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Title	45: Differences in Impurity Accumulation Between Resonant and Non-resonant RMP Plasmas
Name:	Thomas Petrie petrie@fusion.gat.com	Affiliation:	General Atomics
Research Area:	ELM Control	Presentation time:	Not requested
Co-Author(s):	--	ITPA Joint Experiment :	No
Description:	A direct comparison of resonant (q95=3.5) - and non-resonant (q95=4.5) cases for plasmas with applied RMP will establish whether or not their respective impurity ion transport is measurably different. The even parity I-coil configuration is used. The main comparison test involves density scans at different deuterium injection rates at a fixed impurity (argon) injection rate. This experiment will determine whether the buildup of injected impurity in the main plasma has any dependence on whether the plasma is set up in an RMP resonant or an RMP non-resonant state.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	High performance discharges, e.g., "hybrid", are the preferred starting-point plasmas for this comparison, although standard high confinement ELMing H-modes are also acceptable. The base-case plasmas are long-pulse with Ip-flattop time ~5 s (minimum) fixed 1.2 MA. The direction of the ion grad-B drift is toward the lower SN X-point. Deuterium injection is done from the top of the vessel and argon impurities are injected into the lower divertor private flux region. Particle pumping is done at the outer divertor target. The approach is straightforward. There are three values of I-coil current (0, 3, and 6 kA) and three gas puff rates (0, 40, and 80 torr l/s) to be considered for each of the two q95 cases (3.5 (resonant) and 4.5 (non-resonant)).
Background:	In previous experiments, we compared impurity buildup in the main plasma for a control case without RMP with two cases at "high" and "intermediate" I-coil currents. ELMs were completely suppressed at both I-coil currents. During the H-mode phase of the discharges, argon was injected at a near-trace level but no deuterium was puffed. For these shots, the buildup in argon density was 20%-25% higher for plasmas with the I coil activated than without. There was little difference in argon accumulation between the intermediate and high I-coil cases. We also showed that argon accumulation inside the main plasma as a function of the deuterium injection rate for RMP-resonant and the corresponding non-RMP ELMing H-mode plasmas. For both RMP and non-RMP cases, the concentration of argon in the main plasma trended downward with increasing the deuterium injection rate. The return of Type-1 ELMing activity at higher pedestal density (and pedestal collisionality) may be responsible for the similarity in argon impurity accumulation in the main plasma between RMP-resonant and non-RMP discharges. Our analysis suggests that these RMP resonant results for impurity transport at higher density would carry over to RMP non-resonant cases. This is important to establish since ELM mitigation and heat flux reduction with RMP under non-resonant conditions provide considerable flexibility in selecting plasma parameters.
Resource Requirements:	Six beam sources. This is a 0.5-1.0 day experiment.
Diagnostic Requirements:	IR camera, CER, Thomson scattering, bolometers, CO2 interferometers, and SPRED.
Analysis Requirements:	MIST (or equivalent), ONETWO
Other Requirements:	--