An Electromagnetic Control Method for Regulating the Propulsion Performance and Discharge Oscillations in a Wall-less Hall Thruster

The rapidly developing microsatellites have put forward new requirements of small volume and low power for propulsion systems. The wall-less Hall thruster (WLHT) is proposed as a promising method to help the Hall thruster overcome the issues of wall loss and erosion to apply in microsatellites. However, the in-orbit application of WLHTs is hindered by two key issues: large beam divergence and discharge oscillations, which require further research for effective control. In this work, a novel electromagnetic-controlled wall-less Hall thruster was developed and tested to regulate the propulsion performance including beam divergence angle and low-frequency oscillations. Experiments show that adjusting the magnetic fields near the anode and cathode respectively makes it possible to achieve high thrust performance with low anode current oscillations. At the anode voltage of 300 V and volume flow rate of 6 SCCM using xenon gas as propellant, the electromagnetic control can increase the thrust by 10.4% (5.79 mN Vs 6.39 mN) and the anode efficiency by 2.6 percentage points (19.1% Vs 21.7%), and reduce the 90% plume half-angle is reduced by 14.3% (76.1°to 65.2°). The breathing oscillation's amplitude of the anode current decreases from 37.2% to 2.6% by adjusting the coil current from +3 A to +4 A, while the thrust only decreases by 0.7% (6.39 mN Vs 6.35 mN). The performance of the proposed thruster at the anode power of 200 W is comparable to the state-of-the-art low-power wall-less Hall thrusters.