Resolution and spectral characteristics of ultra high pressure proportional counters using various quench gases

We present the results of a systematic search for the best gas mixture for use in proportional counters operating at high pressures. The data were gathered using a variety of quench gases with argon or xenon as the primary fill gas. The gas gain and the energy resolution broadly follow the complex ionization within the gas volume. The data show that the spectral response for argon does not change significantly with pressure. However, for xenon the spectral response is dominated by secondary shell interaction processes, and charge loss due to recombination.