Experimental study on beam characteristics of µHT-1 thruster under wide range adjustment of operating parameters

The beam properties of the micro Hall thruster µHT-1, which is intended for space gravitational wave detection, are being experimentally investigated for the first time. A Faraday probe combined with a three-dimensional mobile mechanism was used for diagnosis, and the beam ion current density distribution under a wide range of the anode voltage from 700 to 1200 V and the anode mass flow from 0.1 to 0.5 sccm was obtained. Moreover, the variation trend of total ion beam current, anode current, current utilization efficiency, beam divergence angle and other parameters were further analyzed. According to test data, the spatial distribution of beam ions changes from dense to sparse as one moves away from the axial direction of the µHT-1 thruster. Additionally, the beam becomes more flat due to the diffusion motion of beam ions in space and the binding motion of electrons and ions. The µHT-1 thruster can work stably under a wide range of conditions (anode voltage 700～1200 V, anode mass flow 0.1～0.5 sccm), and the beam current presents a good axis-symmetric distribution. With the increase of anode voltage, the average temperature of electrons can be increased, which further leads to the increase of ionization rate, that is, the current utilization efficiency increases from 53.4% to 67.7%; and the magnetic field restraint ability of high-energy electrons is weakened, affecting the electric field focusing, and the beam divergence angle increases from 41.3 ° to 56.1 °. With the increase of anode mass flow, the neutral atom density distribution in the channel is affected, the current utilization efficiency fluctuates in the range of 57.1 % ～ 66.8 %; and the ion collision zone is transferred to the outlet, making the beam divergence angle increase from 43.4 ° to 56.7 °. The total ion beam current of the thruster changes linearly with anode mass flow and anode voltage, which provides the data basis for the subsequent thrust wide range adjustment and thrust resolution analysis.