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	373: Pedestal optimization in VH mode
Name:	Philip Snyder snyderpb@ornl.gov	Affiliation:	Oak Ridge National Lab
Research Area:	Pedestal Structure	Presentation time:	Not requested
Co-Author(s):	T. Osborne, R. Groebner, G. Jackson, R. Maingi	ITPA Joint Experiment :	No
Description:	Very high pedestals (or possibly, double barriers) and high performance have been achieved in DIII-D VH-mode operation. However, nearly all VH mode operation occurred well before recent pedestal diagnostic upgrades and advances in understanding pedestal physics. The goal is to re-visit, study, and optimize pedestal structure in VH-mode discharges, employing recently upgraded diagnostics. Primary objectives include: 1) Determine whether the VH-mode ETB is a single broad barrier, or a pair of separate barriers with a narrow gap in between. 2) Study dependence of VH-mode pedestal on density and impurity content (ideally with Ne or N puffing) 3) Make extensive predictions with EPED before expt, and compare to observations to determine whether VH mode observations can be understood in terms of this model, and also to determine the relationship between VH-mode and the "Super H-Mode" regime predicted by EPED 4) Develop stationary VH-mode discharges either as ELMing discharges (eg recovering high Zeff rapidly after each ELM with impurity injection), pellet-paced ELM discharges, or as ELM-free (employing working model of RMP ELM to predict necessary q and other conditions)	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Establish a high performance VH mode in a configuration consistent with good pedestal diagnostic coverage. Jog plasma slowly across edge diagnostics to study ETB structure in detail. Vary density and impurity injection rates. Establish stationary VH mode by employing one of the above 3 techniques.
Background:	VH mode operation may be relevant to the JRT, particularly to comparisons with NSTX
Resource Requirements:	at least 1 day
Diagnostic Requirements:	pedestal profile and turbulence diagnostics
Analysis Requirements:	EPED study before experiment, revisiting old VH mode discharges
Other Requirements: