Locked Mode Instability in HL-1M Tokamak

Locked modes are observed in many Tokamaks. The locked mode is typically a purely growing, non-rotating, non-axisymmetric magnetic field perturbation with poloidal mode number m=2 or 3 and toroidal mode number n=1. Major disruption often appears after mode locking. Locked mode is often triggered by error field, which is resulting from slight irregularities and shape variation of poloidal or toroidal field coils, magnetic material or eddy current in the vacuum vessel. It may be produced due to the change of