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Spectroscopic imaging using Ge and CdTe based detector systems for hard x-ray applications.

Astromskas, Vytautas (2016) Spectroscopic imaging using Ge and CdTe based detector systems for hard x-ray applications. Doctoral thesis, University of Surrey.

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Third generation synchrotron facilities such as the Diamond Light Source (DLS) have a wide range of experiments performed for a wide range of science fields. The DLS operates at energies up to 150 keV which introduces great challenges to radiation detector technology. This work focuses on the requirements that the detector technology faces for X-ray Absorption Fine Structure (XAFS) and powder diffraction experiments in I12 and I15 beam lines, respectively. A segmented HPGe demonstrator detector with in-built charge sensitive CUBE preamplifiers and a Schottky e- collection CdTe Medipix3RX detector systems were investigated to understand the underlying mechanisms that limit spectroscopic, imaging performances and stability and to find ways to overcome or minimise those limitations. The energy resolution and stability of the Ge demonstrator detector was found to have the required characteristics for XAFS measurements. Charge sharing was identified as a limiting factor to the resolution which is going to be addressed in the future development of a full detector system as well as reductions in electronic noise and cross-talk effects. The stability study of the Schottky CdTe Medipix3RX detector showed that polarization is highly dependent on temperature, irradiation duration and incoming flux. A new pixel behaviour called tri-phase (3-P) pixel was identified and a novel method for determining optimum operational conditions was developed. The use of the 3-P pixels as a criterion for depolarization resulted in a stable performance of the detector. Furthermore, the detector was applied in powder diffraction measurement at the I15 beam line and resulted in the detector diffraction pattern matching the simulated data. CdTe Medipix3RX and HEXITEC spectroscopic imaging detectors were applied in identification and discrimination of transitional metals for security application and K-edge subtraction for medical applications. The results showed that both detectors have potential to be applied in fields outside synchrotron radiation.

Item Type: Thesis (Doctoral)
Subjects : Semiconductor, radiation, detectors, Medipix, HEXITEC, Spectroscopic imaging
Divisions : Theses
Authors :
Date : 29 April 2016
Funders : SEPnet
Copyright Disclaimer : That I have exercised reasonable care to ensure that the Work is original, and does not to the best of my knowledge break any UK law or infringe any third party's copyright. If my thesis does include any substantial subsidiary material owned by third-party copyright holders, I have sought and obtained permission to include it in any version of my Work available in digital format and this permission encompasses the rights that I have granted to the University of Surrey and to the British Library. I understand that ensuring that the thesis abides by UK copyright law and does not infringe any third party copyright is my own responsibility and that the University of Surrey is not liable in case of copyright infringement. If permission has been necessary to reproduce any third party material, I supply the relevant documents. By uploading this form I agree that: my thesis does not to the best of my knowledge infringe any other Intellectual Property Right or contain any confidential material.If I have requested that this thesis is restricted for a specific embargo period, it is my responsibility to review and pending commercial, IPR or confidentiality issues affecting online availability of the thesis at the end of the embargo period, and to request an extension via the University Library if this is required. I understand that neither the University of Surrey nor the British Library have any obligation to take legal action on behalf of myself,or other rights holders, in the event of infringement of intellectual property rights, breach of contract or of any other right, in the Work. I understand that the University of Surrey Library can remove the thesis from view if they receive a complaint that the thesis infringes intellectual property rights or moral rights of a third party or if it is offensive or unacceptable in some other way. (See University of Surrey Take-Down Policy)
Contributors :
Depositing User : Vytautas Astromskas
Date Deposited : 13 May 2016 09:19
Last Modified : 31 Oct 2017 18:12

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