Discharge characteristics and fluctuation study in low power hall thruster plasmas

Abstract

Research and development of micro and small size low power electric thrusters have recently been paid much attention because they enable small satellites to perform multipurpose missions such as tandem operation and formation flying in addition to their classical functions including attitude and position control. Two types of low power Hall thrusters, i.e., the annular type and the cylindrical type, have been designed and developed, and their performances have been investigated. In the present research, a vertical pendulum type thruster stand was utilized, where changes in its suspension angle are caused by the horizontal movement of the thruster. For the accurate measurement of thrust, an optical method using a low cost and low power laser, a Position Sensitive diode Detector (PSD), and some standard optics was employed. The calibration was performed in the range up to $15~mN$ with weight of several $0.11~g$ masses with the optical setup. Plasma parameters such as plasma density, electron temperature, ion current density, and ion energy distribution were measured by electrical diagnostic tools, and the one dimensional fluid modeling was also conducted on the purpose of understanding detailed performance and underlying physics. An array of single Langmuir probes was utilized in the near-field plume plasma, and electron density and temperature profile were obtained. RPA and Faraday probe were developed to diagnose the far-field plume plasma, and ion energy distributions with the ion current densities were measured at various angular positions. The one dimensional fluid modeling was performed by solving four independent differential equations, which are continuity equation, ion momentum equation, electron transport equation, and Poisson`s equation. The present work focused also on the various physical phenomena associated with the fluctuation in Hall thruster plasmas. The fluctuations in Hall thruster plasmas were investigated using electrical and opt...