Stuttgart 2012 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 7: Präzisionsmessungen und Metrologie 3
A 7.6: Vortrag
Montag, 12. März 2012, 17:45–18:00, V7.03
Interferometry-Based CTE Measurement Facility with Demonstrated 10 ppb/K Accuracy — •Ruven Spannagel1, Martin Gohlke2,3, Thilo Schuldt1, Ulrich Johann2, Dennis Weise2, and Claus Braxmaier1 — 1University of Applied Sciences Konstanz, Germany — 2Astrium GmbH, Friedrichshafen, Germany — 3Humboldt-University, Berlin, Germany
Structural materials with extremely low coefficient 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-fiber 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 in our measurement facility. 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. Using a Zerodur tube as a reference, it is shown that this effect can be reduced in post processing to achieve a minimum CTE measurement sensitivity < 10 ppb/K.