The triple-to-double coincidence ratio-?erenkov (TDCR-?erenkov) method can be applied to the activity measurement of radionuclides by detecting the ?erenkov 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).
This study aims to analyze the influence of the wall effect on the computation of detection efficiency.
The transport process of emitted β from the solution to the vial wall was analyzed in sections. Thereby the relationship between the number of ?erenkov 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-?erenkov 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 ?erenkov 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.
The results derived from the improved TDCR-?erenkov 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-?erenkov and TDCR-LS methods is reduced from 0.47% for the original method to 0.02% (90Y), and 0.64% to -0.16% (32P).
The TDCR-?erenkov method is more accurate when considering the wall effect in the activity measurement of high-energy β-emitters.
