9 July 2008 Cryogenic tests of bimetallic diamond-turned mirrors for the FRIDA integral field unit
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Abstract
We describe diamond-turned material tests for the integral field unit (IFU) for the FRIDA instrument (inFRared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias). FRIDA is closely based on the design of the successful FISICA cryogenic infrared image slicing device, which used "monolithic" mirror arrays, diamond turned into single pieces of metal. FRIDA, however, will require better roughness characteristics than the 15nm RMS of FISICA to avoid light scatter in FRIDA's shorter wavelength limit (900nm). Al 6061 seems to be limited to this roughness level by its silicate inclusions so some new combination of materials that are compatible with FRIDA's Al 6061 structure must be found. To this end, we have tested six diamond-turned mirrors with different materials and different platings. We used the Zygo interferometer facility at IA-UNAM to do warm and cold profile measurements of the mirrors to investigate possible bimetallic deformation effects. We present a detailed comparison of the various performance characteristics of the test mirrors.
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Curtis DeWitt, Curtis DeWitt, Stephen Eikenberry, Stephen Eikenberry, Salvador Cuevas Cardona, Salvador Cuevas Cardona, Oscar Chapa, Oscar Chapa, Carlos Espejo, Carlos Espejo, Carolina Keiman, Carolina Keiman, Beatriz Sanchez, Beatriz Sanchez, "Cryogenic tests of bimetallic diamond-turned mirrors for the FRIDA integral field unit", Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70142X (9 July 2008); doi: 10.1117/12.788419; https://doi.org/10.1117/12.788419
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