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	248: Investigate elongation limit in low li discharges with/without applied 3D magnetic fields
Name:	Andrea Garofalo garofalo@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Torkil Jensen Award	Presentation time:	Not requested
Co-Author(s):	L. Lao, R. Buttery, M. Chu, N. Ferraro, A. Reiman, A. Turnbull	ITPA Joint Experiment :	No
Description:	The goal of this experiment is to produce high kappa ~ 2.7 discharge with low li to provide target for high beta + 3D perturbation study	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Using the formation technique employed to produce low-li DIII-D discharge #122976 (early beam heating, Bt and Ip ramps), attempt to reproduce the profiles of 122976 in a discharge of smaller minor radius (a~50 cm). At li~0.5, the elongation is predicted stable even beyond k~2.6. Look for n=0 stability limit. Apply maximum n=3 I-coil perturbation, look for an effect. Compare with MHD calculations.
Background:	A possible upgrade of DIII-D, currently under study, consists in the installation of nonaxisymmetric coils above and below the midplane, capable of applying a field large enough to improve the vertical stability of highly elongated plasmas [Rieman, PRL 99, 135007 (2007)]. High elongation is expected to be beneficial for both confinement quality and stability. FNSF and DEMO studies rely on high elongation to reach very high fusion performance. Stable highly elongated plasmas can also be produced by using very low li (~0.5). Recent calculations by Lang Lao show that a low li DIII-D discharge like 122976 would be stable to n=0 with kappa up to 2.66 with the DIII-D plasma-wall distance. This proposed experiment would provide us low li plasmas with the very high elongation that 3D fields could enable in moderate li as well.
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