Development of large area and of position-sensitive timing RPCs

Resistive Plate Chambers (RPC) made with glass and metal electrodes forming accurately spaced gas gaps of a few hundred micrometers have reached timing accuracies below 50 ps sigma with efficiencies above 99% for MIPs. This type of detector, operating at atmospheric pressure with non-flammable gases, seems well suited for large TOF systems, providing performances comparable to the scintillator-based TOF technology with significantly lower price per channel and being compatible with magnetic fields. In this work, we report recent developments of the timing RPC technology, including a large area counter (0.16 m(2)) and smaller, position-sensitive, single-gap counters. The latter devices are aimed to be applied in small and accurate TOF systems using a multilayer structure. The large counter has shown a timing resolution between 50 and 75 ps sigma over the whole active area, with 960 efficiency and very small timing tails, along with a longitudinal position-resolution of 1.2 cm sigma. The single-gap counters had a timing resolution of 55 ps sigma and a bi-dimensional position-resolution better than 3 mm FWHM. It was calculated that a 4-layer configuration of such counters would yield a time resolution of 33 ps a essentially free from timing tails. (C) 2002 Elsevier Science B.V. All rights reserved.