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Plasma Diagnostics inside a Microwave Discharge Ion Thruster
| Content Provider | Semantic Scholar |
|---|---|
| Author | Arakawat, Y. |
| Copyright Year | 1998 |
| Abstract | A microwave ion thruster for detailed plasma diagnostics was designed and fabricated. Plasma properties such as ion saturation current, space potential_ floating potential, electron temperature, electron density and microwave E-field intensity inside a discharge chamber were experimentally investigated. Ion loss distribution right over the magnets was also measured. Half-width of ion leakage distriion in ECR discharge plasma is twice that of DC discharge plasma in the same ion source. This large leakage half-width is caused by ionization near the chamber wall and increases the ion loss fraction. This is the reason why the ion production cost of ECR ion thrusters has been so much higher than state-of-the-art electron bombardment ion thrusters with DC discharge. Nevertheless, the ion cost for all the ions produced in the discharge chamber is ahnost the same value, about 100 eV/ion, for both DC and ECR discharge. In order to improve the ion beam production cost., a short discharge chamber is desirable because the extracted ion f&action increases. For interplanetary scientifk space missions, a microwave discharge ion thruster system up to a power range of 300 W has been under development” at the In&t&e of Space and Astronautical Science (ISAS) since 1988. So Ear, however, diagnostic information in the discharge chamber is insuf?icient for performance l G&uate Sb_ukz& Department of Aeromutics and Amonautics, JSPS Researcl~ Fellow. ** Research Associate, Member AlAA. t Profmr, FeUow AIAA. Release A: Copyright 1997 by the Electric Roe& Repulsion soci*. Au rights reserved. R&ease B: This paper is de&red a work of the U.S. Govemmet and is not subjmzt to copyright proteetion in the United States. improvement. Thus, parallel to the thruster development, a special electron cyclotron resonance (ECR) discharge ion source with a re&nguk discharge chamber and square magnetic tracks was built for the purpose of a detailed experimental investigation of the ECR plasma. Fig. 1 shows the discharge chamber without grids. This thruster is equipped with two optical windows on opposite sides, o&ring a fke view through the discharge chamber. Two dimensiormlity of the ECR region in the cusped magnetic field is assured to simplify the obsuvation without Abel transfknation. Argon was chosen as propellant for the optical diagnostic investigations. The result of optical emission spectroscopy of argon ions and absorption spectroscopy of argon neutmls using tunable diode laser was reported in the last IEPC?. Fig. 1 View into the discharge chamber of the ECR ion source, designed for diagnostic measurements After the spectroscopic measurem enQ we performed several experiments with this ion source in order to obtain the plasma parameters all over the discharge chamber and to correlate it with the thruster performance. Electrostatic probes were used to measure ion saturation current densi@ and electron temperature. A microwave probe was used for electric field intensity measurement. Ion current lost to the discharge chamber |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/1997index/7061.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
