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.

Slow waves launched by phased waveguides in the frequency interval between the lower hybrid and the electron plasma frequencies have been studied with an RF probe. The data demonstrate wave penetration to the plasma interior only if the accessibility criterion is satisfied.

A dielectric-loaded waveguide array has been used to launch fast waves into a plasma in which omega //p//i less than omega VM LS TH OMEGA //p//e approximately equals OMEGA //c//e. The wave propagates when accessibility and cut-off requirements are satisfied. Reflection coefficients as low as 1% have been measured. Use of the fast wave for steady-state current drive is suggested.

Low-power (<50 W) lower-hybrid waves excited in a linear plasma were observed to drive electron currents (a few milliamperes per watt) in the direction of the wave momentum when the waves were collisionally damped. An approximate solution of an electron kinetic equation with a Lorentz collision operator predicts an electron current in this experimental regime (k vt 1). © 1980 The American Physical Society.