A new method of measuring the response of a 4 πβ-counter to γ-rays and internal conversion electrons

Abstract

Precise measurements of the response of a 4πβ gas counter to γ-rays and internal conversion electrons were performed by combining 4πβ-γ and 2πβ-γ coincidence measurements. This method requires no additional absorber and the measurements can be made without changing any physical parameter. The method offers a significant improvement in counting statistics in addition to a considerable reduction of the error due to spurious pulses, noise, radioactive contaminants and background fluctuations provided that the two sets of coincidence measurements are recorded simultaneously by the use of a double channel β-counting system. The γ-ray response, measured as a function of γ-ray energy, is in general agreement with those obtained by Williams and Campion, and Merritt and Taylor. Measurements were also made to demonstrate the effects of the type of gas used and the size of the diaphragm between the two halves of a 4π-counter. These results show that the latter effect can make a major contribution to the intrinsic γ-sensitivity of the 4πβ-counter. The γ-sensitivity of the 4πβ-counter with a source sandwiched between absorbers and the response to the internal conversion electrons from 203Hg were also measured.