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	145: Explore RMP ELM suppression mechanism at moderate collisionality
Name:	Richard Moyer moyer@fusion.gat.com	Affiliation:	University of California, San Diego
Research Area:	ELM Control	Presentation time:	Not requested
Co-Author(s):	--	ITPA Joint Experiment :	No
Description:	Use new diagnostics and emerging understanding of plasma response and RMP ELM suppression at low collisionality to explore the mechanisms for ELM suppression at moderate collisionality in DIII-D. Initial RMP ELM control results were obtained in ITER shape at moderate pedestal collisionalities of ~ 1 and above due to the lack of lower divertor pumping at high collisionality; representative "trophy" discharges include: 115467 and 119690. These discharges used an odd parity RMP which didn't produce density pump-out, a major advantage to ITER. In addition, to within experimental uncertainty, the pedestal profiles remained Peeling-Ballooning unstable,suggesting that an alternate path to ELM suppression may exist. Moyer et al. {PoP 2005] have shown that there is a significant increase in broadband magnetic and density fluctuations which are correlated with an increase in intermittent "blobby" transport. Because this path to RMP ELM control avoids the loss in core performance associated with existing RMP ELM suppression experiments, the mechanism(s) for this approach should be determined and the suitability for ELM control in ITER addressed. Another aspect of these ELM suppression shots is breaking of the plasma rotation across the plasma, making this one route to ITER-relevant low rotation.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Re-establish RMP ELM suppression at moderate pedestal collisionality (~1) in the ITER shape. May be difficult due to lower divertor changes. Vary RMP current, phasing, and parity. Vary input momentum. Document plasma response at wall with new magnetics. Document plasma rotation, Er, pedestal profile, turbulence and transport changes. Scan collisionality (0.5 -> 4).
Background:	Previous RMP ELM suppression results at moderate pedestal colllisionality has some key aspects that make it appealing for ITER: the pedestal profiles are unchanged to within measurement uncertainty, and there is no core density/beta pump-out to lower core performance. Instead, ELMs are replaced by increased intermittent transport correlated with increased broadband magnetic and density fluctuations [Moyer PoP 2005]. Since upgrading diagnostics, and forming a picture of RMP ELM suppression at low pedestal collisionality, we haven't returned to these conditions to test the model.We should establish that this ELM suppression is either equivalent to or different from that at low collisionality. If different, we will need to determine the compatibility of this approach with low collisionality (that it doesn't require higher collisionalilty) to establish whether or not it can be used for ITER.
Resource Requirements:	I-coils for n= 3 even and odd parity; SPAs well-conditioned vessel; glow to 7 min; no cryo-pumping co and counter NBI to vary torque input and power
Diagnostic Requirements:	CER (1 ms integration time) for ion channel profiles Thomson scattering, ECE, and profile reflectometry for electron channel profiles Divertor and periscope IRTV; DiMES TV to monitor heat and particle flux splitting SXR imaging and X point tangential TV fast cameras with spectrometer and image intensifier ECEI (higher density makes this more feasible) turbulence diagnostics (DBS, BES, PCI, FIR) lithium beam to measure edge pitch angle and current profile
Analysis Requirements:	'Standard' profile analysis and kinetic corrections to equilibrium profile and fluctuation analysis
Other Requirements:	--