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Daniel Guggenheim School of Aerospace Engineering

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search.filters.applied.f.advisor: Walker, Mitchell L. R. × Item Type: Publication × search.filters.applied.f.isSeriesOfPublicationTitle: Doctor of Philosophy with a Major in Aerospace Engineering × Type: Dissertation ×

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Laser Thomson Scattering Measurements of the Plasma Structure in the Front Pole Region of a Magnetically-shielded Hall Effect Thruster

2024-04-27 , Suazo Betancourt, Jean Luis

Laser Thomson scattering (LTS) is a diagnostic that provides direct access to electron properties in a plasma. This diagnostic is calibrted via laser Raman scattering (LRS). The goal of this thesis was to probe the electron properties in the near field plasma plume of a magnetically shielded (MS) Hall effect thruster (HET), a type of electrostatic electric propulsion device (EP), to provide insight into the applicability of the isothermal magnetic field line model and a notional description of the electron-property-predicted plasma structure traversing the front pole region from the discharge to cathode centerline. To this end, this thesis provides the following contributions: 1. Implementation of a Bayesian analysis and model selection framework for LRS-calibrated LTS diagnostics. 2. Detailed design and implementation of a discharge plasma cell and LTS system for near plasma boundary and laser plasma and laser neutral interactions. 3. Detailed design and implementation of a large vacuum test facility LTS system for measurements in live EP devices benchmarked on a hollow cathode. 4. Detailed upgrade to the large vacuum test facility LTS system for measurements in the near field discharge of a high current density MS HET. Specifically, axially resolved electron property measurements along the discharge channel centerline, spatially resolved method traversing the front pole region from the channel centerline to the cathode centerline, and measurements along two distinct magnetic field lines.

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Impedance Characterization of a Hall Effect Thruster Discharge in a Ground-based Vacuum Test Facility

2024-04-17 , Jovel, David Rene

Hall effect thrusters (HETs) are known to perform differently in space compared to what is measured when operated inside ground-based vacuum test facilities. The environment inside test facilities can replicate only some of the electrical boundary conditions observed in space. Specifically, most vacuum test facilities are metallic, electrically grounded, and finite in volume whereas the space environment possesses a low-density, cold plasma that varies in time due to space weather activity. Therefore, it is essential to understand how HETs electrically couple to, and are affected by, their local operating environment. The purpose of this dissertation is to quantify the dynamic electrical characteristics of the HET discharge as it electrically interacts with the metal vacuum chamber during ground-based test campaigns. To accomplish this, a novel impedance measurement diagnostic was used to characterize the resistive, capacitive, inductive, and resonant characteristics of the HET discharge in the band 100 Hz – 300 kHz as the electron current to the facility walls was reduced. The results show that ground-based vacuum test facilities participate in the HET discharge circuit in three main ways: 1) introduce capacitive effects that may suppress the inherent dynamic nature of HETs via the plasma-chamber wall sheath, 2) reduce inductive effects due to the increased plasma densities contained within the facility, and 3) facilitates ion-electron neutralization processes via its electrically conductive walls. Furthermore, the work in this dissertation shows that these artificial effects become more pronounced as the HET discharge current level increases

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