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	242: q95 < 2 Tokamak Operation Via Dynamic Error Field Correction
Name:	Andrea Garofalo garofalo@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Stability & Disruption Avoidance	Presentation time:	Not requested
Co-Author(s):	--	ITPA Joint Experiment :	No
Description:	Attempt to sustain plasma operation at q95<2 by using RWM feedback for dynamic error field correction, similar to what was done ~10 years ago to show for the first time sustainment of plasma operation at beta above the no-wall limit.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Repeat Aug. 2012 experiment with I-coil on SPAs, follow recipe for DEFC: Preprogram I-coil currents matching time average of feedback-driven currents in Aug. 2012 experiment Apply RWM feedback (poloidal field sensors) on top of preprogrammed offset currents Use proportional gain only (large) Use long time constant Update preprogrammed currents shot-to-shot
Background:	Aug. 2012 experiment (Miniproposal # 2012-09-02) failed to maintain q95<2 tokamak operation. The experiment performed a C-coil compass scan to determine the optimal EFC currents. Session Leader Summary states "we believe we eliminated the possibility of residual n=1 error fields affecting plasmas or feedback". However, simple analysis of the q95<2 experiment shows I-coil currents driven by feedback overlay shot after shot, showing the presence of a significant uncorrected error field. This behavior is similar to what was observed in pioneering RWM stabilization experiments of ~10 years ago, where RWM feedback was shown to maintain stability by successfully find the optimal error field correction.
Resource Requirements:	--
Diagnostic Requirements:	--
Analysis Requirements:	--
Other Requirements:	--