Inductive energy extraction from a plasma

Efficient operation of a moving-ring reactor requires inductive energy extraction from the plasma after the thermonuclear burn is complete. The process of inductive energy extraction from a plasma is studied in this paper. An energy conservation theorem is proven, whose content is that the amount of energy which may be extracted inductively from a plasma is the sum of three terms: the self-inductance energy of the plasma, the energy associated with the mutual inductance between the plasma and the external field coils, and the plasma thermal energy. These terms are evaluated for a spherical Hill's vortex equilibrium. For this equilibrium, the sum of the first two terms is negative, i.e. for fixed external field the magnetic energy is lower when the plasma is present than when it is absent. This surprising fact is discussed and shown not to lead to any unphysical consequences. A careful analysis of a conceptual energy extraction device is given, with emphasis on the role of inductive interactions between the plasma and the external coils. (author)