A CZT high efficiency detector with 3D spatial resolution for Laue lens applications

For X- and γ-ray astronomy in the coming decades, both ESA and NASA have indicated in their guidelines the importance of developing innovative instrumentation operating in the hard X- and soft γ-ray range where important scientific issues are still open, exploiting high sensitivity (50–100 times better than current instruments) for spectroscopic imaging and polarimetric observations. In this framework, the development of new focusing optics based on wide band Laue lenses operating from ∼60 keV up to several hundred keV is particularly challenging. These new high energy focusing optics require high performance focal plane detectors in order to exploit to the maximum the intrinsic capabilities of these new high energy telescopes. We describe the ongoing development of a three dimensional (3D) position sensitive device suitable as the basic unit of a high efficiency focal plane detector for a Laue lens telescope and the results obtained during preliminary functional tests. The sensitive unit is a drift strip detector based on a CZT crystal, (19×8 mm2 area, 2.4 mm thick), irradiated transversally to the electric field direction. The anode is segmented into 4 detection cells, each comprising one collecting strip and 8 drift strips. The drift strips are biased by a voltage divider. The cathode is divided into 4 horizontal strips for the reconstruction of the third coordinate of the interaction. The final 3D prototype is made by packing 8 linear modules, each composed of one basic sensitive unit, bonded onto a supporting ceramic layer. The readout electronics implements the new RENA-3 Asics and the data handling system uses custom designed FPGA based electronics to provide both the ASIC operation and the acquisition logic.