Theory Weekly Highlights for February 2005

February 25, 2005

Nonlinear GYRO simulations with kinetic electrons predict a strong turbulent particle pinch for positive magnetic shear with or without finite alpha (Shafranov shift) stabilization included. These calculations are being performed to create a transport database from GYRO scans over magnetic shear around a standard (STD) test case. The simulations are electrostatic and assume shifted circle geometry in an annulus with flat profiles. The particle diffusivity switches sign with weak positive shear, and is positive (outward flux) for reversed shear. The electron and ion energy diffusivities, however, remain positive for all values of magnetic shear and alpha. The database is part of a larger scan that also includes ExB shear scans for ITG and TEM transport, as well finite beta, safety factor, and alpha scans. The database will be used for benchmarking and to fit and test our new GLF transport model that is currently under development.

February 18, 2005

Instant Messaging (IM) service has been deployed in the fusion group. A secure server and multi-user chat module were installed, configured and tested. With this service, DIII-D researchers and collaborators can exchange text messages and present information in approximately real time. Multiple users can hold text conferencing as well. Two public chat rooms have been created and connected to several DIII-D operations-related software applications. By simply entering these chat rooms, users can monitor the experiment status, electronic logbook entries, and Data Analysis Monitor messages.

February 11, 2005

In a new calculation of angular momentum flux in the small rotation limit of neoclassical transport theory, a significant correction to a 34-year old result of M.N. Rosenbluth et al. from the 1970 IAEA (Plasma Physics and Controlled Nuclear Fusion Research Vol. 1, p495, 1971) was obtained. This correction involves both a sign and magnitude change, predicting a steady-state rotation in the opposite direction from the earlier theory. The new calculation relies on recent large-aspect-ratio perturbative results on distribution functions and involves a formulation using an equation adjoint to the customary linearized drift kinetic equation, bypassing the need to solve a second-order (in ion poloidal gyroradius over scale length) drift kinetic equation. The result can be used to predict steady-state toroidal rotation profiles for discharges with no momentum source using density, temperature, and q profiles.

February 04, 2005

The raw compute power of the LSF cluster was doubled and the number of processors increased by 42% with the addition of three new dual Xenon Linux computers. Each new machine is a 3.06 GHz Xeon, supporting hyperthreading, with 4 GB RAM and Gigabit Ethernet and is comparable to or better than the existing machines on the cluster in compute power. The new machines can be accessed directly using the new hostnames Eos, Hestia, and Phoebe. However, since most DAAG applications are automatically load leveled on the cluster, users do not need to change anything to take advantage of the new machines.

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