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Using iridium films to compensate for piezo-electric materials processing stresses in adjustable x-ray optics

Date Issued
2015
Author(s)
Ames, A.
•
Bruni, R.
•
•
Johnson-Wilke, R.
•
Kester, T.
•
Reid, P.
•
Romaine, S.
•
Tolier-McKinstry, S.
•
Wilke, R. H. T.
DOI
Abstract
Adjustable X-ray optics represent a potential enabling technology for simultaneously achieving large effective area and high angular resolution for future X-ray Astronomy missions. The adjustable optics employ a bimorph mirror composed of a thin (1.5 μm) film of piezoelectric material deposited on the back of a 0.4 mm thick conical mirror segment. The application of localized electric fields in the piezoelectric material, normal to the mirror surface, result in localized deformations in mirror shape. Thus, mirror fabrication and mounting induced figure errors can be corrected, without the need for a massive reaction structure. With this approach, though, film stresses in the piezoelectric layer, resulting from deposition, crystallization, and differences in coefficient of thermal expansion, can distort the mirror. The large relative thickness of the piezoelectric material compared to the glass means that even 100MPa stresses can result in significant distortions. We have examined compensating for the piezoelectric processing related distortions by the deposition of controlled stress chromium/iridium films on the front surface of the mirror. We describe our experiments with tuning the product of the chromium/iridium film stress and film thickness to balance that resulting from the piezoelectric layer. We also evaluated the repeatability of this deposition process, and the robustness of the iridium coating....
Coverage
Optics for EUV, X-Ray, and Gamma-Ray Astronomy VII
All editors
O'Dell, Stephen L.; Pareschi, Giovanni
Series
Volume
9603
Start page
96031I
Conferenece
SPIE Optical Engineering + Applications
Conferenece place
San Diego, CA, USA
Conferenece date
9-13 August, 2015
Uri
Url
Issn Identifier
0277-786X
Ads BibCode
2015SPIE.9603E..1IA
Rights
open.access
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