Thrust Measurements of a Helicon Plasma Source

There is interest in using a helicon plasma source in propulsive applications as both an ion source and as a thruster. Developing a helicon thruster requires a performance baseline as a basis for future optimization and expansion. The thrust of a helicon is measured using an null-type inverted pendulum thrust stand at a pressure of 2x10 -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 6.27 mN at 142 s of specific impulse, and maximum specific impulse at 377 s at 5.55 mN. Thrust is primarily increased by increasing RF power, with smaller gains from magnetic field strength and mass flow rate. Maximum efficiency is 1.37% and is limited by a combination of low mass utilization and high beam divergence.