能量拓展型长中子计数器响应特性研究

Simulation and experimental characterization of an energy-extended neutron long counter

高能中子的测量在空间中子所致剂量评估和高能粒子加速器辐射防护等方面越来越重要。介绍了一种能量拓展型长中子计数器的性能研究模拟及测试结果。这种能量拓展型长中子计数器是基于De Pangher的设计,通过在长中子计数器内层慢化体嵌入金属铅和铬材料,利用中子与金属材料的(n,xn)增殖反应,改善了其高能响应。采用蒙特卡罗模拟优化了长中子计数器的结构,获得在1 keV~20 MeV、1 keV~150 MeV能量范围内最大值相对平均值偏差为12.2%响应特性曲线。利用Am-Be中子源和D-T中子源标准辐射场测试了长中子计数器的有效中心和能量响应,验证了长中子计数器在20 MeV内的能量响应。将实验结果与蒙特卡罗模拟计算相比较,结果表明:理论计算与实验在误差范围内一致。

[Background]The measurement of high-energy neutrons is becoming more and more important in the evaluation of dose caused by space neutrons and the radiation protection of particle accelerators.[Purpose]The study aims to investigate the performance of an energy-extended neutron long counter.[Methods]The energy-extended neutron long counter was designed based on De Pangher type.The(n,xn)multiplication reaction between neutrons and metallic materials was utilized to improve the high-energy response of neutron long counter by adding metal chromium and lead materials into the moderator of the neutron long counter.Then,the structure of the neutron long counter was optimized by using Monte Carlo simulation to obtain the maximum value within the energy range of1 keV~20 MeV and 1 keV~150 MeV,respectively.Finally,the effective center and energy response of the long neutron counter were measured by Am-Be neutron source and D-T neutron source in the standard radiation field.[Results]The calculated response curve shows that the deviation of the maximum value from the average value is12.2%in above energy range.The comparison between experimental results and the Monte Carlo simulation results shows that the theoretical calculation is consistent with the experiment within the error range.[Conclusion]The upper energy limit of the long neutron counter can be extended by embedding metallic lead and chromium materials in the inner polyethylene layer of the long neutron counter.