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	351: Confinement enhancement via impurity-seeding of H-mode plasmas
Name:	George McKee mckee@fusion.gat.com	Affiliation:	University of Wisconsin
Research Area:	Turbulence & Transport	Presentation time:	Not requested
Co-Author(s):	C. Holland, L. Schmitz, S. Smith, T. Rhodes, G. Wang, A. White, Z. Yan	ITPA Joint Experiment :	No
Description:	Inject low-Z to medium-Z impurities into standard (or hybrid) ELM'ing H-mode plasmas and examine the response of global energy and particle confinement, local transport and turbulence.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Establish a low-current (~1 MA) hybrid or standard H-mode discharge. Hybrids are desirable for their long duration and lack of sawteeth (142019 could be a reference). Inject neon, argon and/or nitrogen in progressively increasing quantities and examine the turbulence, transport, confinement, and neutron rate response with the fluctuation and profile diagnostics. These experiments will also support validation efforts by comparing measured turbulence/transport response with predictions from TGLF, GYRO and other codes.
Background:	Recent experiments in ASDEX have demonstrated improved confinement in discharges that utilize nitrogen seeding to radiatively cool the plasma edge, thereby mitigating damage to the tungsten first wall (Kallenbach et al. PPCF 52 (055002 (2010); IAEA-2010, OV/3-1.) This is suggested to possibly result from a change in critical gradient as a result of increased Zeff. Confinement factors were increased from H(98,y-2)=0.9 to 1.1, and stored energy and neutron rates increased accordingly. No fluctuation measurements were presented and the mechanism is not identified. These results reminiscent of the RI-mode experiments performed on TEXTOR and DIII-D in L-mode conditions, where a significant confinement improvement with injected neon is correlated with a large reduction in turbulence (McKee-PRL-2000). Given the importance of radiative cooling for burning plasma experiments, it will be very important to understand the impacts of impurity seeding on turbulence and transport, along with the potentially beneficial increase in confinement.
Resource Requirements:	All fluctuation and profile diagnostics
Diagnostic Requirements:	BES (8x8), UF-CHERS, DBS, CECE, FIR, PCI, etc.
Analysis Requirements:	lots
Other Requirements: