Hezhi Sun

Visual evidence of suppressing the ion and electron energy loss on the wall in Hall thrusters

A method of pushing down magnetic field with two permanent magnetic rings is proposed in this paper. It can realize ionization in a channel and acceleration outside the channel. The wall will only suffer from the bombardment of low-energy ions and electrons, which can effectively reduce channel erosion and extend the operational lifetime of thrusters. Furthermore, there is no additional power consumption of coils, which improves the efficiency of systems. We show here the newly developed 200 W no wall-loss Hall thruster (NWLHT-200) that applies the method of pushing down magnetic field with two permanent magnetic rings; the visual evidence we obtained preliminarily confirms the feasibility that the proposed method can realize discharge without wall energy loss or erosion of Hall thrusters.

Effect of oblique channel on discharge characteristics of 200-W Hall thruster

In an experiment involving a 200-W Hall thruster, partial ionization occurs in the plume area because of the extrapolation of the magnetic field. To improve the thruster performance, the concept of an oblique channel is proposed for improving the ionization degree in the plume area. Calculations performed using a Particle-in-cell (PIC) simulator and the experimental results both show that an oblique channel structure can reduce the wall loss. Compared with a straight channel under similar conditions of the discharge voltage and current, the ionization degree in the plume area, thrust, specific impulse, propellant utilization, and anode efficiency are improved by ∼20%. The oblique channel is an important design consideration for improving the partial ionization of the plume area in the thruster.

Growth mechanism of vertical compositional inhomogeneities in AlInN films

The growth mechanisms of vertical compositional inhomogeneities were investigated in lattice-matched AlInN films prepared by metalorganic chemical vapour deposition. X-ray diffraction and secondary ion mass spectrometry measurements demonstrated a fluctuation of the indium (In) atomic fraction at the initial growth stage. Some In droplets formed on the surface of the inhomogeneous AlInN films, when In was excess caused by the initial Al-rich AlInN layer. The compositional inhomogeneities were attributed to the self-assembled In droplets by increasing the surface In content.

Experimental test of 200 W Hall thruster with titanium wall

We designed a 200 W Hall thruster based on the technology of pushing down a magnetic field with two permanent magnetic rings. Boron nitride (BN) is an important insulating wall material for Hall thrusters. The discharge characteristics of the designed Hall thruster were studied by replacing BN with titanium (Ti). Experimental results show that the designed Hall thruster can discharge stably for a long time under a Ti channel. Experiments were performed to determine whether the channel and cathode are electrically connected. When the channel wall and cathode are insulated, the divergence angle of the plume increases, but the performance of the Hall thruster is improved in terms of thrust, specific impulse, anode efficiency, and thrust-to-power ratio. Ti exhibits a powerful antisputtering capability, a low emanation rate of gas, and a large structural strength, making it a potential candidate wall material in the design of low-power Hall thrusters.

Effect of vortex inlet mode on low-power cylindrical Hall thruster

This paper examines a new propellant inlet mode for a low-power cylindrical Hall thruster called the vortex inlet mode. This new mode makes propellant gas diffuse in the form of a circumferential vortex in the discharge channel of the thruster. Simulation and experimental results show that the neutral gas density in the discharge channel increases upon the application of the vortex inlet mode, effectively extending the dwell time of the propellant gas in the channel. According to the experimental results, the vortex inlet increases the propellant utilization of the thruster by 3.12%–8.81%, thrust by 1.1%–53.5%, specific impulse by 1.1%–53.5%, thrust-to-power ratio by 10%–63%, and anode efficiency by 1.6%–7.3%, greatly improving the thruster performance.