Theory Weekly Highlights for August 2000

August 18, 2000

A new version of the GATO ideal MHD stability code has been released for public use. The new version contains options for timing both the cpu and wall clock time in each of the key sections of the code, as well as options for controlling the buffering of data read from disk into memory during the matrix decompositions. The matrix decompositions are presently the most time consuming part of the code. The new release also includes several minor bug fixes and improved error checking and diagnostics to make it more useful to novice users. The new code has been fully benchmarked for a standardized set of sixteen separate cases and no significant differences were detected. The new timing and I/O options are expected to prove especially useful for optimizing the eigenvalue solver at large mesh sizes.

August 11, 2000

Results on neoclassical poloidal rotation have been derived which are relevant to the interesting situation of gradient lengths comparable to the ion banana width. A new expression for the ion poloidal flow velocity has been derived for the case of zero ion temperature gradient. It was necessary to carry the expansion in ion banana width to higher order than in standard neoclassical theory. The poloidal flow given by the new expression is proportional to the third power of the banana width, and would be zero in the usual small banana width limit of standard neoclassical theory. It depends on derivatives of the ion density and the radial electric field, and contains the effect of orbit squeezing as well as nonuniform toroidal rotation. In the case of uniform toroidal rotation, the expression gives zero poloidal flow, in agreement with general arguments based on particle constants of motion.

August 04, 2000

CERQUICK has been ported to Linux and has been running on the 12-processor Linux PC cluster STAR, between shots this past week. It produces the complete CERQUICK analysis (Ti, Vr, impurity density of all 40 chords at full time resolution) in about 4 minutes. Results are loaded to MDSplus as they come in. Previously only a few chords at selected times could be calculated between shots and the full profiles had to be done overnight.

A new, fully parallel particle code, FISH, is now available at GA for the study of nonlinear fishbone oscillations. FISH computes the self-consistent interaction of fact ions with the n=1 internal kink mode, and can be used to calculate the fast ion transport due to fishbone oscillations in reactor-size plasmas.

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