Plasma Diagnostics of the μ 10 ECR Ion Thruster Using Optical Fiber Probes

In order to reveal the physical processes taking place within the ECR ion thruster “ μ10 ”, internal plasma diagnosis is indispensable. However, the ability of metallic probes to access microwave plasmas biased at a high voltage is limited from the standpoints of he disturbance created in the electric field and electrical isolation. This study demonstrates two kinds of plasma parameter measurements using optical fibers. Firstly, an optical fiber probe is a single-mode optical fiber. It is used to guide laser into the discharge chamber in the measurement of Xe I by the laser absorption spectroscopy. The other is an EO probe to measure the electric field of microwaves. From the both results, it can be deduced that there is plasma in the waveguide in the propellant injection from a waveguide. To improve the thrust force, it is important to suppress the electron in the waveguide.