Feedback stabilization of axisymmetric MHD instabilities in tokamaks

A stability principle is derived and applied to simple tokamak configurations in order to study feedback stabilization of unstable, vertically elongated tokamak plasmas. For practical applicability it is assumed that the fast instabilities are slowed down by passive conductors so that only slow motions have to be considered. Numerical results are presented for a surface current model of plasma with one conjugate pair of axisymmetric feedback loops. Stabilization is possible, except in a limited region of loop positions. The optimum loop position in the region with possible stabilization is determined.

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