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Simulation of the Spectral Response of a Pixellated X-Ray Imaging Detector in Single Photon Processing Mode
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (STC)ORCID iD: 0000-0002-5619-409X
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (STC)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (STC)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (STC)
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2010 (English)In: 2010 Nuclear Science Symposium and Medical Imaging Conference, IEEE conference proceedings, 2010Conference paper, Published paper (Refereed)
Abstract [en]

X-ray imaging with spectral resolution, “Color X-ray imaging” is a new imaging technology that is currently attracting a lot of attention. It has however been observed that the quality of spectral response is degraded as the pixel size is reduced. This is an effect of charge sharing where the signal from a photon absorbed close to the border between two pixels is shared between pixels. This effect is caused by both diffusion during the charge transport and X-ray fluorescence in heavy detector materials. In order to understand the behavior of pixellated detectors with heavy detector materials operating in single photon processing mode, we have simulated the X-ray interaction with the sensor and the transport of the charge to the readout electrode using a Monte Carlo model for the X-ray interaction and a drift diffusion model for the charge transport. By combining these models, both signal and noise properties of the detector can be simulated.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2010.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-12856OAI: oai:DiVA.org:miun-12856DiVA, id: diva2:378814
Conference
2010 Nuclear Science Symposium and Medical Imaging Conference, Oct 30-Nov 6, Knoxville, Tennessee
Available from: 2011-01-09 Created: 2010-12-16 Last updated: 2015-03-31Bibliographically approved
In thesis
1. Monte Carlo and Charge Transport Simulation of Pixel Detector Systems
Open this publication in new window or tab >>Monte Carlo and Charge Transport Simulation of Pixel Detector Systems
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is about simulation of semiconductor X-ray and particledetectors. The simulation of a novel coating for solid state neutrondetectors is discussed as well as the implementation of a simulationframework for hybrid pixel detectors.Today’s most common thermal neutron detectors are proportionalcounters, that use 3He gas in large tubes or multi wire arrays. Globalnuclear disarmament and the increase in use for homeland securityapplications has created a shortage of the gas which poses a problemfor neutron spallation sources that require higher resolution and largersensors. In this thesis a novel material and clean room compatible pro-cess for neutron conversion are discussed. Simulations and fabricationhave been executed and analysed in measurements. It has been proventhat such a device can be fabricated and detect thermal neutrons.Spectral imaging hybrid pixel detectors like the Medipix chipare the most advanced imaging systems currently available. Thesechips are highly sophisticated with several hundreds of transistors perpixel to enable features like multiple thresholds for noise free photoncounting measurements, spectral imaging as well as time of arrivalmeasurements. To analyse and understand the behaviour of differentsensor materials bonded to the chip and to improve development offuture generations of the chip simulations are necessary. Generally, allparts of the detector system are simulated independently. However, itis favourable to have a simulation framework that is able to combineMonte Carlo particle transport, charge transport in the sensor as wellas analogue and digital response of the pixel read-out electronics. Thisthesis aims to develop such a system that has been developed withGeant4 and analytical semiconductor and electronics models. Further-more, it has been verified with data from measurements with severalMedipix and Timepix sensors as well as TCAD simulations.Results show that such a framework is feasible even for imagingsimulations. It shows great promise to be able to be extended withfuture pixel detector designs and semiconductor materials as well asneutron converters to aim for next generation imaging devices.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2015. p. 95
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 215
Keywords
Monte Carlo Simulation, TCAD, pixel detectors, Medipix, Timepix, Finite Element Simulation
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:miun:diva-24763 (URN)STC (Local ID)978-91-88025-06-7 (ISBN)STC (Archive number)STC (OAI)
Public defence
2015-04-08, M102, Mittuniversitetet, Holmgatan 10, Sundsvall, 10:00 (English)
Opponent
Supervisors
Available from: 2015-03-31 Created: 2015-03-31 Last updated: 2016-12-23Bibliographically approved

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Authority records BETA

Krapohl, DavidNorlin, BörjeFröjdh, ErikThungström, GöranFröjdh, Christer

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