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Simulations of thermionic suppression during tungsten transient melting experiments
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SYSNO ASEP 0482343 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Simulations of thermionic suppression during tungsten transient melting experiments Author(s) Komm, Michael (UFP-V) RID, ORCID
Tolias, P. (SE)
Ratynskaia, S. (SE)
Dejarnac, Renaud (UFP-V) RID, ORCID
Gunn, J. P. (FR)
Krieger, K. (DE)
Podolník, Aleš (UFP-V) ORCID
Pitts, R.A. (FR)
Pánek, Radomír (UFP-V) RIDArticle number 014069 Source Title Physica Scripta. - : Institute of Physics Publishing - ISSN 0031-8949
T170, December (2017)Number of pages 5 s. Publication form Print - P Action PFMC 2017: 16th International Conference on Plasma-Facing Materials and Components for Fusion Applications Event date 16.05.2017 - 19.05.2017 VEvent location Düsseldorf Country DE - Germany Event type WRD Language eng - English Country SE - Sweden Keywords tokamak ; thermionic emission ; tungsten ; melt ; plasma-facing component Subject RIV BL - Plasma and Gas Discharge Physics OECD category 1.3 Physical sciences R&D Projects GA16-14228S GA ČR - Czech Science Foundation (CSF) 8D15001 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) Institutional support UFP-V - RVO:61389021 UT WOS 000417694700014 DOI 10.1088/1402-4896/aa9209 Annotation Plasma-facing components receive enormous heat fluxes under steady state and especially during transient conditions that can even lead to tungsten (W) melting. Under these conditions, the unimpeded thermionic current density emitted from the W surfaces can exceed the incident plasma current densities by several orders of magnitude triggering a replacement current which drives melt layer motion via the J x B force. However, in tokamaks, the thermionic current is suppressed by space-charge effects and prompt re-deposition due to gyro-rotation. We present comprehensive results of particle-in-cell modelling using the 2D3V code SPICE2 for the thermionic emissive sheath of tungsten. Simulations have been performed for various surface temperatures and selected inclinations of the magnetic field corresponding to the leading edge and sloped exposures. The surface temperature dependence of the escaping thermionic current and its limiting value are determined for various plasma parameters, for the leading edge geometry, the results agree remarkably well with the Takamura analytical model. For the sloped geometry, the limiting value is observed to be proportional to the thermal electron current and a simple analytical expression is proposed that accurately reproduces the numerical results. Workplace Institute of Plasma Physics Contact Vladimíra Kebza, kebza@ipp.cas.cz, Tel.: 266 052 975 Year of Publishing 2018
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