Steady-state electron currents were driven by fast waves with cice in an initially current-free plasma in the Irvine Torus. Current direction was controlled by the fast-wave phased-array antenna. Low power experiments (<25 W) generated up to 1.3 A of electron current with a peak effeciency of =InR/P(6×10-2 A/W)(1013 cm-3)m. Up to 14% of the wave energy was converted to poloidal magnetic field energy. © 1986 The American Physical Society.

We report the development of a new diagnostic capable of measuring plasma ion distributions as a function of all three velocity-space coordinates. The diagnostic makes use of laser-induced fluorescence (LIF) and computer-assisted image reconstruction techniques. LIF yields high-resolution, nonperturbing measurements of one-dimensional distributions that are integrated in two directions through three-dimensional velocity space. Computer tomography allows for the unambiguous determination of the complete ion velocity distribution. In addition to a description of the diagnostic, examples of recovered distributions obtained from experiments are given, and the effects of the major steps in the data processing are discussed.

Laboratory experiments have examined particular elements of proposed mechanisms for ion conic formation seen in the Earth's auroral-zone magnetosphere. A laser-induced fluorescence diagnostic measured the ion distribution function at many angles in velocity space, allowing tomographic techniques to reconstruct the multidimensional ion distribution function. Ion conics, as well as drifting Maxwellians, were observed. © 1986 The American Physical Society.

Calculations show that the fast wave near the lower hybrid frequency may be launched efficiently into large tokamak plasmas. Coupling efficiency is calculated for waves, which may be useful for current drive experiments in the Princeton Large Torus, the Tokamak Fusion Test Reactor, and reactor grade plasmas.

Fast waves with frequencies near the mean gyrofrequency [̂Ä(cice)12] were excited in a toroidal, magnetized plasma. Experimental measurements were made of wavelengths and phase velocities perpendicular to the toroidal magnetic field, and wave energy trajectories in the plasma, with varying wave frequency, plasma density, and magnetic field values. Experimental results agree with predictions from the cold-plasma dispersion relation. © 1986 The American Physical Society.

Convective flow zones were found to surround the discharge current in an electron-beam generated argon plasma. Flow zones were created by the electric field associated with the injected electron beam. A sheet-beam was injected along a confining magnetic field. The discharge current and voltage were varied, and the ion flow near the beam was studied via laser-induced fluorescence. It was observed that the drift velocity, and thus the inferred electric field, was nearly constant even with increasing current, yet the electron density of the beam did increase. © 2007 IOP Publishing Ltd and SISSA.

Temporal evolution of a depression of plasma edge density was observed near and away from a phased-array antenna launching lower-hybrid waves in a nearly fully ionized plasma. When equilibrium is reached, the magnitude of the depression is in agreement with ponderomotive theory. © 1982 The American Physical Society.

The ion phase space development and anomalous configuration-space and velocity-space transport in the near wake of a plasma-obstacle system have been investigated. The experiments were performed on the UCI Q-machine, using laser-induced fluorescence to measure the spatial evolution of the perpendicular ion velocity distribution. Ion and electron configuration-space transport and ion velocity-space transport were consistent with turbulent wave-particle interactions and agreed with observations in edge plasma-limiter regions of tokamaks. Near-wake ion acceleration resulted in local twofold increases in ion perpendicular kinetic energy densities over ambient plasma values. Large-amplitude, low-frequency noise (f ≤ 20 kHz), probably drift wave turbulence, was observed. Large density fluctuations (δn/n ~ 0.25) were inferred at the obstacle edge. The obstacle prewake exhibited density enhancements many Debye lengths upstream of the obstacle, indicating a collisionless shock front. The obstacle midwake displayed an ion flux peak. Numerical simulations were carried out to differentiate particle ballistic effects from other plasma effects. Results scale to several space-plasma-obstacle systems.

Electron currents can be driven in a linear plasma by the absorption of lower-hybrid waves excited primarily in one direction. Current-drive has been demonstrated both for collisional and resonant-electron absorption. The magnitude of the excited current is compared with the predictions from an electron kinetic equation with a Lorentz collision operator in the regime k ∥vte/ω ≪1. © 1981 American Institute of Physics.

We report the development of an improved optical tomography diagnostic which measures the velocity-space distribution of a laboratory plasma in two dimensions. The new device is capable of imaging plasma distributions over a wider range of magnetic fields and plasma column diameters than the previous design, while minimizing the risk of misdiagnosis due to perturbations caused by inserting the device in the plasma. Computer-aided control of the diagnostic allows a greater number of single-dimensional scans to be collected in a shorter amount of time, resulting in increased resolution of the reconstructed image while freeing up more time for the user to perform the experiment. Recent data using the new device are presented to show improvement of resolution gained by doubling the number of total scans. Finally, we present a method to identify velocity-space nonuniformities without the need to reconstruct a complete image.