Numerical and Theoretical Investigations of Z - Plasma Channels for Light Ion Beam Inertial Confinement Fusion.

Z-pinch plasma channels are investigated as beam transport channels for light ion beam inertial confinement fusion. The channels are intended to provide a high efficiency propagation path for the ion beams as they travel a distance of several meters from the extractor diodes to the target. The channels must satisfy several conditions to be useful as beam transport channels: their azimuthal magnetic field must be strong enough to confine the intense beams to a small radius, and the mass density in the channel must be great enough to provide a high degree of current neutralization for the beams. This research uses numerical simulations and theoretical models to investigate how the radial evolution of the z-pinch plasma channel can be controlled to satisfy these conditions. A theoretical model of the injection of an ion beam into the end of a channel is used to derive a condition that the channel must meet to confine a given amount of ion beam power to certain radius. This condition states that the peak magnetic field times the cube of the channel's radius must exceed a certain value that depends on the ion beam properties to be able to confine a given amount of ion beam power. Numerical investigations of the blast-wave expansion of the channel were used to develop a new blast-wave model. This model predicts that by properly changing the initial mass density and the peak discharge current, channels with identical hydrodynamic behaviors can be created. The inductive effect of the channels on the discharge circuit can be expected to be significant since the channels are several meters long. Numerical simulations and theoretical models are used to study this effect and to determine the factors that control the growth of the discharge current. Finally, a radiatively driven expansion of the electrically conductive channel is examined with numerical simulations. The investigations have demonstrated that the creation of channels that are capable of transporting light ion beams with power levels in the terawatt range appears to be feasible. However, channels that are capable of transporting tens to hundreds of terawatts of ion beam power appear more difficult to create. (Abstract shortened with permission of author.).