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Effect of thermal cycling on stress in metallic films on ceramic substratesThe hydrogen maser is the most stable frequency standard currently available for averaging intervals of hours to weeks. A major contributor to maser frequency variations is the maser's microwave resonant cavity: by means of the cavity pulling effect, a change in the cavity's resonance frequency produces a proportional change in the maser's output frequency. To minimize variations in the cavity's dimensions, and thus in its resonance frequency, maser cavities are often constructed of a low-expansivity glass-ceramic material coated on its surface with a conductive metallic film. It was previously shown that silver films like those used in SAO maser cavities develop tensile stress when cooled to room temperature after being fired onto the cavity, and that the stress in such films relaxes with time at a rate proportional to the level of stress. Stress relaxation in maser cavity coatings can alter the shape, and hence the resonance frequency, of the cavity, resulting in a slow variation in the maser's output frequency. The possibility was investigated of reversing the initial tensile stress by precooling the coated cavity material. It was hypothesized that cooling the material well below its normal working temperature and then warming it to its normal temperature would result in a lower tensile stress or even a compressive stress. Under such a condition stress relaxation, and thus any consequent frequency drifts, might be reduced or reversed.
Document ID
19910016465
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Mattison, Edward M.
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Vessot, Robert F. C.
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1990
Publication Information
Publication: JPL, The 22nd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting
Subject Category
Nonmetallic Materials
Accession Number
91N25779
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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