Coincidence corrections for a multi-detector gamma spectrometer

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2015-01, Vol.769, p.20-25
• Main Authors: Britton, R., Burnett, J.L., Davies, A.V., Regan, P.H.
• Format: Article
• Language: English
• Subjects: Accelerators; Accidental coincidence; Accidents; Coincidence systems; Coincidences; Delay; Gamma spectroscopy; Gates; Low energy; Spectra; Spectrometers; Time-walk
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2014.09.054

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 137Cs and 60Co 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.