反冲质子卡阈中子探测靶室偏转磁场设计  

Deflecting Magnetic Field Design for Recoil-Proton Neutron Detection System With High Energy Threshold

作　　者：刘金良[1] 何世熠 张显鹏[1] 陈亮[1] 张建福[1] 欧阳晓平[1] LIU Jinliang;HE Shiyi;ZHANG Xianpeng;CHEN Liang;ZHANG Jianfu;OUYANG Xiaoping(State Key Laboratory of Intense Pulsed Radiation Simulation and Effect,Northwest Institute of Nuclear Technology,Xi’an 710024,China)

机构地区：[1]强脉冲辐射模拟与效应国家重点实验室,西北核技术研究所,西安710024

出　　处：《现代应用物理》2023年第1期46-53,共8页Modern Applied Physics

基　　金：国防科技卓越青年基金资助项目(2022-JCJQ-ZQ-011)。

摘　　要：准确测量脉冲辐射场特征参数对研究核装置反应过程、开展核技术应用具有重要意义。为解决ICF聚变初级中子等高能中子的精确测量及面临的伴随X/γ干扰问题,研究了反冲质子高能量卡阈中子探测靶室的γ和中子灵敏度随偏转磁场的变化。首先,分析了中子探测靶室的X/γ干扰主要来源,在密封窗口处和靶腿位置分别设置清扫磁场和偏转磁场,降低探测器对X/γ和次级电子的响应。然后,详细计算了靶室灵敏度随所加磁感应强度和方向的变化。模拟结果表明:在密封窗口处设置高强度清扫磁场可一定程度降低靶室对X/γ灵敏度,在靶腿处设置偏转磁场对X/γ响应的抑制效果更好;靶腿处偏转磁场使聚乙烯靶上产生的次级电子向靶腿内侧方向偏转时效果更优;偏转磁场对中子灵敏度的影响与靶室反冲质子卡阈能量和磁场方向有关,强偏转磁场会使系统的高能中子灵敏度响应曲线发生显著变化,在应用中必须仔细考虑。最后,精细测量了探测靶室靶腿内偏转磁场的3维分布,计算了靶室中子和X/γ灵敏度随射线能量的变化。理论计算数据与CPNG-400高压倍加器14.9 MeV准单能中子灵敏度标定结果对比,相对偏差小于3%,理论值与实验结果评价在不确定度范围内一致。It is of great significance to measure characteristics of pulsed radiation field accurately for researches on nuclear device reaction and nuclear technology applications.Pulsed neutron radiation field is always accompanied with X/γ.To solve the problem of high-energy neutron detection such as ICF fusion and to avoid the associated X/γinterference in the detection,a recoil-proton neutron detector with high-energy threshold is proposed.The variation of X/γand neutron sensitivity in response to magnetic field is studied in this paper.Firstly,the main interference points of X/γin the neutron detection chamber are analyzed.Magnetic fields near the sealing window and around the detection legs of the detection chamber are designed to reduce sensitivity of incident X/γwhich generate secondary electrons through the action in sealing window and polyethylene target.Secondly,the variation of the X/γand neutron sensitivity with the magnetic induction strength is calculated.The simulation results show that the high strength magnetic field near the sealing window can reduce the chamber's X/γsensitivity to some extent,while the deflection magnetic field around the leg will reduce X/γsensitivity more effectively.The effect is more effective when the magnetic field deflects the secondary electron towards the direction of incident particle beam.The influence of deflecting magnetic field to neutron sensitivity is related to the recoil-proton energy threshold of the detection chamber and direction of magnetic field in the chamber legs.It must be carefully considered in practical application that a high strength deflection magnetic field will make the sensitivity response to high-energy neutrons obviously changed.Finally,a tri-dimensional distribution of deflection magnetic field in chamber legs is carefully measured,and the sensitivity response curves to neutrons and X/γare calculated.The experimental neutron sensitivity of the chamber to 14.9 MeV quasi-single neutrons measured at CPNG-400 Cockcroft-Walton accelerator corres

关 键 词：反冲质子卡阈 高能中子探测 偏转磁场 灵敏度响应 

分 类 号：TL81[核科学技术—核技术及应用]