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Title: Fractal structure of films deposited in a tokamak

Abstract

The surface of amorphous films deposited in the T-10 tokamak was studied in a scanning tunnel microscope. The surface relief on a scale from 10 nm to 100 {mu}m showed a stochastic surface topography and revealed a hierarchy of grains. The observed variety of irregular structures of the films was studied within the framework of the concept of scale invariance using the methods of fractal geometry and statistical physics. The experimental probability density distribution functions of the surface height variations are close in shape to the Cauchy distribution. The stochastic surface topography of the films is characterized by a Hurst parameter of H = 0.68-0.85, which is evidence of a nontrivial self-similarity of the film structure. The fractal character and porous structure of deposited irregular films must be considered as an important issue related to the accumulation of tritium in the ITER project. The process of film growth on the surface of tokamak components exposed to plasma has been treated within the framework of the general concept of inhomogeneous surface growth. A strong turbulence of the edge plasma in tokamaks can give rise to fluctuations in the incident flux of particles, which leads to the growth of fractal films withmore » grain dimensions ranging from nano-to micrometer scale. The shape of the surface of some films found in the T-10 tokamak has been interpreted using a model of diffusion-limited aggregation (DLA). The growth of films according to the discrete DLA model was simulated using statistics of fluctuations observed in a turbulent edge plasma of the T-10 tokamak. The modified DLA model reproduces well the main features of the surface of some films deposited in tokamaks.« less

Authors:
;  [1]
  1. Russian Research Centre Kurchatov Institute, Nuclear Fusion Institute (Russian Federation)
Publication Date:
OSTI Identifier:
21072492
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 104; Journal Issue: 4; Other Information: DOI: 10.1134/S1063776107040139; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AGGLOMERATION; CRYSTAL GROWTH; DIFFUSION; DISTRIBUTION FUNCTIONS; FILMS; FLUCTUATIONS; FRACTALS; ITER TOKAMAK; PARTICLES; PLASMA; POROUS MATERIALS; PROBABILITY; SCALE INVARIANCE; SIMULATION; STOCHASTIC PROCESSES; SURFACES; T-10 TOKAMAK; TOPOGRAPHY; TRITIUM; TURBULENCE

Citation Formats

Budaev, V. P., and Khimchenko, L. N. Fractal structure of films deposited in a tokamak. United States: N. p., 2007. Web. doi:10.1134/S1063776107040139.
Budaev, V. P., & Khimchenko, L. N. Fractal structure of films deposited in a tokamak. United States. doi:10.1134/S1063776107040139.
Budaev, V. P., and Khimchenko, L. N. Sun . "Fractal structure of films deposited in a tokamak". United States. doi:10.1134/S1063776107040139.
@article{osti_21072492,
title = {Fractal structure of films deposited in a tokamak},
author = {Budaev, V. P. and Khimchenko, L. N.},
abstractNote = {The surface of amorphous films deposited in the T-10 tokamak was studied in a scanning tunnel microscope. The surface relief on a scale from 10 nm to 100 {mu}m showed a stochastic surface topography and revealed a hierarchy of grains. The observed variety of irregular structures of the films was studied within the framework of the concept of scale invariance using the methods of fractal geometry and statistical physics. The experimental probability density distribution functions of the surface height variations are close in shape to the Cauchy distribution. The stochastic surface topography of the films is characterized by a Hurst parameter of H = 0.68-0.85, which is evidence of a nontrivial self-similarity of the film structure. The fractal character and porous structure of deposited irregular films must be considered as an important issue related to the accumulation of tritium in the ITER project. The process of film growth on the surface of tokamak components exposed to plasma has been treated within the framework of the general concept of inhomogeneous surface growth. A strong turbulence of the edge plasma in tokamaks can give rise to fluctuations in the incident flux of particles, which leads to the growth of fractal films with grain dimensions ranging from nano-to micrometer scale. The shape of the surface of some films found in the T-10 tokamak has been interpreted using a model of diffusion-limited aggregation (DLA). The growth of films according to the discrete DLA model was simulated using statistics of fluctuations observed in a turbulent edge plasma of the T-10 tokamak. The modified DLA model reproduces well the main features of the surface of some films deposited in tokamaks.},
doi = {10.1134/S1063776107040139},
journal = {Journal of Experimental and Theoretical Physics},
number = 4,
volume = 104,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}