Semiconductor Pixel Detectors for Imaging Applications

Da Via', Cinzia (1997) Semiconductor Pixel Detectors for Imaging Applications. PhD thesis, University of Glasgow.

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In this thesis the work is presented as follows: Chapter 1 introduces the ideal detector characteristics for medical imaging. The requirements of the ideal diagnostic method are related to the various types of medical examinations, comparing the existing techniques and discussing results of Monte Carlo simulation studies. A review of existing detectors based on semiconductor microstrip and semiconductor pixel detectors introduces the hybrid Omega family, the pixel readout electronics used by the author for the tests presented in the following chapters. Chapter 2 describes a material defect characterisation study of semi-insulating gallium arsenide using a near-infrared absorption technique. Generally this technique is applied to "as-grown" materials but in this case, using a set-up proposed by the author, the concentration of the deep defect EL2 was monitored in a biased detector for different values of the applied electric field. The results obtained seem to support a theoretical model which predicts the presence of a "quasi"-neutral region inside the detector active volume. The tests performed by the author using silicon and gallium arsenide pixel detectors coupled with the Omega2 and Omega3 read-out electronics are discussed in Chapter 3. The results reported include images of phantoms of different contrasts illuminated by X-ray sources, biological samples traced with beta- emitters and pixel detector characterisation using particle beams. Chapter 4 describes the characterisation made by the author of a photosensitive version of the silicon pixel detector associated with the OmegaD and Omega2 read-out electronics. The tests were performed using light sources at different wavelengths, scintillating plastic fibres and scintillating crystals excited by radioactive sources and particle beams. The aim of this study was the search for a fast, high spatial resolution alternative to CCDs and multi-anodes photomultipliers for scintillating fibre particle tracking and for nuclear medicine based on scintillating crystals. The advantages and limitations of the present system are discussed with possible future improvements The final chapter draws some conclusions about the work reported and offers some considerations for future developments. In particular, a description is given of a new pixel detector electronics chip with single photon counting capabilities, which followed the experience gained with the present versions of the Omega family electronics. The new electronics chip consists of a 64 x 64 array of pixels, each measuring 170 x 170 mum2 and including a 15-bit binary counter. This chip is therefore extremely well-matched to a wide range of X-ray imaging applications, some of which are reviewed here.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Kenway Smith
Keywords: Medical imaging, Nuclear physics and radiation
Date of Award: 1997
Depositing User: Enlighten Team
Unique ID: glathesis:1997-75476
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 19:50
Last Modified: 19 Nov 2019 19:50

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