Year
2001
Abstract
In the area of Safeguards, the high resolution gamma spectra obtained with high-purity germanium (HPGe) detectors is absolutely necessary for acceptable analysis results. However, the necessity for using liquid nitrogen (LN2) to cool HPGe detectors has been a hindrance to their use in some applications. The most commonly cited problems are unreliable supplies of LN2, irregular detectorfilling and the associated costs of the LN2 supplies. In addition, in unattended monitoring stations or remote monitoring locations, a LN2-free solution is a requirement for operation. Until now, LN2 free cooling has suffered from two major limitations: cost and reliability. The mechanical coolers needed to cool the detectors to the required temperature of 90 to 100 °Kelvin have typically had much higher cost than the cost of LN2 for a considerable time. The reliability or working life of previously available coolers has not been high enough to justify their use in remote stations. For example, the time between necessary service for the coolers has been shorter than the time between service for the detector elements themselves. This means that the mechanical system would require service in a shorter time than the LN2 system. A low-cost, low-power cooler system has been developed to address these issues. The system has the high cooling capacity needed for use with modular detector capsules. The use of modular detector capsules greatly reduces the service costs especially in remote systems. Spectrum data has been collected for several different types of detectors over several months. Performance data will be shown for various detector-cooler combinations.