In beam performance of a low pressure UV rich detector

A low-pressure multistep, TMAE-filled, UV-sensitive detector has been developed for Cerenkov ring imaging for ultrarelativistic heavy-ion experiments (HELIOS-CERN). A description is given of the detector structure and its basic properties, and the experimental setup and the detector performance in tests with high-energy electrons are presented. Three modes of readout are used: three-wire coordinates and flash analog-to-digital converters; pad readout; and optical recording of the avalanches. Single photons can be localized with an accuracy of sigma approximately=2 mm, mainly due to single-photoelectron diffusion and to chromatic dispersion in the radiator gas. The experimental N/sub 0/ values obtained by the three methods are close to those expected, taking into account the various losses due to the test conditions. >