[en] Two new methods are proposed and illustrated for spectroscopic diagnostics of nonthermal electric fields in plasmas. These methods were used to analyse H_α and H_β profiles from a Plasma Opening Switch experiment

[en] Abstract only

[en] Two new methods are proposed and illustrated for spectroscopic diagnostics of nonthermal electric fields in plasmas. These methods were used to analyse H_α and H_β profiles from a Plasma Opening Switch experiment. copyright 1997 American Institute of Physics

[en] Published in summary form only

[en] Plasma wave-wave and wave-particle interactions are studied in a linear magnetized plasma. The relatively quiet plasma is produced by an argon gas-discharge. The plasma density is n_e ≅ 10⁹ cm^-3 and the electron/ion temperatures are T_e ≅ 5eV and T_i = 0.05eV. A grid and a four ring antenna, both mounted on a scanning carriage, are used to launch electrostatic ion waves in the plasma. Laser Induced Fluorescence measurements of both the linear and the nonlinear plasma response to the wave fields are presented. The Vlasov-Poisson equations are used to explain the measured zero, first and second order terms of the ion distribution function in the presence of wave fields. In addition to the broadening (heating) of the ion distribution as the authors increase the wave amplitudes, induced plasma flows are observed both along and across the magnetic field

[en] A novel gaseous plasma gun (PG) was developed for spectroscopic investigations of the plasma behavior in a cylindrical Plasma Opening Switch (POS) in the nanosecond time region. The PG injects the plasma radially outward from inside the high-voltage inner conductor to fill the region between the two conductors. The PG uniformity, reproducibility, electron density and temperature, and plasma flow velocity were determined using floating probes, biased charge collectors, fast photography, and spectroscopic methods. The POS operation was examined for various plasma parameters for a positive polarity of the inner conductor. Eight β loops and two Rogowski coils were used to measure the upstream and downstream currents. Ion current flowing during the switch operation from the plasma through the cathode was measured by two arrays of four collimated Faraday cups placed on two opposite sides of the plasma switch. Spectroscopic observations of high spatial and spectral resolutions of various particle velocities in the plasma were made. Excited level populations, velocity distributions, and directed velocities for various ions are discussed. Measurements of a secondary plasma originating from both electrodes are presented

[en] Abstract only

[en] Published in summary form only

[en] Electrostatic ion cyclotron wave fields are determined in a magnetized and weakly collisional plasma. A phased-locked Laser Induced Fluorescence (LIF) diagnostic is used to directly measure the wave perturbed ion velocity distribution. Comparing these local LIF measurements with a theoretical model uniquely determines the wave parameters, such as the wave potential, the three-dimensional wave vector, and the effective wave damping. The self-consistent wave endash particle interaction is modeled by Boltzmann endash Poisson equations in the limit of weak collisions. The wave parameters determined from local measurements agree with those determined from spatial scans. copyright 1996 American Institute of Physics

[en] The electron density, the electron kinetic energy, the particle motion, and electric fields in a coaxial positive-polarity plasma opening switch (POS) were studied using spectroscopic diagnostics. A gaseous source that injects the plasma radially outward from inside the inner POS electrode was developed. The plasma was locally seeded with various species, desired for the various measurements allowing for axial, radial, and azimuthal resolutions both prior to and during the 180 ns long current pulse. The electron density was determined from particle ionization times and the electron energy from line intensities and time dependent collisional-radiative calculations. Fluctuating electric fields were studied from Stark broadening. The ion velocity distributions were obtained from emission-line Doppler broadenings and shifts. The early ion motion, the relatively low ion velocities and the nearly linear velocity dependence on the ion charge-to-mass ratio, leads to the conclusion that the magnetic field penetrates the plasma early in the pulse. The ion velocity dependence on the axial location were thus used to infer the time dependent axial distribution of the magnetic field, indicating the formation of a relatively high current density at the load-side edge of the plasma. This is expected to cause plasma acceleration towards the load, found to be supported by charge-collector measurements. The fast magnetic field penetration could be explained by mechanisms based on the Hall effect. copyright 1995 American Institute of Physics