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Published September 13, 2011 | Published + Submitted
Book Section - Chapter Open

Spectral calibration and modeling of the NuSTAR CdZnTe pixel detectors


The Nuclear Spectroscopic Telescope Array (NuSTAR) will be the first space mission to focus in the hard X-ray (5-80 keV) band. The NuSTAR instrument carries two co-aligned grazing incidence hard X-ray telescopes. Each NuSTAR focal plane consists of four 2 mm CdZnTe hybrid pixel detectors, each with an active collecting area of 2 cm x 2 cm. Each hybrid consists of a 32x32 array of 605 μm pixels, read out with the Caltech custom low-noise NuCIT ASIC. In order to characterize the spectral response of each pixel to the degree required to meet the science calibration requirements, we have developed a model based on Geant4 together with the Shockley-Ramo theorem customized to the NuSTAR hybrid design. This model combines a Monte Carlo of the X-ray interactions with subsequent charge transport within the detector. The combination of this model and calibration data taken using radioactive sources of ^(57)Co, ^(155)Eu and ^(241)Am enables us to determine electron and hole mobility-lifetime products for each pixel, and to compare actual to ideal performance expected for defect-free material.

Additional Information

© 2011 SPIE Society of Photo-Optical Instrumentation Engineers. This work was supported under NASA Contract NNG08FD60C. T.K. is supported by JSPS postdoctoral fellowships for research abroad. We thank Csaba Szeles for useful discussions.

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Submitted - 1109.0378v2.pdf


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