Title:
Impedance Characterization of a Hall Effect Thruster Discharge in a Ground-based Vacuum Test Facility
Impedance Characterization of a Hall Effect Thruster Discharge in a Ground-based Vacuum Test Facility
Author(s)
Jovel, David Rene
Advisor(s)
Walker, Mitchell L. R.
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Abstract
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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Date Issued
2024-04-17
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Dissertation