Theory Weekly Highlights for November 2015

November 13, 2015

The GA Theory group prepared three invited talks for the APS Meeting next week in Savannah, Ga. The three invited papers by N. Ferraro, O. Meneghini, and J. Candy are scheduled for the Tuesday November 17 session on Magnetic Fusion Energy Model Development and Simulation. Jeff Candy will present the paper “Unification of Plasma Fluid and Kinetic Theory via Gaussian Radial Basis Functions” (paper GI2.00001, 9:30 am). Orso Meneghini will be presenting the work done for “Validation of a coupled core-transport, pedestal-structure, current-profile and equilibrium model” (paper GI2.00003, 10:30 am). Nate Ferraro will discuss the work done on “Free-Boundary 3D Equilibria and Resistive Wall Instabilities with Extended-MHD” (paper GI2.00005, 11:30 am).

November 06, 2015

Accounting for large energetic particle (EP) drift orbits in DIII-D, solves a longstanding problem for the local critical gradient model (CGM) of Alfven eigenmode (AE) transport of EPs. Typically AEs become unstable at mid-core radii (r/a ~ 0.5) where the driving EP pressure gradient is largest. Mode amplitudes are insignificant at central radii (r/a < 0.25). The active region of the critical gradient profile, determined by local GYRO linear (and nonlinear) simulations, does not extend to the central radii. When the local CGM is employed for local transport of the local flux surface averaged EP density (as in the local ALPHA EP transport code), the transported EP density profile is flattened at mid-core but remains peaked in the center where the AEs do not reach. This is in disagreement with the measured DIII-D EP profile. The remedy is to account for the central EPs having an orbit drift outward, off their local flux surface, into the mid-core region, which has large AE amplitudes. Broadening the local critical gradient profile with a simple estimate of the radial orbit drift solves the problem. The TRANSP-NUBEAM EP transport code follows EP gyro-particles and no ad hoc estimate of a drift orbit broadened local CGM is required.

Lang Lao visited the University of Science and Technology of China (USTC) in Hefei, China and gave a series of lectures on Integrated Modeling of Tokamak Experiments and Burning Plasma Devices to the EAST scientists, as well as the CFETR Physics Team, which consists of scientists and students from USTC, ASIPP, SWIP, Peking University, and Huazhong University.
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These highlights are reports of research work in progress and are accordingly subject to change or modification