Proton-Rich Nuclei Studied by Multi-Nucleon Transfer Reactions

本研究的目的是通过多核子转移反应研究富质子核的结构。这些信息将有助于理解恒星环境中发生的快质子过程和宇宙中化学元素的演化。对于上述反应的实验研究，由于与巨大的背景反应相比，预期反应的截面很小，因此开发高性能的粒子识别计数器系统是必不可少的。1996年，我们订购了一家公司来制造一个大的BSO晶体。大小达到了30 mm x 30 mm x 200 mm，这是世界上最大的晶体。通过增加几套相同的组件，这种晶体可以很容易地扩展到用于伽马探测的全立体角计数器系统。1997年，在增加了光导和光电倍增器后，用伽马源进行了离线测试，以考察计数器的性能。此外，利用Tanashi高能加速器研究机构的电子同步加速器的电子束进行了广泛的研究。作为相关研究，我们还利用同一加速器上的电子束对CSI和PWO晶体的性能进行了研究。前者广泛应用于低能区，后者广泛应用于高能区。BSO可以被视为位于两者之间。

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.