Measurements of the Gamma Abundance of Silicon-31

Abstract

Direct determination of the induced 31p concentrations in neutron transmutation doped silicon may be obtained by measurements of absolute activities of ³¹Si by detection of the 1.266 MeV gamma-rays that are emitted, provided the gamma abundance is known. In previous work it was inferred that the gamma abundance of ³¹Si is significantly lower than the accepted value of 7 × 10^-4. To confirm this result a 4 π proportional counter and a calibrated Ge(Li) detector were used to measure both the absolute beta and gamma activities, respectively, of thin silicon samples. The resultant gamma abundance of ³¹Si was found to be 5.9 × 10^-4 ± 5%.