Characterization of Different Types of Micro-Fission and Micro-Ionization Chambers Under X-Ray Beams

Abstract

This research has been funded by EU 2020 research and innovation programme under grant agreement No 101008126, corresponding to the RADNEXT project, and co-financed by International Fusion Materials Irradiation Facility-Demo Oriented Neutron Source (IFMIF-DONES), co-financed by the European Regional Development Fund-FEDER, the project PID2022-137543NB-I00 funded by MCIN/AEI/10.13039/501100011033 and ERDF “A way of making Europe”, and by the Junta de Andalucía (FQM387), and granted within the program “Precompetitive Research Projects for Young Researchers. Modality B—Projects for Doctoral Students” of the Institutional Research and Transfer Plan of the University of Granada for the year 2023.Various models of ionization and fission chambers for ionizing radiation detection, designed to operate under harsh conditions such as those found in fusion reactors or particle accelerators, have been experimentally characterized and numerically simulated. These models were calibrated using a photon beam in the X-ray spectrum. Irradiations were performed at the Biomedical Research Center of the University of Granada (CIBM) with a bipolar metal-ceramic X-ray tube operating at a voltage of 150 kV and a dose rate ranging from 0.05 to 2.28 Gy/min. All detectors under study featured identical external structures but varied in detection volume, anode configuration, and filling gas composition. To assess inter- and intra-model response variations, the tested models included 12 micro-ionization chambers (CRGR10/C5B/UG2), 3 micro-fission chambers (CFUR43/C5B-U5/UG2), 8 micro-fission chambers (CFUR43/C5B-U8/UG2), and 3 micro-fission chambers (CFUR44/C5B-U8/UG2), all manufactured by Photonis (Merignac, France). The experimental setup was considered suitable for the tests, as the leakage current was below 20 pA. The optimal operating voltage range was determined to be 130–150 V, and the photon sensitivities for the chambers were measured as 29.8 ± 0.3 pA/(Gy/h), 43.0 ± 0.8 pA/(Gy/h), 39.2 ± 0.3 pA/(Gy/h), and 96.0 ± 0.9 pA/(Gy/h), respectively. Monte Carlo numerical simulations revealed that the U layer in the fission chambers was primarily responsible for their higher sensitivities due to photoelectric photon absorption. Additionally, the simulations explained the observed differences in sensitivity based on the filling gas pressure. The detectors demonstrated linear responses to dose rates and high reproducibility, making them reliable tools for accurate determination of ionizing photon beams across a range of applications.EU 2020, 101008126International Fusion Materials Irradiation Facility-Demo Oriented Neutron Source (IFMIF-DONES)European Regional Development Fund-FEDERMCIN/AEI/10.13039/501100011033 PID2022-137543NB-I00ERDF “A way of making Europe”Junta de Andalucía (FQM387)University of Granad