基于2.5 MeV质子加速器BNCT装置的中子慢化材料性能模拟研究

基于加速器中子源的硼中子俘获治疗(Boron Neutron Capture Therapy, BNCT)是新一代的放射治疗方法，束流整形体(Beam Shaping Assembly, BSA)作为硼中子俘获治疗装置的重要组成部分，其作用是将中子源中的快中子束流慢化至超热中子能区(0.5 eV~10 keV)，并尽可能减少快中子、热中子以及$gamma $射线的成分，使其满足BNCT用于治疗的中子束要求。本工作基于蒙特卡罗软件包Geant4(Geometry and Tracking)，以2.5 MeV，10 mA质子流强的7Li(p, n)7Be中子源为对象，研究分析了AlF₃ 、Fluental、Al₂O₃、Al作为慢化体材料时，不同的厚度对束流出口处的超热中子注量率、超热中子注量与热中子注量比值、快中子成分、$ gamma $成分所产生的影响。计算表明，当选用厚度为25 cm的AlF₃作为慢化体材料时，经过整形慢化后的超热中子束的束流参数，均满足国际原子能机构(International Atomic Energy Agency, IAEA)的中子束流参数推荐值。

Simulation of Neutron Moderating Materials Performance Based on BNCT of 2.5 MeV Proton Accelerator

Boron Neutron Capture Therapy (BNCT) based on accelerator neutron source is a new generation of radiation therapy. As an important part of the BNCT facility, Beam Shaping Assembly (BSA) aims to moderate the fast neutron beam in the neutron source to the epithermal neutron energy region (0.5 ev~10 keV), and to minimize the components of fast neutron, thermal neutron and $gamma $ ray during the treatment. The 7Li(p, n)7Be reaction with a 2.5 MeV/10 mA proton intensity was taken as the method for generating neutrons. In this paper, the Monte Carlo software package Geant4 (Geometry and Tracking) was used to study and analyze the effects of different thicknesses of AlF₃, Fluental, Al₂O₃ and Al as moderator materials on the epithermal neutron flux rate, epithermal neutron flux to thermal neutron flux ratio, fast neutron and $gamma $ ray components at the beam exit. The results show that when AlF₃ with a thickness of 25 cm is selected as the moderator material, the neutron beam parameters of the epithermal neutron beam after shaping and moderation all meet the recommended value by the International Atomic Energy Agency (IAEA).