Document Type : Research paper
Authors
1 Plasma Physics and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, Tehran, Iran
2 Plasma and Nuclear Fusion Research School, Nuclear Science & Technology Research Institute
3 Energy Engineering and Physics Department, Amirkabir University of Technology, P.O. Box 1591634311 Tehran, Iran
Abstract
Glow discharge cleaning (GDC) is a regular conditioning procedure for fusion devices such as tokamaks. Due to the low energy of ions in glow discharge plasmas, the probability of any considerable damage to the plasma-facing components was mainly ignored among researchers in the field. In this work, Tungsten (W) and Molybdenum (Mo), as the primary candidates for the plasma-facing materials in tokamaks, are considered for studies regarding the effects of the hydrogen and helium GDC procedure on these materials during a routine vacuum vessel conditioning in Damavand tokamak. After performing routine GDC using pure hydrogen and Helium, the formation of loosely attached nano-structure bundles (NSBs) on the surface of the tungsten and molybdenum samples has been observed. The presence of the NSBs, which can be a source of dust, would be significant due to their possible effects on the functionality of future fusion plasma devices such as ITER. The surface modifications of specimens exposed to hydrogen and helium GDC were examined and compared using a material probe experiment and several surface analysis techniques such as SEM, XRD, and EDX. Therefore, the formation of loose nanostructures on the wall of plasma confinement vessels, due to GDC draws attention to the probable damaging effects of this phenomenon upon functionality and outcomes of tokamaks.
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