Precise measurements of the thick target neutron yields of the 7Li(p,n) reaction

Abstract

Thick target neutron yield of the 7Li(p,n) 7Be reaction was measured in the proton energy range from 1.95 to 2.3 MeV by determining induced activity of the 7Be. A HPGe detector was used to detect the 478 keV gamma-rays emitted through 7Be decay. A series of irradiations with nominal proton energies of 1.95, 2.0, 2.1, 2.2, and 2.3 MeV were carried out. In an independent experiment, raw neutron spectra were collected by a 3He ion chamber for the same series of proton energies. From the raw neutron spectra, it was noted, that the effective proton energies were lower than the nominal by 50–58 keV. After corrections for the proton energy offsets were applied, the measured neutron yields matched the analytically calculated yields within 20%. Long term stability of neutron yield was tested at two nominal proton energies, 2.1 and 1.95 MeV over an experimental period of one year. The results show that the yield at 2.1 MeV was stable within rmse variation coefficient of 4.7% and remained consistent even when the lithium target was replaced, whereas at 1.95 MeV, the maximum fluctuations reached a factor of 10.