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13 September 2012 Progress in UCO's search for silver-based telescope mirror coatings
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We report on the on-going effort at University of California Observatories Astronomical Coatings Lab to develop robust protected-silver coatings suitable for telescope mirrors. We have identified a very promising recipe based on YF3 that produces excellent reflectivity at wavelengths of 340 nm and greater, has ~1.5% emissivity in the thermal IR, and does not contain problematic materials for the Mid-IR, such as SiO2 and Al2O3. The recipe holds up extremely well to aggressive environmental testing (80C and 80% RH; high-H2S atmosphere), and currently is being evaluated under real observatory conditions. This coating may satisfy the need for telescope mirror coatings that are long-lasting (~5 years or more) and have good reflectivity into the UV. We also evaluate and compare some other silver-based coatings developed elsewhere that should be useful in the same role. In addition, we describe recent upgrades to our coating facilities allowing us to deposit ion-assisted e-beam coatings on optics up to ~1m. This novel arrangement places the e-gun and ion source on a pivoting "swing-arm", allowing the position to move radially without changing the e-gun/ion source/ substrate geometry. Large substrates can be coated with good uniformity using single-axis rotation only. This technique is scalable to arbitrarily large substrate sizes.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andrew C. Phillips, Joseph S. Miller, Michael Bolte, Brian DuPraw, Matthew Radovan, and David Cowley "Progress in UCO's search for silver-based telescope mirror coatings", Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84502G (13 September 2012);

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