Beam shaping assembly design of Li(p,n) neutron source with a rotating target for boron neutron capture therapy

With rapid development in recent years, the accelerator-based boron neutron capture therapy (AB-BNCT) has been paid more and more attention. Our team designed a set of AB-BNCT facility based on the Li(p,n) reaction. We suppose to use a radio frequency quadrupole field accelerator with a 2.8 MeV, 20 mA proton beam to bombard a rotating lithium target. The generated neutrons were moderated by a beam shaping assembly (BSA) to get an epithermal neutron beam for tumor treatment. This paper introduced the parameter calculation and analysis of back reflector, rotating gap and moderator in BSA, discussed the influence of the density of magnesium fluoride block as a moderator on the outgoing neutron beam in detail, and evaluated epithermal neutron beam with a water and Snyder phantom. Finally, it is concluded that a 20 cm lead as the back reflector, the rotation gap of 6 cm, and the density of magnesium fluoride blocks of above 2.5 g/cm3 could make the neutron beam meet the treatment needs. And the density of 2.8 g/cm3 as a compromise choice could obtain an epithermal neutron beam with good therapeutic potential with consideration of the processing difficulty and cost.