Electrostatic Mode Locking and Mode Suppression in RFPs and Tokamaks by Richard Nebel (x lead researcher at EMC2 Fusion)
In this paper we show that it is possible to lock and amplify m=1 modes from the boundary in an RFP by using electrostatic fields. Furthermore, it is possible to do this without any magnetic field lines penetrating the boundary (i.e. the normal component of the magnetic field vanishes at the boundary).
These can result in single-helicity states which have good flux surfaces everywhere. The key to forming these states is to drive one of the unstable RFP modes. For the unstable modes, perturbations from the boundary amplify into the interior (Resonant Field Amplification). This is consistent with the theory developed 20+ years ago that boundary perturbations can be described by the marginal ideal MHD equations.
We believe that these same ideas can be applied to suppressing modes as well, such as edge modes in Tokamaks. We derive the required phasings to implement this scheme. We also present a conceptual feedback control scheme for suppressing instabilities. This system consists of an array of electrostatic plates and radial magnetic field probes. This system forms an electrostatic smart shell which essentially uses the plasma to heal itself. This system eliminates the inductive losses and resistive timescale restrictions present in magnetic field systems
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