Cadmium-Zinc-Telluride Detectors

To complement the new generation of hard-x-ray telescopes (HERO) under development at MSFC requires focal plane detectors with high efficiency, good imaging properties and energy resolution, low background, low power consumption, and rugged construction. Cadmium-Zinc-Telluride (CdZnTe) detectors currently offer the best combination of these parameters. In particular, the high-angular resolution, 15-arcsec-Half Power Diameter (HPD), Hard X-ray Replicated Optics mirrors require detector resolution 250 microns FWHM for a focal length of 6m. Further, the detector must have 128 x 128 pixels, either in one single unit or in a tiled array of detectors, to sample the full focal plane.

We are testing the performance of several prototype detectors and evaluating custom readout electronics in our test facilities at the National Space Science and Technology Center (NSSTC) in Huntsville AL. Key measurements include energy resolution, interpolated spatial resolution, and charge loss (detector quantum efficiency). Technical details and results of detector testing can be found in our numerous recent publications.

Below is an example (left) of observed and reconstructed (shared events added which strengthens the photopeak) for a single pixel illuminated by an uncollimated 60 keV (Am241) source. Below right are results of Monte Carlo simulations of the same experiment. Note the two weak features corresponding to the escape peaks of Cd and Te in the reconstructed spectrum.