Conducting wall Hall thrusters in magnetic shielding and standard configurations

• Published in: Journal of applied physics 2017-07, Vol.122 (3)
• Main Authors: Grimaud, Lou, Mazouffre, Stéphane
• Format: Article
• Language: English
• Subjects: Acceleration; Boron nitride; Dielectric properties; Engineering Sciences; Graphite; Hall thrusters; Magnetic shielding; Plasma jets; Plasmas; Silicon dioxide; Voltage drop; Walls
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4995285

Traditional Hall thrusters are fitted with boron nitride dielectric discharge channels that confine the plasma discharge. Wall properties have significant effects on the performances and stability of the thrusters. In magnetically shielded thrusters, interactions between the plasma and the walls are greatly reduced, and the potential drop responsible for ion acceleration is situated outside the channel. This opens the way to the utilization of alternative materials for the discharge channel. In this work, graphite walls are compared to BN-SiO2 walls in the 200 W magnetically shielded ISCT200-MS and the unshielded ISCT200-US Hall thrusters. The magnetically shielded thruster shows no significant change in the discharge current mean value and oscillations, while the unshielded thruster's discharge current increases by 25% and becomes noticeably less stable. The electric field profile is also investigated through laser spectroscopy, and no significant difference is recorded between the ceramic and graphite cases for the shielded thruster. The unshielded thruster, on the other hand, has its acceleration region shifted 15% of the channel length downstream. Lastly, the plume profile is measured with planar probes fitted with guard rings. Once again the material wall has little influence on the plume characteristics in the shielded thruster, while the unshielded one is significantly affected.