Development of a 4pi position-sensitive detectors and a study on the measurement of nuclear-reaction cross sections induced by polarized neutrons in the energy region around MeV

为了研究中子核反应的双微分截面，研制了一套宽角接受带电粒子对角望远镜系统。对焦系统具有粒子种类识别、总能量测量和通过路径的光线跟踪等功能，作为该系统的一部分，新设计和制造了一种二维位置灵敏气体计数器。在该气体计数器中，每个轴采用两种不同的方法相结合的方法来实现二维位置传感：一种是双陆棋形电极的电荷分割法，另一种是基于电子漂移时间的测量方法。该位置灵敏气体计数器的灵敏度约为100×100 mm^2，固有位置分辨率为0.75 mm，具有传输能力。因此，当多个这样的探测器堆叠在一起时，可以通过光线追踪来确定通过粒子的角度。在光线追踪系统后面放置了一个48x48 mm^2敏感面积和300微米厚度的SSD来测量入射带电粒子的总能量。利用CAMAC电子设备开发了一种基于个人计算机的数据采集系统。最后，在九州大学串列加速器装置上，利用中子束从聚乙烯靶上弹性散射的约9 MeV质子，成功地验证了该反望远镜系统的实用性。

In the present research, a charged particle counter-telescope system with wide angular acceptance has been developed for the investigation of the double differential cross section of neutron-induced nuclear reactions. The counter-telescope system is capable of identification of particle sorts, measurement of the total energy and ray-tracing of the passing path.As a part of this counter-telescope system, a two-dimensional position-sensitive gas counter was newly designed and constructed. In this gas counter, two-dimensional position sensing is achieved with a combination of two different methods for each axis ; one is the charge division method with a backgammon-shaped electrode and the other method is besed on the measurement of electron drift time. The sensitive area is about 100x100 mm^2 and the inherent position resolution has been estimated at 0.75 mm in FWHM.This position-sensitive gas counter has transmission capability. Therefore, angle determination of passing particles is available by the ray-tracing when several such detectors are stacked.A SSD,48x48 mm^2 sensitive area and 300 mum thickness, was put behind the ray-tracing system to measure the total energy of incident charged particles. A personal-computer based data-acquisition system has been developed with CAMAC electronics. On-line data analysis is possible in this data-acquisition system.Finally, the practicability of this counter-telescope system was successfully demonstrated at the Tandem Accelerator facility of Kyushu university using about 9 MeV protons which were elastically scattered from a polyethylene target by the neutron beam.