Summary


Objectives

The Second International Atomic Energy Agency Technical Meeting (IAEA-TM) on Theory of Plasma Instabilities is to provide a forum for open discussion on the physics issue of linear and non-linear theory in large and small scale plasma instabilities, integrated modelling, turbulence and magneto-hydrodynamic (MHD) effects. Special attention is to be paid to the modelling and prediction of instabilities generated by fast alpha particles and their role in the plasma confinement in burning plasmas. This subject is of significant importance in view of the International Thermonuclear Experimental Reactor (ITER) project and future fusion power plants performance.


Relevance for the IAEA activities

The relevance of this meeting for the IAEA activities is directly linked with the objectives stated in the Agency’s Subprogramme D.4. – Nuclear Fusion Research: to strengthen cooperation amongst major institutions and world wide commitment for plasma physics and nuclear fusion in order to create a viable source of nuclear energy through support to new and alternative fusion confinement concepts.


Scientific Summary

The meeting gave the opportunity for 49 scientists from 21 countries actively involved in this research field to present their latest work and discuss their results since the last meeting of this series held in 2002 in Kloster Seon.

New ideas for explaining and modeling the new different types of plasma instabilities and turbulence that have been found in plasma devices have recently emerged such as the interplay between different types of instabilities, cascades of instabilities and their interaction with plasma turbulence, etc. Plasma turbulence results in cross-field transport of one or two orders of magnitude larger than transport arising from neoclassical transport due to the binary collisions. The consequent reduction in plasma performance has implications on the development of fusion energy as an economic alternative power source. Thus a comprehensive understanding of plasma turbulence remains an important scientific objective.

In the turbulence topic, there were two common themes emphasized in many presentations.The first one consisted of examples of subtle nonlinear physics which are better understood in configuration space than in k-space, such as scale dependent anisotropy in MHD turbulence and turbulence spreading in tokamak plasmas. The second one was detailed studies of turbulent eddy shearing by zonal flows and zonal flow generation, which are two different manifestations of the same phenomenon.

In the transport area, recent advances in implementing more realistic and sophisticated physics models in various gyrokinetic simulation codes were highly visible.

Addressing the reactor relevant issues, there were continuous efforts in understanding collisional and turbulence induced toroidal momentum transport, and external control of turbulence via RF heating.

In the energetic particle physics area, there was a recurring message from all the speakers as to how well they understand the general features of toroidal Alfven eigenmodes. It was pointed out that, for ITER, it is important to understand the effects of two classes of fast particles (isotropic alpha particles and anisotropic fast ions due to auxiliary heating).

In the MHD area, mechanisms for the threshold island width for neoclassical tearing mode excitation were discussed in detail, including ion sound effects, finite orbit size effects, and effects of flows. A code was developed to address the interaction of small scale turbulence and large scale MHD phenomena. The status of mean field dynamo theory was reviewed as well.