Study of Spin-Isospin Excitation in Nuclei by the (n, p) Reaction with Monochromatic Neutrons

本研究的目的是：（1）发展单色中子束，使之能够用于En - 40 MeV区的核光谱学和反应动力学研究;（2）研究核中（n，p）反应而不是迄今研究的（p，n）反应对自旋-同位旋的激发。为了实现这样一个困难的研究与二次光束，发射的带电粒子已被分析的磁谱仪配备了检测器阵列，在本工作中构建。我们购买了同位素富集的^<6，7>Li金属用于中子产生靶。利用回旋加速器和放射性同位素中心的中子飞行时间装置对中子束流特性进行了测试。利用由靶、中子准直器和束流阻挡器组成的中子束产生系统，我们获得了强度为5 × 10 ~（-4）<-6>/μ A/sr，分辨率小于7 关于我们 00keV。(ref.（1）在本项目中进行了中子散射实验。用37 MeV质子束轰击7 Li靶，产生35 MeV中子束。用飞行时间系统分析了被^ Si弹性散射和非弹性散射的中子<28>。利用光学模型分析了散射截面的角分布，研究了核平均场中的核极化效应。(ref. 2）在对（n，p）反应可行性研究的基础上，我们的最终目标是研究^<12>C（n，p）^<12>B和^<26>Mg（n，p）^<26>Na反应。我们得到了^<12>C（n，p）^<12>B反应的初步结果.然而，对于后者，我们无法成功地进行实验，主要是由于其横截面较小。作为总结，我们已经建立了一个单能快中子装置，它有足够的规格为中子散射实验，虽然它需要更强的初级束的（n，p）反应更重的核。少

The purposes of this research are (1) development of monochromatic neutron beams, being capable for the studies in nuclear spectroscopy and reaction dynamics in the En - 40 MeV region, and (2) study of spin-isospin excitation by the (n, p) reaction in nuclei, instead of the so far investigated (p, n) reaction. In order to realize such a difficult research with seconderly beams, emitted charged particles have been analyzed by a magnetic spectrometers equipped with a detector array, constructed in the present work. Also developed are data-taking and analyzing soft-wares.We purchased isotonically enriched ^<6, 7>Li metal for the neutron production targets. The properties of neutron beams were tested using the neutron time-of-flight facilities located in Cyclotron and Radioisotope Center. With the neutron-beam production system including target, neutron collimator and beam stopper, we have obtained a neutron beam with its intensity of 5 x 10^<-6> /muA/sr, and with resolution of less than 7 … More 00keV. (ref. 1) We have carried out the neutron scattering experiments in the course of this project. The 7Li target was bombarded by 37-MeV proton beams to produce 35-MeV neutron beams. Elastically and inelastically scattered neutrons by ^<28>Si were analyzed by the time-of-flight system. The angular distribution of scattering cross-section have been analyzed by the optical-model to investigate the core-polarization effects in the nuclear mean fields. (ref. 2) With the feasibility study of the (n, p) reaction, our final aim of this research is to study ^<12>C(n, p)^<12>B and ^<26>Mg(n, p)^<26>Na reactions. We have obtained preliminary results for the ^<12>C(n, p)^<12>B reaction. For the latter, however, we could not perform the experiment successfully, mainly due to its small cross-sections. A more intense proton beam of 100 muA is needed.As a summary, we have constructed a monoenergetic fast-neutron facilities, which has sufficient specification for a neutron scattering experiment, though it needs more intense primary beams for the (n, p) reaction for heavier nuclei. Less