4.3.3.1 HPGe detectors

HPGe detectors are used for in-situ gamma ray spectrometry in terrestrial and underground measurements in shallow coastal areas. They are also used for radiological characterization of indoor/outdoor areas in routine and emergency situations. High purity germanium detectors are characterized by their high energy resolutions. Portable germanium detectors now exist with relative efficiencies of 20 to 50 %. Special HPGe detectors are also designed for detection of low energy gamma and X-ray emissions.

In-situ HPGe detectors need to operate at ∼-160°C and traditionally, this is done using liquid nitrogen. However, some HPGe detection systems can now operate in portable mode with thermo-electrically cooled systems. The main advantage of thermo-electrically cooling systems is to not require of liquid nitrogen supplies in remote areas. The power consumption of such systems is around 100 W when cooling and 30 W during normal operation with autonomy of several hours.