Multi-device study of MHD modes locking in tokamaks*

Tearing modes amplitude is a key ingredient to develop physics based disruption prediction methods. Depending on the experimental situation, these modes may rotate or be locked prior to the disruption, which complicates their amplitude incorporation into a multi-machine approach. The aim here is to characterise the mode locking process across several devices. A database of >150 COMPASS, >220 AUG and >40 JET discharges with an initially rotating disruptive mode was therefore assembled. Database entries vary from quasi-stable NTMs to immediately locking radiative instabilities. The deceleration of an initially rotating resistive mode to the locked state via an interaction with the resistive wall and error fields has been described by a mode locking model in the past^1,2,3. Capability of the model to characterize the phenomenon in devices of various plasma sizes under broad distribution of plasma parameters (n_e, q₉₅, l_i etc.) will be tested.

¹M.F.F. Nave et al Nucl. Fusion 30 2575 (1990

²D.A. Gates et al Nucl. Fusion 36 273 (1996)

³R.J. La Haye et al Nucl. Fusion 46 451 (2006)