A compact VLPC photon transducer system

We have developed a compact visible light photon counter (VLPC) system. A VLPC is a solid state, silicon impurity band conduction device transducer for single photons. VLPCs have a quantum efficiency of 60-70%, a gain greater than 10/sup 4/ and rate capabilities greater than 10/sup 7/ photons/sec, without decreased operating efficiency. We use the device as a transducer for scintillating fibers. The complete system is capable of operating 16 cryogenic modules each containing 256 VLPC channels for a total of 4096 channels. The system uses about one liter of liquid He per hour and is capable of operating in various orientations. Using this compact cryogenic system we have measured the noise, gain and the effect of rate vs. the working temperature of the VLPCs.