The dependence of pulse height on anode diameter and gas composition in limited streamer tubes

Results are presented of a study of charge spectra using plastic streamer tubes as a function of anode diameters and for an extensive selection of three component gas mixtures of argon, isobutane, and carbon dioxide. Chambers instrumented with longitudinal strip and pad readout are constructed with plastic streamer tubes using anode wires of one of six different diameters: 25, 50, 75, 100, 150, and 200 mu m. The six chambers are simultaneously triggered by cosmic-ray muons, and the charge distributions are recorded for various voltages and gas mixtures. An unexpected scaling law may be at work during the transition to streamer mode.<
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