Active feedback stabilization of axisymmetric modes in highly elongated tokamak plasmas
Active feedback stabilisation of the vertical instability is studied for highly elongated tokamak plasmas (values of kappa in the range 2 to 3), and evaluated in particular for the TCV configuration. It is shown that the feedback can affect strongly the form of the eigenfunction for these highly elongated equilibria, and this can have detrimental effects on the ability of the feedback system properly to detect and stabilise the plasma. A calculation of the vertical displacement that uses poloidal flux measurements, poloidal magnetic field measurements, and corrections for the vessel eddy currents and active feedback currents was found to be effective even in the cases with the worst deformations of the eigenfunction. The paper examines how these deformations affect differently shaped equilibria, and it is seen that the magnitude of the deformation of the eigenfunction is strongly dependent on the plasma elongation.
Bibliographic Reference: Report: LRP 480/93 EN (1993) 36 pp.
Availability: Available from Confédération Suisse, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, 21 avenue des Bains, 10 07 Lausanne (CH)
Record Number: 199311116 / Last updated on: 1994-11-29
Original language: en
Available languages: en