Theory Weekly Highlights for October 2012

October 26, 2012

The shortfall in predicted L-mode near-edge turbulence and transport in gyrokinetic (GK) simulations and transport models like TGLF (fitted to GYRO simulations) is a persistent problem. GYRO simulations with ion drift-kinetics (and no gyro-averaging) substantially increase the low-k turbulence and transport intensity (3 to 4-fold). This suggests that the 5D gyrokinetic approximation, which averages over the gyro-phase and precludes any effect of high ion cyclotron frequencies, may be breaking down at the high turbulence levels in the L-mode edge. A reduced model, implemented in the code rCYCLO, has been developed for 6D cyclokinetics (CK), to test the breakdown of 5D gyrokinetics by following dynamics in the gyro-phase. Comparing CK and GK simulated transport levels in a simple geometry will be used to test the breakdown of gyrokinetics.

October 19, 2012

Recent developments to OMFIT (One Modeling Framework for Integrated Tasks) have facilitated its use in a variety of DIII-D applications. OMFIT is a development environment aimed at easing the integration among different codes. The OMFIT framework has been used for control-room analysis of gyro-kinetic stability and MHD stability of non-inductive, high qmin, H-mode experiments. Recently the OMFIT framework has been used to test the RMP-induced magnetic flutter transport model with the DIII-D experiments and to compare the experimentally measured torque with predicted Neoclassical Toroidal Viscosity models using data from the two-fluid MHD code M3D-C1. Recent developments of the framework include: The ability to run the code in parallel, both locally and remotely, possibly on multiple machines; direct access to PTDATA in addition to MDS+; comparison and merging of files/modules/projects; descriptions of variables based on an innovative context-based system; support for the LLNL PDB and GA input files. Also the GKS/TGLF gyro-kinetic stability and the ONETWO/GCNMP and FASTRAN transport modules are available. Finally the ability to interactively edit plots generated within OMFIT has been added, which speeds up the process of data analysis and production of publication quality graphics.

October 12, 2012

A rigorous, unified theory of pellet ablation was developed that includes pellet materials of arbitrary atomic number Z, and covers the entire domain of pellet sizes and plasma parameters relevant to toroidal fusion devices. Such large data sets can be systematically reduced to a manageable form, where the physical properties of the pellet-plasma system may be judiciously combined to form only two non-dimensional parameters. Analytical formulae and a graphical calculator, involving the two non-dimensional parameters, are derived allowing ablation rates and pellet penetration distances to be readily computed and compared with experiments. In the limit that the sublimation energy of the pellet becomes vanishing small the ablation rate of “iceball” pellets of arbitrary Z is recovered.

October 05, 2012

Nagios, a widely used open source infrastructure monitoring application, has been installed on several DIII-D systems. It has been used for monitoring and alerting for services and resources including machine availability, CPU load, disk space, and number of IDL licenses. Nagios has also been customized for code regression testing on GYRO and TORAY. More features and systems are expected to be added to Nagios in the near future.

Eric Bass, Nate Ferraro, Val Izzo, Phil Snyder, and Gary Staebler will be presenting recent work at the IAEA Conference in San Diego next week.

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