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 20$^\circ$ 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 $\mu$s$\cdot$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.