First TDCR measurements at low energies using a miniature X-ray tube

E. Halter (1, 2) , Cheick Thiam (1, 2) , Christophe Bobin (1, 2) , Jacques Bouchard (1, 2) , Dominique Chambellan (3, 2) , Bruno Chauvenet (1, 2) , Matthieu Hamel (4, 2) , Licinio Rocha (4, 2) , Mathieu Trocmé (4, 2) , Romuald Woo (4, 2)

1 LNHB - Laboratoire National Henri Becquerel
2 LIST (CEA) - Laboratoire d'Intégration des Systèmes et des Technologies
3 LIC - Laboratoire Instrumentation et Capteurs
4 LCAE - Laboratoire Capteurs et Architectures Electroniques

Developed for radionuclide standardization using liquid scintillation, the Triple to Double Coincidence Ratio (TDCR) method is applied using coincidence counting obtained with a specific three-photomultiplier system. For activity determination, a statistical model of light emission is classically used to establish a relation between the detection efficiency and the experimental TDCR value. At LNE-LNHB, a stochastic approach of the TDCR modeling was developed using the Monte Carlo code Geant4. The interest of this TDCR-Geant4 model is the possibility to simulate the propagation of optical photons from their creation in the scintillation vial to the production of photoelectrons in photomultipliers. As an alternative to the use of radionuclide sources, first TDCR measurements are presented using a miniature x-ray tube closely coupled to the scintillation vial. The objective of this new set-up was to enable low-energy depositions (lower than 20 keV) in liquid scintillator in order to study the influence of both time and geometrical dependence between PMTs already observed with radioactive sources. As for the statistical TDCR model, the non-linearity of light emission is implemented in the TDCR-Geant4 model using the Birks formula which depends on the kB factor and the scintillation yield. Measurements performed with the x-ray tube are extended to the assessment of these parameters and they are tested afterwards in the TDCR-Geant4 model for activity measurements of $^3$H

Keywords: Geant4 simulation code; Monte Carlo; simulation; modelling; particle transport; X-ray tube; X-rays; ionizing radiation; radioactivity; Triple to Double Coincidence Ratio (TDCR); Radionuclide metrology; liquid scintillation; metrology; Primary activity measurement

Domains: Nuclear Experiment [nucl-ex]; Signal and Image processing; Computation [stat.CO]

E. Halter, Cheick Thiam, Christophe Bobin, Jacques Bouchard, Dominique Chambellan, et al.. First TDCR measurements at low energies using a miniature X-ray tube. Applied Radiation and Isotopes, 2014, 93, pp.7 - 12. ⟨10.1016/j.apradiso.2014.03.007⟩. ⟨cea-01832170⟩