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Proceedings Paper

Ray-tracing critical-angle transmission gratings for the X-ray Surveyor and Explorer-size missions
Author(s): Hans M. Günther; Marshall W. Bautz; Ralf K. Heilmann; David P. Huenemoerder; Herman L. Marshall; Michael A. Nowak; Norbert S. Schulz
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Paper Abstract

We study a critical angle transmission (CAT) grating spectrograph that delivers a spectral resolution significantly above any X-ray spectrograph ever own. This new technology will allow us to resolve kinematic components in absorption and emission lines of galactic and extragalactic matter down to unprecedented dispersion levels. We perform ray-trace simulations to characterize the performance of the spectrograph in the context of an X-ray Surveyor or Arcus like layout (two mission concepts currently under study). Our newly developed ray-trace code is a tool suite to simulate the performance of X-ray observatories. The simulator code is written in Python, because the use of a high-level scripting language allows modifications of the simulated instrument design in very few lines of code. This is especially important in the early phase of mission development, when the performances of different configurations are contrasted. To reduce the run-time and allow for simulations of a few million photons in a few minutes on a desktop computer, the simulator code uses tabulated input (from theoretical models or laboratory measurements of samples) for grating efficiencies and mirror reflectivities. We find that the grating facet alignment tolerances to maintain at least 90% of resolving power that the spectrometer has with perfect alignment are (i) translation parallel to the optical axis below 0.5 mm, (ii) rotation around the optical axis or the groove direction below a few arcminutes, and (iii) constancy of the grating period to 1:105. Translations along and rotations around the remaining axes can be significantly larger than this without impacting the performance.

Paper Details

Date Published: 18 July 2016
PDF: 10 pages
Proc. SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, 990556 (18 July 2016); doi: 10.1117/12.2232157
Show Author Affiliations
Hans M. Günther, MIT Kavli Institute for Astrophysics and Space Research (United States)
Marshall W. Bautz, MIT Kavli Institute for Astrophysics and Space Research (United States)
Ralf K. Heilmann, MIT Kavli Institute for Astrophysics and Space Research (United States)
David P. Huenemoerder, MIT Kavli Institute for Astrophysics and Space Research (United States)
Herman L. Marshall, MIT Kavli Institute for Astrophysics and Space Research (United States)
Michael A. Nowak, MIT Kavli Institute for Astrophysics and Space Research (United States)
Norbert S. Schulz, MIT Kavli Institute for Astrophysics and Space Research (United States)


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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