Coincidence corrections for a multi-detector gamma spectrometer

摘要

List-mode data acquisition has been utilised in conjunction with a high-efficiency γ-γ coincidence system, allowing both the energetic and temporal information to be retained for each recorded event. Collected data is re-processed multiple times to extract any coincidence information from the γ-spectroscopy system, correct for the time-walk of low-energy events, and remove accidental coincidences from the projected coincidence spectra. The time-walk correction has resulted in a reduction in the width of the coincidence delay gate of 18.4 ± 0.4％, and thus an equivalent removal of 'background' coincidences. The correction factors applied to ～5.6% of events up to ～500keV for a combined ~(137)Cs and ~(60)Co source, and are crucial for accurate coincidence measurements of low-energy events that may otherwise be missed by a standard delay gate. By extracting both the delay gate and a representative 'background' region for the coincidences, a coincidence background subtracted spectrum is projected from the coincidence matrix, which effectively removes ～100% of the accidental coincidences (up to 16.6 ± 0.7% of the total coincidence events seen during this work). This accidental-coincidence removal is crucial for accurate characterisation of the events seen in coincidence systems, as without this correction false coincidence signatures may be incorrectly interpreted.