Beams of charge-and current-neutralized plasma will cross a transverse-magnetic field by a combination of collectiveplasma processes. These processes were studied for a high -to-low beta (/3 == plasma energy density/magnetic field energy density) hydrogen-plasma beam injected into a vacuum transverse magnetic field with nominal

Evidence is presented that an axial magnetic field of 100 kG has been compressed to 42 MG by an imploding neon gas-puff Z pinch on a 800 kJ, 7.5 MA, 60 nsec pulsed power generator. Machine electrical diagnostics and x-ray pinhole photographs indicate that this 420-fold field compression was produced by imploding plasma at high magnetic Reynolds number.

C:0ntrolled, ultrahigh axial :naglletic fields have been produced and measured in a gas-puff Z pmch. A O.S-MA. 2-cm-radlus annular gas-puff Z pinch with a 3-min repetition rate was imploded radially onto an axial seed field, causing the field to compress. Axial magnetic field com~ressions up to 180 and peak ~agnetic fields up to 1.6 MG were measured. Faraday rotation of an Argon laser (5154 A) in a quartz fiber on-axis was the principal magnetic field diagnostic. Other diagnostics included a nitrogen laser interferometer, x-ray diodes, and magnetic field probes, The magnetic field compression results are consistent with simple snowplow and self-similar analytic models, which are presented here. Even small axial fields help stabilize the pinches, some of which exhibit several stable radial bounces during a current pulse. The method of compressing axial fields in a gas-puff Z pinch is extrapolable to the order of 100 MG. Scaling laws are presented. Potential applications of ultrahigh axial fields in Z pinches are discussed for x~ray lasers, inertial confinement fusion, gamma-ray generators, and atomic physics studies. 3831

The propagation of plasmoids (neutralized ion beams) in a vacuum transverse-magnetic field has been studied in the University of California, Irvine laboratory for several years [Phys. Fluids 24, 739 (1981); 25, 730, 2353 (1982); 26, 2276 (1983); J. Appl. Phys. 64, 73 (1988)]. These experiments have confirmed that the plasmoid propagates by the E×B drift in a low beta and high beta plasmoid beam (0.01<β<300), where β is the ratio of beam kinetic energy to magnetic field energy. The polarization electric field E arises from the opposite deflection of the plasmoid ions and electrons, because of the Lorentz force, and allows the plasmoid to propagate undeflected at essentially the initial plasmoid velocity. In these experiments, plasmoids (150 keV, 5 kA, 50–100 A/cm2, 1 μ sec) were injected into transverse fields of Bt=0–400 G. Anomalously fast penetration of the transverse magnetic field has been observed as in the ‘‘Porcupine’’ experiments [J. Geophys. Res. 91, 10,183 (1987)]. The most recent experiments are aimed at studying the plasmoid propagation dynamics and losses in the presence of a background, magnetized plasma which is intended to short the induced polarization electric field and stop the beam. Background plasma was generated by TiH4 plasma guns fired along Bt to produce a plasma density, np =1012 −1014 cm−3 . Preliminary results indicate that the beam propagation losses increase with the background plasma density; compared to vacuum propagation, roughly a 50% reduction in ion current density was noted 70 cm downstream from the anode for np∼1013 cm−3 . Principal diagnostics include magnetically insulated Faraday cups, floating potential probes, calorimeters, microwave interferometer, and thermal-witness paper.

Radio frequency (RF) waves can provide heating, current and flow drive, as well as instability control for steady state operations of fusion experiments. A particle simulation model has been developed in this work to provide a first-principles tool for studying the RF nonlinear interactions with plasmas. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation. This model has been implemented in a global gyrokinetic toroidal code (GTC) using real electron-to-ion mass ratio. To verify the model, linear simulations of ion plasma oscillation, ion Bernstein wave, and lower hybrid wave are carried out in cylindrical geometry and found to agree well with analytic predictions.