Hybrid pixel photon counting X-ray detectors for synchrotron radiation

Abstract

Detectors operated in single-photon-counting mode have radically transformed basic research at synchrotron light sources since 2006. Hybrid photon-counting (HPC) pixel detectors proved to be a disruptive technology for almost all X-ray diffraction applications in the energy range from 2 to 30 keV. Themain reason for this success is the accurate determination of scattering and diffraction patterns at the level of individual photons over an extremely high dynamic range. The technology of photon-counting detectors is based on segmented semiconductor sensors, predominantly silicon arrays, which allow direct detection of X-rays and guarantee very high stability and simple operation at room temperature. The sensors are coupled to application-specific integrated circuits (ASICs), which process the electrical signal pulses from the sensor and are designed using modern CMOS processes. The implementation of energy thresholds gives counting detectors the unique capability to determine the number of photons in a specific energy range for very high local and global count rates. The digital detection and storage avoids any readout noise and permits very high frame rates. Combining these features in one device led to a transition from CCD-based detector systems to HPC detectors for applications like protein crystallography, small-angle scattering, and surface and powder diffraction and offers new opportunities in time-resolved experiments. This chapter covers the technology of HPC detectors and their usage at synchrotrons. It describes the basic principles of the sensor, readout ASIC and interconnection technology and highlights the properties of the detectors. In addition details about data correction procedures are given.