Properties of Very Low Pressure Multiwire Proportional Chambers

We describe some properties of multiwire proportional chambers operated at very low gas pressure (0.3-10 torr), with 5.5 MeV α-particles and 27 MeV 160 ions. Due to a double gaseous amplification process, high gains associated with fast charge collection are achieved, leading to a time resolution of 100 ps (fwhm). The operation mechanism, timing properties, rate capability, and induced charge distribution are described; possible applications are discussed.