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Two-proton relative momentum ($q_{pp}$) and opening angle ($\theta_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$Al $\rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $\rightarrow$ p + p + $^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}\sim20$ MeV/c as well as a peak in $\theta_{pp}$ around 30$^\circ$ are seen in the two-proton break-up channel from a highly-excited $^{22}$Mg. In contrast, such peaks are absent for the $^{23}$Al case. It is concluded that the two-proton emission mechanism of excited $^{22}$Mg is quite different from the $^{23}$Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

We measured the reaction cross sections of the two-neutron halo nucleus 14Be with proton and carbon targets at about 41 and 76 MeV/nucleon. Based on a Glauber model calculation, we deduced the matter density distribution of 14Be in which previously measured interaction cross sections at relativistic energies were also included. An s-wave dominance in 14Be has been confirmed, although the halo tail of 14Be is not distributed as much as that of 11Li. Significant mixing of the p-wave in addition to the s- and d-wave is also suggested.

Interaction cross sections (sigma(1)) for Me isotopes from the stability line to the vicinity of the neutron drip line have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN, The sigma(1) for Ne27-32 in every case exceed the systematic mass-number dependence of sigma(1) for stable nuclei, which can be explained by considering the nuclear deformation. In particular the sigma(1) for Ne-29 and Ne-31 are significantly greater than those of their neighboring nuclides. These enhancements of sigma(1) for Ne-29 and Ne-31 cannot be explained by a single-particle model calculation under the assumption that the valence neutron of Ne-29 (Ne-31) occupies the 0d(3/2) (0f(7/2)) orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of Ne-29 and s- or p-orbital halo in Ne-31. (C) 2011 Elsevier B.V. All rights reserved.

A thick and large solid hydrogen target (SHT) for radioisotope (RI) beams was developed. A target with 100 mm thickness and 50 mm diameter equipped with thin Kapton windows (25 μm) was achieved. We developed a new method to fill solid hydrogen into a large target cell by eliminating any void or porous regions. The expansion of thin Kapton windows and the real thickness of SHT were measured by a laser distance meter and an energy-loss of RI beams, respectively. They gave the same thickness confirming the complete solidification of hydrogen in the cell. We obtained a window expansion of about 2.5 mm (about 1.25 mm for each side).