Synchrotron characterisation of non-uniformities in a small pixel cadmium zinc telluride imaging detector

A small pixel cadmium zinc telluride detector has been fabricated, assembled and tested at the Rutherford Appleton Laboratory. The detector consists of 74×74 pixels on a 250 μm pitch with a 50 μm spacing. Flat field irradiations with an 241Am γ-ray source have demonstrated that there are significant variations in the number of counts detected by each pixel as well as large differences in the FWHM of the X-ray photo-peak. A 10×10 μm microbeam of 20 keV X-rays has been used to characterise these non-uniformities. These measurements have shown that variations in the counting and spectroscopic performance of individual pixels are due to the presence of a non-uniform electric field within the detector.