Characteristics of Hyperthermal Atomic Oxygen Source Using Electron Cyclotron Resonance Discharge and Neutralization Grid

Abstract

Electric propulsion systems allow satellites to fly in very low-earth orbits. The rarefied atmosphere in such orbits consists mainly of atomic oxygen with kinetic energy that corresponds to the orbital velocity, and the reaction of atomic oxygen with spacecraft materials is a significant issue. Here we develop a hyperthermal atomic oxygen source using electron cyclotron resonance discharge plasma and a neutralization grid to simulate orbital conditions. The hyperthermal atomic oxygen is produced by surface neutralization of oxygen ions in the plasma. This paper reports on simulated beam properties. Atomic oxygen flux is measured by the erosion of a polyimide film on a quartz crystal microbalance. The flux is 2.55×10 15 cm -2 s -1 , which corresponds to orbital conditions at an altitude of 240 km. The neutralization efficiency, which indicates the performance of the neutralization grid, is much higher than 99%. The beam divergence angle is about 4°, as measured by the radial distribution of the atomic oxygen flux. From the ion energy, we estimate that the atomic oxygen beam has kinetic energy of about 3-7 eV.