基于加速器的多终端硼中子俘获治疗装置的束流整形组件设计

硼中子俘获治疗(Boron Neutron Capture Therapy, BNCT)是一种新型的精准放射治疗方法，束流整形组件(Beam Shaping Assembly, BSA)作为硼中子俘获治疗装置的重要组成部分，对于产生适用于BNCT的中子束至关重要。通过BSA可以将快中子慢化到适当的能量范围，并且减少其他不需要的束流成分，进而满足BNCT用于治疗的中子束要求。本文利用蒙特卡罗模拟软件MCNP，基于2.5 MeV/30 mA的质子加速器，设计出可将质子打Li靶产生的快中子束慢化到热中子能量范围(<0.5 eV)和超热中子能量范围(0.5 eV~10 keV)的多终端BSA方案。提出的热中子BSA方案使用D₂O作为慢化体，BeO作为反射体，Bi作为$\gamma $过滤体，而超热中子BSA方案使用MgF₂作为慢化体，Pb作为反射体，6LiF作为热中子过滤体。热/超热中子方案在BSA出口处的束流参数，均满足国际原子能机构(IAEA)对BNCT治疗提出的束流指标要求。

Design of Beam Shaping Assembly for an Accelerator-based Multi-terminal BNCT Facility

Boron Neutron Capture Therapy (BNCT) is a new treatment of precision radiotherapy. Beam shaping assembly (BSA) is one of the key components in the facility of BNCT and of vital importance in producing neutron beams appropriate for BNCT treatment. BSA is used to moderate and fast neutrons to suitable energy range, reduce other unwanted ingredients, and meet the requirements for BNCT. In this work, based on a neutron source which produced by a 2.5 MeV/30 mA proton accelerator, the Monte Carlo simulation software MCNP was employed to design BSAs. A multi-terminal BSA scheme was designed to slow down the fast neutron beam generated by proton bombarded Li target to the thermal neutron energy range (<0.5 eV) and the epithermal neutron energy range (0.5 eV~10 keV). The proposed thermal neutron BSA scheme uses D₂O as moderator, BeO as reflector, Bi as $\gamma $ filter, and for epithermal BSA, MgF₂ was used as moderator, Pb as reflector, and 6LiF as thermal neutron filter. All the parameters of the thermal and epithermal neutron beams at the exit ports of the designed BSAs both meet the recommended values proposed by the International Atomic Energy Agency (IAEA).