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Proceedings Paper

The (55)Fe x-ray energy response of mercury cadmium telluride near-infrared detector arrays
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Paper Abstract

The accurate determination of a detector's fundamental parameters, including read noise, dark current, and QE, relies on a proper measurement of a detector's conversion gain (e- ADU-1). Charge coupling effects, such as interpixel capacitance, attenuate photon shot noise and result in an overestimation of conversion gain when implementing the photon transfer technique. An approach involving 55Fe X-rays provides a potentially straightforward measurement of conversion gain by comparing the observed instrumental counts (ADU) to the known charge (e-) liberated by the X-ray. This technique is already preferred within the CCD community, as the pair production energy for silicon is well established. In contrast, to date the pair production energy is unknown for HgCdTe, a material commonly used for near-infrared detectors. In this paper, we derive a preliminary calibration of the 55Fe X-ray energy response of HgCdTe using 8 HST WFC3 1.7 μm flight grade detectors. Our conversion of the X-ray intensities from counts into electrons implements a technique that restores the "true" gain via classical propagation of errors. For these detectors, our analysis yields preliminary results of good statistical precision: each Kα event generates 1849 ± 46 electrons, which corresponds to a pair production energy of 3.21 ± 0.08 eV. We are continuing to assess potential systematic effects to further refine the accuracy of this result.

Paper Details

Date Published: 22 July 2008
PDF: 12 pages
Proc. SPIE 7021, High Energy, Optical, and Infrared Detectors for Astronomy III, 702123 (22 July 2008); doi: 10.1117/12.789052
Show Author Affiliations
Ori Fox, Univ. of Virginia (United States)
NASA Goddard Space Flight Ctr. (United States)
Augustyn Waczynski, Global Science and Technologies, Inc. (United States)
Yiting Wen, Muniz Engineering, Inc. (United States)
Roger D. Foltz, Sigma Space, Inc. (United States)
Robert J. Hill, Conceptual Analytics, LLC (United States)
Randy A. Kimble, NASA Goddard Space Flight Ctr. (United States)
Eliot Malumuth, Wyle Information Systems (United States)
Bernard J. Rauscher, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 7021:
High Energy, Optical, and Infrared Detectors for Astronomy III
David A. Dorn; Andrew D. Holland, Editor(s)

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