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

这项研究的目的是(1)发展单色中子束，能够在En-40 MeV范围内研究核谱学和反应动力学；(2)研究由核中的(n，p)反应激发的自旋同位旋激发，而不是目前所研究的(p，n)反应。为了实现对二次束流的这种困难的研究，用本工作构建的带有探测器阵列的磁谱仪对发射的带电粒子进行了分析。我们还开发了数据采集和分析软件。我们购买了用于中子生产靶标的同位素浓缩^&lt；6，7；Li金属。利用回旋加速器和放射性同位素中心的中子飞行时间设施测试了中子束的性质。利用包括靶、中子束准直器和束流挡板在内的中子束产生系统，我们获得了强度为5×10~(-6)/µA/sr、分辨率小于7…的中子束更多的00keV。(参考文献)1)在本项目过程中进行了中子散射实验。用37 MeV的质子束轰击7Li靶，产生35 MeV的中子束。用飞行时间系统分析了28&gt；Si的弹性和非弹性散射中子。为了研究核平均场中的核偏振效应，用光学模型分析了散射截面的角分布。(参考文献)2)随着(n，p)反应的可行性研究，本研究的最终目的是研究^&lt；12&gt；C(n，p)^&lt；12&gt；B和^&lt；26&gt；mg(n，p)^&lt；26&gt；Na反应。我们得到了^&lt；12&gt；C(n，p)^&lt；12&gt；B反应的初步结果。然而，对于后者，我们不能成功地进行实验，主要是因为它的横截面很小。综上所述，我们已经建立了一个单能快中子装置，它有足够的规范来进行中子散射实验，但对于较重的核，它需要更强的初级束流来进行(n，p)反应。较少

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