Automated gradient-based calibration of the anomalous electron scattering frequency profile in a Hall effect thruster

Partially magnetized plasmas often exhibit anomalous electron transport, wherein the measured electron mobility is greater than 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. In Hall effect thruster modeling, anomalous electron transport has traditionally been included using 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.