Influence of trapped thermal particles on internal kink modes in high temperature tokamaks
The effects of thermal trapped particles on the n = 1 internal kink mode are studied using drift kinetic theory. Strong modifications of the magnetohydrodynamic (MHD) results are found, and marginal stability generally occurs at non-zero rotation frequency. For equal electron and ion temperatures, the trapped particles increase the marginal poloidal beta at q = 1 substantially above the MHD value. For unequal electron and ion temperatures, the drift resonance with the hotter species becomes increasingly destabilising, and for sufficiently unequal temperatures, this leads to instability below the ideal MHD threshold. Treatment of trapped thermal particles requires consideration of the effects of an electrostatic potential. The potential is weakly stabilising for the internal kink mode. Furthermore, finite beta couples unstable, nearly electrostatic, trapped particle modes to the internal kink mode. At high beta, thermal fluctuations of the trapped particle modes can lead to significant internal kink displacements.
Bibliographic Reference: Report: LRP 476/93 EN (1993)
Availability: Available from Confédération Suisse, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, 21 avenue des Bains, 1007 Lausanne (CH)
Record Number: 199311067 / Last updated on: 1994-11-29
Original language: en
Available languages: en