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Thick Beryllium Coatings by Magnetron Sputtering

Published online by Cambridge University Press:  22 June 2011

H. Xu
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
C. Alford
Affiliation:
Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Avenue, Livermore, CA 94550, USA
Eric Chason
Affiliation:
Brown University, Department of Engineering, Providence, RI, USA
A. Detor
Affiliation:
Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Avenue, Livermore, CA 94550, USA
T. Fuller
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
A. Hamza
Affiliation:
Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Avenue, Livermore, CA 94550, USA
J. Hayes
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
K.A. Moreno
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
A. Nikroo
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
T. van Buuren
Affiliation:
Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Avenue, Livermore, CA 94550, USA
M. Wang
Affiliation:
Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Avenue, Livermore, CA 94550, USA
J. Wu
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
K.P. Youngblood
Affiliation:
General Atomics, P.O. Box 85608, San Diego, CA 92186-5608, USA
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Abstract

Thick (>150 μm) beryllium coatings are studied as an ablator material of interest for fusion fuel capsules for the National Ignition Facility (NIF). As an added complication, the coatings are deposited on mm-scale spherical substrates, as opposed to flats. DC magnetron sputtering is used because of the relative controllability of the processing temperature and energy of the deposits. We used ultra small angle x-ray spectroscopy (USAXS) to characterize the void fraction and distribution along the spherical surface. We investigated the void structure using a combination focused ion beam (FIB) and scanning electron microscope (SEM), along with transmission electron microscopy (TEM). Our results show a few volume percent of voids and a typical void diameter of less than two hundred nanometers. Understanding how the stresses in the deposited material develop with thickness is important so that we can minimize film cracking and delamination. To that end, an in-situ multiple optical beam stress sensor (MOSS) was used to measure the stress behavior of thick Beryllium coatings on flat substrates as the material was being deposited. We will show how the film stress saturates with thickness and changes with pressure.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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