A hybrid pixel detector with two counters for x-ray imaging

A semiconductor hybrid pixel detector for dynamic X-ray imaging is being developed. The detector consists of a 500 μm thick silicon sensor and a pixel readout chip. The two parts are interconnected by means of anisotropic conductive film. The basic building block of the detector is approximately one square centimeter large and consists of 992 pixel cells arranged in 31 columns and 32 rows. Each pixel has an area of 270 micrometer square and the readout chip contains amplifier, discriminator and two 12 bit counters. An externally adjustable threshold level can be changed within one microsecond from one image to another in order to select different parts of the X-ray spectrum. The chip can be tuned to assign different weighting functions to photons with energies exceeding the threshold. It is possible to either operate the detector as a photon counter or as an energy integrator.