Coulomb dissociation of O-16 into He-4 and C-12

We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4

Coulomb dissociation of 16O into 4He and 12C

We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision

Experimental studies on the doubly magic 100 Sn and neighboring N≈ Z nuclei with EURICA

© 2022, The Korean Physical Society.In low-energy nuclear physics, the doubly magic nucleus 100Sn has received much theoretical and experimental attention due to its profound implications on shell evolution, proton–neutron interaction, and the astrophysical rp-process of nucleosynthesis. A dedicated experimental campaign to advance the knowledge of 100Sn and similar proton-rich nuclei was launched at the RI Beam Factory, RIKEN Nishina Center. In addition to the discovery of new proton-rich isotopes, comprehensive β-decay and γ-ray spectroscopy was performed by the EUROBALL-RIKEN Cluster Array (EURICA) collaboration. The highlights of the 100Sn experiment are presented, including many outstanding questions and ongoing efforts in this region of nuclides.11Nsciescopuskc

Decay spectroscopy of N ~ Z nuclei in the vicinity of ¹⁰⁰Sn

The nuclear shell model (SM) has been very successful in describing the properties and the structure of near-stable and stable isotopes near the magic nuclei. Today, the advent of powerful facilities capable of producing radioactive isotopes far from stability has enabled the test of the SM on very proton-rich or neutron-rich magic nuclei. 100/50Sn50 is a proton-rich doubly-magic nucleus, but is nearly unstable against proton emission. Key topics of nuclear structure in this region include the location of the proton dripline, the effect of proton-neutron interactions in N ~ Z nuclei, single-particle energies of orbitals above and below the N = Z = 50 shell gaps, and the properties of the superallowed Gamow-Teller decay of ¹⁰⁰Sn. A decay spectroscopy experiment was performed on ¹⁰⁰Sn and nuclei in its vicinity at the RIKEN Nishina Center in June 2013. The isotopes of interest were produced from fragmentation reactions of 124/54Xe on a 9/4Be target, and were separated and identified on an event-by-event basis. Decay spectroscopy was performed by implanting the radioactive isotopes in the Si detector array (WAS3ABi) and observing their subsequent decay radiations. β⁺ particles and protons were detected by WAS3ABi, and γ rays were detected by a Ge detector array (EURICA). Of the proton-rich isotopes produced in this experiment, over 20 isotopes as light as ⁸⁸Zr and as heavy as ¹⁰¹Sn were individually studied. New and improved measurements of isotope/isomer half-lives, β-decay endpoint energies, β-delayed proton emission branching ratios, and γ-ray transitions were analyzed. In general the new results were well reproduced by the SM, highlighting a relatively robust ¹⁰⁰Sn core. However, the level scheme of ¹⁰⁰Sn's β-decay daughter nucleus ¹⁰⁰In was not conclusively determined because of several missing observations which were expected from various SM predictions. Significantly higher β-decay and γ-ray statistics are required on several nuclei, including ¹⁰⁰Sn, to evaluate the limit of the current understanding of their structure.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Toward the limit of nuclear binding on the N=Z line: Spectroscopy of 96Cd

A γ-decaying isomeric state (τ1/2=197+19−17 ns) has been identified in 96Cd, which is one α particle away from the last known bound N=Z nucleus, 100Sn. Comparison of the results with shell-model calculations has allowed a tentative experimental level scheme to be deduced and the isomer to be interpreted as a medium-spin negative-parity spin trap based on the coupling of isoscalar (T=0) and isovector (T=1) neutron-proton pairs. The data also suggest evidence for the population of a 9+ T=1 state, which is predicted by shell-model calculations to be yrast. Such a low-lying T=1 state, which is unknown in lighter mass even-even self-conjugate nuclei, can also be interpreted in terms of the coupling of T=0 and T=1 neutron-proton pairs

The ESS neutrino super-beam near detector

The ESS Neutrino Super-Beam (ESSnuSB) is a proposed long-baseline neutrino oscillation experiment, performed with a high-intensity neutrino beam, to be developed as an extension to the European Spallation Source proton linac currently under construction in Lund, Sweden. The neutrinos would be detected with the near and far detectors of the experiment, the former within several hundred meters of the neutrino production point and the latter within several hundred kilometers. The far detector will consist of a megaton-scale water-Cherenkov detector, and the near detector will consist of a kiloton-scale water-Cherenkov detector in combination with a fine-grained tracking detector and an emulsion detector. The purpose of the near detector is to constrain the flux of the neutrino beam as well as to extract the electron-neutrino interaction cross-section in water, which requires high-performance energy reconstruction and particle flavor identification techniques. These measurements are crucial for the neutrino oscillation measurements that will be conducted using the far detector. Year 2021 sees the finalization of the conceptual design of the near detector after a thorough evaluation of the performance of a number of different design options, and a characterization of the neutrino reconstruction and flavor identification performances. In this talk we report on these studies

Transfer and breakup reactions involving 7Be at ISOLDE

CERN Europe/Zurich, 5-6 diciembre 2019Peer reviewe