Development and Study of an Electron Cyclotron Resonance Waveguide PlasmaCathode for Electric Propulsion Applications.

Plasma Physics;Electric Propulsion;Plasma Cathode;Electron Cyclotron Resonance;Nuclear Engineering and Radiological Sciences;Engineering;Nuclear Engineering & Radiological Sciences

Weatherford, Brandon RobertKushner, Mark ;

University of Michigan

关键词: Plasma Physics;    Electric Propulsion;    Plasma Cathode;    Electron Cyclotron Resonance;    Nuclear Engineering and Radiological Sciences;    Engineering;    Nuclear Engineering & Radiological Sciences;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/89714/brweathe_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In electrostatic ion thrusters and Hall thrusters, electron sources are used for propellantionization and neutralization of the thruster beam. Thermionic emitter-basedsources are commonly used, but they possess inherent lifetime limitations due toemitter depletion, poisoning, and sputtering of the emitter surface. For long durationelectric propulsion (EP) driven missions or semi-permanent plasma contactor installations,these emitters have become primary limiting components on thruster life.There are two goals to this work: first, to develop and demonstrate the feasibility ofan emitterless plasma cathode for EP; and second, to study the underlying physicsof emitterless cathodes. The waveguide plasma cathode uses traveling 2.45 GHz microwavesin a cylindrical waveguide geometry, with permanent magnets, to generatean electron cyclotron resonance (ECR) discharge. Electron current is extracted fromthis source plasma through a downstream aperture. This device delivered up to 4.2amperes of electron current, at low power (90 W/A) and high gas utilization.The device was tested with argon, krypton, and xenon. Probe diagnostics wereused to measure axial profiles of electron density, electron temperature, and plasma potential, inside the device and in the external plume. These measurements show thatsome trace plume ionization is necessary for substantial current extraction. Plasmapotential in the plume tracks with a biased anode, and a weak electric field in theplume transports current across the anode-cathode gap. Internal plasma conditionsare also discussed. The plasma density in the extraction aperture increased by ordersof magnitude, relative to the source discharge density, during electron currentextraction. This is attributed to the formation of a dense plasma structure at the aperture.Laser collision-induced fluorescence (LCIF) was used to create two-dimensionalimages of plasma density and effective electron temperature at the aperture. Thestructure had a high density core, surrounded by a layer of high energy electronsaccelerated by a double layer. Probe diagnostics verified the existence of a potentialgradient between the aperture and bulk plasma. The aperture plasma acts as aneffective loss area for electrons, and may be a common feature of plasma cathodesthat should be included in models of these devices.