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Proceedings Paper

Studies of prototype DEPFET sensors for the wide field imager of Athena
Author(s): Wolfgang Treberspurg; Robert Andritschke; Alexander Bähr; Davide Bianchi; Anna Koch; Norbert Meidinger; Johannes Müller-Seidlitz; Sabine Ott; Matteo Porro
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Paper Abstract

The Wide Field Imager of the Athena telescope will combine an excellent spectroscopic performance and high count rate capability with a large field of view. For these purposes, its focal plane consists of two complementary detectors, using DEPFET active pixel sensors. One is the high count rate detector with a small field of view, which has to be operated with a readout speed of 80 μs per frame. In contrast, the large area detector will cover a large field of view and has to be read out with a frame rate ≤ 5 ms. Its sensitive area is covered by four identical active pixel arrays, consisting of 512 x 512 pixels, each. Since a column parallel readout will be used, 512 pixels are connected to one single channel of a readout ASIC. The readout will be accomplished by either sensing a voltage step on the source node or a change of the transistor drain current. The former so-called source follower mode requires long settling times - proportional to the load capacitances - but can cope with local inhomogeneities. Alternatively, the latter so-called drain current mode provides a fast readout - independent to the load capacitance - but implicates a higher sensitivity on local variations of the DEPFETs bias currents. Both modes are implemented in the VERITAS 2.1 readout ASIC and were studied with 64 x 64 pixels arrays. Drain current devices could be operated with significantly smaller settling times but suffer from a slightly increased noise at similar shaping times in comparison to the source follower ones. By using an optimized timing with dedicated settling and shaping times, the devices of both modes feature a comparable spectral performance.

Paper Details

Date Published: 11 July 2016
PDF: 7 pages
Proc. SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, 99052C (11 July 2016); doi: 10.1117/12.2235407
Show Author Affiliations
Wolfgang Treberspurg, Max-Planck-Institut für extraterrestrische Physik (Germany)
Robert Andritschke, Max-Planck-Institut für extraterrestrische Physik (Germany)
Alexander Bähr, Max-Planck-Institut für extraterrestrische Physik (Germany)
Davide Bianchi, Max-Planck-Institut für extraterrestrische Physik (Germany)
Anna Koch, Max-Planck-Institut für extraterrestrische Physik (Germany)
Norbert Meidinger, Max-Planck-Institut für extraterrestrische Physik (Germany)
Johannes Müller-Seidlitz, Max-Planck-Institut für extraterrestrische Physik (Germany)
Sabine Ott, Max-Planck-Institut für extraterrestrische Physik (Germany)
Matteo Porro, Max-Planck-Institut für extraterrestrische Physik (Germany)


Published in SPIE Proceedings Vol. 9905:
Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray
Jan-Willem A. den Herder; Tadayuki Takahashi; Marshall Bautz, Editor(s)

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