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	78: 3D magnetics plasma response measurements of n=1 perturbations for RWM analysis & model validation
Name:	Josh King kingjd@fusion.gat.com	Affiliation:	Department of Energy
Research Area:	Stability & Disruption Avoidance	Presentation time:	Requested
Co-Author(s):	Edward (Ted) Strait	ITPA Joint Experiment :	No
Description:	Using the first plasma data obtained from the 3D magnetics upgrade, reconstruct the full 3D structure of the plasma response to an applied n=1 perturbation. The goals are to quantitatively validate code predications of MARS-F (and others) in full 3D, and determine mechanisms for code over prediction of the plasma response above 80% of the no-wall βN limit.	ITER IO Urgent Research Task :	Yes
Experimental Approach/Plan:	The emphasis of this experiment is obtaining the largest applied kink mode perturbation possible to maximize signal strength for initial measurements. This will be achieved by applying a full current, slowly rotating, I-coil n=1 perturbation to a neutral beam heated H-mode plasma. Because of the small predicted signals (δB3D/B0 ~ 10-4), synchronous detection is required. (1) Generate a high βN discharge with q95 and I-coil phasing set to maximize the n=1 perturbation (240 degree upper-lower phase difference) (2) Scan βN between 1.2 and 2.4 at fixed q95 and plasma shape. The maximum βN will need to exceed the no-wall limit. For each shot, measure the toroidal variation of response (Bp and Br) at 7 poloidal locations (4 new). Generate a full 3D reconstruction of the plasma response at the vessel wall on both the HFS and LFS. Models predict the finest structure on the HFS, so the two vertical arrays of the 3D magnetics upgrade will be absolutely necessary to this experiment.
Background:	It was shown in M.J. Lanctot, et.al, Phys. Plasmas (2011) that the magnetic plasma response amplitude of an n=1 applied perturbation quantitatively agrees with linear ideal MHD predictions up to 80% the no-wall βN limit. Physics not included in this model results in significant over predictions of the response measurement above this point. The full structure of the mode has never been measured. This experiment will test the hypothesis that the poloidal spectrum varies with βN as the no-wall limit is approached.
Resource Requirements:
Diagnostic Requirements:	The complete installation, testing and calibration of the 3D magnetics upgrade is required. Also, soft x-ray measurements are desired for determining the internal toroidal amplitude and phase of the perturbation.
Analysis Requirements:	Existing magnetics plasma response analysis tools are needed. 3D reconstruction tools, used for 3D magnetics design work, will need to be further developed to use new sensor data and synchronous detection. Also, predictive modeling with MARS-F & IPEC will be a benefit.
Other Requirements:	For reconstructions at the vessel wall to be related to the full 3D equilibrium at the surface of the plasma both the shape and q-profile need to be nearly identical for each value of βN scanned.