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	326: Understand mechanisms by which ECH influences NTM stablility
Name:	Wayne Solomon solomon@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Stability & Disruption Avoidance	Presentation time:	Not requested
Co-Author(s):	R. Prater	ITPA Joint Experiment :	No
Description:	The goal of this experiment is to document and better understand the means and conditions whereby ECH (with or without current drive) can lead to improved stability against 2/1 NTMs.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Conditions for 2/1 NTM onset will be measured by ramping the torque down at different levels of betaN and at different q95's. During these ramp downs, ECCD should be applied and scanned shot-to-shot inward from the q=2 surface toward the axis. This should also be repeated in a nominally heating only configuration, and varying between narrow and broad radial deposition. Document which conditions ECH is successful in expanding into the otherwise unstable operating regions. Use density feedback control to maintain constant density, choose a shape for optimal edge TS for good edge BS measurement, and optimize beams for best MSE. For consistency, check some key points at fixed torque with betaN ramp up.
Background:	Experiments in FY11 showed that EC power was typically needed to access high beta, low torque states in advanced inductive plasmas. In most cases, the EC was configured to drive current *near* (but without any optimal alignment) at the q=2 surface. This, however, was realized as a limitation in terms of being able to go to lower field and higher betaN. Since we were not especially well-aligned in any case, we decided to do a deposition scan. To our surprise, EC power could be deposited well inside the q=2 surface, and even configured for heating instead of current drive, yet the same benefits to stability were realized.
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