RFQ - HPGe Gamma Ray Spectrometer for Portable Primary Counter

The National Physical Laboratory (NPL) is the UK's National Measurement Institute and is a world-leading centre of excellence in developing and applying the most accurate measurement standards, science, and technology available.

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. Some radionuclides have radioactive decay rates that make transport from the production site to NPL impracticable. Therefore, primary standardisations need to be performed at or near the production facility and requires a system that can be transported.

The Nuclear Metrology group requires a compact mechanically cooled high-purity germanium (HPGe) gamma-ray spectrometer to be part of portable primary counting 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. This detector will also be used for the assay of the samples for radioactive contaminants and will require excellent resolution.

To this effect, NPL is seeking a compact 60% relative efficiency n-type HPGe gamma-ray spectrometer with an integrated electro-mechanical cryogenic cooling system.