Accurate Determination of Correction Factors for β-Ray Self-Absorption in Gold Foils

Abstract

A new method has been developed for obtaining the β-ray self-absorption correction factor of a Au-foil with uniformly distributed A-ray source. The method is essentially to average the β-ray self-absorption correction factor of Au-foil packs composed of non-activated Au-layers and an activated Au-layer placed at the various depths. The β-ray self-absorption correction factors of the Au-foil with thicknesses ranging 0.15–80mg/cm2 were measured within an experimental error of less than 0.5%. Between the thicknesses of 0 and 10mg/cm2, a sharp decrease was observed. In the range of thickness below 45mg/cm2 the present experimental results diverge from the currently used formula (f a = (l–e μt)/μt), but are in good agreement with a semi-empirical expression (f a = (l/2–E 3(μt)/μt), formulated on the assumption of isotropic penetration of β-rays. The escape probability of β-rays emitted from a certain depth of Au-foil was also measured as a function of source depth. By using this escape probability it is possib...