S. Bagchi

Neutron-skin thickness from the study of the anti-analog giant dipole resonance

The γ-decay of the anti-analog of the giant dipole resonance (AGDR) to the isobaric analog state has been measured following the p( 124Sn,n) reaction at a beam energy of 600 MeV/nucleon. The energy of the transition was also calculated with state-of-the-art self-consistent relativistic random-phase approximation (RPA) and turned out to be very sensitive to the neutronskin thickness (ΔRpn). By comparing the theoretical results with the measured one, the ΔRpn value for 124Sn was deduced to be 0.21 ± 0.07 fm, which agrees well with the previous results. The present method offers new possibilities for measuring the neutron-skin thicknesses of very exotic isotopes.

A neutron spectrometer for studying giant resonances with (p,n) reactions in inverse kinematics

A neutron spectrometer, the European Low-Energy Neutron Spectrometer (ELENS), has been constructed to study exotic nuclei in inverse-kinematics experiments. The spectrometer, which consists of plastic scintillator bars, can be operated in the neutron energy range of 100 keV-10 MeV. The neutron energy is determined using the time-of-flight technique, while the position of the neutron detection is deduced from the time-difference information from photomultipliers attached to both ends of each bar. A novel wrapping method has been developed for the plastic scintillators. The array has a larger than 25% detection efficiency for neutrons of approximately 500 keV in kinetic energy and an angular resolution of less than 1 degrees. Details of the design, construction and experimental tests of the spectrometer will be presented

First Nuclear Reaction Experiment with Stored Radioactive 56Ni Beam and Internal Hydrogen and Helium Targets

The investigation of light-ion induced direct reactions using stored and cooled radioactive beams, interacting with internal targets of storage rings, can lead to substantial advantages over external target experiments, in particular for direct reaction experiments in inverse kinematics at very low momentum transfer, q. This new and challenging experimental technique enables high-resolution measurements down to very low q and provides a gain in luminosity from accumulation and recirculation of the stored beams. For performing first experiments of this kind a dedicated experimental setup housing several DSSD (Double-sided Silicon Strip Detector) and Si(Li) detectors for recoil particles, well suited for meeting the demanding UHV (Ultra High Vacuum) conditions of a storage ring, was recently designed, constructed and installed at the internal target of the ESR storage ring at GSI. From the interaction of a stored 56Ni beam with an internal H2 target, good quality differential cross section data for elastic proton scattering, measured with the aim to determine the radial shape of the nuclear matter distribution of 56Ni, were obtained. Preliminary results are presented. Being the first reaction experiment ever performed with a stored radioactive beam on a world-wide scale, this experiment can be considered as a breakthrough for nuclear structure and astrophysics studies, and, in addition, as a successful proof-of-principle of the new experimental concept. In addition, preliminary results from a feasibility study on inelastic α-scattering from 58Ni in inverse kinematics, where it was demonstrated that the Isoscalar Giant Monopole Resonance in 58Ni can be investigated by the present technique down to CM angles below 1 degree, are discussed. Such an experiment, performed in the future with the doubly magic 56Ni, would provide important information on the EOS of nuclear matter.

Isoscalar giant resonance studies in a stored-beam experiment within EXL

In the first campaign of the exotic nuclei studied with light-ion induced reaction in storage rings (EXL) collaboration at the existing storage ring experimental heavy-ion storage ring (ESR) at Helmholtz Center for Heavy Ion Research (GSI), we performed the first experiments using a stored beam of 58Ni and an internal helium gas-jet target aiming for the investigation of isoscalar giant resonances in inverse kinematics. In this experiment, inelastically scattered recoil particles (at very forward angles, °) were detected with a dedicated setup, including ultra-high vacuum (UHV)-compatible double-sided silicon strip detector (DSSDs). Preliminary results show evidence for the excitation of the isoscalar giant monopole resonance (ISGMR) in the 58Ni nucleus. This opens the opportunity to study in the near future giant resonances also with stored radioactive beams, like 56Ni, and extract important information about the nuclear matter incompressibility. In the present work the current status of the data analysis and results are shown and discussed.

Nuclear reactions in the storage ring ESR with EXL

The EXL project aims to study nuclear structure by direct reactions in inverse kinematics at the storage rings of the future FAIR facility. In this contribution, we present the status of the project: the technical implementation at the ESR at GSI and preliminary results of the EXL campaign in 2012, the first using also a radioactive beam.

Nuclear transfer reaction measurements at the ESR-for the investigation of the astrophysical O-15(alpha,gamma)Ne-19 reaction

Astrophysical x-ray bursts are thought to be a result of thermonuclear explosions on the atmosphere of an accreting neutron star. Between these bursts, energy is thought to be generated by the hot CNO cycles. The O-15(alpha,gamma)Ne-19 reaction is one reaction that allows breakout from these CNO cycles and into the rp-process to fuel outbursts. The reaction is expected to be dominated by a single 3/2(+) resonance at 4.033 MeV in Ne-19, however, limited information is available on this key state. This work reports on a pioneering study of the Ne-20(p, d)Ne-19 reaction, performed in inverse kinematics at the experimental storage ring (ESR) as a means of accessing the astrophysically important 4.033 MeV state in Ne-19. The unique, background free, high luminosity conditions of the storage ring were utilized for this, the first transfer reaction performed at the ESR. The results of this pioneering test experiment are presented along with suggestions for future measurements at storage ring facilities.

Status of the analysis of the first EXL experiment at the ESR

M. von Schmid †1, J.C. Zamora1, S. Bagchi 2, S. B̈onig1, M. Csatĺos3, I. Dillmann4, C. Dimopoulou4, P. Egelhof 4, V. Eremin5, T. Furuno6, H. Geissel 4, R. Gernḧauser7, M.N. Harakeh2, A-L. Hartig1, S. Ilieva1, N. Kalantar-Nayestanaki 2, O. Kiselev4, H. Kollmus4, C. Kozhuharov 4, A. Krasznahorkay 3, T. Kröll1, M. Kuilman2, S. Litvinov4, Yu.A. Litvinov4, M. Mahjour-Shafiei 2,8, M. Mutterer4, D. Nagae9, M.A. Najafi2, C. Nociforo4, F. Nolden4, U. Popp4, C. Rigollet2, S. Roy2, C. Scheidenberger 4, M. Steck4, B. Streicher 2,4, L. Stuhl 3, M. Tḧurauf1, T. Uesaka10, H. Weick4, J.S. Winfield4, D. Winters4, P.J. Woods 11, T. Yamaguchi 12, K. Yue1,4,13, J. Zenihiro10 for the EXL collaboration‡1 1IKP, TU Darmstadt;2Univ. of Groningen, KVI-CART, Groningen; 3MTA-Atomki, Debrecen;4GSI, Darmstadt; 5PTI, St. Petersburg; 6Kyoto University; 7TU München; 8University of Tehran;9University of Tsukuba; 10RIKEN, Tokio; 11University of Edinburgh;12Saitama University;13IMP, Lanzhou

Alpha cluster structure in56Ni

The inelastic

Alpha cluster structure in 56Ni

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First EXL experiment with stored radioactive beam: Proton scattering on 56Ni

−scattering experiment on 56Ni in inverse kinematics was performed at an incident energy of 50 MeV/u at GANIL. A very high multiplicity for