Controlling H-Mode Particle Transport with Modulated Electron Heating in DIII-D and Alcator C-Mod via TEM Turbulence
Abstract not provided
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Engineering topics
Greenwald, M
Publications and source records attributed to Greenwald, M.
Measurement of plasma current dependent changes in impurity transport and comparison with nonlinear gyrokinetic simulation
Measured impurity transport coefficients are found to demonstrate a strong dependence on plasma current in the core of Alcator C-Mod. These measurements are compared directly with linear and nonlinear gyrokinetic simulation in an attempt to both qualitatively and quantitatively reproduce the measured impurity transport. Discharges constituting a scan of plasma current from 0.6 to 1.2 MA were performed during the 2010 run campaign. The impurity transport from these discharges was determined using a novel set of spectroscopic diagnostics available on Alcator C-Mod. This diagnostic suite allowed for the effective constraint of impurity transport coefficient profiles inside of r/a = 0.6. A decrease in the measured impurity diffusivity and inward convection is found with increased plasma current. Global, nonlinear gyrokinetic simulations were performed using the GYRO code [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] for all discharges in the experimental scan and are found to reproduce the experimental trends, while demonstrating good quantitative agreement with measurement. A more comprehensive quantitative comparison was performed on the 0.8 MA discharge of the current scan which demonstrates that simultaneous agreement between experiment and simulation in both the impurity particle transport and ion heat transport channels is attainable within experimental uncertainties.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
ICRF Mode Conversion Flow Drive Experiments on Alcator C-Mod
We have carried out a detailed study of the dependence of ICRF mode conversion flow drive (MCFD) on plasma and RF parameters. The flow drive efficiency is found to depend strongly on the {sup 3}He concentration in D({sup 3}He) plasmas, a key parameter separating the ICRF minority heating regime and mode conversion regime. At +90 deg. antenna phasing (waves in the co-I{sub p} direction) and dipole phasing, the driven flow is in the co-I{sub p} direction, and the change of the rotation velocity increases with both P{sub RF} and I{sub p}, and scales unfavorably vs. plasma density and antenna frequency. When MCFD is applied to I-mode plasmas, the plasma rotation increases until the onset of MHD modes triggered by large sawtooth crashes. Very high performance I-mode plasmas with H{sub ITER98,y2}{approx}1.4 and T{sub e0}{approx}8 keV have been obtained in these experiments.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Full wave effects on the lower hybrid wave spectrum and driven current profile in tokamak plasmas
A numerical modeling of current profile modification by lower hybrid current drive (LHCD) using a fullwave/Fokker-Planck simulation code is presented. A MHD stable LHCD discharge on Alcator C-Mod was analyzed, and the current profile from full wave simulations was found to show better agreement with the experiment than a ray-tracing code. Comparison of full wave and ray-tracing simulation shows that, although ray-tracing can reproduce the stochastic wave spectrum broadening, the full wave calculation predicts even wider spectrum broadening, and the wave spectrum fills all of the kinematically allowed domain. This is the first demonstration of LHCD current profile modeling using a full wave simulation code in a multi-pass absorption regime, showing the clear impact of full wave effects on the LHCD driven current profile.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗