Tandem-mirror end plugs for future fusion reactors

Electrostatic fields for confining central-cell plasma are achieved by heating the electrons in end-plugs via electron-cyclotron-resonance heating. Four end-plug magnetic configurations are being developed and tested to determine which will provide the best thermal barrier between plug- and central-cell electrons in a fusion reactor: (1) the inside barrier, with its auxiliary solenoid (2) the auxiliary-mirror-cell (A-cell) barrier, which makes use of C-shaped magnet coils (3) the axisymmetric-cusp barrier, using circular coils and (4) the electron-ring barrier, in which two magnetic coils are stabilized by a ring of hot electrons. Calculations of the magnetohydrodynamic (MHD) stability are being performed with respect to the magnetic curvatures of each end-plug configuration. Models for describing the behavior of plasmas with finite ion orbits are being developed to predict MHD stability. Charge-exchange pumping systems for reactors with inside, A-cell, and axisymmetric-cusp barriers have already been designed, and a pumping system for removing thermalized helium ions is being explored