Development of a 24×24 CZT-FEE pixel detector block for the CSTD project

The CSTD project aims at developing a gamma pixel detector to be used as first detector in a Compton imager. Due to the strong requirements demanded by this application, the detector must provide high energy and spatial resolution, together with high detection efficiency in the energy range of interest, namely, between 15 keV and 1 MeV. A first family of CdZnTe pixel detectors has been designed and developed for this purpose. The detectors have a pattern of 24 × 24 pixels 0.3 mm pitch, and a nominal thickness of 5 mm, as a compromise of the maximum figure needed. Two designs have been considered: a regular pixel design and a design with steering grid. The detectors have been manufactured by Bruker Baltic, Latvia, making use of Yinnel Tech. (USA) monocrystals. A front end electronics ASIC has been manufactured by Gamma Medica-Ideas in Norway specifically for this project. This electronics has been designed to be directly coupled to the detector via bump-bonding. The detectors were bump-bonded to the ASICs at the bonding facilities in the Rutherford Appleton Laboratory, UK. In this paper, a description of the hardware and the first results provided by the detectors are shown.