Theory Weekly Highlights for December 2003

December 19, 2003

Three Toshiba 50-inch DLP rear projection units purchased for the DIII-D Control Room will be mounted side by side near the physics operator's console to build 3072×768 pixel tiled-display. This new facility is expected to make the information of common interest easily available during the shot cycle and promote data analysis collaboration among scientists. It will be used to display real time shot status information, including plasma shape and between shot analysis, as well as plots from common data analysis applications. The latter includes both applications configured by the session leader and shared displays from scientists within the Control Room.

December 12, 2003

The Monte-Carlo RF orbit code, ORBIT-RF was upgraded to treat steady-state NB injection and ICRF absorption at higher ion cyclotron harmonics (ω=n*Ω, n > 2). Using a simple model for the magnitude of |E+|, simulations for the interaction of 80 keV D beam ions and 60 MHz ICRF waves at 4th harmonic resonance surface now reproduce the absorption observed experimentally in DIII-D in 1999. The energy spectrum from the neutral particle analyzer showed a strong enhancement of the tail energy above the NB injected energy, and, in the simulations, extended tail energies of beam ions above the injected beam energy are found in the central plasma region. An enhanced D-D reaction rate of about 20-30 % is also calculated due to the interaction of ICRF and beam ions, consistent with the significantly enhanced measured neutron rate. Additional DIII-D experimental results on the damping of waves on H and He3 beam ions at the second and third harmonic resonance, respectively, are being simulated. For quantitative comparisons and predictions, a more accurate wave model will be implemented to estimate the magnitude of |E+|.

December 5 2003

In collaboration with Scott Kruger of SAIC, simulations of several DIII-D and ITER discharges with NIMROD successfully utilized the new implementation of the vacuum region and wall. These include physics studies of tearing and interchange mode onset, and of high beta disruptions, for which the detailed geometry of the vacuum region is critical for comparing the simulations directly with DIII-D experiments. The high beta disruption simulations show field stochastization but toroidal and poloidal localization of heat deposition to the wall. The nonlinear generation of NTM seed islands in ITER from a sawtooth was simulated at very high spatial and temporal resolution, with realistic Lundquist number of S ~ 108 and real geometry; the size and nonlinear evolution of the driven island are sensitive to the geometry at high beta. Also, linear studies of edge localized modes in DIII-D equilibria have begun as a preliminary step to understanding the nonlinear evolution of ELMs.

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