The ratio of K characteristic to total radiation emitted from a tungsten target X-ray tube

Abstract

Three methods were developed to assess the proportion of characteristic radiation emitted from an x-ray tube operated at voltages up to 250 kv. Firstly, a gas proportional counter was used to derive a spectral distribution of the Kα peak, which was evaluated in terms of exposure rate by using a calibrated gamma-ray source, the total exposure rate in the beam being measured with an ionization chamber. Secondly, Ross balanced filters were used to isolate K lines, two ionization chambers being used as detectors. Solutions of rare-earth salts formed the most important filters. Thirdly, theoretical calculation of the ratio was developed from other published methods. This showed that, despite fairly severe self absorption, indirect characteristic emission is more important than direct. The two experimental methods gave results which agreed well with each other and with published results derived from scintillation spectrometry, but were rather higher than those predicted theoretically.