The microwave ion thruster μ10's ion beam current saturated at a large mass flow rate when propellant gas was injected from a waveguide inlet and it was improved by additional propellant inlets to a ...discharge chamber. In order to understand the mechanism of these phenomena, it is important to measure distributions of the microwave electric field inside the discharge chamber, which is directly related to plasma production. In this study, we applied an electro-optic (EO) probe to measuring the microwave electric field. The probe contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. We measured electric-field profiles along the centerline and in the ECR area of μ10 with the EO probe. Consequently, this paper revealed that when the propellant was injected from the waveguide inlet, microwave was reflected in the waveguide at large mass flow rate, which disturbed a propagation of microwave to the ECR area. It also revealed that when the propellant was injected from the discharge chamber inlet, the mass flow rate where the microwave reflection occurred shifted to larger rate, which resulted in the increase of the beam current．
The microwave discharge ion engine mu10'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)6s3/202 inside of mu10 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.
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)6s3/202 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.
PDF
