Measurement of Continuous Energy Neutron Incident Neutron Production Double Differential Cross sections

在洛斯阿拉莫斯中子科学中心(LANSCE)测量了800 MeV以下的中子产生双微分截面。入射的中子具有连续的能量，因为在该设施中发射的中子。出射中子的能量由散热器反冲质子的沉积能获得。首先，利用美国国家放射科学研究所(NIRS)的Ar束与铅靶的散裂反应产生的连续能中子，搭建了由NaL(Tl)和塑料闪烁体组成的两种尺寸的光敏型反冲质子探测器，并对其进行了测试。接下来，我们在高能加速器研究机构(KEK)用高达500 MeV的单能质子对探测器进行了检验，通过实验获得了探测器的特性，然后在LANSCE上测量了中子入射中子产生(n，xn)的双微分截面。受辐射的目标是一块铁和一根铅。探测角度分别为15度、30度和90度。对于较小的光伏探测器来说，很难将中子事件与背景事件区分开来。为了提高探测效率，采用了有机闪烁体和飞行时间法相结合的方法。该方案对100 MeV以下较低能量发射的中子具有很好的分辨能力，对连续入射能量中子的(n，xn)双微分截面的测量具有较高的实用价值。

The neutron-production double-differential cross sections for neutron incidence up to 800 MeV were measured up to 800 MeV at Los Alamos Neutron Science Center (LANSCE). The incident neutrons have continuous energies as emitted neutron at the facility. The energy of emitted neutron was obtained by the deposition energy of recoil proton from the radiator. The energy of incident neutron was determined by the time-of-flight method and the emitted neutron energy.First, the two sizes of phoswich type recoil proton detectors consist of Nal(Tl) and plastic scintillator were constructed and tested by the continuous energy neutron generated from the spallation reaction by Ar beam and Pb target at National Institute for Radiological Science (NIRS). Next, the detectors were checked by mono energetic proton up to 500 MeV at High Energy Accelerator Research Organization (KEK), We obtained the characteristics of the detectors experimentally.Then we measured the neutron-incident neutron-production (n, xn) double-differential cross sections at LANSCE. The irradiated targets were an iron and a lead. The detection angles were 15, 30 and 90 degrees. It was difficult to discriminate the neutron events from the background ones for the smaller phoswich detectors. To increase the detection efficiency, the combination of organic scintillator and the time-of-flight method was adopted. The scheme made the discrimination much clear and was effective for lower energy emitted neutron below 100 MeV.The capability of the measurement of (n, xn) double-differential cross sections for the continuous incident energy neutron was shown in this study.