A Compton suppression high resolution spectrometer for low level radioactivity measurements

In radio environmental measurements performed by high resolution γ-ray spectroscopy with Ge(Hp) there is a significant background as a result of incomplete energy deposition of incident photons undergoing Compton scattering in the germanium detector. In consequence, photons with certain energy introduce at lower energies a Compton continuum that increases the limit of detection for other radionuclides in the sample. This Compton continuum can be reduced by surrounding the Ge(Hp) detector with a second detector, usually made of NaI(T1) or BGO. The guard detects Compton scattered radiation occurred in the main detector, and these events are rejected from the final spectrum by means of a coincidence condition through an appropriate electronic circuit. The Laboratory of Environmental Radioactivity at the University of Valencia and the Laboratory of Environmental Radioactivity of the Physics Department at the Veterinary School of Caceres, UEx, have designed, assembled and adjusted a detection system for high resolution gamma-ray spectroscopy with Compton effect suppression. The purpose of the design has been the optimising of the limit of detection and the measuring time for radionuclides with representative photopeak between 300 keV and 900keV. This has been achieved by simplifying the instrumentation and at a reasonable cost. (Author)