Evolution of the RICH technique

This paper presents recent advances in development of Ring Imaging Cherenko v counters. Work on bare and protected reflective CsI photocathodes is revi ewed and compared with gaseous UV photosensors. Development of multipixel-v isible light-vacuum photosensors allows much improved Cherenkov angular res olution (by factor 10) relative to the available gaseous UV photosensors. T he Hybrid PhotoDiode and MultiAnode PMT concepts are reviewed with prototyp e realizations described and test results compared with expectations. The u se of the Gas Electron Multiplier (GEM) with gaseous RICH counters is prese nted and discussed. Its advantages for single electron detection are shown by new experimental data. (C) 1999 Elsevier Science B.V. All rights reserve d.