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	36: Natural ELM Pacing in High-Beta, Steady-State Plasmas
Name:	Clinton (Craig) Petty petty@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Steady State Heating and Current Drive	Presentation time:	Not requested
Co-Author(s):	T. Luce	ITPA Joint Experiment :	No
Description:	High-beta, steady-state plasmas naturally have a very high ELM frequency (~300 Hz). We have not studied the size and footprint of the transient heat pulses in such plasmas, and therefore it is premature to assume that ELM suppression is required. Even if some type of ELM mitigation is needed in high-beta, steady-state plasmas, it will likely be easier to further increase the ELM frequency rather than completely suppress ELMs, and we need to determine what ELM mitigation (if any) is actually required.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Using the established methods of characterizing the ELM size, as well as using the new capabilities of the IR periscope camera, we will study the ELM heat characteristics in AT plasmas with beta_N~3.5 and q_min~1.5. This should be done as a function of (1) beta_N, (2) collisionality, (3) q_95, and (4) triangularity.
Background:	ELM pacing experiments in DIII-D have demonstrated the ability to trigger ELMs with pellet injection, up to the 60 Hz capability of the hardware. However, another proven method to strongly vary the ELM frequency is to adjust the plasma beta (as well as the plasma shape). The ELM frequency is a strongly nonlinear function of the plasma beta, increasing from a few Hz at beta_N=1.8 to 300 Hz at beta_N=3.6. Therefore, it is not clear that, depending on details of the plasma shape, high-beta, steady-state plasmas cannot be naturally ELM pacing.
Resource Requirements:	NBI: 6 co-sources are required. EC: 6 gyrotrons are desired.
Diagnostic Requirements:	Fast magnetics, MSE, LIBEAM, IR camera.
Analysis Requirements:
Other Requirements: