Development and Modelling Innovative Techniques for Neutron Dosimetry

In the field of ionising radiation dosimetry, the evaluation of neutron exposures still constitutes nowadays one of the most challenging problems. The origin of the enhanced difficulty resides in the physical mechanisms through which neutrons deposit energy in matter. During the past decades, a number of techniques and devices have been conceived to detect and measure neutrons. An extensive characterisation of a neutron field, needed for precise dosimetry, can be performed with dedicated equipment, which however cannot be worn and used as a personal dosimeter, given the bulky size. Alternatively, a number of compact detectors to monitor the neutron doses of exposed personnel have been developed, among which the most widely used poly allyl diglycol carbonate detectors (PADC), but are usually subject to limitations, such as the sensitivity to a narrow portion of the neutron spectrum. Fluorescent Nuclear Track Detectors (FNTD), a relatively recent radiation detection technology, has the ability to overcome some of the limitations affecting the other dosimeters, potentially improving the dose assessment. The objectives of this PhD project comprise the investigation on the performance of the FNTD technology applied to fast neutron dosimetry and the comparison of such performance with the one of more established PADC detectors. Additionally, the studies presented are devoted to identify and propose improvements in the current dosimeters evaluation technique and explore innovative assessments that can further enhance the accuracy of fast neutron dose estimations. The studies were supported by data obtained with Monte Carlo simulations and experimental irradiations, which were used to conceive and verify the newly developed analyses. A new image analysis of the FNTDs readouts was proposed, allowing, on the one hand, a more precise characterisation of the track-spots and, on the other hand, demonstrating the trajectory reconstruction of recoil protons that interacted with the detectors. The image processing results were used to develop a more effective technique to reject the spurious track-spots generated by concomitant photon-induced delta electrons in neutron exposures, and to formulate and corroborate a new analysis method, based on the collective evaluation of the reconstructed recoil proton trajectories, to infer the angles of exposures and the mean energy of a neutron field, providing the information to correct for the angular and energy dependence of the dosimeter, thereby improving the dose estimation.