Modeling transport in toroidal plasmas: Status and issues

Abstract

The scope and detail of physics contained in computational models for fluid (density, momentum, energy) transport in toroidal plasmas have steadily increased during the past two decades. There has been considerable success in the development and verification of models for sources and sinks of particles, energy, momentum, and magnetic flux. Transport codes have collectively become very useful tools in interpreting experimental data and in providing guidance for new experiments. However, a more thorough understanding of the fundamental transport processes of magnetically confined plasmas and development of improved computational models are needed to enhance the predictive capabilities of transport codes. It is argued that fluid transport modeling by itself cannot lead to a complete understanding of transport—there must be a very strong collaboration among theory, experiment, and modeling on both the fluid and kinetic levels.

Self-sustained turbulence and H-mode confinement in toroidal plasmas

“…In equations ( 1)-( 3), the finite ion gyro-radius effect and electron pressure term in Ohm's law are neglected. Namely, cold ion approximation is made in vorticity equation (1), which leads to the neglect of the ion diamagnetic frequency. Furthermore, no parallel term is employed in equations ( 2) and ( 3).…”

“…Although the phenomenological knowledge has increasingly been improved, the fundamental understanding is far from satisfactory. (For a review of recent status see [1][2][3][4][5][6].) One of the working hypotheses to explain the anomalous transport is that it is caused by fluctuations in the confined plasma, and that the fluctuations are sustained by microscopic instabilities (e.g.…”

Effect of power deposition and current evolution on the formation of internal transport barriers

“…Due to the physical complexity of magnetically confined plasmas, much effort has been devoted to the task of building a predictive transport model with a fair general applicability [1,2], and this is still an active field of research. Aside from the vast family of processes that can determine equilibrium profiles, an added complication arises from the realization that transient phenomena can be of importance in addressing the path that the plasma follows to reach a final state.…”

Visualization of magnetically confined plasmas

“…However, despite a considerable, world wide, effort over the last few decades the understanding of confinement is still relatively poor. As an unsatisfactory consequence, the next generation of large scale experiments are presently designed with the use of empirical or semi-empirical scaling laws [13,15]. Consequently, an increased understanding of transport of energy and particles across magnetic fields is of extreme importance.…”