Yield of Alpha-Particles from Lithium Films Bombarded by Protons

The absolute yield of alpha-particles from a thick target of lithium bombarded by protons has been determined using proton energies up to a maximum of 400 kv. The values obtained for the yield in alpha-particles per ${10}^9$ protons, at several different voltages are 16.3 at 250 kv, 33.4 at 300 kv, 58.0 at 350 kv and 92.8 at 400 kv. The yields of several thin films have been studied in considerable detail. Results show that the thin film yield increases linearly with voltage from 180 kv up to 400 kv and at the upper voltage shows no tendency to approach a constant value. The thin film yield curves were smooth, giving no evidence for the existence of resonance levels.