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This work describes a silicon tracker system developed for experiments with proton-rich radioactive ion beams at the SAMURAI superconducting spectrometer of RIBF at RIKEN. The system is designed for accurate angular reconstruction and atomic number identification of relativistic heavy ions and protons which are simultaneously produced in reactions motivated by studies of proton capture reactions of interest for nuclear astrophysics. The technical characteristics of the tracking array are described in detail as are its performance in two pilot experiments. The physics justification for such a system is also presented. [ABSTRACT FROM AUTHOR]

By using para-hydrogen and a mechanical press made of neodymium magnets, we have succeeded in making a 1-mm-thick and 30-mm-diameter solid hydrogen target (SHT), and have measured elastic scattering of protons with radioactive ion beams at 300 MeV/u. We also succeeded in making not only a 0.5-mm-thick and 10-mm-diameter SHT but also a 2-mm-thick and 30-mm-diameter SHT to study excited-state properties of nuclei via ( p, p′) reactions, and quasi-free ( p, pα) reactions at intermediate energies. The ortho-para converter and the simple mechanical press show possibilities for making SHTs which have various radii and thicknesses. [ABSTRACT FROM AUTHOR]

The C nucleus has been investigated by the neutron knockout reaction of C on a liquid hydrogen target. Applying the invariant mass method in inverse kinematics and γ-ray spectroscopy, the energy spectrum was reconstructed by triple-coincidence measurement, in which neutrons, charged fragments, and γ rays from the decay of the reaction residue (C*) were detected. A peak at 0.47 MeV was observed in the invariant mass spectrum in coincidence with a peak at 0.74 MeV in the γ-ray spectrum, which indicates the presence of an unbound state with an excitation energy of 5.46 MeV. Comparison of the experimental cross section with the value derived by a theoretical calculation provided evidence that the spin-parity of this state is 2. [ABSTRACT FROM AUTHOR]

The one-neutron removal cross section from Ne, Mg, and Si on a Pb target have been measured at around 240 MeV/nucleon at the RIBF (RI-Beam Factory) at RIKEN. This main goal of the experiment was to extract the inclusive Coulomb breakup cross sections in order to probe possible halo structures through their enhanced low-energy E1 strengths - so-called soft E1 excitations. The results showed significant enhancement of the one-neutron removal Coulomb breakup cross section for Mg. This in turn provides evidence for the existence of halo structure in Mg. [ABSTRACT FROM AUTHOR]

The neutron-rich oxygen isotope O has been investigated via proton inelastic scattering on a liquid hydrogen target at 63.5 MeV/nucleon. The invariant mass method in inverse kinematics was employed to reconstruct the energy spectrum. A sharp resonance state was observed at 42(5) keV above the neutron threshold. A comparison of the differential cross section leading to this state with a microscopic DWBA calculation allowed a J assignment of 5/2 for this state. [ABSTRACT FROM AUTHOR]

The unbound excited states of the most neutron-rich dripline oxygen isotope, O, have been investigated by using the O( p, p′)O reaction at the beam energy of 62 MeV/nucleon in inverse kinematics. The first and second unbound excited states of O have been observed at $${E_{\rm x}= 4.63_{-0.14}^{+0.30}}$$ MeV and $${E_{\rm x}= 5.13_{-0.24}^{+0.19}}$$ MeV (preliminary) along with the evidence for another higher lying state at around 7.3 MeV. The quadrupole deformation parameter $${\beta_{2^+}}$$ was deduced to be $${0.15_{-0.03}^{+0.08}}$$ (preliminary) for the first time. The systematics of the $${\beta_{2^+}}$$ and the $${E_{\rm x}(2_1^+)}$$ in the Z = 8 isotopes shows the N = 16 spherical shell closure in O. [ABSTRACT FROM AUTHOR]

Data on the spectroscopy of [sup 5]H and [sup 7]He from recent experiments with radioactive beams in Dubna and in RIKEN are presented. [ABSTRACT FROM AUTHOR]

Proton elastic scatterings of neutron-rich nuclei F and F have been measured for the first time at 289 and 298 MeV/nucleon, respectively, using the MUST2 silicon strip detector array and RIBF facility at RIKEN. The differential cross section of F was found to be smaller than the calculation with the global potential by Koning and Deraloche. The small cross section of F can be well reproduced by an optical model calculation with a shallow and long-tail potential. [ABSTRACT FROM AUTHOR]

We investigated defect formation within nanostructured materials using a transmission electron microscope (TEM) and ion accelerators. Controlling diffusion coefficient of the defects we have first observed changes in pattern of defect clusters, namely, the diffusion-limited reaction of defects in nanocrystals. [ABSTRACT FROM AUTHOR]

High energy np-pairs from aCf source were searched for. They are expected to be emitted with the absorption of negative pions which can be created through spontaneous fissions. The branching ratio is deduced as γ/γ 1.3×10 at the confidence level of 90%. [ABSTRACT FROM AUTHOR]

Searching for effective pathways for the production of proton-rich and neutron-rich isotopes is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. To produce nuclei effectively, an optimal combination of reaction mechanism and energy is required. We report a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for 107Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential for incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste. Revealing how to effectively produce nuclei remains one of the main motivations of recent nuclear reaction and nuclear transmutation studies of radioactive waste. The authors show the enhancement of proton rich isotope production using incomplete fusion mechanism on weakly bound nuclei using the incomplete fusion mechanism by the inverse kinematics technique, in which a radioactive beam of Palladium bombards a proton/deuteron target. [ABSTRACT FROM AUTHOR]