Pulse rise time discrimination in X ray proportional counters

Abstract

The factors affecting the pulse rise time in a coaxial proportional counter are discussed, and it is shown that under certain conditions the dependence of rise time upon the length of the radial component of the primary ionisation track may be considerable. A rise time discrimination system based on these arguments has been constructed; it was found possible to remove a significant fraction of the small pulses arising from gamma rays which would normally interfere with the recording of a low intensity of soft X rays from the same radioactive source. The advantages and disadvantages of the technique in coincidence experiments are discussed.