Geometry independent indium activation analysis

A geometry independent method has been derived for calculating the ratio of the spectrum averaged cross-sections for the reactions 115In(γ, γ′)115mIn and 113In(γ, γ′)113mIn in the energy region of interest 300–500 keV. The technique is unique as it eliminates the need for a detailed detector efficiency formulation for varying source–detector geometries, thereby removing a source of systematic uncertainty. The validity of the technique is demonstrated experimentally by comparing the cross-section ratios for a geometrically diverse set of source–detector configurations. The average ratio value for seven independent measurements is 0.778±0.0033 with a reduced χ2 of 1.2, which is within 1.15% of the previously published value.