Thrust Measurements of a Radio Frequency Plasma Source

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 x 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 63 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.