Very High Rate X-ray Photon Counting 2D Detectors with Small Pixels: the SPHIRD Project

The SPHIRD project is a study towards the development of a new generation of X-ray photon counting pixel detectors for synchrotron radiation applications operating between 10 and 35 keV, with very high count rate capabilities and small pixels. The study relies on the design and construction of test prototypes complemented by detector simulations. The strategy to boost count rate consists in combining a fast analog front-end with pile-up compensation techniques and the option of pixel binning. The project intends to explore and compare different time-based and amplitude-based pile-up compensation methods. As a complementary study, the project is investigating the exploitation of charge sharing in very small pixels to relocate photon hits within sub-pixel matrices and increase the effective spatial resolution of the detectors. The first SPHIRD prototypes consist of small 64×32 pixel matrices with p-type Si pixelated sensors bonded to a test readout integrated circuit designed in CMOS 40nm technology. Although the test prototypes are built with 50 µm pixels, one of the objectives of the study is to explore how small the pixels could be potentially made in a final system.