A three-dimensional CZT detector as a focal plane prototype for a Laue Lens telescope

The importance of hard X-ray astronomy (10 keV) is now widely recognized. Recently both ESA and NASA have indicated in their guidelines for the progress of X- and g-ray astronomy in the next decade the development of new instrumentation working in the energy range from the keV to the MeV region, where important scientific issues are still open, exploiting high sensitivity for spectroscopic imaging and polarimetry observations. The development of new concentrating (e.g. multilayer mirror) telescopes for hard X-rays (10 -100 keV) and focusing instruments based on Laue lenses operating from ~60 keV up to a few MeV is particularly challenging. We describe the design of a threedimensional (3D) depth-sensing position sensitive device suitable for use as the basic unit of a high efficiency focal plane detector for a Laue lens telescope. The sensitive unit is a drift strip detector based on a CZT crystal, (10×10 mm2 area, 2.5 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, whereas the anode strips are held at 0 V. The cathode is divided in 4 horizontal strips for the reconstruction of the Z interaction position. The 3D prototype will be made by packing 8 linear modules, each composed of 2 basic sensitive units, bonded onto a ceramic layer together with the readout electronics.