Abstract
Abstract
Lithium is generally adopted as the target to generate
epithermal neutrons based on 7Li(p,n)7Be nuclear reaction
for the application of accelerator-based boron neutron capture
therapy (AB-BNCT). The stability of neutron yields and neutron
energy spectrum are key factors for the therapeutic effects of the
AB-BNCT. Owing to the active chemical properties of lithium, the
surface oxidation formation of lithium may influence the soundness
of the target system and the stability of neutron
yields. Experimental and simulation methods were performed for a
better understanding of the passivation layer formation after air
exposure and the influence of the passivation layer on the neutron
yield and energy spectrum. On one hand, X-ray photoelectron
spectroscopy was adopted to study the chemical states of lithium
after air exposure. On the other hand, particle and heavy ion
transport code system (PHITS) was used to evaluate the effect of
surface chemical states variation on neutron yield and energy
spectrum. The simulation results indicate that the formation of
Li2O with a thickness of 2 μm could mainly influence the
neutron yields at the neutron emission angle of 20–90°
with a maximum reduction of ∼ 10.4%.