Feedback stabilization of magnetic islands in tokamaks

The major tokamak disruption limits the operation of present tokamaks, and present experimental evidence points to the m = 2, n = 1 tearing mode as being primarily responsible for its occurrence. Numerical codes capable of following the full nonlinear history of this mode have been used to develop and test feedback stabilization schemes utilizing helical coils mounted on the interior of the tokamak wall. It is found that a phase detecting feedback system is capable of stabilizing the magnetic island at an island width of a few percent of the tokamak minor radius, requiring a coil current of one to two kiloamps for typical discharge parameters