Microwave Discharge Oxygen Ion Source for Ionospheric Plasma Environment Simulation

Abstract

In recent years, concern has been raised about the interference phenomena (chemical reaction, sputtering etc.) between ionospheric plasma and high-voltage space systems such as the International Space Station and so on. In order to solve the physical mechanisms of these phenomena and establish the prevention technology, it is important to accumulate experimental data based on ground simulation tests. Therefore we have developed a cathode-less microwave discharge oxygen ion source for an ionospheric plasma simulator. The oxygen ion source for ionospheric plasma simulation demands plasma density more than 10¹²m^{- 3} and high durability (our target is more than 70hours). This ion source is capable of generating oxygen plasma of the order of 10¹⁴m^{- 3} for more than 100hours with 25W microwave power and 3sccm oxygen gas. In order to investigate the operational performance of the oxygen ion source, we conduct various measurement tests such as plasma diagnosis using a single probe, ionic mass spectroscopy by a Quadrupole Mass Spectrometer (QMS), atomic oxygen flux measurement using a silver coated QCM (Quartz Crystal deposition Monitor) and 70hours operating test etc. This paper reports the experimental results of each measurement tests and assesses performance as an ion source for ionospheric plasma simulator.