A compact and fast photon detector for COSY-status report on the design study

A compact photon detector with nearly 4/spl pi/-coverage in solid angle has been proposed to be implemented into the magnetic spectrometer ANKE at COSY, Julich. Based on the physics program and experimental constraints a first concept will be presented. As part of the R&D program, the response to monoenergetic photons between 45 and 770 MeV has been measured at the tagged photon facility at MAMI, Mainz for arrays consisting of large CeF/sub 3/ and PbWO/sub 4/ scintillation detectors. The applicability of a fine-mesh photomultiplier (Hamamatsu R5505) has been tested in static and variable magnetic fields.