By injecting the lower hybrid wave into the microwave discharge plasma at the electron-cyclotron resonance in the WT-2 toroidal device, the toroidal plasma current is generated, started up to /^^ 5 IcA, and sustained by rf power alone, without the Ohmic heating power (rf tokamak). This lower-hybrid-wave-driven current is produced only when high-energy tail electrons, which interact resonantly with the lower hybrid wave, are present in the initial electron-cyclotron resonance plasma.

By injection of microwave power P EC near the electron cyclotron (EC) frequency into an Ohmically heated (OH) plasma in the WT-2 tokamak after OH power is shut off, the plasma current is sustained and ramped up by the EC wave only, without OH power. Here, EC-driven current is generated by EC heating of the suprathermal electron beam in OH plasma. Further, when P EC is injected into plasma sustained by lower-hybrid-(LH-) driven current, the plasma current and its rampup rate increase. Here, EC-driven current is generated by EC heating of the mildly relativistic electrons in LH-driven plasma.

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Slow cyclotron and Cherenkov instabilities are analyzed self-consistently for unbounded and cylindrical slow wave systems considering electron beam propagating along the direction of a guiding magnetic field. There are two electromagnetic modes present in the beam that are self-consistent solutions of Maxwell's equations. The wave equation in the beam becomes the Altar-Appelton-Hartree equation in the limit of zero beam velocity. For the unbounded system, the beam couples with the electromagnetic modes corresponding to the X and O modes, resulting in the slow cyclotron and Cherenkov instabilities, respectively. For the cylindrical system, axisymmetric electromagnetic modes in the beam are obtained by superposing the plane normal modes of the unbounded system. Since self-consistent boundary conditions require all field components, axisymmetric electromagnetic modes of cylindrical system are hybrid modes, which are classified as axisymmetric EH and HE modes. The slow cyclotron and Cherenkov instabilities occur for both axisymmetric modes. The temporal growth rate is calculated for each of the instabilities and compared.

Off-axis electron-cyclotron heating in an axisymmetric barrier mirror produces a cylindrical layer with energetic electrons, which flow through the central cell and into the end region. The layer, producing a localized bumped ambipolar potential Phi(C), forms a strong shear of radial electric fields E(r) and peaked vorticity with the direction reversal of E(r)xB sheared flow near the Phi(C) peak. Intermittent vortexlike turbulent structures near the layer are suppressed in the central cell by this actively produced transverse energy-transport barrier; this results in T(e) and T(i) rises surrounded by the layer.

A divertor magnetic configuration is an alternative method of obtaining interchange mode stability in the central cell of the GAMMA10 tandem mirror (Cho et al 2005 Phys. Rev. Lett. 94 085002). Various divertor configurations are investigated in the central cell of GAMMA10 to determine the best configuration. The equilibrium in the divertor configuration is calculated using the generalized Grad–Shafranov equation with anisotropic plasma pressure to estimate how high a plasma pressure is sustained by the magnetic divertor.

Experimental studies of electron cyclotron heating in a stellarator plasma have been carried out by injecting 40 kW of 35.5 GHz microwave power. Electron cyclotron heating with the ordinary and the extraordinary modes injected from the low-field side show almost the same heating efficiency of 2.2 × 1013 eV·cm−3·kW−1 at the average electron density of 6 × 1012 cm−3. Efficient heating by the extraordinary mode in the presence of the cyclotron cut-off is interpreted to be achieved by the penetration of scattered waves from high- and low-field sides, polarization being disturbed by microwave reflection from the vacuum chamber wall.

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