamma array. DEGAS will have a significantly higher efficiency and sensitivity as the current benchmark array RISING. The active/passive shielding of DEGAS will open new perspectives for isomer decay experiments. The set-up is planned to be already available for experiments from 2018 on at the FRS of GSI, employing the high beam intensities from SIS18, the upgraded injector of the FAIR facility. The physics programme will concentrate on very heavy nuclei far off stability, with investigations of isotopes around N=126, important for our understanding of the r-process nucleosynthesis.

Speaker: Dr Juergen Gerl (GSI)

Slides 28m04_Gerl.pdf

11:00 Coffee break

Radiatiactive Beam and Istrumentation

Convener: Silvia Leoni (MI)

14 The FRIB project and prospects for gamma-ray spectroscopy

The Facility for Rare Isotope Beams (FRIB) is presently under construction on the Michigan State University campus adjacent to the National Superconducting cyclotron Laboratory (NSCL). FRIB will provide fast, stopped, and reaccelerated beams of rare isotopes at intensities exceeding NSCL's capabilities by three orders of magnitude. An outlook will be provided on the enormous opportunities that will arise upon completion of FRIB in the early 2020s, with a particular focus on the prospects for gamma-ray spectroscopy.

Speaker: Dr Alexandra Gade (MSU)

Slides 28m05_Gade.pdf

15 Developments and perspectives with the FATIMA array

FATIMA is an array of LaBr3-Ce detectors that has been constructed as part of the DESPEC experiment at NUSTAR. The array will be used with the AIDA implantation detector at the focal plane of the super-FRS to measure sub-nanosecond lifetimes of levels in exotic nuclei. In preparation for operation at NUSTAR, a portion of the array has been utilised in experiments e.g. at RIKEN and at the Argonne National Laboratory where it has operated in coincidence with an array of germanium detectors (EURICA and Gammasphere respectively). Information will be presented about the design of the array and results of the experiments at RIKEN and at Argonne will be discussed.

Speaker: Prof. Alison Bruce (University of Brighton)

Slides 28m06_Bruce.pdf

16 The PARIS array – concept, status and first experiments

The PARIS (Photon Array for studies with Radioactive Ion and Stable beams) is the gamma calorimeter under construction within large international collaboration, for experiments at GANIL/SPIRAL2 and other European and worldwide nuclear physics facilities. It is a modular detector, each module is a rectangular detector based on the phoswich concept – made from 2 connected scintillators: LaBr3 and NaI. 9 phoswiches are grouped in the 3x3 matrix, forming one cluster. In the talk the current status, as well as the timeline of the PARIS construction will be presented. In addition the experimental program, including the first experiment, will be discussed.

Speaker: Prof. Adam Maj (IFJ PAN)

Slides 28m07_Maj.pdf

17 Perspectives of high spin gamma-ray spectroscopy of heavy nuclei produced in fusion-evaporation reactions using GALILEO/AGATA arrays and the Recoil Filter Detector at stable and radioactive beams.

Great progress in understanding of both individual excitations of nucleons and collective phenomena has been made possible by use of germanium multi-detector arrays. However, the still new information on those excitations is often hard to reach for heavy nuclei (A>200) due to a strong background caused by fission. An observation of properties of such nuclei populated in heavy ion induced fusion-evaporation reactions with only of a few microbarns cross-section can be possible when filtering by detecting the recoiled nuclei after particle evaporation. A considerable improvement of a selectivity can be achieved when gamma-rays are detected in coincidence with those evaporation residues. The coincidence condition allows to suppress gamma-rays from competing fission and, moreover, from transfer processes, Coulomb excitation, target contaminations, etc. For lighter fast recoiling evaporation-residues the determination of the velocity vector of recoils in event-by-event mode allows for significant Doppler broadening reduction which can lead to considerable improvement in the gamma energy resolution, especially when high energy gamma-rays are emitted. The Recoil Filter Detector (RFD) measures evaporation residues in coincidence with gamma-rays detected in a germanium array. It was used in several experiments as an ancillary detector for EUROBALL and GASP. At present, an application of the RFD at GALILEO is proposed. In the talk will be given an overview of the RFD, it’s so far performance in-beam and the new application at the GALILEO setup. A perspective of using the RFD in studies of heavy evaporation residues produced with radioactive beams at very high spins will be also discussed.

Speaker: Dr Piotr Bednarczyk (IFJ PAN, Krakow)

Slides 28m08_Piotr.pdf

13:00 Lunch break

Meeting of Working Groups

NUSPIN Scientific Committee Meeting

16:00 Coffee break

Meeting of Working Groups: continuation

NUSPIN Scientific Committee Meeting: continuation

Wednesday, 29 June

Nuclear Structure and Reactions I

Convener: Dr Gilles de France (GANIL)

18 Direct Reactions for Nuclear Spectroscopy

Several direct reaction mechanisms have emerged as providing valuable and reliable nuclear spectroscopy information that contributes to our understanding of the evolution of shell structure in some of the most exotic light and medium mass nuclei - as are produced at fragmentation facilities. These mechanisms include Coulomb and nuclear dissociation, the fast nucleon removal mechanism, and light-heavy-ion induced transfer (pickup) reactions. Furthermore, if used in combination, these different reaction mechanism sensitivities can prove highly complementary and remove ambiguities. These reactions and their sensitivities will be reviewed through the use of examples of recent applications to studies of very weakly-bound (Ne isotopes) and more well-bound (N~28) neutron-rich systems.

Speaker: Prof. Jeffrey Tostevin (University of Surrey, UK)

Slides 29m01_Tostevin.pdf

19 Status of the NuPECC long range plan

This talk is intended to present the status of the preparation of the Long Range Plan of NuPECC. The focus will be in particular on the chapters concerning nuclear structure and reaction dynamics, nuclear astrophysics and applications. Many scientific and technical issues discussed in this meeting represent important material for the NuPECC long range plan and this will be highlighted in the presentation. The aim is to motivate discussions with the participants on this important work which will define the future of our field.

Speaker: Prof. Angela Bracco (Università di Milano and INFN)

Slides 29m02_Bracco.pdf

20 GRETINA: Status and Recent Results

GRETINA [1] is a first implementation of a gamma-ray spectrometer which is capable of tracking gamma-rays through its active detector volume. It currently consists of eight, four-detector modules. Each crystal (6x6 segments) is individually encapsulated with all four crystals sharing a common cryostat. The irregular, tapered hexagonal geometry packs into a spherical shell with the eight modules spanning just over 1π solid angle. GRETINA was constructed and commissioned at LBNL, and has already completed two physics campaigns, at NSCL/MSU and at ATLAS/ANL. I will give a short overview of the project, discuss some of the technical aspects and the performance of the array, and present highlights from the experimental program above. Future plans for GRETINA as well as its evolution into GRETA, a full 4π array, will also be discussed. [1] S. Paschalis, I.Y.Lee, A.O.Macchiavelli, et al. NIM A709 (2013) 44-55

Speaker: Dr Augusto Macchiavelli (Lawrence Berkeley National Laboratory)

21 Experiental Studies of Isospin-Breaking Interactions

See attached file

Speaker: Prof. Michael Bentley (University of York)

Slides 29m04_Bentley.pdf

22 Isospin Symmetry Breaking in Mirror Nuclei 23Mg − 23Na

The differences between the excitation energy of analogue states, called mirror energy differences (MED), are an important signature of isospin symmetry breaking and constitute a very delicate probe of several nuclear structure properties. We present the results of an experiment performed in GANIL to study isospin symmetry breaking in mirror nuclei 23Mg − 23Na up to high spin. Experimental MED values are compared with state-of-the-art shell model calculations. This permits to enlighten several nuclear structure properties, such as the way in which the nucleons alignment proceeds, the radius variation with J, the role of the spin-orbit interaction and the importance of isospin symmetry breaking terms of nuclear origin.

Speaker: Alberto Boso (PD)

Slides 29m05_Boso.pdf

11:10 Coffee break

Nuclear Structure with Stable Beams

Convener: Dr Araceli Lopez-Martens (CSNSM/JYFL)

23 Shape coexistence effects on isospin-symmetry breaking and beta decay of proton-rich A~70 nuclei

Proton-rich nuclei in the A$\sim$70 region manifest exotic structure and dynamics generated by the interplay of shape coexistence and mixing, competing like-nucleon and neutron-proton T=1 and T=0 pairing correlations, and isospin-symmetry-breaking interactions. Their properties could bring insights into fundamental symmetries and interactions of relevance for the astrophysical $rp$ process. In particular the $\beta$-decay properties of the Z=N+2 members of the isovector triplets are expected to reveal fingerprints of T=0 pairing. Self-consistent results on isospin-related phenomena in A$\sim$70 nuclei within $complex$ Excited Vampir beyond-mean-field model using an effective interaction derived starting from Bonn CD potential have been recently obtained [1]. Weak interaction rates under terrestrial and stellar conditions have been also investigated [2]. We will present an unitary scenario of these related phenomena suggesting challenges for future experiments according to our predictions.\\ \noindent [1] A.~Petrovici, Phys. Rev. C {\bf 91}, 014302 (2015).\\ \noindent [2] A.~Petrovici and O. Andrei, Phys. Rev. C {\bf 92}, 064305 (2015). \\

Speaker: Prof. Alexandrina Petrovici (IFIN-HH)

Slides Petrovici.pdf

24 In-beam gamma ray and conversion electron spectroscopy at JYFL

The Accelerator Laboratory at the University of Jyväskylä has a long history in studies of nuclear structure through in-beam gamma ray and internal conversion electron spectroscopy. After starting with devices operated "stand-alone" the modest DORIS array was coupled to the gas-filled recoil separator RITU for studies using the Recoil-Decay Tagging technique in the early 1990s. Since those times, developments at JYFL have slowly progressed using the JUROSPHERE, JUROGAM and JUROGAMII arrays of germanium detectors. In parallel, internal conversion electron studies were carried out with the SACRED electron spectrometer, which was also coupled to RITU. Finally, the two techniques were combined to form the SAGE spectrometer for combined gamma ray and conversion electron studies. In future, experimental campaigns using the recently commissioned MARA mass spectrometer are envisaged. An overview of highlights from recent studies and an outlook to future perspectives at JYFL will be presented.

Speaker: Prof. Paul Greenlees (University of Jyväskylä)

Slides 29m07_Greenless.pdf

25 Lifetimes of nuclear states in proton-emitting nuclei from Differential Plunger measurements.

Over the last few years, a programme of research at the University of Jyvaskyla, Finland has established the first measurements of the nuclear state lifetimes built above proton emitting states [1-5]. Lifetimes have been deduced in several nuclei; 109I [1], 151Lu [2,3] and 113Cs [4] for the first time using a specially constructed Differential Plunger for Unbound Nuclear States (DPUNS) plunger [5]. The new experimental results have led to the development of a non-adiabatic quasi-particle code which has been required to explain proton emission based on the experimentally deduced deformations extracted from the lifetime measurements. This talk will show how the new lifetime values for the ground- and isomeric-state proton decays in 151Lu are best interpreted by a mildly oblate deformation, settling a long-standing theoretical debate about the shape of 151Lu. The very recent lifetime results for the more deformed proton emitter 113Cs will also be discussed. In this case the wavefunctions extracted from the non-adiabatic quasi-particle code were used separately to evaluate both proton emission and gamma-ray transition rates as a function of deformation. In this study, a consistent quadrupole deformation was found to match both the experimental proton emission half-life and the lifetime of the electromagnetic state in 113Cs. This deformation is in agreement with the earlier proton emission studies, but is now more firmly supported based on the measured electromagnetic transition rates. [1] M. Procter, D.M. Cullen et al. Phys. Lett. B704 (2011) 118–122. [2] M. Procter, D.M. Cullen et al. Phys. Lett. B 725 (2013) 79–84. [3] M. Taylor, D.M. Cullen et al. Phys. Rev. C 91, 044322 (2015). [4] D. Hodge, D.M. Cullen et al. To be submitted to Phys. Rev. C. May 2016. [5] M. Taylor, D.M. Cullen et al. Nuclear Instr. and Methods in Phys. Res. A 707 (2013) 143–148.

Speaker: Dr David Cullen (The University of Manchester)

Slides cullen.pdf

26 Effect of high-j orbitals on the high-spin states in nuclei around Z = 82

Speaker: Mr Tanmoy Roy (Variable Energy Cyclotron Centre)

Slides Tanmoy.pdf

13:05 Lunch break

Nuclear Instrumentation

Convener: Dr Juergen Eberth (University of Cologne)

27 Total absorption studies of beta decays for applications and nuclear structure

Gamma-ray detection plays a key role in many experimental nuclear physics studies and practical applications. As an example in this talk I will present recent results of the application of the total absorption technique to beta decay studies, which are relevant for reactor applications. The total absorption technique is based on the use of highly efficient, calorimeter-like detectors. It aims for the detection of the full gamma cascades that follow the beta decay. The application of this technique is presently the only way we know to avoid the Pandemonium effect; a systematic error associated to the low peak efficiency of high-resolution gamma setups. Avoiding Pandemonium is necessary for practical applications like the prediction of the decay heat in a reactor during operation and after shut down, and the prediction of the neutrino-spectrum from a reactor. I will present some of the examples of studies we have performed recently along this line, discuss their impact and show their implications for nuclear structure and astrophysics.

Speaker: Prof. Berta Rubio (CSIC Valencia)

Slides 29m10_Rubio.pdf

28 Probing nucleon-nucleon correlations in heavy ion transfer reactions

Transfer reactions play an essential role in the understanding of collision dynamics and nuclear structure. Low energy multinucleon transfer reaction is one of the most important tool to probe nucleon-nucleon correlations in nuclear systems. The recent revival of transfer reaction studies greatly benefited from the construction of the new generation instrumentations that reached an unprecedented efficiency and selectivity. Transfer cross sections obtained from excitation functions for the closed shell 40Ca+96Zr and super fluid 60Ni+116Sn systems have been measured from the Coulomb barrier energy to energies corresponding to very large distances of closest approach where the nuclear absorption is negligible. We also performed a gamma-particle AGATA-PRISMA coincidence experiment for the 60Ni+116Sn system in order to investigate the ground and excited state population of the two-neutron transfer channel. The experimental transfer probabilities have been compared with microscopic calculations that incorporate nucleon-nucleon correlations, essential for the population pattern of the single particle levels around the Fermi energy. These calculations very well reproduce the experimental data in the whole energy range. In particular, for the first time in a heavy ion collision, one- and two-neutron transfer channels have been very well reproduced in shape and magnitude.

Speaker: Dr Suzana Szilner (Ruder Boskovic Institute)

Slides szilner.pdf

29 FIssion Product Prompt gamma-ray Spectrometer, a new instrument for the ILL

FIPPS (Fission Product Prompt gamma-ray Spectrometer) is a new instrument under construction at the ILL in the context of ILL ENDURANCE program. FIPPS addresses two fundamental domains of nuclear physics: fission of heavy elements and structure of neutron rich matter. Neutron capture induced reactions provide a suitable way to investigate these domains. FIPPS will complement the existing Nuclear Physics instrument suite at the ILL. FIPPS consists of a high efficiency Ge detector array surrounding a fission target with a thick backing, coupled to a fission fragment spectrometer based on a gas filled magnetic (GFM) device. The new instrument will be positioned at a finely collimated halo-free thermal neutron beam at the ILL. The combined spectrometer will give access to new nuclear spectroscopy information of neutron-rich nuclides by tagging the complementary fragment and new insight into the fission process via combined measurements of mass A, nuclear charge Z, kinetic energy Ek and population of excited states. The status of the future instrument will be presented.

Speaker: Mr Aurelien Blanc (Institut Laue Langevin)

Slides 29m12_BLANC.pdf

30 Silicon detectors for the EXL project

EXL (EXotic nuclei studied in Light-ion induced reactions at storage rings) is a project within NUSTAR at FAIR [1, 2]. It aims for the investigation of light-ion induced direct reactions in inverse kinematics with radioactive ions in storage rings at GSI and at the future FAIR facility. The heart of EXL will be its recoil detector array, a 4π-array of several layers of silicon detectors surrounding the internal target of a storage ring. Because of the demanding vacuum conditions inside a storage ring, all components have to be UHV (Ultra-High Vacuum) compatible. At the same time, an energy threshold as low as possible is vital for EXL which excludes the use of detector pockets with vacuum-window foils as these dead layers would inevitably raise the low-energy threshold. To meet both demands at the same time, we have developed a solution in which a first layer of DSSDs (Double-sided Silicon Strip Detectors) is used as the actual vacuum window – hence, an active vacuum window – which separates the UHV from an auxiliary vacuum with less demanding vacuum conditions where additional detectors, cablings and read-out electronics can be placed [3, 4]. With a first implementation of this concept using two DSSDs, we have performed an experiment at the ESR (Experimental Storage Ring) at GSI using 58Ni as well as radioactive 56Ni beams in which we have successfully measured the nuclear matter distribution of 56Ni by investigating elastic proton scattering in inverse kinematics [5, 6]. The experiment marks the first successful investigation of a nuclear reaction with a stored radioactive beam ever. The contribution will detail the development of the UHV compatible detector array and discuss the performance of the detectors in the experiment. This work was supported by BMBF (06DA9040I, 05P12RDFN8, 05P15RDFN1), the European Community FP7-Capacities, contract ENSAR № 262010, HIC for FAIR, GSI-RUG/KVI collaboration agreement and TU Darmstadt-GSI cooperation contract. References [1] http://www.rug.nl/kvi/Research/hnp/Research/EXL/index [2] H.H. Gutbrod et al. (Eds.), FAIR Baseline Technical Report, ISBN-3-9811298-0-6, 2006. [3] B. Streicher et al., Nucl. Instrum. Methods Phys. Res., Sect. A, 654(1):604, 2011. [4] M. Mutterer et al., Physica Scripta T166, 014053. [5] M. von Schmid et al., Physica Scripta T166, 014005. [6] M. von Schmid, doctoral thesis (TU Darmstadt), 2015. http://tuprints.ulb.tu-darmstadt.de/5028/

Speaker: Mirko von Schmid (Institut für Kernphysik, Technische Universität Darmstadt, Germany)

Slides MvonSchmid.pdf

31 Highly efficient 4Pi light charged particle segmented detector EUCLIDES for in-beam gamma-spectroscopy at GALILEO array

One of the key-feature of the modern γ-ray spectrometers, such as GALILEO at LNL Legnaro is its capability to identify and to study exotic excited states produced at very low cross section. To improve the selectivity of GALILEO the EUCLIDES Si-ball ancillary detector was renewed. Here it is reported the performance of EUCLIDES in the latest experiment using 12C+24Mg reaction: the selectivity; the efficiency; an event-by-event kinematic reconstruction of the trajectory of the recoiling nuclei. The devoted configuration of EUCLIDES can be coupled to the plunger device allowing, therefore, to benefit its advantageous in the experiment using Recoil Distance Doppler-Shift method.

Speaker: Dmitry Testov (PD)

Slides Testov.pdf

32 SPIDER: a new particle detector for Coulomb excitation measurements

The science of exotic nuclei is a vast and very active field of research and facilities to produce radioactive ion beams (RIB) are under construction in many countries. Low-energy Coulomb excitation is one of the simplest and well known tools to study the properties of low-lying excited levels of atomic nuclei. For this reason is widely used at radioactive beam facilities: in particular in the case of ISOL facilities the energy and the intensity of the first available beams is suitable for safe-energy Coulomb Excitation. In a near future the SPES facility will provide the first exotic beams at the National Laboratories in Legnaro. At the same time the AGATA array will be likely installed at LNL. To this aim the gamma spectroscopy group of Florence have developed and assembled an apparatus to be used at the SPES facility. It consists of up to 8 sector shaped silicon detectors (aperture angle about 45 degrees) arranged in a pie shape. Each sector is segmented into eight independent annular strips on the front surface. This Silicon PIe DEtectoR (SPIDER) will provide a clean trigger to an array of germanium detectors (like GALILEO or AGATA) allowing the development of the Coulomb excitation technique at LNL. The first commissioning experiment with SPIDER coupled with the GALILEO gamma ray spectrometer will be performed and hopefully will be followed by a Coulomb excitation experimental campaign with stable beams. In this talk details about the detector, simulations and recent tests at the LABEC laboratory in Florence will be shown.

Speaker: Marco Rocchini (FI)

Slides Rocchini.pdf

16:30 Coffee break

Nuclear Structure and Reaction II

Convener: Dr Alexandre obertelli (CEA Saclay)

33 Transverse wobbling and chiral modes in lanthanide nuclei

34 Interplay between collective and single particle excitations around neutron-rich doubly-magic nuclei

In nuclei with one or two particles outside of a doubly-closed core the lowest structures are dominated by the couplings between phonon excitations and valence particles, giving rise to series of multiplets. The identification of these multiplets can provide precise, quantitative information on the phonon-particle couplings. In fact, the energy and transition probability for states belonging to phonon-particle multiplets can be calculated within mean-field based models and comparisons with experiment can provide a unique test of various theoretical approaches. From a broader perspective, understanding the coupling of a single particle to vibrational motion in nuclei is of primary importance, as this coupling is responsible for the quenching of spectroscopic factors [1] and it is also the key process at the origin of the damping of giant resonances [2]. This talk will present the situation in nuclei lying in close proximity of doubly-magic systems, such as 41,47,49Ca [3,4] and 133Sb. Various types of reactions will be discussed: from multinucleon transfer with heavy ions, to cold neutron capture (n,) and neutron induced fission on 235U and 241Pu targets. The results of measurements performed at Legnaro National Laboratory and ILL (Grenoble), using complex detection systems based on HPGe arrays coupled to magnetic spectrometers (PRISMA) or fast LaBr3 scintillator detector arrays for lifetime measurements will be presented. Experimental data will be compared with theoretical calculations using a newly developed model which takes into account coupling between core excitation (both collective e and non-collective) of the doubly magic core and the valence particle. Perspectives for studies with cluster transfer reactions employing radioactive beams from ISOLDE and SPES will be finally given.

Speaker: Giovanni Bocchi (MI)

Slides 29m17_Bocchi.pdf

35 Shape coexistence in the neutron-deficient Hg isotopes studied via lifetime measurements

Near-degenerate states characterised by different shapes, i.e. shape coexistence, appear in various mesoscopic quantum systems, such as atomic nuclei. The shape of atomic nuclei is due to the complex interplay of closed shells, sub shells and residual interaction between protons and neutrons. The neutron-deficient isotopes close to the Z = 82 shell closure exhibit an extensive manifestation of shape coexistence. In particular, in the even-even mercury isotopes around 184Hg (N = 104, midshell) besides the predominant oblate-deformed ground-state band, a second relatively low-lying mainly prolate-deformed band was observed. The observed states are constituted by a configuration mixing of the underlying structures. This mixing changes as a function of the neutron number and the transition strength between two nuclear levels is very sensitive to their wave functions, hence it can be used to further understand the shape coexistence and the degree of the mixing. In order to study the shape coexistence in 188Hg, which is at the edge of the shape coexistence region, the first direct lifetime measurement experiment with a plunger device and the GALILEO array was performed using a fusion-evaporation reaction. The preliminary results including the transition strengths of the low-lying excited states in 188Hg will be presented.

Speaker: Mr Philipp Rudolf John (PD)

Slides 29m18_John.pdf

36 High-spin spectroscopy after multinucleon transfer

Multinucleon transfer reactions (MNT) are a competitive tool to populate exotic neutron-rich nuclei. Excited reaction products have been measured (i) in transfer products of $^{136}$Xe+$^{238}$U and $^{136}$Xe+$^{208}$Pb MNT reactions and (ii) as a fission product after the $^{136}$Xe+$^{238}$U reaction employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the mass spectrometer PRISMA at LNL (INFN, Italy). Furthermore, the $^{136}$Xe+$^{198}$Pt MNT reaction was studied with the $\gamma$-ray spectrometer GAMMASPHERE in combination with the gas detector array CHICO at LBNL. Mass yields of the $^{136}$Xe+$^{238}$U reaction have been extracted and compared with calculations based on the GRAZING model for MNT reactions. Population yields for nuclei in the actinide region were obtained and compared to x-ray yields measured by AGATA. An extension of the ground-state rotational band in $^{240}$U was achieved and evidence for an extended first negative-parity band in $^{240}$U is found. The results were compared to recent mean-field and DFT calculations. Several high-spin states on top of long-lived isomers in the $N\sim 82$ nuclei $^{134}$Xe, $^{135}$Xe, and $^{137}$Ba were discovered based on $\gamma\gamma$-coincidence relationships and information on the $\gamma$-ray angular distributions as well as excitation energies from the total kinetic energy loss and fission fragments. Latest shell model calculations employing different effective interactions reproduce the experimental findings and support the new spin and parity assignments. Supported by the German BMBF (05P12PKFNE TP4), ENSAR-TNA03, BCGS.

Speaker: Mr Andreas Vogt (Institute of Nuclear Physics, University of Cologne)

Slides 29m19_vogt.pdf

Social dinner

Thursday, 30 June

Perspectives in Nuclear Structure I

Convener: Dr Magdalena Gorska (GSI Darmstadt)

37 Exploring shell structure of nuclides in proximity of doubly-magic 132Sn

The shell structure of the atomic nucleus is one of the main ingredients underlying our understanding of nuclear systems. During the last two decades we have recognized that the shell structure may significantly change when going far from valley of stability. Various aspects of the underlying nuclear forces have been shown to be relevant in determining its evolution as a function of the neutron-to-proton ratio, but we are still far from a comprehensive assessment of the phenomenon. Within this context, the region around the doubly-magic nucleus 132Sn is of particular importance. It is, in fact, the only region around a heavy, neutron-rich doubly-closed shell nucleus far-off stability experimentally accessible today. Experimental information on 132Sn neighborings is also relevant for testing the main ingredients of the nuclear-shell model, to be then used to predict the properties of still unknown nuclei towards the neutron drip line. Besides the nuclear structure aspect, nuclei around 132Sn play a key role in the dynamics of the rapid neutron-capture process of nucleosynthesis, the so-called r-process, since some of these nuclei are acting as bottleneck for the reaction flow. The unknown evolution of the shell structure in this region is one of the main sources of nuclear physics uncertainty in r -process calculations. This has provided significant motivation for experiments on 132Sn neighborings as well as for a number of theoretical calculations. In this contribution, we shall focus on nuclei with a few valence particles and/or holes close to 132Sn by comparing the available experimental data with the results of realistic shell-model calculations. The full N=50–82 major shell for neutrons and the Z=28–50 shell for protons are considered and the two-body matrix elements of the effective interaction derived from the CD-Bonn potential [1], whose high momentum repulsive components are smoothed out using the Vlow-k approach [2], by way of many-body perturbation theory [2]. The single-particle energies are taken, whenever possible, from experiment. The comparison between theory and experiment will be performed for nuclei situated in all four quadrants around 132Sn, including those in the south quadrants for which data are very scanty. This approach has the major merit that no adjustable parameter is required, which makes it particularly appropriate to investigate regions, where the lack of experimental information precludes, for the moment, the development of empirical interactions. On the other hand, it has proved to lead to an accurate description of nuclear structure in various mass regions and also around 132Sn (see, for instance [4]), where, however, attention has been focused in particular on nuclei with Z>50. [1] R. Machleidt, Phys. Rev. C 63, 024001(R) (2001) [2] L. Coraggio, A. Covello, A. Gargano, N. Itaco, and T. T. S. Kuo, Prog. Part. Nucl. Phys. 62, 135 (2009) [3] L. Coraggio, A. Covello, A. Gargano, and N. Itaco, Phys. Rev. C 88, 041304(R), and references therein

Speaker: Angela Gargano (INFN- Sezione di Napoli)

Slides 30m01_Gargano.pdf

38 Perspectives in Nuclear Physics at ELI-NP

Speaker: Dr Calin Alexandru Ur (ELI-NP)

Slides 30m02_Ur.pdf

39 Recent results and perspectives on gamma spectroscopy research at TRIUMF

The Gamma-Ray Spectroscopy at ISAC group operates the GRIFFIN and TIGRESS HPGe arrays in pursuit of a variety of nuclear structure, nuclear astrophysics, and fundamental symmetries investigations at TRIUMF's Isotope Separator and Accelerator (ISAC) ISOL radioactive beam facility. The GRIFFIN spectrometer provides unique opportunities in decay spectroscopy research with stopped radioactive beams. The HPGe array is complimented by a powerful suite of ancillary detector sub-systems that includes plastic-scintillators for beta tagging, LN2-cooled Si(Li) detectors for conversion electron measurements and an array of eight LaBr3 scintillators for fast-timing measurements. In addition, GRIFFIN will couple to the DESCANT array of neutron-detectors for beta-delayed neutron emission studies with exotic neutron-rich beams. GRIFFIN has most recently been used to study neutron-rich isotopes in the vicinity of 132Sn, and around the island of inversion. The TIGRESS spectrometer is used for studies with accelerated radioactive beams and is operated in conjunction with a range of particle detector sub-systems. The BAMBINO and SHARC silicon arrays are ideally suited to study Coulomb excitation and transfer reactions. A plunger device has recently been commissioned for the measurement of excited state lifetimes. The SPICE detector for in-beam internal conversion electron spectroscopy has been developed. The future EMMA recoil mass analyzer will also be coupled with TIGRESS. Recent measurements have examined transition strengths in light nuclei and transfer strengths in the neutron-rich Sr isotopes. An overview of the experimental setups will be given with details of recent results.

Speaker: Dr Adam Garnsworthy (TRIUMF)

Slides 30m03_Garns.pdf

40 Gamma spectroscopy in Bucharest using the ROSPHERE array

The ROSPHERE array, a gamma-ray spectrometer composed of Germanium and LaBr3(Ce) detectors and optimized for lifetime measurements, has been built and is now in operation at the TANDEM Laboratory of IFIN-HH Bucharest. During several experimental campaigns this setup proved to be a very useful tool for measuring in-beam lifetimes of excited nuclear levels in the sub-nanosecond range, complementing in this way the experimental data obtained using larger gamma detection arrays. Moreover, the experience gained by building and using this in-beam fast timing setup in Bucharest is presently used for building similar setups for other experimental facilities. This presentation intends to offer a brief description of ROSPHERE and a quick overview of the experimental results obtained using it in Bucharest.

Speaker: Dr Nicolae Marginean ("Horia Hulubei" National Institute of Physics and Nuclear Engineering Bucharest-Magurele, Romania)

Slides 30m04_Marginean.pdf

10:55 Coffee break

Perspectives in Nuclear Structure II

Convener: Prof. Thorsten Kröll (TU Darmstadt)

41 QRPA with the Gogny force: description of vibrational states up to octupole

The QRPA approach, well known to be adapted for giant resonance description, is also a good formalism to describe low energy vibrational states for all multipolarities and parities with the same accuracy. We will present selected recent successful results obtained within the QRPA approach using the Gogny interaction. First, we will compare the first 2+ collective state obtained in QRPA and in 5DCH (a GCM-like method, including rotation) in tin (Z=50), N=16 isotones, and in the Nickel isotopic chain, from drip line to drip line [1]. Concerning octupolar modes, predictions for first 3- states (energies and transition probabilities) in the tin isotopic chain will be discussed, before presenting the low energy spectra obtained in super heavy nuclei such as Cm, Cf and Fm. Secondly low energy dipole resonances in light nuclei and giant resonances in doubly magic exotic nuclei [3] will be addressed, enlightening the role of the intrinsic deformation [4]. The first fully coherent microscopic description of the multipolar spectrum of the heavy deformed nucleus 238U [5] will be used to summarize our know-how. On the basis of all these satisfactorily results, large-scale calculations of dipole responses, both electric and magnetic, for all nuclei for which data exist have been undertaken. Preliminary results [6] will be displayed. A strategy for an application to odd-A and odd-odd nuclei will be discussed with few examples. Finally, we present the generalization of QRPA to the charge-exchange nuclear excitation (pnQRPA) [7] namely the Isobaric Analog and Gamow-Teller resonances which play a crucial role in several fields of physics (nuclear physics, astrophysics and particle physics). A comparison of the results with existing experimental data on Fermi and Gamow-Teller strength distributions is presented and the role of nuclear deformation analyzed. A special attention is paid to the reproduction of β-decay half-lives as well as for the specific N = 82 isotonic chain relevant for the r-process nucleosynthesis [8]. For these charge-exchange modes possible extension to odd systems will be presented too. REFERENCES [1] S. Péru and M. Martini, Eur. Phys. J. A (2014) 50: 88 ; [2] M. Martini, S. Péru and M. Dupuis, Phys. Rev. C 83, 034309 (2011) ; [3] S. Péru, JF. Berger, PF. Bortignon, Eur. Phys. J. A 26, 25-32, (2005) ; [4] S. Péru, H. Goutte, Phys. Rev. C 77, 044313, (2008); [5] S. Péru, G. Gosselin, M. Martini, M. Dupuis, S. Hilaire and J. -C. Devaux, Phys. Rev. C 83, 014314 (2011) ; [6] M. Martini, S. Péru, S. Hilaire, S. Goriely, F. Lechaftois, submitted to PRC ; [7] M. Martini, Péru and S. Goriely, PRC89, 044306 (2014) ; [8] M. Arnould, S. Goriely and T. Takahashi, Phys. Rep. 450, 97 (2007).

Speaker: Dr Sophie Peru (CEA)

Slides Peru.pdf

42 The GALILEO Array at LNL and its first physics campaign

Speaker: Mr Philipp Rudolf John (PD)

Slides 30m06_John-Galileo.pdf

43 NEDA

One of the possible methods of studying yrast and yrare states of extremely neutron deficient nuclei is by using heavy-ion induced fusion-evaporation reactions. In such experiments, the nuclei of interest are produced with very low cross sections, therefore clean reaction channel selection is essential. State-of-the-art gamma spectrometers coupled to high performing ancillary detectors are the key instruments to study the nuclear structure of this neutron deficient N~Z nuclei. The most exotic (and the most interesting) reaction channels are almost always associated with the emission of neutrons, two or more. Currently, a new neutron multiplicity filter named NEDA (NEutron Detector Array) is being constructed for this purpose. NEDA will operate with germanium arrays (AGATA, GALILEO, EXOGAM) on both intense stable and radioactive ion beams. This will enable to investigate the structure of exotic neutron-deficient nuclei, which were not experimentally achievable so far. The efficiencies of clean identification of 2n and 3n reaction channels are expected to be a few times higher for NEDA with respect to existing arrays. The findings from the R&D phase and the status of the NEDA project will be presented. This involves results of Geant4 simulations on optimal single detector size, scintillator materials and geometry of the whole array. The results of measurements with the prototype and first NEDA detectors will be presented. Comparison between analog and digital procedures for the neutron-gamma discrimination and timing will also be discussed.

Speaker: Grzegorz Jaworski (LNL)

Slides jaworski.pdf

12:40 Lunch break

AGATA Physics Workshop

Convener: Johan Nyberg (Uppsala University)

44 Some highlights from the AGATA@LNL campaign 2010 - 2011

Speaker: Prof. Sean Freeman (University of Manchester)

Slides 30p01_Freeman.pdf

45 Highlights from the AGATA@GSI campaign 2012 - 2014 and plans for AGATA at FAIR after 2022

Speaker: Dr Juergen Gerl (GSI)

Slides 30p02_Gerl.pdf

46 Status and perspectives of the GANIL campaign

Speaker: Dr Emmanuel Clement (GANIL)

47 Reaction and structure studies with the MUGAST+AGATA setup at VAMOS

New-generation silicon arrays with high granularity, such as GASPARD and TRACE, have been natively designed for optimal integration in state-of-the-art γ-ray spectrometer like AGATA to perform high-resolution reaction studies. Such coupling allows a considerable gain in excitation-energy resolution compared to recoil charged-particle detection only and thus opens unique opportunities to study intermediate-mass exotic nuclei with a large density of excited states. While these Si arrays are being developed in collaboration, a project of “intermediate” configuration (named “MUGAST” for MUST2-GASPARD-TRACE) has been proposed in 2015 to perform reaction studies in combination with AGATA~1π at VAMOS. This configuration provides a large angular coverage that allows the study of stripping reaction such as (d,p), (3He,d), (3He,p), (6Li,d), .... requiring detection of the recoil particle at very backward angles to 90 degrees or lower. In this talk, the status and specificities of this configuration will be presented together with selected physics cases submitted as letters of intent.

Speaker: Mr Freddy Flavigny (IPN Orsay)

Slides 30p04_Flavigny.pdf

48 The VAMOS Gas-Filled Mode

The VAMOS-GFS project consists to upgrade the existing VAMOS spectrometer by equipping it with a Gas-Filled Separator (GFS) mode. This separator will be one of the most efficient in the world (in terms of transmission and selectivity) for the spectroscopy of rare nuclei produced by fusion-evaporation reactions and for studies of the associated reaction mechanisms. Since the coupling with AGATA is foreseen in a next future, several letters of intent have been discussed within the AGATA collaboration, and the physics program has been submitted to the last GANIL PAC. Mainly three regions of are covered: alpha emitters north-east 100Sn, neutron-deficient lead region, and region of the heaviest elements. In this presentation, we will give status report of the project and summarize the physics program foreseen with VAMOS-GFS and AGATA.

Speaker: Dr Christophe THEISEN (CEA Saclay)

Slides Theisen.pdf

16:10 Coffee break

AGATA Collaboration Meeting

Convener: Prof. Peter Reiter (IKP University of Cologne)

49 Proton – neutron pairs in N≈Z nuclei: a theory perspective

The short-range proton-neutron interaction favors the formation of p-n pairs with parallel or antiparallel spin. They may appear as three species: T=1,J=0 (“isovector pairing”), T=0,J=1 (“isoscalar pairing”), and T=0, J=2j (“spin-aligned”). In N≈Z nuclei, so far accessible, there is clear evidence for strong isovector pair correlations. Evidence for isoscalar pair correlations is elusive. The reason seems suppression by spin-orbit splitting. Weakening of spin-orbit splitting is predicted for the region N≈Z>50, which may lead to a rise of isoscalar pair correlations. Based on Shell Model calculations, the formation of a “condensate” of spin-aligned pairs was suggested. The nature of such spin-aligned coupling scheme, its coexistence with isovector pairing, and the limits of pair classification due to the finite nucleon number will be discussed.

Speaker: Prof. Stefan Frauendorf (University Notre Dame)

50 Report from the AMB

Speaker: Andres Gadea Raga (INFN)

Slides 30p07_Gadea.pdf

51 AGATA and the NuPECC LRP

Speaker: Dr Wolfram KORTEN (CEA)

Slides 30p08_Korten.pdf

52 Performance measurements with tracking arrays

Speaker: Mrs Amel Korichi (CSNSM-IN2P3/CNRS)

Slides 30p09_Korichi.pdf

Friday, 1 July

Status of AGATA@GSI 2012-2014 experiments

Convener: Dr Juergen Gerl (GSI)

53 Lifetime measurement in the even-even neutron-rich molybdenum isotopes with the PresPEC-AGATA setup

Speaker: Mr Damian Ralet (CSNSM)

54 B(E2) values of p - rich A=46 nuclei

Speaker: Alberto Boso (PD)

55 Coulomb excitation of the band-terminating 12+ yrast trap in Fe-52

Speaker: Mr Tayfun Huyuk (IFIC (CSIC - Universidad de Valencia))

Status of GANIL 2015-2016 experiments

Convener: Prof. Silvia Monica Lenzi (PD)

56 Collectivity along the neutron-magic 92Mo and 94Ru

Speaker: Ms Rosa Perez Vidal

57 Gamma-ray spectroscopy of neutron-rich nuclei beyond N=50 shell closure in the vicinity of 78Ni using AGATA coupled to VAMOS++

Speaker: Dr Jérémie Dudouet (IPNL)

58 Towards lifetime and g-factor measurements of short-lived states in the vicinity of 208Pb

Speaker: Mr Damian Ralet (CSNSM)

59 Lifetime measurements in "fpgd" nuclei - E663

As first out in the AGATA@Ganil physics campaign an experiment aiming at both lifetime measurements and determination of g-factors for nuclei close to \(^{68}\)Ni was performed. The experiment was run using 19 AGATA crystals and using the Orsay Universal Plunger System. The lifetimes of excited states in \(^{59}\)Mn, \(^{62,64}\)Fe, and \(^{61,63}\)Co have been determined. These new results will be discussed as well as some of the difficulties encountered during the analysis of the experiment. In particular it will be shown how a factor of two of statistics could be recuperated and how the yrast structure of the even-even nuclei in the region makes precise lifetime measurements very challenging. Finally an example of simulations used to estimate the effective peak shapes used to estimate the effect of relatively long flight time through the degrader will be shown.

Speaker: Dr Joa Ljungvall (CSNSM)

60 Study of Quadrupole Correlations in the 106,108 Sn Isotopes via Lifetimes Measurements

The shell structure of nuclei with few nucleons outside the double-shell closure Z=N=50 has attracted a large interest. Several studies were performed in this region to examine the robustness of the proton shell closure when N=50 is approached. The excitation energy of the 2+ states in the Sn isotopes as well as the reduced transition probabilities B(E2; 2+ → 0+) provide a clear evidence of the shell evolution along the whole isotopic chain. The systematic of the first 2+ state excitation energy is well known and the behaviour is rather constant along all the Sn isotopic chain; on the contrary the information on the reduced transition probabilities for the neutron-deficient Sn isotopes suffer from large experimental uncertainties which makes the interpretation of the shell evolution controversial.

Speaker: Marco Siciliano (LNL)

11:00 Coffee break

Closed Meeting of the AGATA Collaboration Council

Convener: Johan Nyberg (Uppsala University)

61 Report from the ASC

Speaker: Dr Juergen Gerl (GSI)

62 ACC meeting

Speaker: Johan Nyberg (Uppsala University)