Dead zone characteristics of SQS and GM modes in Kr-, Ar-, and Ne-mixtures

Dead zones of a gas counter have been studied systematically for various gas mixtures at gas pressures equal to and lower than 1 atm. Evaluated values of the dead zone for the self-quenching streamer (SQS) mode were 190-390 mu s-cm at 1 atm. Characteristics of the dead zone were explained by considering the effect of SQS ions. The critical gas pressure, at which the operation mode changes from the SQS mode to the GM mode, was determined for each gas mixture on the basis of the dead zone measurement. Operation mode diagrams of the counter were drawn according to those results.<>