Traveling-Wave Antenna for Exciting Waves in a Cylindrical Anisotropic Plasma

Several variations of a newly proposed device for exciting ion cyclotron waves in a magnetoplasma are analyzed theoretically and numerically. The results of this analysis are compared with those of a similar analysis of a Stix coil. The new coupler is composed of a set of identical helical straps driven by a multiphase rf source and excites waves that vary azimuthally as ejmθ where m =±1, ±2,…. The analysis reveals that the new coupler offers the following advantages over the Stix coil: (i) a certain degree of control over radial variations of accelerating fields, (ii) a preferred direction of propagation, (iii) more energy coupled into propagating waves (for a given input current), (iv) maximum loading resistance at a higher plasma density, and (v) a slightly wider effective density range for propagating waves.