3D MHD Equilibrium and Stability

                   

Principal Investigator

Henry Gardner

Department of Computer Science,

Faculty of Engineering and Information Technology

For some decades there has been an international scientific and engineering program to study the
containment of plasmas by toroidal magnetic fields with the aim of developing a fusion power reactor. Australia presently makes a major contribution to this program through the H-1NF Heliac which is a "stellarator" experiment located at ANU and is funded through the Major National Research Facility Program. Stellarators are an alternative to the better known "tokamak" types of experiments but have the great advantage of not needing large currents within the plasma in order to generate helical field lines. On the debit side, the lack of axial symmetry of stellarators makes their theory more complicated and simulation more computationally expensive than for tokamaks. In particular, the simply nested magnetic surfaces found in tokamaks can be broken and give rise to magnetic islands and regions of chaotic magnetic field lines.
This project aims to simulate plasma equilibrium within H-1NF. The simulation treats the plasma as a single conducting fluid which is a sufficiently accurate approximation to find reasonable equilibrium solutions. A major part of the study concentrates on understanding the growth of magnetic islands with plasma pressure.

 

Co-Investigators

Sally Lloyd

Department of Theoretical Physics

Robert Dewar

Department of Theoretical Physics,

Research School of Physical Sciences and Engineering

David Singleton

ANUSF

     

Projects

k12 - VPP

     
             
                   

   
                   

What are the results to date and the future of the work?

Much of 1998 was spent studying the long-term convergence of the HINT code and analysing the effects of longitudinal currents in the plasma on the equilibrium characteristics. It turns out that the flat "rotational transform" profile of H-1NF makes it very susceptible to small longitudinal currents and considerable effort needs to be made to determine whether these are real effects or not. On the answer to this question, could hinge the determination or otherwise of island "self-healing" in H-1NF.

   
                     
- Appendix A
   

     
                     

       

What computational techniques are used?

The HINT code, developed by T. Hayashi, is used as the basis of this study. This code solves time-dependent, resistive MHD equations on a specially-shaped coordinate grid. Relaxation along field lines is much slower than perpendicular to them and is treated using a special interpolation algorithm which has been developed as part of this project (pressure is averaged along field-lines and interpolated back to the fixed grid).

Publications

S. S. Lloyd, H. J. Gardner, T. Hayashi and S. R. Hudson, Self Healing of Magnetic Islands in a Heliac, J. Plasma Fusion Res. SERIES, 1, 484 (1998).

       
Appendix A -