Excitation of Trivelpiece–Gould Waves and Helicon Waves by Double-Saddle Antenna in H-1 Heliac Plasma

The threshold conditions for Trivelpiece–Gould (TG) wave and helicon wave excitation by double-saddle antenna in H-1 are studied. The propagation condition for TG waves is more lenient than that for helicon waves, and the transparency region of helicon waves is smaller than that of TG waves in the plasma density–magnetic field strength plane. At low magnetic fields B < 0.14 T, the threshold density for the excitation of helicon waves gradually increases with B. The temporal evolutions of the wave eigenmodes, radial field structure, power deposition, and density are interdependent on each other, and the excitation of helicon waves with quenched TG waves drives |Re(Er)| up to a maximum in the plasma core, which may be an important factor affecting the L–H transitions in H-1.