Development of a SQUID-type detector and a study on systematics of neutron optical potential in the energy region from 0 to a few MeV.

光学模型是核工程领域中计算中子截面最有效、最有用的模型。该模型用复光学势U(r，E)=V(r，E)+iW(r，E)描述了中子与原子核在宽能量范围内的平均相互作用。另一方面，最近的研究表明，由色散理论导出的光学势既代表了广泛的中子能量范围内的中子散射态，也代表了束缚态。色散关系为更精确地估计光学势能提供了一种有用的方法。通常W(r，E)必须在较宽的能量范围内已知，才能进行基于该关系的分析。然而，到目前为止，由于虚表面势W(r，E)小于费米表面能的值不是直接从实验中获得的，所以它还没有得到很好的研究。我们利用RCNP(大阪大学)的偏振束对几个原子核进行了(d，P)或(p，d)反应实验，并估算了单粒子态或空穴态的扩散宽度G。在关系G=2W的基础上计算相应的W(r，E)。以同样的方式重新分析先前获得的数据。此外，我们还对一种新型的SSD望远镜系统进行了一些基础性的研究，为以后的相关实验做了准备。通过本项目的工作，我们建立了一种估算中子光学势虚表面势W(r，E)的方法，为进一步的研究找到了可行性。

The optical model is the most valid and useful model for neutron cross-section evaluation in the nuclear engineering field. The model describes an averaged interacton between neutrons and nuclei in the wide neutron energy range by using the complex optical potential, U(r, E) = V(r, E) + iW(r, E). Continuing efforts have been devoted to a more precise determination of the neutron optical potential.On the other hand, recent studies have shown that an optical potential derived from the dispersion theory represents both the neutron scattering states and bound states in the wide neutron energy range. The dispersion relation offers a useful method to evaluate optical potential more precisely. Usually W(r, E) must be known in the wide energy range for the analysis based on the relation. So far, however, the imaginary surface potential W(r, E) less than the Fermi-surface energy has not been well investigated because the value is not obtained from experiments directly.From this point of view, in the present work, we have studied the systematics of neutron optical potential. We carried out (d, P) or (p, d) reaction experiments for several nuclei by using polarized beam at RCNP (Osaka University) and evaluated the spreading width, G, of the single particle or hole states. The corresponding W(r, E) was calculated on the basis of the relation G = 2W.Previously obtained data were reanalyzed in the same manner. In addition to this, we made some basic investigation on a new type SSD telescope system for the future experiments related to this subject.From the work in this project, we have established an evaluation method of imaginary surface potential W(r, E) of the neutron optical potential and found the feasibility for further investigations.