Position Resolution of a Gas Counter in the SQS Transition Region

Position resolutions around the transition region from the proportional to self-quenching streamer (SQS) modes in a gas counter has been measured. The counter used is of a strip-cathode type, which is filled with a mixed gas Ar70% + CH430% adding an adequate concentration of ethanol. Transition in the position resolution was clearly observed between the SQS mode and the double SQS mode in any concentration of the ethanol, while not so clearly between the proportional mode and the SQS mode. The best position resolution, 0.11mm (FWHM), was obtained in the double SQS mode operation.