Helium Production Cross Sections for 15-MeV Neutrons on ⁶Li and ⁷Li

Total ⁴He production cross-section measurements have been made for ⁶Li and ⁷Li for 15-MeV neutrons. Isotopically enriched samples of lithium metal were bombarded with an intense flux of T(d,n) neutrons from a rotating target neutron source. Following the irradiation, the accumulated ⁴He was determined by isotope-dilution mass spectrometry. The lithium samples and the incident neutron spectrum were accurately characterized, both by experimental methods and by calculational simulations. The measured ⁴He production cross sections are 0.512 ± 0.026 b for ⁶Li and 0.336 ± 0.016 b for ⁷Li, at an average neutron energy of 14.95 MeV.