Gain reduction due to space charge in a multiwire proportional chamber irradiated by a uniform beam of rectangular section

Abstract

Previous theoretical and experimental work has shown that space-charge reduction in gas gain in proportional chambers may be described by the simple relationship In( q/ q 0) = − qn 1 k m/ I m. Here q is the mean avalanche charge at counting rate n 1 per unit length per wire, q 0 the mean charge at zero rate, I m a constant that depends on the chamber parameters and k m a constant depending also on the “width” L of the chamber irradiated. The irradiation “height” H was assumed to be very large compared with anode wire spacing. It is shown below how the previous theory may be developed to treat the more general case in which the chamber is irradiated with a uniform intensity beam of rectangular section. It is found that the same simple expression applies, approximately, with k m( L) replaced by a two-dimensional function d m( L, H).