Kinetic theory of magnetic island stability in tokamaks
The non-linear behaviour of low and large wave number tearing modes is studied with emphasis on diamagnetic effects. A kinetic equation is used to describe the electron component. Transport processes are shown to play a significant role in the adjustment of density and temperature profile and also in the calculation of the island rotation frequency. The fluctuating electric potential is calculated self-consistently, using the differential response of electrons and ions. Four regimes relating to island width and transport regime are considered. It is shown that diamagnetism does not influence the island stability for small island width in the viscous regime, as long as the constant A constraint is maintained. However, release of this constraint may strongly modify the previously calculated stability thresholds. Finally, it is found that diamagnetism is destabilising (stabilising) for island width smaller (larger) than an ion Larmor radius, in both resistive and viscous regimes. A typical island evolution scenario is studied and the main results of the work are summarised.
Bibliographic Reference: Report: EUR-CEA-FC-1500 EN (1993) 29 pp.
Availability: Available from CEA, Département de Recherches sur la Fusion Contrôlée, Saint-Paul-lez-Durance (FR)
Record Number: 199311518 / Last updated on: 1994-11-28
Original language: en
Available languages: en