Theory Weekly Highlights for October 2003

October 31 2003

Two invited talks were delivered at the 2003 APS Meeting in Albuquerque, NM on “Effects of Electromagnetic Turbulence in the Neoclassical Ohms Law” by F.L. Hinton, and “Modeling of Feedback and Rotation Stabilization of the Resistive Wall Mode in Tokamaks” by M.S. Chu. These respectively described the theory work at GA and DIII-D on turbulent dynamo contributions to Ohms Law and on resistive wall mode stabilization. Both were well received.

October 24 2003

In collaboration with H R Wilson of Culham, an extension of the peeling-ballooning formalism to incorporate subsonic toroidal flows has been included in the ELITE stability code and used to study the effect of sheared flows on intermediate to high n edge stability. Sheared flows narrow the radial extent of the modes and drive the mode frequency to balance the rotation frequency in the sharp gradient region in the center of the pedestal. Complex behavior is found, including both stabilization and destabilization of modes by rotation shear, as well as convergence of different roots. While subsonic flow shear can have significant impact on the mode structure, with possible implications for ELM size, the effects on the growth rates tend to be relatively small, so that stability constraints on the pedestal are not dramatically affected. In order to study the effects of larger flows, an extended formalism allowing for sonic flows was recently derived, and will be implemented in the near future.

October 17 2003

The “alpha version” of the Signal Analysis Code, SAVE, has been released. This code provides several basic data functionalities for analysis of DIII-D signals, including time domain-based smoothing, de-trending, Fast Fourier Transform computation, cross spectrum analysis and SVD analysis. It also provides a scripting functionality that can be used to store the current status of the code and restore it later, which is useful for repetitive analysis. The overall user interface is composed of 3 principal parts: data selection, process selection, and result display. SAVE can be launched from Hydra or the other LSF hosts by typing 'sav' at the command-line.

October 10 2003

A set of TOQ equilibria was used to test an enhanced version of the MARS MHD code with RWM feedback from Bondeson and Liu of Chalmers University, MARS-F. In the absence of flow, results from MARS-F agree well with those computed using the DCON-VACUUM plus feedback package. In the presence of toroidal flow, the two-ion sound wave and the kinetic damping models give results within a factor of two of each other. MARS-F will be used in conjunction with other stability tools to analyze discharges from the DIII-D RWM experiments.

October 03 2003

The latest version of NTCC Monte Carlo fast ion physics package, NUBEAM, together with all supporting libraries and ancillary NTCC modules has been installed on local GA Linux based workstations. NUBEAM is an updated version of the beam package originally developed for the TRANSP transport code. An interface to the ONETWO transport code has been written and rudimentary testing of the calculations and benchmarking against MCGO have begun. Combined with other recent improvements in ONETWO and the current update to use the inverse equilibrium solver TOQ, this will significantly enhance ONETWO capability to analyze DIII-D experimental data and perform theoretical modeling.

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