Pixel-level Analog-To-Digital Converters for Hybrid Pixel Detectors with energy sensitivity

Single-photon counting hybrid pixel detectors have shown to be a valid alternative to other types of X-ray imaging devices due to their high sensitivity, low noise, linear behavior and wide dynamic range. One important advantage of these devices is the fact that detector and readout electronics are manufactured separately. This allows the use of industrial state-of-the-art CMOS processes to make the readout electronics, combined with a free choice of detectors material (high resistivity Silicon, GaAs or other). By measuring not only the number of X-ray photons but also their energies (or wavelengths), the information content of the image increases, given the same X-ray dose. We have studied several possibilities of adding energy sensitivity to the single photon counting capability of hybrid pixel detectors, by means of pixel-level analog-to-digital converters. We show the results of simulating different kinds of analog-to-digital converters in terms of power, area and speed.