Practical aspects of hybrid cooling devices engineering design for HPGe detectors

Abstract

The article discusses some practical aspects of engineering design associated with the use of Stirling cryocoolers in liquefiers of hybrid cooling devices for HPGe detectors. A feature of hybrid cooling devices is the presence of two modes: the recondensation mode when the cryocooler is operating, and the power interruption mode with a non-renewable LN 2 boil-off. Based on the Thermal Networks Method, models for each mode are proposed, for analyzing heat fluxes between standard components forming the liquefier unit. The proposed models were validated by comparing calculated parameters of the transition process between the two above-mentioned operating modes with those obtained experimentally. It is shown that the minimization of heat gain through the liquefier unit into Dewar for both operating modes of the hybrid cooling device leads to contradictory engineering design requirements. Preliminary conclusions based on the thermal network models are confirmed experimentally on a serial hybrid cooling device, produced by the Baltic Scientific Instruments Company. This resulted in practical recommendations on the choice of condenser position, which depended on operating conditions of hybrid cooling device, for example as a laboratory equipment or as a part of remote radiation monitoring stations.