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. How ever, lithium metal is highly reactive and possesses a low melting poi nt, which creates difficulty in target design, manufacturing and opera tion. As a result, lithium compounds should be considered as candidate s for the target. As the stopping powers differ among lithium compound s, different compounds lead to different total neutron yields and diff erent epithermal fluxes. This paper presents a quantitative analysis o f the relative neutron yields for a series of thick targets made of li thium compounds and the corresponding achievable epithermal neutron fl uxes by moderation suitable for BNCT applications. It is shown that th e 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 ener gy increases over 3 MeV. For Li3N and Li2O targets, a proton current o f 5-6 mA may be sufficient for producing a beam of 10(9) n/cm(2)/s epi thermal 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 B NCT. (C) 1997 Elsevier Science Ltd. All rights reserved.