Effects of cable extension and photon irradiation on TNRD neutron detector in radiotherapy

Abstract

A new thermal neutron detector (TNRD), developed for nuclear research, has shown to be effective for clinical use in peripheral neutron dose estimation, either in patient and ‘in-phantom’ measurements. This work shows some TNRD difficulties when adapting it to radiotherapy environments, mainly due to the fact that it has shown structural limitations. Two problems have been studied: (1) the influence of cable lengthening, necessary to be operative in a radiotherapy environment and (2) cable irradiation during the measurements. As we are measuring very small signals, we have to take into account not only these two facts but also the quality of the materials and connectors used. Thus, we studied cable elongation and irradiation influences in conventional and extreme situations once the setup was improved, in order to avoid uncertainties which could be of the order of the signal. Mean deviations of -0.15% from the original TNRD cable extension have been noticed. For the wide variety of conditions tested, in terms of both dose delivered and setup of the radiotherapy exposure, uncertainties smaller than 1.2% have been estimated.