Development of solid state microdosimetric tools for quality assurance in proton and heavy ion therapy

Microdosimetry has been used for decades to characterise radiation fields using gas detectors with effective volume similar to that of human cells. The tissue-equivalent proportional counter (TEPC) is the gold-standard microdosimetric device, however silicon microdosimeters have shown to be a viable replacement which offer many advantages including a slimline form factor and submillimeter resolution. This thesis continues the development of silicon-on-insulator (SQQ microdosimeters for use in hadron therapy beams and mixed radiation fields, designed at the Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia. Three new SOI microdosimeters were investigated, including two based on state of the art 3D silicon technology, utilising deep reactive ion etching. This technology was used to provide well-defined sensitive volumes with enhanced charge collection properties, which were lacking in previous CMRP microdosimeters. Electrical characterisation was undertaken as well as scanning electron microscopy and energy-dispersive x-ray spectroscopy, revealing the physical and chemical properties of the microscopic detection volumes. Using the ion beam induced charge collection technique, the spectroscopic response to high LET alpha particles was measured and the charge collection geometry mapped.