Study of the Accumulation of Impurities in a Thin Lithium Target by Ion Scattering Spectroscopy

An accelerator-based epithermal neutron source (VITA) has been created and is now operating at the Budker Institute of Nuclear Physics. VITA includes an original tandem electrostatic accelerator (vacuum-insulated tandem accelerator), which produces a monoenergetic beam of protons or deuterons with energies from 0.3 to 2.3 MeV and currents up to 10 mA, and a thin lithium target that generates a powerful neutron flux in ⁷Li(p, n)⁷Be and Li(d, n) reactions. The facility is used to develop boron neutron capture therapy and many other applications. Heavy impurities contained in a lithium target are known to significantly decrease the neutron yield and make the target unusable. The purpose of this study was to examine the accumulation of impurities in a thin lithium target. The elemental composition of the sample was determined by ion scattering spectroscopy. The composition of the lithium layer immediately after sputtering on a copper substrate was determined in the experiments. The interaction of lithium with air and the effect of the impurities on the neutron yield were studied. The accumulation of impurities during proton beam irradiation of the target at a beam power density of 1 kW/cm² and up to 3.4 kW/cm² was investigated.