There is interest in the use of a helicon plasma source in propulsive applications as both an ion source and a thruster. Development of a helicon thruster requires a performance baseline as a basis for future optimization and modification. For the first time, the thrust of a helicon plasma source is measured using a null-type inverted pendulum thrust stand at an operating pressure of 2 × 10 −5 torr through the operating range of 215-840 W RF power, 11.9 and 13.56 MHz RF frequency, 150-450 G magnetic field strength, and 1.5-4.5 mg∕s propellant flow rate for argon. Maximum thrust is found to be 6.3 mN at a specific impulse of 140 s and a maximum specific impulse of 380 s at 5.6 mN. Thrust efficiency is less than 1.4% and demonstrates very-low-power coupling to ion acceleration.

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Helicon plasma sources are capable of efficiently ionizing propellants and have been considered for application in electric propulsion. The literature suggests that the ion acceleration mechanism is a current-free double layer. Previous work shows that single-stage helicon thrusters can produce thrust in the range of 1-6 mN, but it is unknown whether the thrust contribution is due to direct ion acceleration versus thermal expansion. The ion energy and current density profiles in the plume of a helicon plasma source are measured across a range of operating conditions: 343-600 W RF power at 13.56 MHz, 50-350 G, and 1.5-mg/s Ar at a pressure of 1.6 × 10 −5 torr-Ar. The plasma potential, electron temperature, and ion number density are also measured inside the discharge chamber and in the plume up to 60 cm downstream of the exit plane and 45-cm radially outward from the device axis. Ions are found to have energies in the range of 20-40 V, with total beam currents in the range of 7-47 mA. The plume has an average divergence half angle of 82°, either evenly distributed across all angles or focused at large angles to the centerline. From these measurements, it is found that the estimated thrust due to ion acceleration is far less than what has been directly measured on the same device in previous work.

Helicon plasma sources are capable of efficiently ionizing propellants and have been considered for application in electric propulsion. However, studies that estimate the ion production cost of the helicon plasma source are limited and rely on estimates of the extracted ion current. The ion production cost of a helicon plasma source is determined using a gridded ion thruster configuration that allows accurate measurement of the ion beam current. These measurements are used in conjunction with previous characterization of the helicon plasma to create a model of the discharge plasma within the gridded thruster. The device is tested across a range of operating conditions: 343-600 W radio frequency power at 13.56 MHz, 50-250 G and 1.5 mg s −1 of argon at a pressure of 1.6 × 10 −5 Torr-Ar. The ion production cost is 132-212 ± 28-46 eV/ion, driven primarily by ion loss to the walls and anode, as well as energy loss in the anode and grid sheaths.

An annular helicon plasma source for the ionization stage of a two-stage Hall effect thruster is considered. The magnetic and electric field structures in the plasma source are computed considering classical helicon wave and Trivelpiece-Gould wave. The antenna coupling and power deposition mechanism model is developed to determine the effective antenna geometry. Methodology for selecting the antenna power, frequency, and applied magnetic field strength is presented. Using the theoretical model, the annular helicon source compatible with a 5-kW Hall thruster is sized and built. Nomenclature