In beam performance of a low-pressure UV rich detector

We have developed a low-pressure multistep, TMAE- filled, UV sensitive detector for Cerenkov ring imaging (RICH) for ultrarelativistic heavy ion experiments (HELIOS-CERN). In the present work we describe the detector structure and its basic properties and we present here the experimental setup and the detector performance in tests with high energy electrons using three modes of readout: 3 wire coordinates and flash ADC's Pad readout - optical recording of the avalanches. Single photons can be localized with an accuracy of σ⋍a 2 mm, mainly due to single photoelectron diffusion and to chromatic dispersion in the radiator gas. The experimental No values, obtained by the three methods, are close to those expected, taking into account the various losses due to the test conditions.