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Proceedings Paper

A low-noise HAWAII detector system and new cold optics for the CLASSIC/CLIMB beam combiner instrument of the CHARA array
Author(s): Udo Beckmann; Claus Connot; Matthias Heininger; Karl-Heinz Hofmann; Eddy Nußbaum; Dieter Schertl; Walter Solscheid; Theo ten Brummelaar; Nils Turner; Gerd Weigelt
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Paper Abstract

As part of a new collaboration between CHARA and the Max Planck Institute for Radio Astronomy, we have developed a new detector system for the CLASSIC/CLIMB beam combiner of the CHARA Array. This detector is based on the Rockwell HAWAII-1 HgCdTe focal plane array and has lower readout noise (∼5 electrons) than the current PICNIC based system. Presently, CLASSIC/CLIMB observations at different wavelength bands can be made only successively by selecting individual filters in a filter wheel. Therefore, another upgrade goal is to install a non-deviating prism in order to image the H- and K’-band light onto separate detector pixels and to simultaneously observe in the H and K’ bands. The detector control electronics were built at the Max Planck Institute for Radio Astronomy. The goal was to achieve the lowest possible readout noise and electronic pick-up noise. The detector readout noise can be significantly reduced by the following approach: First, the analog detector output signal is processed by a moving boxcar filter consisting of an analog approximation of a finite impulse response filter with a response time adapted to the 10 MHz sample rate of an analog-to-digital converter. Second, a digital filter averages up to 1024 samples for each addressed pixel. This hybrid (analog plus digital) filter approach gives a unique flexibility of a programmable bandwidth for optimum noise reduction.

Paper Details

Date Published: 24 July 2014
PDF: 6 pages
Proc. SPIE 9146, Optical and Infrared Interferometry IV, 91461W (24 July 2014); doi: 10.1117/12.2055850
Show Author Affiliations
Udo Beckmann, Max-Planck-Institut für Radioastronomie (Germany)
Claus Connot, Max-Planck-Institut für Radioastronomie (Germany)
Matthias Heininger, Max-Planck-Institut für Radioastronomie (Germany)
Karl-Heinz Hofmann, Max-Planck-Institut für Radioastronomie (Germany)
Eddy Nußbaum, Max-Planck-Institut für Radioastronomie (Germany)
Dieter Schertl, Max-Planck-Institut für Radioastronomie (Germany)
Walter Solscheid, Max-Planck-Institut für Radioastronomie (Germany)
Theo ten Brummelaar, CHARA (United States)
Nils Turner, CHARA (United States)
Gerd Weigelt, Max-Planck-Institut für Radioastronomie (Germany)

Published in SPIE Proceedings Vol. 9146:
Optical and Infrared Interferometry IV
Jayadev K. Rajagopal; Michelle J. Creech-Eakman; Fabien Malbet, Editor(s)

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