The first measurements of internal currents in a toroidal heliac are reported. It is suggested that the toroidal current observed in the Small Heliac Experimental Apparatus (SHEILA) [Nucl. Fusion 25, 1485 (1985)] in the low density regime consists mainly of the bootstrap current and the Pfirsch–Schlüter current, the net toroidal component corresponding to the uni-directional bootstrap current, and the asymmetric radial profile of the observed current indicating a mixture of bootstrap current with the bi-directional Pfirsch–Schlüter current.

In this paper a comparison between theoretical calculations and experimental measurements of helicon wave coupling by a partial-tum shielded antenna in a toroidal heliac is presented. Despite the complicated heliac geometry, the wave dispersion, field profiles, and antenna radiation resistance are described well by a cylindrical uniform plasma theory. It also presents a simple formula relating the radiation resistance to the measured wave magnetic field per unit antenna current. Finally, the scaling of these results to the Heliac-l (H-l) [Fusion Technol. 17, 123 (1990)]; a larger heliac now operating at the Australian National University (ANU), is discussed.