Theory Weekly Highlights for September 2007

September 28, 2007

Jeff Candy attended the 26th IDC High-Performance Computing (HPC) User Forum in Santa Fe, NM September 25 through 27 and gave a talk entitled “HPC and Fusion Research: Turbulence in Tokamak Plasmas”.

Ming Chu attended the 6th Workshop on “Nonlinear Plasma Science and IFTS Workshop on Physics of Turbulence & Coherent Structure and Energetic Particles” Sept. 21-26, in Suzhou-Hangzhou, China and made presentations on “Feedback Stabilization of Neoclassical Tearing Modes using ECCD” (for Vincent Chan) and the “Resistive Wall Mode”.

Phil Snyder is attending the ITPA H-Mode Pedestal workshop in Naka, Japan from October 1 through October 3.

September 21, 2007

In collaboration with Y.Q. Liu of Chalmers University, the kinetic effect of particle drift and bounce motions on MHD modes has been formulated in terms of the induced anisotropic pressure due to the MHD motion for tokamak plasmas with toroidal flows. This formulation is thus suitable for treating slowly growing MHD modes where such effects are non-negligible, such as the internal kink or the resistive wall modes.

September 14, 2007

Turbulence not only causes energy transport (the dominant effect) but can also provide some small ohmic heating from fluctuations in the parallel and perpendicular-drift currents. Some months ago an important sign error was discovered in the Hinton-Waltz gyrokinetic heating formulation paper [Phys. Plasmas 13 (2006) 102301], which made the drift component cooling rather than the originally estimated heating. Subsequently we showed analytically that the local average of the combined heating and cooling was actually a small energy exchange between electrons and ions with no net plasma heating. GYRO flux tube simulations of the GA-standard case have now verified the analysis. A “full physics” global GYRO simulation of a DIII-D L-mode shows the integrated electron heating - ion cooling typically less than 10% of the respective gyrokinetic energy transport flows. A short paper will be submitted for publication soon.

September 07, 2007

In collaboration with Clemente Angioni (IPP-Garching), progress was made on GYRO profile feedback adjustment methods to obtain global gyrokinetic transport solutions. This will allow the simulations to predict the profiles, hopefully within experimental error bars, with the transport flows matched to the experimentally measured flows. Application will focus on predicting the observed density peaking via a particle pinch in DIII-D and ASDEX-Upgrade.

These highlights are reports of research work in progress and are accordingly subject to change or modification