Spectral calibration and modeling of the NuSTAR CdZnTe pixel detectors

Takao Kitaguchi; Brian W. Grefenstette; Fiona A. Harrison; Hiromasa Miyasaka; Varun B. Bhalerao; Walter R. Cook III; Peter H. Mao; Vikram R. Rana; Steven E. Boggs; Andreas C. Zoglauer

doi:10.1117/12.896972

arXiv · 1109.0378

Spectral calibration and modeling of the NuSTAR CdZnTe pixel detectors

Takao Kitaguchi·Brian W. Grefenstette·Fiona A. Harrison·Hiromasa Miyasaka·Varun B. Bhalerao·Walter R. Cook III·Peter H. Mao·Vikram R. Rana·Steven E. Boggs·Andreas C. Zoglauer

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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.

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Takao Kitaguchi, Brian W. Grefenstette, Fiona A. Harrison, Hiromasa Miyasaka, Varun B. Bhalerao, Walter R. Cook III, Peter H. Mao, Vikram R. Rana, Steven E. Boggs, Andreas C. Zoglauer. 2011-09-05. Spectral calibration and modeling of the NuSTAR CdZnTe pixel detectors. https://doi.org/10.1117/12.896972

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