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We have measured the γ-ray angular distribution of the 12C(α,γ)16O reaction at TRIAC (Tokai Radioactive Ion Accelerator Complex) to accurately determine the E1 and E2 cross sections. In this experiment, we used high efficiency anti-Compton NaI(T1) spectrometers to detect a γ-ray from the reaction with large S/N ratio, intense pulsed α-beams to discriminate true event from background events due to neutrons from 13C(α,n)16O reaction with a time-of-flight (TOF) method. We succeeded in removing a background events due to neutrons and clearly detected γ-ray from the 12C(αγ)16O reaction with high statistics.

The β decay properties of the neutron‐rich isotopes with neutron number N = 126, out of reach by any reaction well established so far, are very interesting from the astrophysical point of view. We will propose β decay lifetime measurements with a new isotope separation system, which is supposed to separate a single species of the radioactive nuclei among target‐like fragments produced via multi‐nucleon transfer reactions in binary heavy ion collisions, by using a gas catcher cell combined with laser resonance ionization technique. The present proposal aims to measure β decay properties of several nuclei around A∼200 with N = 126 and nearby nuclei by using a stable 136Xe beam on a 198Pt target.

We have developed an active‐target type gas‐detector, a Gas Electron Multiplier Multiple‐Sampling and Tracking Proportional Chamber (GEM‐MSTPC) operating with low‐pressure He‐base mixed gas, where He is used as a target for studies of astrophysical nuclear reaction rates. Different kinds of 400 μm thick GEMs were examined. The gain stability was examined with a configuration of GEMs of 400 μm in thickness fabricated in different ways, against the injection rate of low‐energy heavy ions of 105 particles per second. The gain of GEM with Cu electrodes coated by Au was observed to be stable up to the injection rate of 105 particles per second.

We report a recent experiment about the measurement of wall distribution of ions externally injected for charge‐breeding in an electron cyclotron resonance (ECR) ion source. The ions, radioactive and singly charged 111In, were injected into the ECR ion source (ECRIS) for breeding their charge states at the Tokai Radioactive Ion Accelerator Complex (TRIAC). The residual radioactivity on the wall of the ECR plasma chamber of the source was measured, giving a two‐dimensional distribution of the ions failed to be re‐extracted during charge breeding. The distribution was decomposed, according to azimuthal symmetry, into three components, asymmetric, 120‐degree symmetric, and isotropic ones, whose origins were qualitatively discussed for clarifying ion‐losses in the course of charge breeding in ECRIS.

In order to study the nucleus‐nucleus interaction in Pb‐based cold fusion, we have measured excitation functions for quasi‐elastic scattering of 48Ti, 54Cr, 56Fe, 64Ni, 70Zn and 86Kr projectiles on 208Pb target at backward angles. The barrier distributions were derived from the first derivative of measured quasi‐elastic scattering cross sections relative to the Rutherford scattering cross section. The centroids of the barrier distributions show a deviation from several predicted barrier heights toward the low energy side. The shape of the barrier distributions is well reproduced by the results of a coupled‐channel calculation taking account of the coupling effects of two phonon excitations of the quadrupole vibration for the projectiles and of the octupole vibration for the 208Pb target.

In order to study the nucleus‐nucleus interaction in Pb‐based cold fusion, we have measured excitation functions for quasi‐elastic scattering of 48Ti, 54Cr, 56Fe, 64Ni, 70Zn and 86Kr projectiles on 208Pb target at backward angles. The barrier distributions were derived from the first derivative of measured quasi‐elastic scattering cross sections relative to the Rutherford scattering cross section. The centroids of the barrier distributions show a deviation from several predicted barrier heights toward the low energy side. The shape of the barrier distributions is well reproduced by the results of a coupled‐channel calculation taking account of the coupling effects of two phonon excitations of the quadrupole vibration for the projectiles and of the octupole vibration for the 208Pb target.

Two systems of 64Ni+118Sn and 58Ni+124Sn produce the same compound nucleus 182Pt in the fusion reaction and they show the similar fusion cross sections below and near the Coulomb barriers, although only the system of 58Ni+124Sn has positive Q‐value multi‐neutron transfer channels of 1–11 neutron(s). In order to investigate the possible effect of positive Q‐value multi‐neutron transfer channels on the capture cross sections, the quasi‐elastic back‐scattering for the two systems were measured below and near the Coulomb barriers at the backward angles of 162° and 172°. The beam energies were altered in the energy range and the quasi‐elastic back‐scattering excitation functions were obtained. They were compared with the coupled‐channel calculations of collective excitations and a two‐neutron transfer channel, indicating no evidence of a significant effect of the positive Q‐value multi‐neutron transfer channels on the capture cross sections for the system of 58Ni+124Sn.

The excitation functions of the 8Li(d,t)7Li and the 8Li(d,p)9Li reactions were directly measured using 8Li beams with Ecm = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV irradiating CD2 targets. These beam energies covered the Gamow peaks for 1−3×109 K. Large cross sections were observed at around Ecm = 0.8 MeV for the 8Li(d,t)7Li and Ecm = 1.0 MeV for the 8Li(d,p)9Li, implying the existence of a resonant state of 10Be at the excitation energy of around 22.4 MeV. Enhanced with the present work, the astrophysical reaction rates of the 8Li(d,t)7Li and the 8Li(d,p)9Li reactions are higher by one and two orders of magnitude than the previously evaluated ones, respectively.

We have developed a pulsed neutron Ramsey resonance for a T‐violation experiment on polarized neutron transmission through a polarized nuclear target. Two separated oscillatory fields were placed in a pulsed neutron beam line, which were synchronized with a neutron pulse for precision neutron spin manipulation. We observed neutron Larmor precession between the two oscillatory fields as a function of a neutron time of flight (TOF). We modulated the phase of the second oscillatory field with respect to the first oscillatory field. The effect of the phase modulation was found in a neutron intensity modulation as a function of the TOF. From the neutron intensity modulation, the neutron spin direction as well as the neutron velocity between the two oscillatory fields was precisely obtained.

An ISOL‐based radioactive nuclear beam facility, Tokai Radioactive Ion Accelerator Complex (TRIAC), has been jointly constructed by High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). The facility started to provide RNBs for experiments in 2005. RNBs, including fission fragments with energies up to 1.1 MeV/nucleon, are available. The experiments were performed with accelerated 8Li beams of various energies. Current status of the equipments and preliminary results on these experimental studies are presented.

The 8Li(α,n)11B reaction has been measured directly and exclusively in the energy region of Ecm=0.45–1.75 MeV by using highly efficient detector system covering Ecm= 0.56 MeV, which corresponds to the Gamow window at T9=1. This experiment has been performed in the condition of inverse kinematics by using low‐energy radioactive 8Li beam at the Tandem accelerator facility of Japan Atomic Energy Research Institute. The reaction cross section obtained in the present measurement is consistent with that of the previous exclusive measurements within the errors in an overlapping energy region, but is less than half of that of the inclusive measurements, in particular for lower energy region.

The dependence of the fusion probability on the orientation of deformed nuclei was investigated for the 60Ni+154Sm and 76Ge+150Nd reactions. The fusion of the 82Se+nulCe (spherical) reaction was also measured to compare its fusion probability with that of the 76Ge+150Nd reaction. Evaporation residues were measured for these reaction systems in the vicinity of the Coulomb barrier and the fusion probability was extracted as a function of bombarding energy. It was found that the fusion probability depends strongly on the orientation of the nuclear deformation. The fusion probability is considerably reduced when the projectiles collide at the tip of the deformed nuclei. On the other hand, when the projectiles collide at the side of the deformed nuclei, the fusion occurs without any hindrance. This phenomenon is understood qualitatively by comparing the distance between the mass centers of two colliding nuclei at touching with the position of the saddle point of the compound nucleus.

A Radioactive beam facility using a thick target, an ISOL and heavy ion linacs will soon come into operation at INS, University of Tokyo. The status of the project together with experimental programs are reported.

To study the decay mechanisms of intermediate mass fragments and fission products from a hot compound nucleus, we made an experiment for 84Kr+27Al at the energy of 10.6 MeV/u using Riken Ring Cyclotron Facility. The distributions of nuclear element Z and its isotope mass are extensively analyzed in terms of Extended Hauser‐Feshbach Method (EHFM) and it is concluded that the sequential decay plays an important role in the decay process from the highly excited compound nucleus. The dependence of element distributions on angular momentum is intensively discussed by comparing the two systems 84Kr+27Al and 3He+Ag, which form the same compound nucleus with different angular momentum window at the same excitation energy.