Advanced X-ray Detectors for Industrial and Environmental Applications

Abstract: The new generation of X-ray free electron laser sources arecapable of producing light beams with billion times higherpeak brilliance than that of the best conventional X-ray sources.This advancement motivates the scientific community to pushforward the detector technology to its limit, in order to de-sign photon detectors which can cope with the extreme fluxgenerated by the free electron laser sources. Sophisticated ex-periments like deciphering the atomic details of viruses, filmingchemical reactions or investigating the extreme states of matterrequire detectors with high frame rate, good spatial resolution,high dynamic range and large active sensor area. The PERCI-VAL monolithic active pixel sensor is being developed by aninternational group of scientists in collaboration to meet theaforementioned detector requirements within the energy rangeof 250 eV to 1 keV, with a quantum efficiency above 90%.In this doctoral researchwork, Monte Carlo algorithm basedGeant4 and finite element method based Synopsys SentaurusTCADtoolkits have been used to simulate, respectively, theX-rayenergy deposition and the charge sharing in PERCIVAL. Energydeposition per pixel and charge sharing between adjacent pixelsat different energies have been investigated and presented.Novel methods for industrial and environmental applica-tions of some commercially available X-ray detectors have beendemonstrated. Quality inspection of paperboards by resolv-ing the layer thicknesses and by investigating orientation ofthe cellulose fibres have been performed using spectroscopicand phase-contrast X-ray imaging. It was found that, usingphase-contrast imaging it is possible to set burn-out like qualityindex on paperboards non-destructively. X-ray fluoroscopicmeasurements have been conducted in order to detect Cr inwater. This method can be used to detect Cr and other toxicelements in leachate in landfills and other waste dumping sites.