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Proceedings Paper

CTE measurement setup with 10 ppb/K sensitivity for characterizing lightweight and highly stable materials for space applications
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Paper Abstract

Structural materials with extremely low coecient of thermal expansion (CTE) are crucial to enable ultimate accuracy in terrestrial as well as in space-based optical metrology due to minimized temperature dependency. Typical materials, in particular in the context of space-based instrumentation are carbon-ber reinforced plastics (CFRP), C/SiC, and glass ceramics, e.g. Zerodur, ULE or Clearceram. To determine the CTE of various samples with high accuracy we utilize a highly symmetric heterodyne interferometer with a noise level below 2 pm√Hz at frequencies above 0.1 Hz. A sample tube made out of the material under investigation is vertically mounted in an ultra-stable support made of Zerodur. Measurement and reference mirrors of the interferometer are supported inside the tube using thermally compensated mounts made of Invar36. For determination of the CTE, a sinusoidal temperature variation is radiatively applied to the tube. One of the essential systematic limitations is a tilt of the entire tube as a result of temperature variation. This tilt can simultaneously be measured by the DWS technique and can be used to correct the measurement. Using a Zerodur tube as a reference, it is shown that this eect can be reduced in post processing to achieve a minimum CTE measurement sensitivity <10 ppb/K.

Paper Details

Date Published: 13 September 2012
PDF: 7 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84500Q (13 September 2012); doi: 10.1117/12.926061
Show Author Affiliations
Ruven Spannagel, Univ. of Applied Sciences Konstanz (Germany)
Martin Gohlke, EADS Astrium GmbH (Germany)
Humboldt-Univ. zu Berlin (Germany)
Thilo Schuldt, Univ. of Applied Sciences Konstanz (Germany)
Ulrich Johann, EADS Astrium GmbH (Germany)
Dennis Weise, EADS Astrium GmbH (Germany)
Claus Braxmaier, Univ. of Applied Sciences Konstanz (Germany)
EADS Astrium GmbH (Germany)

Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)

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