Behavior of the SQS mode observed as a function of the radial distance of the position of primary ionization

Abstract

In the transition region from proportional to the self-quenching streamer (SQS) mode in Ar+30% CH 4 gas mixture, the degree of gas amplification and the transition probability to the SQS mode have been studied as a function of r, where r is defined as the radial distance between the position of primary ionization and the anode wire. It is found for the first time that an enhancement of the SQS transition occurs for a small r in the vicinity if the anode wire, however, the degree of gas amplification for the SOS mode is independent of r. The results may indicate that the structural change of primary-electron cloud caused by the diffusion effect influences the transition probability from proportional to SQS mode.