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Proceedings Paper

Analytical computation of stray light in nested mirror modules for x-ray telescopes
Author(s): Daniele Spiga
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Paper Abstract

Stray light in X-ray telescopes are a well-known issue. Unlike rays focused via a double reflection by usual grazing-incidence geometries such as the Wolter-I, stray rays coming from off-axis sources are reflected only once by either the parabolic or the hyperbolic segment. Although not focused, stray light may represent a major source of background and ghost images especially when observing a field of faint sources in the vicinities of another, more intense, just outside the field of view of the telescope. The stray light problem is faced by mounting a pre-collimator in front of the mirror module, in order to shade a part of the reflective surfaces that may give rise to singly-reflected rays. Studying the expected stray light impact, and consequently designing a pre-collimator, is a typical ray-tracing problem, usually time and computation consuming, especially if we consider that rays propagate throughout a densely nested structure. This in turn requires one to pay attention to all the possible obstructions, increasing the complexity of the simulation. In contrast, approaching the problems of stray light calculation from an analytical viewpoint largely simplifies the problem, and may also ease the task of designing an effective pre-collimator. In this work we expose an analytical formalism that can be used to compute the stray light in a nested optical module in a fast and effective way, accounting for obstruction effects.

Paper Details

Date Published: 4 September 2015
PDF: 18 pages
Proc. SPIE 9603, Optics for EUV, X-Ray, and Gamma-Ray Astronomy VII, 96030H (4 September 2015); doi: 10.1117/12.2185414
Show Author Affiliations
Daniele Spiga, INAF - Osservatorio Astronomico di Brera (Italy)

Published in SPIE Proceedings Vol. 9603:
Optics for EUV, X-Ray, and Gamma-Ray Astronomy VII
Stephen L. O'Dell; Giovanni Pareschi, Editor(s)

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