Search

The SπRIT Time Projection Chamber (TPC) was constructed at Michigan State University in the U.S.A. and transported to the Radioactive Isotope Beam Factory at RIKEN in Japan. In October 2015, the SπRIT TPC was commissioned with 200 AMeV 79Se beams outside the SAMURAI dipole magnet. The experimental setup consists of the SπRIT TPC, a Multiplicity Trigger Array, a KATANA array, and a Active Veto array. The TPC is fully equipped with a newly-developed read-out electronics system, GET electronics. The trigger logic to select events of the TPC based on the ancillary detectors was tested. The analysis software, SpiRITROOT, was developed to analyze the SπRIT TPC data to determine the best trigger logic for upcoming experiments.

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: 71Mn, 73,74Fe, 76Co, 79Ni, 81,82Cu, 84,85Zn, 87Ga, 90Ge, 95Se, 98Br, 101Kr, 103Rb, 106,107Sr, 108,109Y, 111,112Zr, 114,115Nb, 115,116,117Mo, 119,120Tc, 121,122,123,124Ru, 123,124,125,126Rh, 127,128Pd, 133Cd, 138Sn, 140Sb, 143Te, 145I, 148Xe, and 152Ba.

The drip-line 24O nucleus combines several properties which are challenging our understanding of the nuclear structure: it has no bound excited state, and is expected as a neutron-skin nucleus with low-lying resonances. It presents a new shell gap effect at N = 16. To investigate the neutron excitations and the characteristics of this gap, the proton elastic and inelastic scattering by 24O were measured, using the light charged particle spectroscopy technique; the excitation energies of the unbound states were deduced via missing mass method. The experiment was carried out at the RIBF facility in the BigRIPS line, combining the unique intensities of the 24O beam with the state-of-the-art Si-telescope array MUST2. The analysis and the preliminary results are discussed.

Coulomb dissociation of loosely bound nuclei 11Be and 15C have been studied in a kinematically complete measurement. For 11Be, the n-10Be relative energy spectrum has been analyzed as a function of the impact parameter, b. The obtained spectrum with b ≥30 fm agrees very well with the first order perturbation theory assuming a pure Coulomb process. It suggests that a selection of the impact parameter is effective to exclude the higher order effect and the nuclear breakup contribution from the measured dissociation cross section. The spectroscopic factor for 10Be(0+) ⊗1s1/2 in the ground state is then extracted to be 0.69(3). The result of 15C has been applied to determine the 14C(n,γ)15C cross section, which is relevant to the stellar nuclear synthesis such as the CNO cycle in low mass AGB stars. The obtained neutron capture cross section is consistent with that of the p-wave direct capture process.