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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:51 |
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Conference: Bucharest University Faculty of Physics 2011 Meeting
Section: Solid State Physics and Materials Science
Title:
Morphological Studies on Ternary Beryllium-Carbon-Tungsten Composite Thin Films Used for Fusion Applications
Authors:
C. Porosnicu (1), I. Jepu (1), C.P.Lungu (1), G. Iacobescu (2), M. Osiac (2)
Affiliation:
(1)National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG-36, Magurele-Bucharest, Romania
(2)Faculty of Physics, University of Craiova, 200585, Craiova, Romania
E-mail
corneliu.porosnicu@inflpr.ro
Keywords:
Thermionic Vacuum Arc, Fusion Aplications
Abstract:
The importance of the morphological and compositional study for Be-C-W co-deposited thin films is proven by the fact that beryllium is a prime candidate material for the first wall in the modern (ITER) thermonuclear devices. Most of the tiles of the first wall will be coated by a beryllium layer which must have high purity and a very compact structure to resist as much as possible to the interaction with the high energetic plasma particles. Carbon and tungsten contained (CFC) tiles are also present. These candidate materials are sputtered in the high flux (1022 m-2s-1 or higher) of the deuterium-tritium plasma and the beryllium, tungsten and hydrocarbon species particles can migrate into the plasma. They will be ionized by the energetic electrons and together with hydrogen isotope ions they will be implanted or redeposited on the divertor, creating composite layers. The films were obtained by Thermionic Vacuum Arc Method (TVA). The principle of TVA method consists in an intense thermal-electron emission from an external heated cathode (tungsten filament) concentrated on the anode (the crucible containing the material to be evaporated) by a Wehnelt cylinder. Applying high voltage between the two electrodes, the plasma was ignited in the evaporated atoms. Due to plasma spatial localization, there can be ignited simultaneous plasma of different materials in the same deposition chamber. This way, composite Be-C-W materials having different relative concentrations were deposited on graphite substrates. The dept profile of the film composition was analyzed by Rutherford backscattering (RBS) spectroscopy. The structure and morphology of the films as well as the beryllium carbide, beryllium-tungsten formation were analyzed by, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS).
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