Longitudinal Drift and Fine dE/dx Sampling in Various Gas Mixtures

Results of measurements realized at 15 GeV/c in a tagged e/π/p beam are presented. A longitudinal drift detector of 88 cm total length consisting of 16 stages of 4.7 cm drift each was used. Fast shaped signals from the detector were processed in a set of Flash ADC's with 25 ns sampling interval, corresponding to 0.3 - 2.6 mm distance in the drift space. Resolution and particle separation efficiency obtained in mixtures of Ne + 10% C3H8, Ar + 5% C3H8, Ar + 20% CO2, C3H8 + 20% C2H6 and in pure CH4 are compared to the performance of a classical method of charge integration over large samples.