Proton-Rich Nuclei Studied by Multi-Nucleon Transfer Reactions

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The aim of this research is to study the structure of proton-rich nuclei by mutli-nucleon transfer reactions. The information will be useful for the understanding of the rapidproton process which occurs in stellar environments and of the evolution of chemical elements in the universe. For the experimental study of the above-mentioned reactions, the development of counter system with high performance of particle identification is essential because the cross section of the expected reaction is very small compared to the huge background ones.We studied the characteristics of the BSO crystal as a scintilator for particle and gamma detection. In 1996, we ordered a company to fabricate a large BSO crystal. The size was as large as 30mm x 30mm x 200mm which is the largest crystal ever made in the world. This crystal can easily be extended to a counter system which covers full solid angle for gamma detection by adding several identical sets.In 1997, after adding a light guide and a photo-multiplier, an offline test to investigate the performance of the counter was made with a gamma source. Further, an extensive study was made by using an electron beam from the electron synchrotron of High Energy Accelerator Research Organization at Tanashi. We could obtain position and energy resolutions as expected.As a related study, the performances of the CsI and the PWO crystals were also investigated using electron beams from the same accelerator. The former is widely used in the low-energy region, and the latter in the high-energy one. The BSO can be regarded as being located between them.