Lithium compounds as targets for (p,n) reactions

It is known that metallic lithium has the highest thick-target neutron yield in (p,n) reactions compared with various lithium compounds. However, lithium metal is highly reactive and possesses a low melting point, which creates difficulty in target design, manufacturing and operation. As a result, lithium compounds should be considered as candidates for the target. As the stopping powers differ among lithium compounds, different compounds lead to different total neutron yields and different epithermal fluxes. This paper presents a quantitative analysis of the relative neutron yields for a series of thick targets made of lithium compounds and the corresponding achievable epithermal neutron fluxes by moderation suitable for BNCT applications. It is shown that the useful epithermal neutron flux in the 4 eV–40 keV range reaches the peak value at about 3 MeV proton energy and decreases when proton energy increases over 3 MeV. For Li3N and Li2O targets, a proton current of 5–6 mA may be sufficient for producing a beam of 109 n/cm2/s epithermal flux under ideal conditions. When other factors are considered, a proton current around 10 mA may be needed for producing a feasible BNCT beam. The results may be useful in target material selection and design and accelerator design for epithermal neutron production for BNCT.