T. Ichihara

Neutron halo in 11Be studied via reaction cross sections

Abstract Reaction cross sections (σR) and fragmentation cross sections (σF) of reactions of a 11Be beam on C, Al targets were measured by a transmission method at 33A MeV. The σR have been determined to be 1.56±0.03 b for 11 Be + 12 C , and 2.27±0.05 b for 11 Be + 27 Al . These values are extremely large compared with the systematics of stable nuclei. A large σF has also been observed for the 11Be→10Be channel. Model calculations using present and 790A MeV data confirm the long neutron tail (neutron halo) in the 11Be density distribution.

Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identi...

New aspect of intermediate energy heavy ion reactions. Large spin polarization of fragments

Abstract The spin polarization, P , of 12 B ejectiles has been measured for projectile fragmentation reactions induced by a 40.6 MeV/u 14 N beam. Large values of P were observed, showing a characteristic dependence on the outgoing momentum including a sign change occurring at a momentum corresponding to the beam velocity. This behavior corresponds well with simple kinematical arguments based on projectile fragmentation models.

Systematic behavior of ejectile spin polarization in the projectile fragmentation reaction

Abstract Ejectile spin polarization P in intermediate-energy projectile fragmentation has been measured for different targets and incident energies using the RIPS fragment separator at RIKEN. The observed P as a function of the fragment momentum shows a systematic change when the atomic number of the target or the incident energy is varied. Most remarkably, P does not vanish at the momentum corresponding to the beam velocity, indicating an important effect which has not been considered in the previously proposed model.

Charge-exchange reaction 12C(12C, 12N)12B at EA = 135 MeV

Abstract The charge-exchange reaction 12 C( 12 C, 12 N) 12 B has been studied at E A = 135 MeV . The elastic scattering of 12 C from 12 C was also measured to determine the optical potential parameters. The differential cross sections for the charge-exchange reaction leading to the 12 B ground state (1 + ) were well described byh the microscopic DWBA calculation, suggesting the dominance of the one-step process. The L = 0 component was found to be about five times stronger than the L = 2 component at 0°.

Negative pion production in subthreshold heavy ion collisions

Abstract Inclusive π− spectra have been measured for 14N+C collisions at 41A, 67A, 80A and 135A MeV, the lowest energies measured for the charged pion. The cross sections fall exponentially with Tπ and the exponential slope factors at 90° in the nucleon-nucleon center of mass frame are determined. Energy distributions below a beam energy of 100A MeV are less steep than expected from the monotonic decrease of the slope factor down to 100A MeV. The production mechanism of energetic pions far below threshold is discussed for several models.

Attempts in detection of neutrons on So-called cold nuclear fusion

Neutron emissions from electrolysis of D 2 O with palladium and palladium-titanium electrodes as well as from pressurized D 2 gas with titanium alloys have been measured. The neutron detector system was so designed to have very low background condition. Neutron-γ separation technique using liquid scintillator was applied to obtain essentially no γ ray background condition for neutron counting. Special care was taken to stabilize the detection system using event-by-event data recording. No significant signal of neutron emission was observed. Upper limits of emission probability of neutron have been determined to be 6×10 -3 s -1 , 1×10 -2 s -1 , and 2.3×10 -2 s -1 for Pd electrode, Pd-Ti electrode, and pressurized gas systems. These values are orders of magnitude lower than that presented by Jones paper (0.4 s -1 ).

DAQ coupling in RIKEN RIBF

The Radioactive Isotope Beam Factory at RIKEN has been constructed to produce intense RI beams over the whole range of atomic masses. MUST2, EURICA, and MINOS detector systems together with dedicated DAQ systems are transported to RIBF from other facilities of GANIL, GSI and Irfu CEA. These data have to be merged with data of RIBFDAQ. There are two types of DAQ coupling methods. One is the common trigger configuration, and the other is the individual trigger configuration. In case of the common trigger configuration, data taken by different DAQ systems are merged in online through Ethernet. This merging is simple because the event number is the same between DAQ systems. However, run control commands and data formats are translated to adapt other DAQ systems. On the other hand, the time-stamping system is adopted for the individual trigger configuration. This case, DAQ systems run independently, and data are taken attached with time-stamp information. Raw data are converted to ROOT Tree file once. Finally, data are merged offline based on time-stamp information. Here, DAQ coupling projects in RIBF are described.

Proton decay measurement with RIPS for astrophysical interest

Abstract The decay property of 20 Na was studied using a 20 Mg beam to obtain a better understanding of the onset mechanism of the rapid proton process. The delayed protons were successfully measured, which correspond to one of the known 1 + states. There is no clear beta decay to the first excited 1 + state above the proton threshold in 20 Na, suggesting that this state would not be the s-wave resonance as was expected before. The present result is preliminary; the final result will be published elsewhere.