[en] A new gaseous active target based on a time projection chamber, named CAT, is introduced. The remarkable feature is a dual gain THGEM to decrease the effective gain for the beam particles while keeping a high enough effective gain for the recoil particles. The measured effective gain of low gain region was a factor of one hundred smaller than that of high gain region. This technique provides a wide dynamic range in order to detect both the beam and recoil particles at the same time even with a very high intensity beam of more than 10⁵ Hz. (author)

[en] An active target system called CAT, has been developed aiming at the measurement of deuteron induced reactions with high intensity beams in inverse kinematics. The CAT consists of a time projection chamber using THGEM and an array of Si detectors or NaI scintillators. The effective gain for the recoil particle is designed to be 5 - 10 x 10"3 , while one for the beam is reduced by 10"2 using mesh grid to match the amplified signal to the dynamic range same as the one for recoil particle. The structure of CAT and the effect of the mesh grid are reported. (author)

[en] A new “separated flow” operating mode has been developed for in-flight proton-decay experiments using the SHARAQ spectrometer. In this mode, the protons and heavy-ion products are separated and measured in coincidence at two different focal planes of the SHARAQ. The ion-optical properties of the new mode were studied using a proton beam at 246 MeV, and the momentum vector was reconstructed from the parameters measured in the focal plane of the SHARAQ. In the experiment with the ("1"6O, "1"6F) reaction at a beam energy of 247 MeV/u, the outgoing "1"5O+p produced by the decay of "1"6F were measured in coincidence with the SHARAQ. High energy resolutions of 100 keV (FWHM) and ∼2 MeV were achieved for a relative energy of 535 keV and a "1"6F kinetic energy of 3940 MeV, respectively. The mode allows a new form of missing-mass spectroscopy using a reaction probe with a particle-decay channel.

[en] Deuteron inelastic scattering (d, d') provides a promising spectroscopic tool to study nuclear incompressibility. In studies of deuteron inelastic scattering of unstable nuclei, measurements of low-energy recoiled particles is very important. In order to perform these measurements, we are developing a GEM-TPC based gaseous active target, called CAT (Center for nuclear study Active Target), operated with pure deuterium gas. The CAT has been tested with deuterium gas at 1 atm and 100-μm-thick GEMs. The low-pressure operation of CAT is planned in order to improve the detection capability for lower-energy recoil particles. A 400 μm-thick gas electron multiplier (THGEM) was chosen for the low-pressure operation of CAT. However, the properties of THGEM in low-pressure deuterium are currently undocumented. In this work, the performance of THGEM with low-pressure pure deuterium gas has been investigated. The effective gas gain of THGEM has been measured in various conditions using a 5.5-MeV ²⁴¹Am alpha source. The effective gas gain was measured for 0.2-, 0.3- and 0.4-atm deuterium gas and a gas gain of about 10³ was achieved by a double THGEM structure at 0.2 atm. The maximum achieved gain decreased with increasing gas pressure. The dependences of the effective gas gain on the electric field strengths of the drift, transfer and induction regions were investigated. The gain stability as a function of time in hydrogen gas was also tested and a relaxation time of THGEM of about 60 hours was observed with a continuous irradiation of alpha particles, which is significantly longer than previous studies have reported. We have tried to evaluate the gas gain of THGEM in deuterium gas by considering only the Townsend ionization process; however, it turned out that more phenomenological aspects, such as transfer efficiency, should be included in the evaluation. The basic properties of THGEM in low-pressure deuterium have been investigated for the first time

[en] The alpha inelastic scattering from ²⁴Mg was measured to obtain the isoscalar natural-parity excitation strengths and to search for the α-condensed states. The multipole decomposition analysis for the measured cross sections was performed. The strength distributions for the ΔL = 0-3 were successfully obtained and the possible candidates for the α-condensed states around the ¹⁶O core were found. (author)

[en] The alpha inelastic scattering from ²⁴Mg was measured to obtain the isoscalar natural-parity excitation strengths and to search for the α-condensed states. The multipole decomposition analysis for the measured cross sections was performed. The strength distributions for the ΔL = 0-3 were successfully obtained and the possible candidates for the α-condensed states around the ¹⁶O core were found.

[en] The alpha inelastic scattering from ²⁴Mg was measured to obtain the isoscalar natural-parity excitation strengths and to search for α-condensed states. Multipole decomposition analysis was performed for the measured cross sections, and the strength distributions for the ΔL = 0–3 transitions were successfully obtained. The decay particles from the excited states in ²⁴Mg were also measured in concidence with the inelastically scattered alpha particles. Candidates were found for α-condensed states around the ¹⁶O core.

[en] We are developing a neutron detector with a position resolution better than 3 mm to study the single particle properties of nuclei by the knockout (p; pn) reaction at intermediate energies. We constructed a prototype detector consisting of scintillating fibers and multi-anode photomultiplier tubes (PMTs). Scintillation photons generated in each fiber are transported via pitch conversion fibers having no scintillation ability, to the photo-cathode planes of a multi-anode PMT (Hamamatsu H7546B). We use the dynode signal for determining the reaction timing and the reaction position along the y-direction, as well as the anode signals for the hit pattern analysis on (x, z)-plane. A test experiment using 70-MeV proton and 68- and 50-MeV neutron was performed for characterizing its performance. In preliminary results, a position resolution of about 3 mm, is realized, as designed. The resulting separation-energy resolution would be 1 MeV, when using this system at a distance of 2 m from the target for measuring the (p,pn) reaction

[en] For the study of three nucleon force (3NF) effects in the intermediate energy region, the differential cross sections and the vector analyzing power A_y were measured for the ²H(p, n) inclusive breakup reaction at 170 MeV. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD2) target and the energy of scattered neutrons were deduce by TOF method. The data was compared with the results of the Faddeev calculations with and without 3NFs. Concerning about the differential cross sections, we can see large discrepancies between the data and the calculations in the region where the energies of scattered neutrons are low, which are similar to the results of the ²H(p, p) inclusive breakup reaction at 250 MeV. (author)

[en] The effects of three-nucleon force (3NF) has been actively studied by using the nucleon–deuteron (Nd) scattering states. The differential cross sections of the elastic Nd scattering at the energy below 150 MeV can be well reproduced by incorporating 3NF in the Faddeev calculation based on modern nucleon–nucleon (NN) interactions. On the other hand, the differential cross sections of Nd elastic and inelastic scatterings at 250 MeV show large discrepancies between the data and the Faddeev calculations with 3NF. It indicates the presence of the missing features of the three nucleon system at this energy region. For the systematic study about the energy dependence of this large discrepancies, we measured the differential cross sections and the vector analyzing power A_y for the ²H(p, n) inclusive breakup reaction at 170 MeV. The experiment was carried out at RCNP by detecting scattered neutrons by using the neutron detector NPOL3. The data was compared with the results of the Faddeev calculations with and without the 3NF. (author)