An Absolute Measurement of the ⁷Li(n,n′αt) Reaction Cross Section Between 5 and 14 MeV by Tritium Assaying

The tritium production cross section of ⁷Li was measured between 5 and 14 MeV by irradiating LiOH pellets with monoenergetic neutrons. The neutron fluence was determined using a calibrated NE-213 liquid scintillator and the tritium produced by β counting in a liquid scintillation spectrometer. The technique for determining the amount of tritium produced was confirmed by a measurement of the ⁶Li(n, t)α cross section at thermal energies using irradiations in the GLEEP reactor. The results for the ⁷Li(n,n′αt) cross section are ∼25% lower than the ENDF/B-IV values with a mean uncertainty of 6%. The results are close to a recent evaluation below 11 MeV, but are 23% lower at 14 MeV.