Helical slow wave antenna for launching lower hybrid waves in a plasma

Abstract

The characteristics of a helical antenna employed for excitation of lower hybrid waves (LHW) in a plasma are investigated. The helical antenna is constructed by winding a cable on a glass discharge tube. It is shown experimentally that the helical antenna can excite LHW in a wide frequency range and with arbitrary refractive index parallel to the magnetic field. An increase of the longitudinal refractive index due to plasma loading is observed and analyzed by transmission line theory. Qualitative agreement is obtained between theory and experiment.