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	245: Investigate the physics of NTM suppression by large externally applied helical fields
Name:	Andrea Garofalo garofalo@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Torkil Jensen Award	Presentation time:	Not requested
Co-Author(s):		ITPA Joint Experiment :	No
Description:	Use stable, locked plasmas observed in QH-mode experiments with n=3 NRMFs in July 2009, to investigate the physics of NTM suppression by large externally applied helical fields [Q. Yu, S. Gunter, K. Lackner, PRL (2000); La Haye, et al., PoP (2002)].	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Reproduce locked QH-mode plasmas like 138611. Document the locking by modulating the NBI torque at varying amplitude. Investigate the presence of locked n=1 islands by providing an additional n=1 seed and then rotating it. Investigate the Yu-Gunter-Lackner model by applying ECH pulses in plasmas with and without the external n=3 field. Compare transport across rational surfaces.
Background:	Theory [Q. Yu, S. Gunter, K. Lackner, PRL (2000)] and DIII-D experimental results [La Haye, et al., PoP (2002)] suggest that the application of 3D fields to a high beta plasma can provide a stabilizing effect on NTMs. The hypothesis is that the applied helical field enhances the perpendicular transport across the NTM's key rational surface, thus weakening the destabilizing effect of the helically perturbed bootstrap current. July 2009 experiments on low NBI torque QH-mode with n=3 NRMFs have shown cases of high beta plasma with rotation locked to zero at the q=2 and 3 surfaces, suggesting the formation of (2:1) and (3:1) islands. These islands remain stable until the n=3 field is removed.
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