Gemini Preprint #32

Development of Silver Coating Options for the Gemini 8-M Telescopes Project

M.R. Jacobson
Optical Data Associates, 5237 E. Seventh St., Tucson AZ 85711

R.A. Kneale, K. Raybould, F.C. Gillett, J.M. Filhaber
Gemini 8m Telescopes Project, 950 N. Cherry Ave., Tucson AZ 85719

C. Carniglia, R. Laird
BOC Coating Technology, 2700 Maxwell Way, Fairfield CA 94533

D. Kitchens, R. Shimshock
Deposition Sciences, Inc., 386 Tesconi Ct., Santa Rosa CA 95401

D.C. Booth
Sigma Laboratories Inc., 10960 N. Stallard Pl., Tucson AZ 85737


Acting as prime contractor to the Gemini Project, the Optical Data Associates, with its major subcontractors BOC Coating Technologies (BOCCT) and Deposition Sciences, Inc. (DSI), developed options for depositing protected silver coatings on the 8-M primary mirrors. The project began with a study that identified sputtering as the preferred deposition technique, defined a set of candidate adhesor and protective coatings for the silver layer, and simulated stack performance. The next phase involved pilot magnetron sputtering studies by BOCCT and DSI of designs involving silicon nitride and hafnia, respectively. ODA also developed mid-IR reflectance standards at lambda=10.6µm to control the silver coating measurements in the critical 8-12µm atmospheric window. The study results were successful, with both BOCCT and DSI producing silver coatings with R=0.9920±0.0001 and protected silver coatings with R=0.9910±0.0001. The Gemini Project coating plants are designed to sputter bare and protected aluminum and silver coatings.

Appears in Proc. SPIE 3352, "Advanced Technology Optical/IR Telescopes".

Ruth A. Kneale / / May 1, 1998