Covariance analysis on the thermal neutron capture cross sections using an Am-Be neutron source

We measured the thermal cross sections of 71Ga(n, γ)72Ga using an Am-Be neutron source having strength of 4 × 107 neutrons/sec using the two monitor reactions 197Au(n, γ)198Au and 55Mn(n, γ)56Mn, and obtained 4.07±0.27 b and 3.97±0.31 b as the values measured relative to Au and Mn neutron captures, respectively. We constructed their covariance matrix by taking into account the correlation of parameters which are not independent in derivation of these two thermal cross sections (e.g., Ga sample weight, decay data of 72Ga, detector efficiency of γ -ray emitted from 72Ga). The off-diagonal weighted mean of the two cross sections 4.04±0.27 b was derived from the two thermal cross sections and their covariance matrix.