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	16: Further development of QH-mode with strong co-Ip NBI torque
Name:	Keith Burrell Burrell@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Inductive Scenarios	Presentation time:	Not requested
Co-Author(s):	T.H. Osborne, P.B. Snyder, W.M. Solomon	ITPA Joint Experiment :	No
Description:	Use systematic, theory-guided parameter scans to broaden operating range for QH-mode with strong co-Ip torque discovered in 2008 and produced serendipitously in 2011	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	The set of experiments listed here are designed to 1) optimize QH-mode operation under the conditions used in the 2011 experiments and to 2) broaden the QH-mode operating space. The discharges will start from the conditions of shots like 147293 and 147354 Optimization of existing conditions: 1) Find minimum possible target density by lowering gas injection rate early in the shot and moving beam start time as early as possible. 2) Extend QH-mode duration by operating at higher input power and torque,3) determine minimum NBI torque which can sustain co-injected QH-mode without using NRMF torque. Expand parameter space: 1) Scan Drsep and upper triangularity. 2) Vary safety factor by changing current and toroidal field. 3) Vary outer gap to see the effect on the EHO.
Background:	QH-mode with all co-injection was discovered during serendipitously during the 2008 campaign and a dedicated experiment was performed for one day. In 2011, we again serendipitously produced co-injected QH-mode without NRMF at NBI torques as low as 2 Nm. We have just barely begun the investigation of the QH-mode with strong co-Ip torque. The goal of the present proposal is to use our knowledge of QH-mode with counter-Ip NBI to find ways to broaden the QH-mode operating space with strong co-Ip NBI so that this QH-mode can be used more routinely. The parameter scans listed in the experimental approach are based on empirical results from counter-NBI QH-mode combined with theoretical understanding of the QH-mode operating boundaries based on peeling-ballooning mode stability analysis. All QH-mode experiments to date indicate that lowering the target density is beneficial for QH-mode. Theory tells us that more strongly shaped plasmas and increased rotational shear are both beneficial for QH-mode. In addition, edge stability depends on safety factor. Finally, the theory of the EHO says there is a range of outer gaps over which the EHO will exist and modify the particle transport.
Resource Requirements:	Reverse Bt operation. 8 NBI sources. Recent boronization with deuterium carrier gas.
Diagnostic Requirements:	All profile and edge fluctuation diagnostics, especially edge BES and ECE-I for EHO studies
Analysis Requirements:	--
Other Requirements:	--