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	158: Expand the high li, betaN >4 operating regime through instability avoidance and higher heating power
Name:	John Ferron ferron@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Steady State Heating and Current Drive	Presentation time:	Not requested
Co-Author(s):	--	ITPA Joint Experiment :	No
Description:	Follow-up on the two high li experiment days in 2008 and 2012. Focus on eliminating the large perturbation of the first ELM that prevents consistent long pulse, high betaN, performance in the high li scenario and prevents operation at lower q95. This may involve testing a new method to form the high li discharge. Take advantage of heating and current drive upgrades since 2008: a neutral beam power level above 11 MW (providing that power is actually available this year) and a sixth gyrotron. Make measurements of the fast ion profile in order to understand anomalous losses.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	In order to operate reliably and at lower values of q95, it is necessary to avoid the early, fast-growing n = 1 mode that has the appearance of the first ELM. Since a number of methods were tried in 2012, with apparent backwards progress, the starting point again would be the scenario used in 2008. Further analysis of the 2012 data is required in order to determine the next steps for the experiment.
Background:	In 2008, high li discharges with betaN >4.5 were obtained that had fNI = 1.2 and betaN above 4 for 1 s. Bootstrap current fraction was above 80%. In the early portion of the high beta phase when li was near 1.4, even with betaN = 4.5 the discharge was operating below the no wall n = 1 ideal stability limit. BetaN was limited by available heating power. The duration of the high-performance phase was limited by onset of a 2/1 tearing mode. Best performance was obtained with q95 near 7. At lower values of q95, the high beta phase was terminated during the beta ramp up by a fast growing n = 1 instability. Comparisons with ONETWO indicate significant anomalous fast ion loss, possibly a result of semicontinuous 1/1 mode activity. Attempts to improve this high li scenario were made during an experiment day during 2012. Those discharges still need to be analyzed carefully in order to determine the best next step.
Resource Requirements:	--
Diagnostic Requirements:	Would make use of FIDA.
Analysis Requirements:	--
Other Requirements:	--