Behaviour and response veracity of large area transmission avalanche counters as elementary detecting devices

Parallel plate avalanche counters (PPAC) with an active area of 80 cm2 and an electrode spacing of 1-4 mm are investigated. The behaviour and the response veracity of the transmission PPAC, when used as an elementary detecting device, i.e. just to count events, with simple spectrometric and timing (without TOF coincidence) mode electronic systems are assessed at n-heptane pressures of 5-30 Torr using low-energy α-particles. Beside the PPAC intensity transmittance (< or approx. 1.05 at the plateau centre), the plateau slope (< or approx. 6x10-4%/1 V) and width (< or approx. 115 V) of the counting rate curve are evaluated. In addition, the counter behaviour beyond the low-voltage plateau and is investigated. High spurious pulse counting rates, almost solely due to charge carrier regeneration under strong electric fields, are reported. Empirical relations are determined among the PPAC characteristic voltages to provide for a safe estimation of the detector electrical strength. (orig.)