Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

TitleGeneration and suppression of runaway electrons in disruption mitigation experiments in TEXTOR
Publication TypeJournal Article
Year of Publication2008
AuthorsS.A Bozhenkov, M. Lehnen, K.H. Finken, M.W Jakubowski, RC Wolf, R. Jaspers, M. Kantor, O.V Marchuk, E. Uzgel, G. van Wassenhove, O. Zimmermann, D. Reiter
JournalPlasma Physics and Controlled Fusion
Volume50
Number10
Pagination18
Date PublishedOct
Type of ArticleArticle
ISBN Number0741-3335
Accession NumberISI:000259254800009
KeywordsAVALANCHE, DIII-D, DISCHARGES, DYNAMICS, FAST PLASMA SHUTDOWN, ITER, JET, JT-60U TOKAMAK, SYNCHROTRON-RADIATION, TERMINATION
Abstract

Runaway electrons represent a serious problem for the reliable operation of the future experimental tokamak ITER. Due to the multiplication factor of exp(50) in the avalanche even a few seed runaway electrons will result in a beam of high energetic electrons that is able to damage the machine. Thus suppression of runaway electrons is a task of great importance, for which we present here a systematic study of runaway electrons following massive gas injection in TEXTOR. Argon injection can cause the generation of runaways carrying up to 30% of the initial plasma current, while disruptions triggered by injection of helium or of mixtures of argon (5%, 10%, 20%) with deuterium are runaway free. Disruptions caused by argon injection finally become runaway free for very large numbers of injected atoms. The appearance/absence of runaway electrons is related to the fraction of atoms delivered to the plasma centre. This so-called mixing efficiency is deduced from a 0D model of the current quench. The estimated mixing efficiency is 3% for argon, 15% for an argon/deuterium mixture and about 40% for helium. A low mixing efficiency of high-Z impurities can have a strong implication for the design of the disruption mitigation system for ITER. However, a quantitative prediction requires a better understanding of the mixing mechanism.

URL<Go to ISI>://000259254800009
Division

Fusion Physics

PID

4ec9e45ba09639a9f235df5281ec7419

Alternate TitlePlasma Phys. Control. Fusion

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