Thrust Measurements of a Radio Frequency Plasma Source

There is interest in the use of a heliconplasma source in propulsive applications as both an ion source anda 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 ismeasured using a null-type inverted pendulum thrust stand at an operating pressure of 2 × 10−5 torr through the operating range of 215–840WRF 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. Maximumthrust is found to be 6.3mNat a specific impulse of 140 s andamaximumspecific impulse of 380 s at 5.6mN. Thrust efficiency is less than 1.4% and demonstrates very-low-power coupling to ion acceleration.