|Title||Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR|
|Publication Type||Journal Article|
|Year of Publication||2008|
|Authors||S.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|
|Journal||Plasma Physics and Controlled Fusion|
|Type of Article||Article|
|Keywords||AVALANCHE, DIII-D, DISCHARGES, DYNAMICS, FAST PLASMA SHUTDOWN, ITER, JET, JT-60U TOKAMAK, SYNCHROTRON-RADIATION, TERMINATION|
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|
|Alternate Title||Plasma Phys. Control. Fusion|
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