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Proceedings Paper

Thermal control modeling approach for GRAPE (GRAntecan PolarimEter)
Author(s): I. Di Varano; M. Woche; K. G. Strassmeier
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Paper Abstract

GRAPE is the polarimeter planned to be installed on the main Cassegrain focus of GTC (Gran Telescopio Canarias), having an equivalent entrance pupil of 10.4 m, located at the Observatorio del Roque de los Muchachos (ORM) , in La Palma, Canary Islands. It’s meant to deliver full Stokes (IQUV) polarimetry covering the spectral range 0.420-1.6 μ, in order to feed the HORS instrument (High Optical Resolution Spectrograph), mounted on the Nasmyth platform, which has a FWHM resolving power of about 25,000 (5 pixel) designed for the wavelength range of 380-800 nm. Two calcite blocks and a BK-7 prism arranged in a Foster configuration are splitting the Ø12.5mm collimated beam into the ordinary and extraordinary components. The entire subunit from the Foster prisms down to the input fibers is rotated by steps of 45 degrees in order to retrieve Q, U components. By inserting a quarter wave retarder plate before the entrance to the Foster unit circular polarization is measured too.

The current paper consist of two main parts: at first CFD simulations are introduced, which have been run compliant to the specifications derived by the environmental conditions and the transient thermal gradients taking into account the presence of the electronic cabinets installed, which are triggering the boundary conditions for the outer structure of the instrument; then a thermal control model is proposed based on heat exchangers to stabilize the inner temperature when compensation via passive insulation is not enough. The tools that have been adopted to reach for such goal are Ansys Multiphysics, in particular CFX package and Python scripts.

Paper Details

Date Published: 9 August 2016
PDF: 8 pages
Proc. SPIE 9911, Modeling, Systems Engineering, and Project Management for Astronomy VI, 991115 (9 August 2016); doi: 10.1117/12.2231439
Show Author Affiliations
I. Di Varano, Leibniz-Institut für Astrophysik Potsdam (Germany)
M. Woche, Leibniz-Institut für Astrophysik Potsdam (Germany)
K. G. Strassmeier, Leibniz-Institut für Astrophysik Potsdam (Germany)

Published in SPIE Proceedings Vol. 9911:
Modeling, Systems Engineering, and Project Management for Astronomy VI
George Z. Angeli; Philippe Dierickx, Editor(s)

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