Photon detectors for the HERA-B RICH

A summary of experimental studies of different photon detectors is presented. A CsI photocathode in a multiwire proportional chamber, a TMAE based gaseous photon detector and a new Hamamatsu multianode photomultiplier tube have been investigated in order to evaluate their suitability as photon detectors in the ring imaging Cherenkov counter of HERA-B. The results of the present work suggest that only the MA-PMT meets the demanding requirements of the HERA-B experimental environment. The CsI-MWPC cannot be routinely produced and maintained with sufficiently high quantum efficiency and the TMAE photon detectors lose gain as a result of relatively quick anode wire ageing.