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Reflectivity, polarization properties and durability of metallic mirror coatings for the European Solar Telescope

 
: Feller, A.; Nagaraju, K.; Pleier, O.; Hirzberger, J.; Jobst, P.J.; Schürmann, M.

:

Ramón Navarro (Ed.); Colin R. Cunningham (Ed.); Eric Prieto (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II : 1.-6.7.2012, Amsterdam, Netherlands
Bellingham, WA: SPIE, 2012 (Proceedings of SPIE 8450)
ISBN: 978-0-8194-9151-0
Art. 84503U
Conference "Modern Technologies in Space- and Ground-based Telescopes and Instrumentation" <2, 2012, Amsterdam>
English
Conference Paper
Fraunhofer IOF ()

Abstract
In the context of the conceptual design study for the European Solar Telescope (EST) we have investigated different metallic mirror coatings in terms of reflectivity, polarization properties and durability. Samples of the following coating types have been studied: bare aluminum, silver with different dielectric layers for protection and UV enhancement, and an aluminum-silver combination. From 2009 to 2011 we have carried out a long-term durability test under realistic observing conditions at the VTT solar telescope of the Observatorio del Teide (Tenerife, Spain), accompanied by repeated reflectivity measurements in the EST spectral working range (0.3 - 20 m), and by polarization measurements in the visible range. The test results allow us to find the optimum coatings for the different mirrors in the EST beampath and to eventually assess aging effects and re-coating cycles. The results of the polarization measurements are a valuable input for an EST telescope polarizatio n model, helping to meet the stringent requirements on polarimetric accuracy.

: http://publica.fraunhofer.de/documents/N-254151.html