[en] The production of anomalous resistivity in a Q-machine plasma by a large amplitude, longitudinal rf electric field is described. Noncontact diagnostics have been developed to measure the longitudinal and azimuthal components of the resistivity. The implication of these measurements with regard to proposed ''catalytic heating'' of toroidal plasmas is described

[en] Linearly polarized electromagnetic waves, with power densities up to 12 watts/cm² (f = 2.45 GHZ) are propagated in a cylindrical waveguide which is located in an external magnetic field. Plasma, with density N/sub e/ approximately 2 x 10¹¹ cm^-3 and T/sub e/ = 8-10 eV and 30 cm axial length, is produced by electron cyclotron resonance. At this density the left component of the incident wave is nominally cut off. For a suitable choice of experimental parameters one finds that approximately 25 percent of the power in the left wave is transmitted through the plasma. The transmission occurs for a period of time 0 less than t less than tau following application of the RF. Transmission ceases suddenly at t = tau and the plasma for t greater than tau is opaque. Dynamic measurements of the plasma density profile and distribution of EM fields within the plasma during the transmission period are presented

[en] Ion loss flux from a line cusp was suppressed to a few percent by using the rf plug whose resonance frequency was somewhat above the ion cyclotron frequency. The loss rate and the resonance frequency as a function of the ion density were obtained experimentally in the range of n/sub i/ = 10⁸ approximately 2 x 10¹¹ cm^-3, and the results were in good agreement with the theory based on the collective behavior of a plasma. The ambipolar potential produced by charge separation and the suppression of electron loss accompanied with it were also observed. The dependence of the loss rate on the ion energy was measured in a mirror configuration. The ion cyclotron resonance plugs have very small effect for heavy impurity-ions with low degree of stripping. The possibility of impurity-free containment thereby conceived was demonstrated experimentally by using a plasma composed of several ion-species

[en] An rf field travelling along the torus is observed to induce a dc toroidal current in a magnetized plasma. The travelling field is applied to the plasma by employing a delay-line wound around the toroidal glass discharge tube. The phase velocity of the field is approximately equal to the electron thermal velocity. The direction of the current is opposite to that of the wave, indicating that the electrons are trapped in the magnetic mirrors composed of the travelling wave. The density of the trapped electrons reaches 10 percent of the background plasma density at an optimum condition. On the basis of the electron trapping model, the required rf power for current sustaining in a Tokamak fusion reactor is estimated and found to be reasonably small in comparison with the output power of the reactor

[en] The accessibility condition and the damping length of the ion--ion hybrid wave are calculated numerically in the density region of 10¹⁰ to 10¹⁷ cm^-3 using the Langevin collision model, with the ion--ion collision frequency, the parallel wave number, and the D-T concentration ratio as the parameters. It is shown that the heating is effective even for very low collision frequencies encountered in thermonuclear plasmas

[en] This review provides a key to the literature describing ionospheric heating experiments carried out at Platteville and Arecibo, and to the theoretical work directed towards explaining detailed features of the results

[en] The design of a large-volume, versatile, efficient microwave plasma source is described. The source consists of a quartz tube surrounded by a cylindrical, variable-length cavity which is connected to a microwave power source. The lossy plasma-cavity eigenfrequencies are computed as functions of plasma density, effective collision frequency and cavity length. The circuit performance of the plasma-cavity system is qualitatively explained based on these eigenfrequency calculations. Experimental results demonstrate that a variable, high-density plasma with densities in excess of 1000 critical densities can be sustained. By adjusting cavity length and coupling, microwave plasmas can be sustained in flowing and nonflowing argon gaseous environments from pressures of several microns to over one atmosphere. Applications of this plasma source in two areas are described: (1) plasma chemistry experiments and (2) parametric instabilities under the influence of strong rf electric fields

[en] One of the more attractive techniques for the supplementary heating of large tokamak devices involves the application of radio frequency power near the lower hybrid frequency (LHF). The fundamental engineering advantages of this approach are twofold: (1) At frequencies corresponding to the LHF (1-3 GHz) in reactor-sized tokamaks, very powerful (approximately 0.5 MW, continuous wave) sources already exist. (2) The power may be transmitted to the plasma by means of waveguide, so that one has a ''coil-less'' rf injection system. The characteristics of the rf produced plasma were studied to develop the parametric gap between the test devices and the ATC Tokamak

[en] Electron and ion heating have been observed when rf at a frequency close to the lower hybrid resonance is coupled electrostatically into a hot electron plasma by means of an appropriate structure. The rf heating frequency is 10 MHz at a power of 500 W. The hybrid layer is identified with a rf interferometer correlated with density measurements. The electron temperature profile shows that the heating zone is located on the low density side of the hybrid layer. Plasma is expelled from the heating zone along the magnetic field lines. Relativistic electrons produced by the ECRH source at low pressure tend to limit the amount of electron heating by the rf, and a slight increase in ion temperature occurs as well. The maximum electron heating appeared to occur whenever the product of the perpendicular wave number and the electron gyro radius was approximately unity

[en] In a computer simulation study, the parametric heating of electrons when an electromagnetic pump wave propagates through the plasma parallel to the dc magnetic field was observed. The heating mechanism is parametric excitation of resonant electrostatic waves which trap electrons. Consequently, the electron distribution function develops a high velocity tail. The details of these processes are discussed. It was found that the energy of the electrons will increase by a factor of about 4. It is determined that the distribution function after heating will relax to Maxwellian in about 11 electron-electron collision times