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	86: Safety Factor Scaling of Turbulence and Transport in Hybrid Scenario Plasmas
Name:	George McKee mckee@fusion.gat.com	Affiliation:	University of Wisconsin
Research Area:	Turbulence & Transport	Presentation time:	Not requested
Co-Author(s):	A. Garofalo, C. Holland, J. Kinsey, T. Rhodes, L. Schmitz, Z. Yan	ITPA Joint Experiment :	No
Description:	Energy confinement in H-mode discharges varies strongly with plasma current (with q as the relevant dimensionless parameter) as approximately tau_E ~ Ip^(0.9). This basic dependence is well known empirically but lacks a clear fundamental explanation in terms of basic turbulent transport that is consistent with theory and simulation. Connecting this empirical dependence with the underlying turbulence behavior is crucial to understanding confinement scaling as well as to validating transport simulations over a wide range of parameters.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	We will perform this experiment in quasi-steady hybrid H-mode plasmas and vary the safety factor systematically. The toroidal field will be held constant (2.0 T) and plasma current will be adjusted to vary q95 in the range of 3.0<q95<8.0. This experiment will employ a nominally "standard" q-profile, with q0>~1 (typical for hybrid discharges.) Comprehensive fluctuation measurements will be obtained at each condition. We will aim for a moderately co-current rotation plasma and adjust co/ctr beam power to maintain pressure, density and rotation (or omega/q) nearly constant. Long-pulse hybrid scenario discharges will be employed to eliminate sawteeth and obtain long, steady conditions over which to ensemble-average fluctuation data. The core 3/2 mode and ELMs are not expected to be a problem since the focus will be on transport and turbulence investigations in the mid radii region (0.3 < r/a < 0.8.)
Background:	Many experiments have shown a strong dependence of confinement and transport on plasma current. Previous DIII-D experiments have shown that turbulence and zonal flow/GAM characteristics vary with q95. This experiment would seek to obtain comprehensive turbulence and full transport measurements with multiple fields, a wide wavenumber range, and over a wide radial extent in well-characterized discharges. Calculations of turbulence and transport by gyrokinetic simulations have generally agreed reasonably well with measured turbulence parameters and inferred heat fluxes at mid-radii in L-mode plasmas [Holland-PoP-2009], while at larger radii, simulations routinely underestimate both fluctuation amplitudes and transport. This experiment will seek to determine wether this "L-mode shortfall" is present in H-mode plasmas; work by Kinsey suggests that there is a larger shortfall at higher q95, which is consistent with preliminary analysis of a 2012 L-mode experiment [T. Rhodes et al.] These experimental results will form a foundation for future investigations aimed at optimizing transport in advanced scenarios with non-monotonic q-profiles.
Resource Requirements:	Neutral beams (all)
Diagnostic Requirements:	Fluctuation diagnostics: BES, DBS, CECE, ECEI, FIR, PCI, UF-CHERS Full Profile diagnostics
Analysis Requirements:	Transport Analysis; TGLF; GYRO
Other Requirements: