2012 Volume 60 Issue 3 Pages 135-141
The microwave discharge ion engine μ10's thrust force was improved by additional propellant inlets to a discharge chamber. However, internal plasma diagnostics was not carried out while ion beam was extracted. In order to understand the effects of the new propellant inlets, we measured excitation temperatures and axial number density distributions of metastable Xe I 5p5(2P03/2)6s[3/2]02 inside of μ10 by a line pair method and laser absorption spectroscopy respectively. Firstly, the measurement of excitation temperatures was operated in two positions of the probe tip: 0cm and 5cm from a screen grid. This measurement confirmed that the temperatures marked between 0.42 and 0.68eV. Secondly, the number density distribution measurements were realized by a novel laser absorption spectroscopy utilizing optical fibers. As a result, 1017m-3 order of metastable neutral particles were measured by coupling with the excitation temperatures. Consequently, this paper will reveal that the propellant injection from a waveguide inlet increased the electron number density in the waveguide, which disturbed a propagation of microwave to the discharge chamber. It will also reveal that the propellant injection from the discharge chamber was effective to suppress the plasma production in the waveguide, which resulted in the increase of the thrust.
