Fabricatie en kalibratie van superheated droplet detectors (SDD’s) voor neutronendosimetrie

The RDA unit of SCK•CEN in Mol performs research in the development of neutron dosimeters. There is a major concern about the carcinogenic risk of secondary neutrons which are inevitably present in proton therapy. In order to measure the secondary neutron dose, commercial bubble detectors can be used. However, these detectors take a lot of space, are very expensive and have limited life time and therefore small SDDs need to be developed to measure the neutron dose in vivo by using a phantom. This master’s thesis aims to improve an existing fabrication protocol to achieve a stable detector to assess neutron doses in anthropomorphic phantoms during proton radiotherapy. Thereafter, the detectors must be characterized and a reproducible calibration method has to be sought. In this thesis, a new fabrication protocol has been developed that must be followed very carefully. The SDDs are irradiated with a 252Cf neutron source and read through an acoustic detection system. Afterwards, registered pulses are analyzed through an optimized software program to provide an objective analysis. To conclude, the SDDs must be manufactured by strictly following a dedicated protocol. The sensitivity of the SDDs can be increased by increasing the amount of added Freon. However, these detectors are limited in sensitivity because of the limited volume. Finally, a reproducible calibration method was obtained by resetting (applying pressure on the vial) the SDDs after each irradiation and with the software analysis of the acoustic pulses.