Analytical approach and calculation of gas gain in Ar-CO2 mixture

The Ar/CO2 mixture is commonly used as a working gas in gas proportional counters. For this mixture, very systematic measurements of the gas gain factor were made in a wide range of changes in CO2 concentration from 1% to 50% and for various mixtures pressures from 400 hPa to 1800 hPa. For the analysis of the obtained results, both well known and well tested analytical formulae for gas gain as well as Monte Carlo methods were used. Characteristic constants (such as: probability of energy transfer in the Penning effect, second Townsend ionization coefficient, effective ionization potential, the critical field at which multiplication commences, the mean potential through which an electron falls between successive ionizing collisions) describing physical processes occurring in Ar/CO2 mixtures as a function of CO2 concentration and mixture pressures were determined.