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	188: Extension of proxy error field experiments to H-mode plasmas
Name:	Carlos Paz-Soldan paz-soldan@fusion.gat.com	Affiliation:	Columbia University
Research Area:	Stability & Disruption Avoidance	Presentation time:	Not requested
Co-Author(s):	R.J. Buttery, M.J. Lanctot, E.J. Strait, R.J. La Haye, J.M. Hanson, J. King, J-K. Park, N. Logan	ITPA Joint Experiment :	No
Description:		ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	The 'high-beta compass scan' technique performed twice in 2011 as part of the TBM campaign will be applied to the proxy field configuration. That is, the C-coils will apply a known (proxy) field while the I-coils will try to correct it. The discharge scenario will be identical to that of the 2011 TBM experiment so that the results from the two may be compared. The reference shot is 147135, with Beta_N = 1.8, q95=4.1. The technique consists of applying the proxy field (C-coil), and then ramping the correcting field (I-coil) at various toroidal phases. It is further proposed to begin the ramp from the optimum levels found in the 2011 low-beta experiment. If the proxy error field induces tearing modes or other unwanted behavior, its amplitude will be reduced to manageable levels. During the ramp, metrics such as the total angular momentum, plasma response, and plasma-wall Maxwell stress will be measured. Fits to these parameters will be made and an optimum for each deduced. These measurements will be much enhanced by the new 3D magnetics capability. The optimum will then be applied in a dedicated discharge to observe the levels of rotation recovery and compare this to the values found with the TBM experiment. Comparison to theory for the various metrics will also be undertaken to benchmark our understanding of the relevant physics (NTV, plasma response, etc). This experiment could be accomplished in 5-6 good shots.
Background:	Previous work with the TBM mock-up in 2011 dramatically illustrated that optimum correction of the n=1 TBM error field only allowed a 25% recovery of the rotation from pre-TBM levels. The TBM spectrum, however, is complex and contains several different toroidal harmonics (n), leading to uncertainty as to whether the rotation degradation is caused by higher n modes or by incomplete n=1 correction. Knowing which path (n>1 or best n=1) leads to the most complete rotation recovery is a critical issue for devising error field control algorithms going forward.
Resource Requirements:
Diagnostic Requirements:	ECE, CER, MSE, SXR, Thomson, 3D magnetics.
Analysis Requirements:	TRANSP runs for all discharges, normal suite of 3D field analysis tools.
Other Requirements: