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	108: Disruption avoidance by forced magnetic spin-up of NTMs
Name:	Daisuke Shiraki shirakid@fusion.gat.com	Affiliation:	Oak Ridge National Lab
Research Area:	Stability & Disruption Avoidance	Presentation time:	Requested
Co-Author(s):	N. Eidietis, R. La Haye, M. Okabayashi, E. Olofsson, F. Volpe	ITPA Joint Experiment :	No
Description:	Disruptions caused by the locking of a 2/1 NTM are to be avoided by using a rotating n=1 field from the I-coils to entrain a mode which would otherwise lock, with possible recovery of H-mode. This is to be done with and without simultaneous application of modulated ECCD to help suppress the island entirely.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	A 2/1 NTM will be created and allowed to approach locking, by a beta ramp in a low-rotation (balanced injection) plasma. When the mode is detected to be near locking (f<1kHz), a fast rotating n=1 field (~100Hz) will be applied to entrain the mode in the rotating frame of the applied field and prevent locking. The required currents for disruption avoidance by entrainment of the mode and/or H-mode recovery are to be studied. The required currents may be reduced if modulated ECCD is simultaneously applied (at the entrainment frequency and "phase") to assist with mode suppression, and the required EC power in combination with the magnetic rotation will also be studied.
Background:	Rotating n=1 fields applied by the I-coils have previously (2011) been used on DIII-D to steer and control 2/1 locked modes. This was done in conjunction with modulated ECCD to help stabilize the mode. A pre-emptively applied fast rotating field may prevent locking to the wall and/or static error field before it happens, and sufficient rotation may stabilize the mode through rotational stabilization and/or rotational shear. If successful, forced magnetic rotation of 2/1 NTMs will help eliminate a leading cause of disruptions due to locked modes, as well as providing valuable data on current and power requirements for disruption avoidance on ITER.
Resource Requirements:	I-coils in 240 phasing with SPAs Modulated ECCD
Diagnostic Requirements:	--
Analysis Requirements:	--
Other Requirements:	--