Spectral calibration and modeling of the NuSTAR CdZnTe pixel detectors

Abstract

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 32 x 32 array of 605 micron 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 Co-57, Eu-155 and Am-241 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.

arXiv comment11 pages, 10 figures, to appear in Proceedings of the SPIE Conference 8145: UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVII

Cited by in corpus (8)

• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Calibration of the NuSTAR High Energy Focusing X-ray Telescope
• Measurement of the absolute Crab flux with NuSTAR
• NuSTAR measurement of the cosmic X-ray background in the 3-20 keV energy band
• Cadmium Zinc Telluride Detectors for a Next-Generation Hard X-ray Telescope
• In-orbit performance and calibration of the Hard X-ray Imager onboard Hitomi (ASTRO-H)
• Measuring the Cosmic X-ray Background in 3-20keV with Straylight from NuSTAR
• IDeF-X HD: a CMOS ASIC for the readout of Cd(Zn)Te Detectors for space-borne applications