Dose Measurements with Radium Beta-ray Applicators

Abstract

A general description is given of radium β-ray applicators, and the method of measurement of the dose in röntgens is explained. For a typical applicator (full strength, 5 mg./cm.2), the surface dose-rate is of the order of 5000 r/hr., while the depth dose in water at 1 mm. is of the order of 50 per cent. the half-value layer in aluminium is of the order of 0·4 mm. The influence of filtration and applicator size is illustrated; backscatter is small, probably less than 10 per cent. Further data on filtration and reflection effects are afforded by measurements with a radium (B+C) source and a radium E source. The specific β-ray dose-rate at zero filtration is 1180 r/mc.hr. for radium (B+C), and 525 r/mc.hr. for radium E, that is 1710 r/mg.hr. for radium in final equilibrium, excluding the extremely soft radium D radiation.