2.45 MeV小型D-D中子管准直屏蔽结构设计

为获取小角度出射的单能中子源，采用蒙特卡罗软件对小型D-D中子管产生的能量为2.45 MeV的4立体角中子源进行了准直屏蔽结构设计。准直屏蔽结构分为准直器和捕获穴，准直器采用铁+含硼聚乙烯+铅的三层过滤结构，用于屏蔽照射野外杂散中子，捕获穴主要功能是增加反方向中子的弹性散射次数，从而降低出射束低能散射中子的比例。通过MCNP模拟得到了准直器各层材料的最佳厚度和出射孔尺寸以及捕获穴最佳结构。经验证，中子照射野处2.45 MeV的中子通量比照射野外大三个量级，中子照射野处低能中子通量比2.45 MeV的中子通量低一个量级，墙壁外总剂量率（中子+）在2.5 Gy/h以下。该研究对于小角度单能中子源的快速获取具有一定的实用价值，获取的中子源可用于中子剂量仪器有效性检验、中子监测仪性能测试等方面的研究。

Design of alignment and shielding structure for small D-D neutron tube with 2.45 MeV neutron source

In order to obtain a small angle monoenergetic neutron source, the Monte Carlo software is used to design the shield collimating structure of the small 4 neutron source with energy of 2.45 MeV produced by a D-D neutron tube. The shield collimating structure is divided into a collimator and a capture cave. The collimator is made of three layers of iron, boron containing polyethylene and lead, which is used to shield the stray neutrons from the irradiation outside. The main function of the capture cave is to increase the number of elastic scattering in the opposite direction, thus reducing the proportion of the low energy scattered neutrons. The optimum thickness of the material and the size of the aperture and the optimum structure of the capture cave are obtained by MCNP simulation. Finally it is proved that the neutron flux of neutrons with 2.45 MeV energy in the radiation field is three orders of magnitude higher than that outside the radiation field. The low energy neutron flux in the radiation field is one order lower than the 2.45 MeV neutron flux, the total dose rate of both neutron and gamma outside the walls is below 2.5 Gy/h. This research has practical value for small angle neutron source with single energy, and it has important significance for the study of the verification of validity of neutron dosimeter and performance test of neutron monitor.