DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
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Title	150: Sensitivity study of toroidally-asymmetric halo current to error field during VDE
Name:	Michio Okabayashi mokabaya@pppl.gov	Affiliation:	Princeton Plasma Physics Laboratory
Research Area:	Disruption Mitigation	Presentation time:	Not requested
Co-Author(s):		ITPA Joint Experiment :	No
Description:	It has been reported that toroidally-asymmetric halo currents associated with VDE are comparable to n=0 component. Configuration of VDE approaches toward helical equilibrium and locking is initiated at some final stage. Halo current characteristics are not fully consistent in various devices. Objective in this proposal is to assess whether toroidally-asymmetric halo current component is related to the intrinsic and/or induced error field during the event of VDE. This assessment will help to understand the nature of halo current characteristics and clarify the possibility of n=1 error field involvement.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	This proposal has passive / active documentation after VDE is induced by forced vertical motion, inducing VDE event. Plasma condition is reasonably high beta before VDE so that the plasma configuration becomes ideal kink unstable for helical distortion Step one: passive documentation. To apply the constant n=1 non-axi-symmetric field by C-coil, Upper-I coil and Lower-I-coil and correlate with the halo current pattern. The toroidal direction of applied field will be scanned in standard compass approach. Step two : active documentation. If the step one implies the correlation between the halo-asymmetry and error field, it is worthwhile to apply the feedback using most promising coil set. According to the experience of NTM-locking avoidance by I-coil feedback, the feedback may be able to rotate the pattern. The feedback field should interact with magnetic islands. There are some cautions: - The available coil current by C- and I-coil are limited. Some homework is to be made for adequacy of asymmetric field availability. Thus, the measurement may face difficulty in analysis. Some homework is to be made for adequacy of asymmetric field availability. - we need to pay attention to the F7 / F6 combination as intrinsic error source. The large error field component may come from these coil current.
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