Doctor of Philosophy
School of Physics
George, Stuart, Dosimetric applications of hybrid pixel detectors, Doctor of Philosophy thesis, School of Physics, University of Wollongong, 2015. http://ro.uow.edu.au/theses/4593
This thesis discusses the application of the Timepix hybrid pixel detector to mixed field characterisation and dosimetry. A brief history of silicon detectors and the physics of radiation detection in semiconductors is presented, and the Timepix ASIC is introduced. A guide is given to the setup, characterisation and the energy calibration of a Timepix detector (a Timepix attached to a silicon sensor). The analysis of tracks left in the Timepix detector to produce characteristics of the impinging particle such as track polar angles and equivalent dose deposited is described. Applications of these methods are demonstrated at the CERF facility at CERN and on the International Space Station. A novel energy independent fast neutron dosimeter based on a multilayer polyethylene converter placed on a Timepix detector is developed using Geant4 Monte Carlo simulations. A version of this converter is 3D printed and characterised using neutrons at the NTOF time of flight facility at CERN. A key capability of this detector is the potential ability to subtract gamma ray and charged particle background. A new detector, the GEMPix is presented. This detector is based on a triple gas electron multiplier coupled to a quad Timepix ASIC for readout. The detector is operated as a highly compact (10 cm3) time projection chamber. Characterisation measurements of this detector with photons, alpha particles and relativistic protons are described. The use of this detector as a microdosimeter is briefly discussed.