A gas Cherenkov beam counter with a timing resolution of 30 ps for relativistic heavy ion experiments

We constructed gas a Cherenkov beam counter for a lead beam to obtain start signals of time of fight measurements for relativistic heavy ion experiments in WA98 at CERN-SPS. The intrinsic timing resolution of the gas Cherenkov counter was found to be ≤ 30 ps at a beam intensity up to 3 × 105 ions/s and the charge resolution (ΔZZ) was 2.0% for lead ions of 160 GeV/c per nucleon. This counter has been successfully operated for more than 112 month of heavy ion run in 1995.