Editing Plasma stability (section)

=== Feedback Control ===

Active feedback control of MHD instabilities should allow operation beyond the “passive” stability limits. Localized RF current drive at the rational surface is predicted to reduce or eliminate neoclassical tearing mode islands. Experiments have begun in ASDEX&ndash;U and COMPASS-D with promising results, and are planned for next year {{clarify|reason=Which year?|date=October 2014}} in DIII&ndash;D. Routine use of such a technique in generalized plasma conditions will require real-time identification of the unstable mode and its radial location. If the plasma rotation needed to stabilize the resistive wall mode cannot be maintained, feedback stabilization with external coils will be required. Feedback experiments have begun in DIII&ndash;D and HBT-EP, and feedback control should be explored for the RFP and other configurations. Physics understanding of these active control techniques will be directly applicable between configurations.