BackgroundThe triple-to-double coincidence ratio-Čerenkov (TDCR-Čerenkov) method can be applied to the activity measurement of radionuclides by detecting the Čerenkov photons produced in a non-scintillation solution. The computation of the detection efficiency of this method is based on the premise that the energy of emitted β is completely deposited in the solution. However, this precondition is ideal and does not apply to the actual measurement because of the counting loss caused by the restrictions of a finite solution and the wall of the counting vial (i.e., wall effect).PurposeThis study aims to analyze the influence of the wall effect on the computation of detection efficiency.MethodsThe transport process of emitted β from the solution to the vial wall was analyzed in sections. Thereby the relationship between the number of Čerenkov photons and the deposition energy spectra of emitted β with different energies in different matrices was obtained. This relationship was used to further improve the calculation model of the TDCR-Čerenkov method. Subsequently, the calculation model was simplified to reduce the required time. Geant4 calculated the deposition spectra of emitted β in different matrices, subsequently, the efficiency of different nuclides was calculated using curves of the number of Čerenkov photons vs. the energy of the emitted β. To verify the accuracy of the improved calculation model, measurements were carried out on a variety of pure β-emitters.ResultsThe results derived from the improved TDCR-Čerenkov method are in good agreement with those of the TDCR-LS method. Especially for high energy β-emitters, the relative deviation of the results between the TDCR-Čerenkov and TDCR-LS methods is reduced from 0.47% for the original method to 0.02% (90Y), and 0.64% to -0.16% (32P).ConclusionsThe TDCR-Čerenkov method is more accurate when considering the wall effect in the activity measurement of high-energy β-emitters.
