Influence of discharge power and grid structure on an RF-biased ion thruster

Abstract

The RF-biased ion thruster applies radio-frequency (RF) power on the grid system, which can extract both ions and electrons to achieve self-neutralization. The performance of the RF-biased ion thruster is significantly influenced by the structure of the grid system and the discharge power since these factors play a crucial role in determining the focusing condition of the grid system. In this paper, the influence of discharge power and grid structure on the RF-biased ion thruster’s voltage parameters is investigated. According to the screen grid voltage waveform results under different discharge power and grid structure, the relationship between self-bias voltage and RF voltage is acquired. In order to explain the different waveform variations, the impacts of the direct impingement current as well as the oscillation of the upstream sheath voltage are considered in the theoretical calculation for self-bias voltage. It has been found that the opposite oscillation of the upstream sheath voltage is the primary reason for the decline in self-bias voltage. Moreover, the mechanisms through which discharge power and grid structure influence the self-bias voltage are explained in terms of their impact on upstream sheath oscillation. Several methods for increasing the self-bias voltage in RF-biased ion thrusters are also proposed.