Gas gain on single-wire chambers filled with pure isobutane at low pressure

The gas gain of single-wire chambers filled with isobutane, with cell cross-section 12×12mm and wire diameters of 15, 25, 50 and 100μm, has been measured at pressures ranging 12-92 Torr. As was shown for the first time in [1], at very low pressures the gas gain on thick wires is higher than that on thin wires at the same applied high voltage. Wires with larger diameters should be used in wire chambers operating at very low pressure if multiple scattering on wires is not an issue.