Measurement of thermal neutron capture cross section of 71Ga with dual monitor foils and covariance analysis

Abstract

The thermal neutron cross section of 71Ga(n,$ \gamma$)72Ga reaction was measured with respect to the 197Au(n,$ \gamma$)198Au and 55Mn(n,$ \gamma$)56Mn monitor reactions using neutrons from an Am-Be source placed inside a concrete bunker. A covariance analysis was performed to obtain the off-diagonal weighted mean of the results determined with the two monitor reactions. The thermal neutron cross section obtained in the present study is $ 4.05 \pm 0.27$ b. The present result is lower than the data measured under neutron fields having broad neutron spectra in general, but more consistent with the thermal neutron cross sections extrapolated from the cross sections measured under monoenergetic neutron fields according to the $ 1/v$ -law. The current status of the 71Ga(n,$ \gamma$)72Ga reaction cross section in the nuclear databases is briefly reviewed in the relation with the Maxwellian spectrum averaged cross section for s -process calculation.