RFQ - HPGe Gamma-Ray Spectrometer for Coincidence Counting

The Nuclear Metrology group within the National Physical Laboratory (NPL) provides the traceability to the SI unit of the becquerel for a radionuclide through its primary standardisation facilities. A powerful technique for determining the absolute activity of a radionuclide is by coincidence counting. These coincidence counting systems are comprised of a particle detector and a gamma-ray detector which can be combined to simultaneously measure the disintegration rate and determine the detection efficiency. The Nuclear Metrology group requires a mechanically cooled high-purity germanium (HPGe) gamma-ray spectrometer to replace an aged LN2-cooled HPGe gamma-ray spectrometer to be part of an upgraded coincidence system. This will provide a high-resolution gamma-ray detection channel that can be used to form coincidences of specific gamma-ray emission with the corresponding particle emission, which is of particular importance for the absolute activity determination of electron-capture radionuclides. Achieving good counting statistics in this gamma-channel is of particular importance and due to the activity limitations introduced by the particle detector a high relative efficiency for the HPGe gamma-ray spectrometer is required. To this effect, NPL is seeking a 100% relative efficiency n-type HPGe gamma-ray spectrometer with an integrated electro-mechanical cryogenic cooling system.