Y. Fuchi

Spin-Isospin Resonances Observed in the (d,2He) and (12C,12N) Reactions at E/A = 135 MeV

Abstract The (d, 2 He) and ( 12 C, 12 N) charge-exchange reactions have been studied at E/A = 135 MeV using the high resolution spectrograph SMART at RIKEN. The similarities were found in the energy spectra of both reactions, indicating the strong selectivity of ΔS = 1 and ΔT = 1 transitions. The 12 C( 12 C, 12 N) 12 B reaction has been studied using the microscopic DWBA calculation, suggesting that the reaction predominantly goes thorough a one-step process. The dominance of the L = 0 component was also found.

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°.

KEKCB electron cyclotron resonance charge breeder at TRIACa)

The KEKCB is an electron cyclotron resonance (ECR) ion source for converting singly charged ions to multicharged ones at Tokai Radioactive Ion Accelerator Complex. By using the KEKCB, singly charged gaseous and nongaseous ions were converted to multicharged ones of A/q approximately 7 with efficiencies of 7% and 2%, respectively. The conversion efficiency was found to be independent of the lifetime of the radioactive nuclei having lifetimes of the order of one second. Three collimators located at the entrance and the exit of the KEKCB defined the beam axis and facilitated beam injection. Grinding and washing the surfaces of aluminum electrode and plasma chamber dramatically reduced impurities originating from the ECR plasma of the KEKCB.

Epitaxial integrated dE1 − dE2 silicon detectors

Abstract Epitaxial integrated d E 1 − d E 2 silicon detectors have been developed by using the multilayer epitaxial crystal growth technique combined with the chemical preferential etching technique. These detectors are useful for eliminating events affected by channeling and blocking effects in the identification of heavy ions using multiple detector telescope systems. Characteristics of d E detectors of the integrated d E 1 − d E 2 type are confirmed to as good as those of integrated E − d E detectors.

High resolution study of24Mg(p, d)23Mg for the Ne-E problem

Nuclear levels of23Mg near and above the proton threshold were investigated with high resolution. A new level has been identified at 7.643 MeV (66 keV above the proton threshold) with a possible Jπ=(3/2, 5/2)+. Some other spin-parity and excitation-energy assignments are also made. These results enable the reaction rate estimate of22Na(p,γ)23Mg with much smaller uncertainties, which is critical for the Ne-E problem in nuclear astrophysics.

Level structure of 21Mg and the 20Na(p, γ)21Mg stellar reaction rate

Abstract The nuclear level structure of 21Mg has been studied by the 24Mg(3He, 6He)21Mg reaction at 74 MeV. Angular distributions of the three-nucleon transfer reaction (3He, 6He) are measured for the first time, and successfully analyzed with exact finite-range distorted-wave-Born-approximation calculations, giving clear transferred angular momentum assignments. More than 20 states have been identified with excitation energy and spin-parity determinations, including a possible s-wave resonance just above the proton threshold. One of the s-wave resonances assumed in the previous stellar reaction rate estimates is found to be a bound state. The stellar reaction rate of the 20Na(p, γ)21Mg process is estimated using the experimental data. The results predict the ignition of the proton radiative-capture process at T = 1×108K under typical nova conditions (hydrogen density, XHϱ = 5×105 g/cm3). This temperature happens to be in agreement with the previous theoretical estimates, but the new reaction rate is a few orders of magnitude smaller than the previous predictions for T ⋍ 2–10×10 8 K . The results also suggest that the nucleosynthesis flow of the rapid-proton process will run up to 21Mg immediately after breakout from the hot-CNO cycle.

The KEK–JAERI joint RNB project

A new ISOL-based radioactive nuclear beam (RNB) facility has been constructed as a joint project of the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Research Institute (JAERI) at the Tandem accelerator of the Tokai site of JAERI. It uses heavy-ion linacs and related equipment of the presently closed KEK-RNB facility. Fission fragments with energy from 0.1 to 8 MeV/u will be available at this facility.

Advanced focal plane detector with improved particle identification

Abstract A focal plane detector for a magnetic spectrograph was developed, which consists of two position counters, two energy-loss counters, and large-area silicon detectors. The energy, energy-loss and time-of-flight signals from this detector system depend on the particle incident angle into the counter and the position on the focal plane. Corrections to the angle and position dependence have improved the resolutions of these signals significantly and given unambiguous particle identification for studying reactions which have very small yields under intense backgrounds. The incident angle into the focal plane detector is found to be very useful to determine the scattering angle of reaction products.

Excitation of spin-dipole states by the 12C(12C,12N)12B reaction at E/A = 135 MeV

Abstract The spin-dipole resonances in 12 B have been studied with the charge-exchange reaction 12 C( 12 C, 12 N) 12 B at E / A = 135 MeV, which has the str excitation. The differential cross sections for the states around E x = 4.5 MeV and 7.5 MeV were well described by the microscopic DWBA calculation. The spin-dipole strength concentrated around E x = 7.5 MeV was found to be dominated by J π = 2 − .

A focal-plane counter equipped with a large silicon detector

Abstract A focal-plane counter for a magnetic spectrometer was fabricated using a large, home-made silicon detector as an energy counter for particle identification. The resolution of the particle identification was tested by measuring rarely-happening 8 He particles in an environment of a large background of other particles. High-resolution energy signals from the silicon detector were essential for the background reduction. The silicon detector covered an energy range as wide as 5.5%.