Theory Weekly Highlights for May 2003

May 23 2003

The Monte-Carlo orbit guiding center code, ORBIT-RF, was improved, in order to study the interaction of ICRF waves with existing energetic particles. This required including the slowing down physics of Neutral Beam (NB) injected fast ions, with the source rate calculated as a function of NB power, beam energy and tangential radius. The first results using a single processor and 1000 Monte-Carlo test particles show that resonant heating with ICRF waves can extend the tail energy of the injected NB ions from their 80 keV birth energy to 100 keV. More quantitative benchmarking, employing parallel processing to permit the number of Monte-Carlo test particles to be significantly increased, is underway. Further progress is also planned, by coupling a full wave solver with ORBIT-RF to describe ICRF wave propagation self-consistently. In addition, the interaction of minority ions with ICRF at higher harmonics will be included in order to model DIII-D experiments.

May 16 2003

The GYRO code has now been modified to predict steady state profiles given experimental power flows. Since core transport power flows have a very stiff dependence on profile gradients, and these are not known very accurately from experiment, comparisons of simulated and experimental power flows for given experimental profiles are not very accurate. However, comparisons between the simulated and experimental temperature and density profiles, given the measured power flows, are meaningful. The new self-consistent transport profiles are obtained by pivoting around experimental temperatures and densities at a given radius, while feedback forcing the simulated flows to match the experimental flows. The method has been shown to work treating electron and ion energy and density flow channels simultaneously with runs about 3 times more expensive than previous standard full radius simulations.

May 09 2003

A new version of the inverse equilibrium code TOQ, version 4.0, has been made publicly available on the General Atomics website at: . In addition to updown asymmetry, this new version allows for direct reading of geqdsk files from EFIT and CORSICA/TEQ codes, and is also fully backward compatible with previous TOQ versions. TOQ allows for various unique physics analyses, such as self-consistent bootstrap current solutions, and this new version is now being coupled to the ONETWO code to provide accurate metric quantities for combined stability and transport physics studies.

May 02 2003

In collaboration with H.R. Wilson of Culham, a new formalism has been derived for the study of intermediate to high-n MHD instabilities, including compression and toroidal rotation shear. The formalism has been implemented in a new version of the ELITE code, which is structured in terms of complex matrices to allow for rotation and to substantially increase efficiency for up-down asymmetric stability calculations. This new version of ELITE was successfully benchmarked against GATO and MARS both with and without compression. Preliminary studies with rotation are now underway, and an appropriate rotational benchmark is being prepared. Studies of the impact of rotation shear on peeling-ballooning modes, thought to be responsible for ELMs, are planned. This new tool will also be used to study the edge stability of EHO discharges with rotation.

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