STABILISATION OF THE M=2 TEARING MODE WITH APPLIED HELICAL FIELDS
The necessary response times for feedback stabilisation of the m=2 tearing mode with externally applied m=2 helical fields are examined. Since the timescales for full penetration of the applied field are much longer than the relevant times for the feedback, the cancellation of the m=2 island by the applied field is necessarily transient. Continued penetration of the applied field leads to an island whose phase is flipped' relative to the initial plasma island. This flip mechanism places constraints on the helical coil current. If the feedback helical field is not exactly anti-phased relative to the plasma island, then a net torque results which also tends to flip the plasma. This torque mechanism places constraints on the tolerable phase error and response times of the feedback helical field. For parameters consistent with JET and a phase error of 10circ, the necessary response time widetilde < 500 mus.
Bibliographic Reference: WRITE TO MAX-PLANCK-INSTITUT FUER PLASMAPHYSIK, 8046 GARCHING BEI MUENCHEN (GERMANY), MENTIONING REPORT IPP 5/21, 1988
Record Number: 1989126109700 / Last updated on: 1989-06-01
Available languages: en