SMALL CRYOSTEM FOR OPERATION OF VISIBLE-LIGHT PHOTON COUNTERS (VLPC)

We have designed, constructed, and operated a small cryostem which sup ports the operation of 32 channels of Visible Light Photon Counters (H ISTE-IV VLPCs). The VLPCs are situated within a small enclosure which can be lowered into a 30-100 liter dewar. The enthalpy of the boil-off helium keeps the VLPCs cold, and allows the system to be operated wit h stability for many days within the desired temperature range of 6.0K -7.5K. The cryostem is instrumented with clear fiber waveguides which transport the light from an optical connector situated at the top of t he cryostem and outside of the dewar to the photosensors at cryogenic temperatures within the dewar. Electrical signals from the VLPCs are a mplified at room temperature using QPA02 preamplifiers. Details of des ign and performance are reviewed.