Monte Carlo simulation of xenon filled cylindrical proportional counters

Single electron avalanche processes in a xenon filled cylindrical proportional counter have been simulated using a detailed Monte Carlo technique. The avalanche gain A and its average value M as well as its frequency distribution and spread parameter b have been calculated for xenon at atmospheric pressure, for a 2.55 cm cathode radius and 12.5 and 50 μm anode radii. A discussion is made of the results obtained for M as a function of the anode voltage in terms of prevailing theories. It is found that Monte Carlo calculated M values are markedly lower than those obtained analytically using the first Townsend ionization coefficient calculated under a uniform field. This puts into evidence the relevance of the non-equilibrium nature of avalanche processes