Journal Article

FZJ-2021-05632

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Characterization of injection and confinement improvement through impurity induced profile modifications on the Wendelstein 7-X stellarator

Lunsford, R. ; Killer, C. ; Nagy, A.FZJ* ; Gates, D. A. ; Klinger, T. ; Dinklage, A. ; Satheeswaran, G.FZJ* ; Kocsis, G. ; Lazerson, S. A. ; Nespoli, F. ; Pablant, N. A. ; von Stechow, A. ; Alonso, A.FZJ* ; Andreeva, T. ; Beurskens, M. ; Biedermann, C. ; Brezinsek, S. (Corresponding author)FZJ* ; Brunner, K. J. ; Buttenschön, B. ; Carralero, D. ; Cseh, G. ; Drewelow, P. ; Effenberg, F. ; Estrada, T. ; Ford, O. P. ; Grulke, O. ; Hergenhahn, U. ; Höfel, U. ; Knauer, J. ; Krause, M. ; Krychowiak, M. ; Kwak, S. ; Langenberg, A.FZJ* ; Neuner, U. ; Nicolai, D.FZJ* ; Pavone, A. ; Puig Sitjes, A. ; Rahbarnia, K. ; Schilling, J. ; Svensson, J. ; Szepesi, T. ; Thomsen, H. ; Wauters, T. ; Windisch, T. ; Winters, V. ; Zhang, D.FZJ* ; Zsuga, L.

2021
American Institute of Physics [S.l.]

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Please use a persistent id in citations: http://hdl.handle.net/2128/29835  doi:10.1063/5.0047274

Abstract: Pulsed injections of boron carbide granules into Wendelstein 7-X stellarator (W7-X) plasmas transiently increase the plasma stored energy and core ion temperatures above the reference W7-X experimental programs by up to 30%. In a series of 4 MW electron cyclotron resonance heating experiments, the PPPL Probe Mounted Powder Injector provided 50 ms bursts of 100 μm granules every 350 ms at estimated quantities ranging from approximately 1 mg/pulse to over 30 mg/pulse. For each injection, the stored energy was observed to initially drop and the radiated power transiently increased, while the radial electron density profile rose at the edge as material was assimilated. Once the injected boron carbide was fully absorbed, the density rise transitioned to the core while the stored energy increased above the previous baseline level by an amount linearly correlated with the injection quantity. During the injection, the ion temperature gradient steepened with peak core ion temperatures observed to increase from a nominal 1.7 keV to over 2.6 keV for the largest injection amounts. Enhanced performance is accompanied by a reversal of the radial electric field at ρ < 0.3, indicating that the core transport has switched to the ion root. These observations are suggestive of a change in transport and provide further evidence that externally induced profile modifications provide a possible path to enhanced W7-X performance metrics.I. INTRODUCTIO

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Contributing Institute(s):

1. Plasmaphysik (IEK-4)

Research Program(s):

1. 134 - Plasma-Wand-Wechselwirkung (POF4-134) (POF4-134)

Appears in the scientific report 2021

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Database coverage:
; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; National-Konsortium ; Nationallizenz ; PubMed Central ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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