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	92: H-mode Optimization of n=1&2 Error Field Control Currents
Name:	Matthew Lanctot matthew.lanctot@science.doe.gov	Affiliation:	Department of Energy
Research Area:	Stability & Disruption Avoidance	Presentation time:	Requested
Co-Author(s):	C. Paz-Soldan, J.M. Hanson, E.J. Strait, J. King, R.J. LaHaye, A.M. Garofalo, N. Ferraro, J.-K. Park, N. Logan	ITPA Joint Experiment :	No
Description:	Maximize the ratio of the plasma rotation to the injected neutral beam torque by optimizing n=1&2 error field control currents in H-mode	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Determine the optimal n=2 I-coil error field control currents in H-mode by measuring changes in the plasma rotation as a function of I-coil current. Identify the amplitude and phase of the n=2 coil currents by maximizing the plasma rotation. Use plasma beta ramps and simultaneous n=1&2 RWM feedback (n=2 algorithm to be developed) with I & C coils to minimize magnetic field asymmetries. Compare H-mode results with other 2013 experiments aimed at developing a standard n=2 error field control algorithm in ohmic discharges.
Background:	Previous experiments by Garofalo and others have shown that the optimal error field control currents in ohmic and high-beta experiments are different. Typically, the toroidal phase of the n=1 control currents are within 10-20 degrees, but the amplitudes can differ by up to 2x. This may be due to differences in the intrinsic error field (say from changes in the F & B coil currents), or in the plasma response. In ohmic discharges, the minimization of the low-density locked mode threshold identifies the optimal currents, while in H-mode, the optimal currents are found by maximizing the plasma rotation or minimizing magnetic field asymmetries using RWM feedback. See proposal #91 for further background on n=2 error field control. Following the completion of the 3D magnetics upgrade in 2013, DIII-D will have a dramatically improved capability to detect n=even magnetic perturbations at multiple poloidal locations. The development of a PCS n=2 RWM control algorithm is planned for 2013, which will allow simultaneous n=1&2 dynamic error field control.
Resource Requirements:	Requires 3 SPAs on C-coil and Audio Amplifiers on I-coil.
Diagnostic Requirements:	3D magnetic arrays, CER rotation measurements, and other diagnostics for kinetic equilibrium reconstructions
Analysis Requirements:	Use established techniques to analyze coil-current-dependent rotation changes. Compare results with first principles error field control metrics. Compare results with standard n=2 EFC algorithm.
Other Requirements:	PCS development of n=2 RWM feedback algorithm