Fusion Science and Technology / Volume 57 / Number 4 / May 2010 / Pages 335-342
This paper, part of a continuing study of means for the stabilization of magnetohydrodynamic interchange modes in axisymmetric mirror-based plasma confinement systems, represents a preliminary look at a technique that would employ a train of plasma pressure pulses produced by electron cyclotron resonance heating (ECRH) to accomplish the stabilization. The use of sequentially pulsed ECRH rather than continuous-wave ECRH facilitates the localization of the heated-electron plasma pulses in regions of the magnetic field with positive field-line curvature, e.g., in the "expander" region of the mirror magnetic field, outside the outermost mirror. The technique proposed relies on the time-averaged effect of plasma pressure pulses generated in regions of positive field-line curvature to overcome the destabilizing effect of plasma pressure in regions of negative field-line curvature within the confinement region. The plasma pulses, when produced in regions of the confining field having a negative gradient, create transient ambipolar electric potentials, an effect studied in 1964 in the PLEIADE experiment in France. These electric fields preserve the localization of the hot-electron plasma pulse for times determined by ion inertia. It may be possible to use this aspect of pulsed ECRH not only to stabilize the plasma but also to plug mirror losses in a manner similar to that employed in the tandem mirror.