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First operation with the JET International Thermonuclear Experimental Reactor-like wall
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2013 (English)In: Physics of Plasmas, ISSN 1070-664X, Vol. 20, no 5, 056111-1-056111-13 p.Article in journal (Refereed) Published
Abstract [en]

To consolidate International Thermonuclear Experimental Reactor (ITER) design choices and prepare for its operation, Joint European Torus (JET) has implemented ITER's plasma facing materials, namely, Be for the main wall and W in the divertor. In addition, protection systems, diagnostics, and the vertical stability control were upgraded and the heating capability of the neutral beams was increased to over 30 MW. First results confirm the expected benefits and the limitations of all metal plasma facing components (PFCs) but also yield understanding of operational issues directly relating to ITER. H-retention is lower by at least a factor of 10 in all operational scenarios compared to that with C PFCs. The lower C content (≈ factor 10) has led to much lower radiation during the plasma burn-through phase eliminating breakdown failures. Similarly, the intrinsic radiation observed during disruptions is very low, leading to high power loads and to a slow current quench. Massive gas injection using a D2/Ar mixture restores levels of radiation and vessel forces similar to those of mitigated disruptions with the C wall. Dedicated L-H transition experiments indicate a 30% power threshold reduction, a distinct minimum density, and a pronounced shape dependence. The L-mode density limit was found to be up to 30% higher than for C allowing stable detached divertor operation over a larger density range. Stable H-modes as well as the hybrid scenario could be re-established only when using gas puff levels of a few 1021 es-1. On average, the confinement is lower with the new PFCs, but nevertheless, H factors up to 1 (H-Mode) and 1.3 (at β N ≈ 3, hybrids) have been achieved with W concentrations well below the maximum acceptable level.

Place, publisher, year, edition, pages
2013. Vol. 20, no 5, 056111-1-056111-13 p.
Keyword [en]
Divertor operation, International thermonuclear experimental reactor, Intrinsic radiation, Joint European Torus, Operational scenario, Plasma facing materials, Protection systems, Vertical stability controls, Electric load forecasting, Plasma simulation, Tokamak devices, Experimental reactors
National Category
Fusion, Plasma and Space Physics
URN: urn:nbn:se:kth:diva-134487DOI: 10.1063/1.4804411ISI: 000320000000082ScopusID: 2-s2.0-84878908451OAI: diva2:666998

QC 20131125

Available from: 2013-11-25 Created: 2013-11-25 Last updated: 2013-11-25Bibliographically approved

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Frassinetti, Lorenzo
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