Tearing modes in tokamaks typically rotate while small and then lock at a
fixed location when larger. Research on present-day devices has focused almost
exclusively on stabilisation of rotating modes, as it has been considered
imperative to avoid locked modes. However, in larger devices, such as those
contemplated for tokamak reactors, the locking occurs at a smaller island size,
and the island can be safely stabilised after locking. The stabilisation of
small locked modes can be performed at lower wave power and broader deposition
compared to rotating islands. On large devices, it thus becomes surprisingly
advantageous to allow the mode to grow and lock naturally before stabilising
it. Calculations indicate that the ITER international megaproject would be best
stabilised through this approach.Comment: 6 pages, 4 figure