Position-Sensitive Gas Proportional Chambers

A number of multiwire, position-sensitive, gas proportional chambers have been constructed which use fast delay line (2.5 ns/cm) readouts to provide trajectory position and angle information for particles near the focal planes of the Energetic Pion Channel and Spectrometer (EPICS) and High Resolution Spectrometer (HRS) at the Clinton P. Anderson Meson Physics Facility (LAMPF). These chambers are two dimensional with anode wires in one direction and cathode wires in the other direction. When operated as ordinary delay line chambers, position resolution of 0.5 mm (FWHM) can be obtained in the cathode direction for short cathode wire lengths. If the drift information from the anodes is used, resolution of less than 0.35 mm (FWHM) can be obtained in this direction. The chambers can be operated at count rates of 5 × 105 pulses/sec with live times of greater than 90%. Efficiences, measured at lower counting rates, are typically greater than 99%.