Wire Counters with a New Gas Mixture

A multiwire chamber using a gas mixture of argon, isobutane and ¿-trichlorethane-1, 1, 1 (CH3.CCl3) has been successfully operated. Although this chamber does not operate in the proportional mode (i.e., pulse height is not a linear function of the primary ionization) we feel it has a substantial advantage over conventional proportional chambers especially when it is used to detect high energy particles. We call these detectors wire counters; their unique feature is in the use of a highly electronegative substance, (CH3.CCl3), to limit the electron avalanche. These counters with wire spacing of 1 mm can provide gas multiplication factors between 105 to 107 without going into spark formation or breakdown. Their detection efficiency approaches 100% with large high voltage plateaus. We have obtained a time resolution of ± 6 nsec at FWHM from pulses with rise times between 6-10 nsec.