A recombination chamber-based measurement system for radiation protection in neutron medical and research centers

Recombination chambers, which operate based on ion recombination in gas and exhibit LET-dependent response, have been successfully used for many years in radiation protection to assess radiation quality (Q) and relative biological effectiveness (RBE). The REM-type chambers are a family of high-pressure, tissue-equivalent detectors designed for such applications. REM-2 and its successors, REM-3, represent successive generations of these chambers, with improvements in construction, electrode materials, gas filling, signal acquisition and mechanical design. The potential application of these detectors in Boron Neutron Capture Therapy (BNCT) addresses the need to assess exposure levels to mixed radiation occurring in medical or research BNCT centers. The main advantage of REM-3 detectors is the possibility to measure separately neutron and gamma doses, radiation quality index and total H^∗(10) values, which are important for the centers working with neutrons, with a portable instrument in a short time. Three novel chambers based on the REM-2 recombination chamber have been manufactured and tested. The introduced changes confirmed the usefulness of modern tools in the design of recombination chambers. The manufactured detectors show the measurement agreement with the one assumed at the design stage. Independent of the development of detectors, a new approach to the problem of measuring the ionization current of recombination chambers was developed and tested using the Keithley 6517A/B electrometer. The new measurement algorithm significantly reduces the measurement time required for recombination methods, making it possible to create a portable dosimetric system for monitoring exposure at workplaces, including medical personnel in particular in BNCT therapy research centers. Tests of the REM-3 detectors were carried out in gamma and neutron sources and finally improved in the neutron facility at the MARIA reactor (H2 channel with thermal neutron beam designed for BNCT).