Perturbation-theory-guided design of beam-shaping assemblies

A variety of facilities for medical applications of nuclear radiation require the design of a beam-shaping assembly (BSA). Its purpose is to shape the spectrum and/or geometry of the beam for maximizing the treatment efficiency. The BSA optimization can be very complex since it may involve dozens of independent variables. Conventional nuclear design tools and practices are not effective for such an optimization. The purpose of this paper is to illustrate how first-order perturbation theory can help in the search for optimal BSAs. The illustration pertains to boron neutron capture therapy (BNCT) based on a neutron source obtained via the {sup 7}Li(p,n) reaction induced by 2.5-MeV protons.