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Long‐Term Hydrogen Outgassing from Plasma Facing Components
Author(s) -
Guterl J.,
Smirnov R. D.,
Krasheninnikov S. I.
Publication year - 2014
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/ctpp.201410034
Subject(s) - outgassing , hydrogen , diffusion , materials science , desorption , tokamak , plasma , thermodynamics , chemistry , physics , adsorption , nuclear physics , organic chemistry
The time evolution of hydrogen outgassing fluxes from plasma facing components (PFCs) in tokamaks at room temperature is investigated using a diffusion‐reaction model with a single trap in the bulk of PFCs material. The release of hydrogen is surface‐limited or diffusion‐limited depending on properties of material and surface processes. In both surface and diffusion‐limited regimes, the long‐term decrease of the hydrogen outgassing flux follows a time power‐law ∼ t – κ , for which κ depends on the concentration of hydrogen in the material and on surface desorption processes. In surface‐limited regime, reaction‐diffusion models of hydrogen outgassing from wall material(with hydrogen diffusion in the material bulk) are shown to be equivalent to models of outgassing from wall surfaces. Experimental results showing power‐law decays of hydrogen outgassing fluxes from PFCs during long off‐plasma events ( κ = 0.7 for graphite and κ = 0.8 for ITER‐like JET configuration) can be then reproduced using a diffusion‐reaction model in surface‐limited regime. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)