Performance of a chip for hybrid pixel detectors with two counters for X-ray imaging

A semiconductor hybrid pixel detector for dynamic X-ray imaging is developed. The detector, called DIXI, consists of a semiconductor sensor mounted onto a readout chip. A detector module with a 500 μm silicon sensor is currently being assembled with the use of anisotropic conductive film as interconnection between the sensor and the readout chip. The basic building block of the detector is 1 cm2 in size and consists of 992 square pixel cells arranged in 31 columns and 32 rows. The pixels have a side of 270 μm. The readout chip is capable of performing photon counting and has an externally adjustable threshold. The readout chip has been characterised by charge injection in the absence of a sensor. The threshold dispersion is measured to 365 e− for hole collection. Even if the chip was not originally designed for electron collection a threshold dispersion of 1650 e− has been achieved. Two counters are implemented in every single pixel cell and the threshold can be changed from one image to the next in order to select different parts of the X-ray spectrum.