Performance of proportional counters under high count rate, high gas gain and at high working gas pressure

The increase of radiation intensity measured by a proportional counter leads to the undesirable changes of its parameters, such as pulse height and energy resolution. It has been found that both the pulse height and the energy resolution significantly decreases with increasing radiation intensity. The spatial resolution measured using a charge dispersive readout technique and the charge centroid determination is also degraded. Possible overlapping of ion tails from successive hits in the detector leads to a continuous but fluctuating current through the counter and its front-end electronics. All those effects might significantly degrade the basic detector properties, especially at very high counting rates of up to 20 MHz as it is expected at LHC Experiments. For higher values of the gas gain and high count rate the total space-charge effect leads to significant non-linearities in the detector response, which in addition depend on the deposited energy, counter geometry, type of working gas and its pressure. The performance of proportional counters under high gas gain and high count rate at high working gas pressure was studied experimentally. The results obtained are presented.