Theory Weekly Highlights for May 2006

May 26, 2006

The latest version of ReviewPlus has been installed at NSTX. ReviewPlus is a generic IDL visualization code developed by the data analysis group for MDSplus signals. Changes were made that were necessary to make the code portable to other sites, in addition to configuration changes specific for NSTX. Feedback from NSTX has been very positive.

Vincent Chan, Lang Lao, and Ron Waltz attended an ITER Simulation Workshop hosted by the Peking University to solicit opinions from international scientists and the Chinese fusion community on how to develop simulation capabilities in China to support ITER.

May 19, 2006

A 64-bit parallel version of the GCNM solver, called GCNMP, (Globally Convergent Newton Method-parallel) was developed. The solver includes the basic tokamak transport equations as originally developed for the ONETWO code with GLF23 as the primary energy transport vehicle. The modular nature of GCNMP allows it to interact with all transport related physics codes (eg. neutral beam, RF heating and current drive, MHD, etc.). In addition, GCNMP can utilize adaptive grids (variable size and spacing) and a variable number of equations by simply creating state files that include the necessary information. GCNMP is now being tested and will be installed shortly at PPPL and ORNL for use by the NTCC and SWIM projects.

Emily Belli arrived at GA to work as an ORISE Postdoctoral Fellow on developing gyrokinetic-based computational models for studying tokamak edge plasmas.

May 12, 2006

The validity of the quasilinear (QL) theory for resonant interactions of ions and ICRF waves with realistic magnitude was examined using the Monte-Carlo code ORBIT-RF for an Alcator C-Mod fundamental heating experiment. Preliminary calculations with just the mean QL “kick” turned on and no collisions in ORBIT-RF show that the relative phase between the wave and particle becomes highly stochastic in the resonance region with a wave electric field of 1 KV/m. This value is typical for the power levels used in the experiment. However, the relative change in particle magnetic moment due to the RF kicks remains small. The relative phase is rapidly randomized on a time scale much shorter than the thermal ion slowing down time. The origin of this randomization is that the rapid changes in particle orbit can lead to sampling of different local cyclotron frequencies and parallel wave numbers, which greatly affects the relative phase. These results appear to justify the use of a QL diffusion model.

May 05, 2006

The formalism for the gyrokinetic implementation of the equilibrium model of Miller et al. has been rederived in detail and extended to up-down asymmetry. In the process, minor errors that appear in the published literature (but had over time been corrected in numerical codes) were also corrected. The possibility of up-down asymmetry of plasma triangularity allows more realistic modeling of experimental tokamak equilibria. The new formulation has been added to GYRO, such that the coding is now fully consistent with the new documentation.

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