ELM-induced arcing on tungsten fuzz in the COMPASS divertor region

Materials exposed to plasma may undergo various forms of surface modifications. Among the important phenomena for tungsten - as the prime candidate plasma-facing material for fusion devices – is a formation of helium-induced fibreform nanostructure, so-called tungsten fuzz. In this paper, we report...

Full description

Saved in:
Bibliographic Details
Published in:Journal of nuclear materials 2017-08, Vol.492, p.204-212
Main Authors: Matějíček, Jiří, Weinzettl, Vladimír, Vilémová, Monika, Morgan, Thomas W., De Temmerman, Gregory, Dimitrova, Miglena, Cavalier, Jordan, Adámek, Jiří, Seidl, Jakub, Jäger, Aleš
Format: Article
Language:English
Subjects:
Densification
Electric arc melting
Electron microscopy
Erosion mechanisms
Erosion rates
Fusion
Helium
Melting
Plasma
Plasmas
Porosity
Scanning electron microscopy
Thickness
Tokamak devices
Tungsten
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Materials exposed to plasma may undergo various forms of surface modifications. Among the important phenomena for tungsten - as the prime candidate plasma-facing material for fusion devices – is a formation of helium-induced fibreform nanostructure, so-called tungsten fuzz. In this paper, we report direct observations of the interaction of the pre-prepared fuzzy tungsten surfaces with ELMy H-mode plasmas in the COMPASS tokamak as well as consequent ex-situ morphological analyses, with a particular focus on arcing as a potential erosion mechanism. Arcing events are documented from high-speed camera imaging. The sample surfaces are examined by scanning electron microscopy. Arc traces were observed on all samples, while their number was dependent on the sample position and orientation. Inside the arc traces, localized melting and densification of the original fuzz was observed, resulting in thickness reduction. The modified structure still retained some porosity and did not extend into the bulk. •The interaction of fuzzy tungsten surfaces with ELMy H-mode plasmas in the COMPASS tokamak was observed.•Arcing was the main interaction mechanism; observed both in-situ and post-mortem.•In the arc traces, localized melting of the fuzz was observed, retaining some porosity, without extending into the bulk.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2017.05.032