Characterization of electron density fluctuations in the plasma of an ECR thruster

Electron density fluctuations are commonly observed in magnetized plasma discharges. They can be generated by different types of instabilities. In the specific case of electric propulsion, plasma instabilities have been mostly characterized in Hall Effect thrusters. In these devices, a large number of different instabilities, leading to various fluctuations’ frequencies and wavelengths, have been characterized [1]. They are shown to influence ionization processes and formation of the accelerating E field with a critical role in the thruster operation. In electron cyclotron resonance thrusters (ECRT), in which a magnetic nozzle is the acceleration stage, plasma fluctuations have been only recently observed [2]. While their exact characterization and their role in the thruster operation was only scarcely studied, it was concluded that plasma fluctuations may be related to anomalous electron transport phenomena [2]. This talk proposes to use two diagnostics, a microwave resonant probe and fast camera imaging, to characterize the plasma fluctuations in the source and in the plume of an ECRT. Such a characterization will open new scopes of analysis for the understanding of ECRTs.

[1] E. Choueiri, Phys. Plasmas 8 1411 (2001)

[2] Hepner et al., Appl. Phys. Lett. 116 263502 (2020)