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）测量了高达800 MeV的中子入射中子产生双微分截面。入射中子作为发射中子具有连续的能量。发射中子的能量由辐射体中反冲质子的沉积能量得到。入射中子的能量由飞行时间法和发射的中子能量确定。首先，构建了Nal（Tl）和塑料闪烁体组成的两种尺寸的光导型反冲质子探测器，并利用美国国家放射科学研究所（NIRS）的Ar束和Pb靶的散裂反应产生的连续能量中子进行了测试。然后，在高能加速器研究组织（KEK）用高达500 MeV的单能质子对探测器进行了检验，实验得到了探测器的特性。然后我们在LANSCE上测量了中子入射中子产生（n, xn）的双微分截面。受辐照的目标是一个铁和一个铅。检测角度分别为15度、30度和90度。对于较小的光子探测器来说，中子事件和背景事件很难区分。为了提高探测效率，采用了有机闪烁体与飞行时间相结合的方法。该方案对100 MeV以下的低能发射中子具有明显的分辨效果。本研究显示了测量连续入射能量中子（n, xn）双微分截面的能力。

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.