The efficiency of halogen-quenched geiger-counters for X-rays

Abstract

SummaryThe efficiency of two argon-bromine counters is determined for Mo-K~, Cu-K= and Cr-K~ quanta as a function of the overvoltage and as a function of the distance from the axis where the quanta are absorbed. The efficiency drops sharply at greater distances from the wire. This effect is partially ametiorated at higher overvoltages. The .more energetic X-ray quanta show a higher relative efficiency in the outer regions. The explanation is to be found in the electronegativity of the halogens. § 1. Introduction. The efficiency of halogen-quenched geiger-counters for X-rays has been measured as a function of the distance between the axis of the counter and the place where the X-ray quantum is absorbed, and as a function of the overvoltage.Halogens are strongly electronegative 1).The electrons are attached so firmly, that usually F/p (where F is the fieldstrength, p the total pressure) in a halogen-quenched geiger-counter around the wire is not strong enough to detach the electron from a negative halogen ion. For this'reason no pulse will result when all primary electrons formed inside the counter by the particle or quantum to be counted are caught by halogen molecules. § 2. Method o! measurement. A stabilized diffraction tube is used as X-ray source. The emission is kept constant at 5 or 8 mA. The anode potential is taken 1 or 2 kV higher than the K-excitation level of the anode material. With the aid of a crystal monochromator the K-radiation is separated. After having passed through a lead diaphragm with a hole 0.6 mm in diameter at a distance of 40 cm from the crystal, the X-ray beam is directed through a mica window