HPGe detector

HPGe detectors can be operated at temperatures higher than that of liquid nitrogen, 77 K, but with a decrease in the energy resolution. 

There are other issues with HPGe detectors, which have made their use for this application problematic. The most obvious operational issue is the requirement for... 

Figure 1 Schematic drawing of the underground HPGe-detector and the Pb/Cu shield together with Marinelli beaker.

Figure 2 Background spectra of the underground HPGe-detector before and after the change to an aluminium endcap.

Table 1 List of background y-ray peaks for the underground HPGe-detector before (2003) and after (2005) the installation of the new endcap as well as with mercury shield (2006-...

In underground laboratories the main source of background in HPGe-detectors is usually from radioactivity inside the detector. It is possible to improve the background by careful selection of radiopure materials. 

Performance of a Portable, Electromechanically-Cooled HPGe Detector for Site Characterization... 

For this work, the liquid nitrogen HPGe detector and MCA in a standard system for field measurements (Iso-Cart) was replaced by a portable HPGe detector with built-in MCA (Trans-SPEC-100). The detector is nominally 40% relative efficiency a size commonly used for field measurements. The tungsten and steel collimators are cylindrical sleeves surrounding the crystal and projecting forward. The absorbing material is 4.7 mm thick. 

In these formulas, W is the thickness of the depletion region measured in mm. For silicon detectors and for planar HPGe detectors, the value of W is provided with each detector. For coaxial Ge detectors, IT is the radius of the cylinder. The formulas given above are indicative only of orders of magnitude and do not give exact values. 

Fig. 5.34. Detection efficiency of the HPGe detector in the Marinelli-beaker configuration.

Fig. 9.28. Configuration of the HPGe probe with relative gamma contribution contour indicated in water for 1 MeV gamma rays. (A) Probe holder (B) liquid-nitrogen dewar (C) styrofoam (D) HPGe detector (E) lead block. (After Chao and Chung, 1992).

Large volume portable coaxial HPGe detector (LOAX type) Precise measurement of weak sources in the field (e.g. smear samples). 

Spinach NBS SRM A1 V Ca Mg Mn Na K La Ba Co Cr Cs Eu Ee Rb Sb Sc Se Sr Th Zn Heat-sealed in PE foil bags [N/MT] Irradiate 30 s and 8 h for short, intermediate and long half-life elements in thermal neutron facility count with HPGe detectors. [INAA] [N/MT-INAA] Becker (1995)... 

FIG. 8.15. Energy spectrum of Co obtained with scintillation and HPGe detectors. 

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