Development of a TDCR counting system with anti-coincidence detectors

When employing the TDCR method for standardization of low-activity liquid scintillation samples, fluctuations in system background can significantly impact both measurement uncertainties and minimum detectable activity (MDA). To mitigate this impact, a TDCR counting system with anti-coincidence detectors was developed. By analyzing the time difference distribution spectrum between the anti-coincidence channel and β channel, optimal parameters for the anti-coincidence module are determined. The objective of the study is to enhance the effectiveness of the anti-coincidence technique while minimizing the removal of real events. Finally, two sets of ³H and ¹⁴C samples with known activities of around 1 Bq are prepared via dilution to validate the performance of the system. Compared to without anti-coincidence, the background has been reduced by nearly 84%, leading to decreased fluctuations in the activity results.