Emulator-based Bayesian inference on non-proportional scintillation models by compton-edge probing.

Scintillator detector response modeling has become an essential tool in various research fields such as particle and nuclear physics, astronomy or geophysics. Yet, due to the system complexity and the requirement for accurate electron response measurements, model inference and calibration remains a challenge. Here, we propose Compton edge probing to perform non-proportional scintillation model (NPSM) inference for inorganic scintillators. We use laboratory-based gamma-ray radiation measurements with a NaI(Tl) scintillator to perform Bayesian inference on a NPSM. Further, we apply machine learning to emulate the detector response obtained by Monte Carlo simulations. We show that the proposed methodology successfully constrains the NPSM and hereby quantifies the intrinsic resolution. Moreover, using the trained emulators, we can predict the spectral Compton edge dynamics as a function of the parameterized scintillation mechanisms. The presented framework offers a simple way to infer NPSMs for any inorganic scintillator without the need for additional electron response measurements.

SUITABILITY OF PORTABLE RADIONUCLIDE IDENTIFIERS FOR EMERGENCY INCORPORATION MONITORING.

The suitability of portable nuclide inspectors for incorporation measurements were tested with three probes (LaBr3(Ce), NaI(Tl) and HPGe) differing in sensitive volume and energy resolution. The efficiencies for the measurement of whole-body and lung radionuclide burden were calibrated using a whole-body block phantom with traceable radionuclide sources of 60Co, 133Ba, 137Cs, 152Eu and 40K. A standing geometry was chosen as it allows rapid positioning of persons for the measurements. Decision and detection limits were determined for the unshielded detector in a normal laboratory radiation environment according to ISO 11929 for 134Cs, 137Cs and 60Co. The detection limits of all three probes were significantly higher compared to well-shielded dedicated whole-body monitors (HPGe and NaI(Tl)) using a sitting geometry. Nevertheless, lung and whole-body burdens derived from dose constraints for routine and emergency conditions could be measured with all three probes with a counting time of one minute.

STABILITY OF THE NEUTRON DOSE DETERMINATION ALGORITHM FOR PERSONAL NEUTRON DOSEMETERS AT DIFFERENT RADON GAS EXPOSURES.

Since 2008 the Paul Scherrer Institute (PSI) has been using a microscope-based automatic scanning system for assessing personal neutron doses with a dosemeter based on PADC. This scanning system, known as TASLImage, includes a comprehensive characterisation of tracks. The distributions of several specific track characteristics such as size, shape and optical density are compared with a reference set to discriminate tracks of alpha particles and non-track background. Due to the dosemeter design at PSI, it is anticipated that radon should not significantly contribute to the creation of additional tracks in the PADC detector. The present study tests the stability of the neutron dose determination algorithm of the personal neutron dosemeter system in operation at PSI at different radon gas exposures.