Theory and simulation has become an essential partner with experiment in developing techniques to improve the confinement and stability of high performance fusion science experiments. Because of the large cost of the most advanced plasma confinement systems, especially those that can approach and enter a regime in which a burning plasma can be achieved, it is essential that we have the scientific understanding to predict the performance of planned devices. Such important insights are gradually built up from efforts to describe and predict the complex behavior of confined plasmas. These ideas have fundamentally transformed our picture of how a future fusion reactor might work and have become integral and essential parts of efforts to explore the burning plasma regime in a laboratory experiment. The development of new confinement concepts arose from the efforts to model and improve techniques for manipulating plasma containment.
There are significant areas where the traditional separation of the dynamics of plasma systems into microscale and macroscale processes breaks down. At large scale, these problems involve the dynamics of magnetic fields and flows while the kinetic dynamics of turbulence, particle acceleration, and energy cascade dominate the smallest spatial scales. The interaction between these vastly disparate scales controls the evolution of the system. The enormous range of temporal and spatial scales associated with these problems impose great challenges to state-of-art simulations intractable even in computations using the largest existing parallel computers. In the absence of new multiscale simulation techniques which exploit the separation of scales while still allowing dynamical interactions between scales, these problems will remain unsolved for the foreseeable future.
Current objectives are researches on the microturbulence, energetic particle physics, macro-instabilities, auxiliary heating and current drive through theory and simulations, where the large scale gyrokinetic toroidal code (GTC) is vastly utilized for physics investigations by extending the code capabilities to include the fast-electron, tearing mode, and fully kinetic ion descriptions.
Recent progress includes:
(1) large scale gyrokinetic particle simulations on fast-ion transport by ITG and TEM microturbulence;
(2) linear and nonlinear particle simulations of the Alfven instabilities;
(3) theoretical and simulation research on the tearing mode instability;
(4) developed physical model for drift-kinetic fast electrons, resistive tearing mode, and fully kinetic ion, which has been used to extend GTC capabilities for studying the fast electron driven modes, tearing mode and auxiliary heating.