A. Mangano

Characterization of a CZT focal plane small prototype for hard X-ray telescope

The promise of good energy and spatial resolution coupled with high efficiency and room temperature operation has fuelled a large international effort to develop cadmium zinc telluride (CZT) for hard X-ray applications. We are involved on the development of a hard X-ray telescope based on multilayer optics and focal plane detector operative in the 10-80 keV energy range. This telescope requires a high efficiency focal plane providing both fine spatial resolution and spectroscopy with a compact and robust design. This paper reports preliminary results on the characterization both in spectroscopic and spatial response of two small pixellated CZT detectors (10times10times1 mm3 and 10times10times2 mm3 single crystals) with 0.45 mm pixel size. We present the results obtained using both standard commercial read-out electronics Readout Electronics for Nuclear Applications (RENA) and innovative low noise and low power dissipation ASICs developed within the collaboration

Measurements of spectral and position resolution on a 16x16 pixel CZT imaging hard x-ray detector

Cadmium zinc telluride (CZT) pixel detectors show very good spectral and spatial resolution and are suitable for use in compact hard X-ray sensors operated without cryogenics. One of the more interesting astrophysical application is their use as focal plane detectors for multilayer hard X-ray telescopes operating in the 15 - 70 keV energy band. Here we report on results obtained using a 16 x 16 CZT pixel detector (10 x 10 x 1 mm3 single crystal) with 500 μm pixels operated at room temperature using standard commercial electronics. The results clearly show that the use of small pixels is effective in reducing one of the major drawbacks of CZT planar detectors i.e. the considerable amount of charge loss, due to hole trapping, which gives rise to a reduced energy resolution and a low energy tail in the pulse-height spectra.

Investigation on pixellated CZT detectors coupled with a low power readout ASIC

In this work, we investigated on the spectroscopic performances of two pixellated CZT detectors coupled with a custom low noise and low power readout ASIC. The detectors (10 x 10 x 1 mm3 and 10 x 10 x 2 mm3 single crystals) consist of an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 μm BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) characterized by a dynamic range from 10 keV to 100 keV, low power consumption (0.5 mW/channel) and low noise (150–500 electrons r.m.s.). The spectroscopic results point out the good energy resolution of both detectors at room temperature (5.8 % FWHM at 59.5 keV for the 1 mm thick detector; 5.5 % FWHM at 59.5 keV for the 2 mm thick detector) and low tailing, confirming the single charge carrier sensing properties of the CZT detectors equipped with a pixellated anode layout. Temperature measurements show optimum performances of the system (detector and electronics) at T = 10 °C and performance degradations at lower temperatures. The detectors and the ASIC, designed by our collaboration, represent two small focal plane detector prototypes for hard X-ray telescopes operating in the 10–100 keV energy range.

Spectroscopic performances and electron transport properties in a 16x16-pixel CZT imaging hard-X-ray detector

Cadmium zinc telluride (CZT) pixel detectors show very good spectral and spatial resolution and are suitable for use in compact hard X-ray sensors operated without cryogenics. One of the more appealing astrophysical applications is their use as focal plane detectors for multilayer hard X-ray telescopes operating in the (10 - 80) keV energy band. This paper reports experimental results obtained from two 16x16 pixellated CZT detectors (10x10x1 mm3 and 10x10x2 mm3 single crystals) with 450x450 μm2 pixel operated at room temperature using standard commercial read-out electronics. We have investigated about energy resolution and material properties of both detectors. Both arrays gave similar results showing an energy resolution less then 5%@59.5 keV and a good material uniformity. The good energy resolution of both detectors demonstrates as the pixellated anode structure reduces (small pixel effect) the incomplete charge collection due to severe hole trapping typically presents in CZT crystals. A calibration curve, obtained using three different energies, shows a linear response of the detectors.

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.