Self Quenching Streamer Mode in Quenching Gases Initiated by Alpha Particles

The transition from a proportional to a self quenching streamer mode, as a function of track length and angle, was investigated in a single wire chamber filled with either pure DME or isobutane. The chamber was irradiated with 241 Am alpha particles. An investigation of multistreamer events in DME due to alpha particles entering the chamber at 20deg with track length ~ 4 mm gave an estimate of a dead zone, defined as the product of dead length and dead time, to be less than 0.1 mus middot cm. This value is 3 orders of magnitude less than those observed by other groups for noble gases based mixtures. No second streamers were observed with pure isobutane for similar tracks.