Doctor of Philosophy (PhD)
Department of Engineering Physics - Faculty of Engineering
Cornelius, Iwan M, Towards silicon microdosimetry based verification of Monte Carlo calculations in Hadron therapy, PhD thesis, Department of Engineering Physics, University of Wollongong, 2003. http://ro.uow.edu.au/theses/206
This thesis continues research into the application of silicon microdosimetry to hadron therapy applications. It proposes the use of silicon microdosimetry for the verification of Monte Carlo calculations in hadron therapy. When applied in this manner, many of the restrictions previously impeding the use of silicon microdosimeters in hadron therapy are relaxed. An ion mircrophone was used to study the charge collection properties of the silicon microdosimeters using ions commonly found in the primary and secondary radiation of hadron therapy. An experimental setup was developed and diagnostic studies were conducted to establish low beam fluence and micron beam resolution necessary for the measurements. GEANT4 Monte Carol simulations of the measurements facilitated the quantification of the charge collection efficiency of the devices for ions with various Linear Energy Transfer values. An ion beam analysis technique was developed to measure the collection time of charge carriers generated following ion strikes on the silicon microdosimeter. The dependence of this charge collection time was studied using the ion microprobe. A pulse shape discrimination technique was then implemented in an attempt to improve the spectral response of the microdosimeter. Simple Monte Carol simulations of silicon microdosimetry measurements in Fast Neutron Therapy and Proton Therapy were conducted using the GEANT4 Monte Carlo toolkit. The charge collection efficiency information obtained from microprobe experiments was incorporated into the simulation. Discrpancies between experimental and theoretical measurements was then used to suggest improvements to the simulations. Future recommendations for the application of silicon microdosimeters in this capacity are discussed along with suggestions for other silicon based instrumentation.