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	302: RMP ELM Suppression at the NTV Offset Rotation
Name:	Clinton (Craig) Petty petty@fusion.gat.com	Affiliation:	General Atomics
Research Area:	ELM Control	Presentation time:	Not requested
Co-Author(s):		ITPA Joint Experiment :	No
Description:	Establish RMP ELM suppression in a plasma with mild counter rotation. Allow the rotation to "lock" to the offset rotation given by NTV, using additional NTV torque from the n=3 C-coil. Evaluate the confinement and stability properties of this discharge. Compare even and odd parity to vary the relative contributions of resonance and nonresonant effects. The NTV offset rotation frequency should be made as large as possible by operating at low Ip (i.e. low Bp) and low density (i.e. high Grad_Ti).	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	(1) Use reverse Ip configuration so that most of the neutral beams are injecting in the counter direction. (2) Establish ELMy H-mode plasmas with Ip=1.0 MA and q_95=3.6. Lower Ip may be used if the beam ion confinement is good enough. (3) Start with even parity of I-coil. Apply RMP to suppress ELMs, with the n=3 C-coil added for additional (counter) NTV torque. Allow the density to pump out to a low level to obtain a high gradient in the ion temperature. (4) Determine the sensitivity of the toroidal rotation rate during RMP application with the amount of counter-torque injection. If the effect of nonresonant braking is large, then the toroidal rotation should be a stronger function of the NTV offset velocity than of the NBI torque. (5) Compare even and odd parity of I-coil, ideally in same discharge if SPAs are used.
Background:	For co-rotation discharges, applying the RMP to suppress ELMs results in a reduction of the toroidal rotation. This reduces the confinement time, and also can lead to locking of the plasma if the resonant braking effect becomes large. It is predicted that the nonresonance braking effects of an RMP coil on ITER may dominate over the co-torque injection from neutral beams, in which case the toroidal rotation on ITER should "lock" to the NTM offset value. This experiment proposes to study the consequences of this effect by starting with a counter rotation frequency close to the NTM offset value.
Resource Requirements:	Reverse plasma current configuration. RMP I-coil configuration. Use SPAs so that even and odd parity can be compared in same discharge. C-coil in n=3 configuration.
Diagnostic Requirements:
Analysis Requirements:
Other Requirements: