Design of a thermally balanced entrance window for the NFIRAOS thermal enclosure

Jeffrey Crane; Guillaume Filion; David Andersen; Jenny Atwood; Tim Hardy; Glen Herriot

doi:10.1117/12.2630397

29 August 2022 Design of a thermally balanced entrance window for the NFIRAOS thermal enclosure

Jeffrey Crane, Guillaume Filion, David Andersen, Jenny Atwood, Tim Hardy, Glen Herriot

Proceedings Volume 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V; 1218839 (2022) https://doi.org/10.1117/12.2630397
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

NFIRAOS is the first-light adaptive optics system for the Thirty Meter Telescope (TMT). It features a sub-cooled thermal enclosure (ENCL) operating at -30 degrees Celsius (˚C), which contains all of the opto-mechanics for the system. A unique entrance window system (NWIND) features a pair of windows separated by vacuum to allow light from the telescope to enter NFIRAOS, while precisely controlling the surface temperatures of the window optics to match the internal and external thermal environments of the enclosure. This ensures that convective currents are not created at the glass surfaces, which are both near the focal plane of the system. NWIND uses a set of multiple temperature controlled warm and cold radiative baffles positioned in the vacuum space between the optics to counteract and balance the radiative thermal load between the two optics, which are typically operated at +5˚C and -30˚C. Presented here are the requirements, design, and engineering of the NFIRAOS entrance window.

Citation Download Citation

Jeffrey Crane, Guillaume Filion, David Andersen, Jenny Atwood, Tim Hardy, and Glen Herriot "Design of a thermally balanced entrance window for the NFIRAOS thermal enclosure", Proc. SPIE 12188, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V, 1218839 (29 August 2022); https://doi.org/10.1117/12.2630397

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