Improving the spectral resolution of a highly pixelated detector by applying a pixel-by-pixel energy calibration for investigating the spectral properties of the anode heel effect

Abstract

The energy deposition spectrum measured with highly pixelated photon-counting pixel detectors with a semiconductor sensor layer (e.g. silicon) differs significantly from the impinging X-ray spectrum. This is the main disadvantage compared to commonly known X-ray spectrometers, e.g. high purity Germanium (hpGe) detector. On the other hand, those hpGe-detectors have a lack of spatial resolution and can not be used for energy-resolved imaging. In case of measurements with highly pixelated detectors, a set of monoenergetic detector response functions is needed for the deconvolution of the measured distribution into the impinging spectrum. We have investigated the possibility of applying a pixel-by-pixel calibration on a highly pixelated detector for gaining a higher energy resolution and for lowering the minimal flux needed for the deconvolution. As a result it is now possible to utilize small ROIs of the pixel matrix for the deconvolution. With this analysis method the detector enables spectral X-ray imaging of high photon rates. This is in particular shown for the angular dependency of the anode heel effect on the emitted spectrum. © 2012 IOP Publishing Ltd and Sissa Medialab srl.