Optimization of a collimator design for an epithermal neutron source based on ⁷Li (p,n) Be reaction and 2.5 MeV...

This work optimized the beam shaping assembly (BSA) for a compact accelerator-based boron neutron capture therapy (AB-BNCT) system with a 2.5 MeV, 10 mA proton beam incident on a lithium target to generate fast neutrons. MgF₂ and Pb were selected as the moderator and reflector materials, respectively. The collimator consisting of a layer of Pb and a layer of ⁶Li enriched polyethylene is studied in detail. ⁶Li enriched PE has greater impact on neutron flux and the ratio of flux and current, and 2.2 cm is chosen to be the thickness of ⁶Li enriched PE layer. Furthermore, a modular collimator design is presented to adjust collimator diameter from 8 cm to 17 cm with a step of 1 cm for different head/neck tumor size and positions. The in-air beam characteristics meet the IAEA criteria published in 2001 and 2023. The in-phantom dose evaluation shows that, with similar beam characteristics, a larger beam diameter can deliver a higher dose rate and deeper advantage depth, double dose depth and triple dose depth.