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20 July 2010 Efficiency measurements performed on the MUSE VPHG
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Volume Phase Holographic Gratings (VPHG) are key elements for the second generation instrument MUSE (Multi Unit Spectroscopic Explorer) developed for the VLT (Very Large Telescope) for ESO (European Southern Observatory). MUSE operates in the visible wavelength range (465-930nm) and is composed of 24 spectrographs including one VPHG each. This article briefly describes the design of the grating manufactured by Kaiser Optical Systems, to reach the MUSE spectral resolution and efficiency. On the other hand the set up developed in CRAL (Centre de Recherche Astrophysique de Lyon) to test the VPHG final performance is deeply discussed. This set up uses a broadband source coupled to a monochromator, and a compensation arm to remove the source intensity fluctuations. The source is amplitude modulated by a chopper, and a lock-in amplifier extracts the modulated signal from the photodiodes. The measurement arm scans the 0, 1st and 2nd diffraction orders of the grating and allows tests of different areas over its whole surface of 120mm*60mm. The accuracy reached is below one percent in efficiency, allows us to validate the performance and its uniformity over the surface of the gratings.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Edgard Renault, Magali Loupias, Louisa Adjali, James A. Arns, Roland M. Bacon, Didier Boudon, Patrick Caillier, Paul Coadour, Hans Dekker, Jean-Pierre Dubois, Johan Kosmalski, Laurent Pinard, and Alban Remillieux "Efficiency measurements performed on the MUSE VPHG", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77394R (20 July 2010);

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