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	162: 210RT MSE and low rotation, elevated q_min steady-state scenario discharges at high betaN
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:	Attempt to operate discharges with q_min >1.5, betaN >3.5 and q95 = 5-7 at less than the maximum attainable toroidal rotation. Do this by adding counter-injection beams to the standard recipe for steady-state scenario discharges. Begin by adding relatively small amounts of counter-beam power from the 210 right source in order to determine whether MSE data viewing this beam can be relied upon to replace the 30 left channels when the 30 left beam line is tilted. Assess the effect on the discharge stability, transport and noninductive current fraction of the addition of counter-injection beams.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Produce a steady-state scenario discharge following the standard procedure and gradually add the two available counter-injection beams. Explore various methods and timing for adding the beams in order to avoid instability. It is likely that at reduced rotation, tearing modes will be a significant problem.
Background:	Steady-state scenario discharges operate at the highest betaN possible in order to maximize fBS. This requires all of the co-injection beams available at DIII-D and results in large toroidal rotation velocities. At these high values of betaN, n = 1 tearing modes are often observed, providing a limit to discharge performance. In the past, when an attempt has been made to add even a small fraction of counter-injection beams in order to obtain additional MSE data, the counter injection beams were almost always removed after only a few shots because of the worry that they make the discharge more susceptible to tearing modes. A serious attempt to add significant counter-injection beam power has never been made. If the goal of the experiment is to maintain high betaN while reducing the rotation, it is likely that all of the co-injection beams will still be needed. That means that the extent to which the rotation can be reduced will be limited. Finally, in the five-year plan proposal, tilting the 30 left beam is contemplated. That would disable the core MSE channels viewing that beam. We need to determine whether new MSE views are necessary or whether the view of the counter beam can be used in steady-state scenario discharges.
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