Attenuation of Radium Gamma Radiation in Cylindrical Geometry

Abstract

One method of measuring γ-ray dose involves the calibration of an “air-wall” cavity ionization chamber against a known mass of radium, using the generally accepted figure for the specific γ-ray output of radium (in 0·5 mm of platinum) of 8·3 or 8·4 r/h at 1 cm per mg. In computing the output of the radium source on this basis, one generally has to correct for the attenuation of the γ radiation in the radium salt itself, and for any difference between the attenuation in the actual capsule wall and that in exactly 0·5 mm of platinum. In connection with the calibration of a number of cavity chambers by this method, the attenuation of the γ rays from radium was measured in cylindrical sleeves of various atomic numbers. The aim was, given a known mass of radium in a capsule of any material and any reasonable size, to be able to calculate the γ-ray output of the source.