Automated calibration of anomalous electron transport in a Hall effect thruster simulation

Cross-field plasma discharges often exhibit anomalous electron transport, wherein the measured electron mobility is greater than that expected from classical collision theory. Depending on the configuration of the plasma, this anomalous transport can be associated with plasma turbulence, particle-wave scattering, or plasma-wall interactions. When modeling these cross-field discharges, a semi-empirical anomalous transport profile is often used to account for these non-classical effects. In Hall effect thruster modeling, the most common approach is to use a manually calibrated Bohm mobility profile, in which the anomalous electron scattering frequency is proportional to the electron cyclotron frequency. In this work, we present an automated gradient-based optimization approach to calibrating such a profile against ion velocity measurements using a one-dimensional fluid model with the quasineutral and drift-diffusion assumptions for electrons. We present a regularized objective function which promotes smooth spatial profiles and demonstrate how the calibration process can be used for inverse uncertainty quantification of both the inferred anomalous scattering frequency profile and accompanying plasma properties.