Theory Weekly Highlights for August 2009

August 28, 2009

TGLF transport simulations of 30 DIII-D hybrid discharges, focused on testing a new collision model against experimental data from DIII-D, show good agreement with both the ion and electron temperature profiles. In XPTOR transport simulations to predict the temperature profiles, using the version of TGLF presented at the 2007 APS meeting with the new collision model, the overall average RMS errors obtained for Ti and Te were both 13%. Analysis of the results shows that the predicted electron energy transport tends to be dominated by ETG modes. For hybrids with low q95 between 3.0 and 3.5, the ion energy transport is close to the neoclassical level. Discharges with higher values of q95 > 4.0 tend to have higher ion energy diffusivities with χi comparable to χe. Within the dataset are discharges with varying toroidal rotation and the TGLF model agrees equally well with both high and low rotation cases.

August 21, 2009

A new version of ReviewPlus has been installed on the LSF cluster. The changes, which were previously available in the ReviewPlus test version, include improvements to plotting speed and bug fixes. Signal resampling was re-enabled and is controllable via Preferences or Set Appearance. For MDSplus signals, tree names are now displayed in the plot label. The major bug fixes in the new version include correcting a problem with dropped characters in the signals table and restoring signal vs. signal plotting functionality.

R.E. Waltz from GA and John Krommes from PPPL represented fusion plasma turbulence at the Turbulent Mixing and Beyond 2009 international conference and advanced school at the International Center for Theoretical Physics, July 27-August 7, Trieste, Italy ( The conference covered a large range of turbulent mixing in many fields: ordinary fluids as well as plasmas, aerodynamics, astrophysics, magnetophysics, atmospheres, and oceans. Waltz gave an invited talk on “Gyrokinetic Simulation of turbulent transport in fusion plasmas”.

August 14, 2009

A new saturation rule based on the geodesic acoustic mode (GAM) frequency has been developed for TGLF that naturally gives the correct ratio of ETG to ITG electron thermal transport and fits the low-k GYRO simulation database better than the previous rule. The new model uses the acoustic mode frequency instead of the curvature drift frequency in the formula and has one less fit parameter than to the previous model. The new rule is consistent with the predator-prey paradigm for nonlinear saturation and was motivated by a recently published paper: R.E. Waltz, and C.G. Holland, “Numerical experiments on the drift-wave-zonal flow paradigm for nonlinear saturation”, Phys. Plasmas, 15, (2008) 0122503.

August 07, 2009

As part of the PTRANSP and IMFIT projects at GA, a standardized set of variables, sufficient to translate to and from a set of application codes, is under development using the self-describing NetCDF data format. An important and substantial part of both projects is the development of suitable interfaces for user-transparent communication between PTRANSP, GCNMP, ONETWO, and XPTOR, as well as other codes in the future. A summer intern student is making a significant contribution to this effort by creating cross-reference maps of the quantities involved.

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