Noise and Oscillatory Disturbances in the T6 Ion Thruster Hollow Cathode

This paper describes one important aspect of the characterisation of the hollow cathode designed for the T6 ion thruster. Although this 22 cm beam diameter Kaufman-type device has a nominal thrust of 150 mN, it is intended to operate over wide ranges of thrust and specific impulse, using xenon propellant. It therefore requires discharge currents of up to 30 A, depending on conditions. The phenomena examined in this paper include the low frequency oscillatory behaviour that results from interactions between the plasma and anode power supply, and the much higher frequency oscillations and noise generated by the plasma. The characterisation of these effects was undertaken using comprehensive instrumentation, including the measurement of internal xenon pressure and of flowrate in real-time. Theoretical studies are also reported which attempt to explain these phenomena in terms of electron emission, plasma and power supply processes.