ANODE WIRE AGING IN PROPORTIONAL-COUNTERS - THE PROBLEM OF ANALOG RESPONSE

The analog response of aged proportional counters is shown to be deter mined by the local charge density distribution on an insulating sense- wire surface. It therefore depends on a number of parameters such as s patial distribution of irradiation, counting rate, gas gain and surfac e conductivity of the insulating layer. Typical charge response time c onstants are derived from a dynamic model of the surface charge densit y. Experimental consequences such as charging-up effects, time depende nce of amplitude in irradiation burst environments, fluctuations of de tector resolution as a function of rate, and the influence of water ad mixtures on counting gases are described. The problem of deriving spec ific ageing parameters is quantified in a typical example.