PERCIVAL (""Pixelated Energy Resolving CMOS Imager, Versatile And Large"") is a monolithic active pixel sensor (MAPS) based on CMOS technology. Is being developed by DESY, RAL/STFC, Elettra, DLS, and PAL to address the various requirements of detectors at synchrotron radiation sources and Free Electron Lasers (FELs) in the soft X-ray regime. These requirements include high frame rates and FELs base-rate compatibility, large dynamic range, single-photon counting capability with low probability of false positives, high quantum efficiency (QE), and (multi-)megapixel arrangements with good spatial resolution. Small-scale back-side-illuminated (BSI) prototype systems are undergoing detailed testing with X-rays and optical photons, in preparation of submission of a larger sensor. A first BSI processed prototype was tested in 2014 and a preliminary result—first detection of 350eV photons with some pixel types of PERCIVAL—reported at this meeting a year ago. Subsequent more detailed analysis revealed a very low QE and pointed to contamination as a possible cause. In the past year, BSI-processed chips on two more wafers were tested and their response to soft X-ray evaluated. We report here the improved charge collection efficiency (CCE) of different PERCIVAL pixel types for 400eV soft X-rays together with Airy patterns, response to a flat field, and noise performance for such a newly BSI-processed prototype sensor.
The new generation of X-ray free electron laser sources are capable of producing light beams with billion times higher peak brilliance than that of the best conventional X-ray sources. This advancement motivates the scientific community to push forward the detector technology to its limit, in order to de-sign photon detectors which can cope with the extreme flux generated by the free electron laser sources. Sophisticated ex-periments like deciphering the atomic details of viruses, filming chemical reactions or investigating the extreme states of matter require 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 an international group of scientists in collaboration to meet the aforementioned detector requirements within the energy rangeof 250 eV to 1 keV, with a quantum efficiency above 90%. In this doctoral research work, Monte Carlo algorithm based Geant4 and finite element method based Synopsys SentaurusTCAD toolkits have been used to simulate, respectively, theX-ray energy deposition and the charge sharing in PERCIVAL. Energydeposition per pixel and charge sharing between adjacent pixels at different energies have been investigated and presented. Novel methods for industrial and environmental applications of some commercially available X-ray detectors have been demonstrated. Quality inspection of paperboards by resolving the layer thicknesses and by investigating orientation of the cellulose fibres have been performed using spectroscopic and phase-contrast X-ray imaging. It was found that, using phase-contrast imaging it is possible to set burn-out like quality index on paperboards non-destructively. X-ray fluoroscopic measurements have been conducted in order to detect Cr inwater. This method can be used to detect Cr and other toxic elements in leachate in landfills and other waste dumping sites.