3D plume reconstruction via multispectral imaging and surrogate modeling for symmetry regulation in magnetically enhanced hollow cathode thrusters

Electric propulsion (EP) systems usually have multiple independent adjustable parameters, such as discharge voltage and operating current which strongly influence thruster performance, plume morphology, and plasma stability. For magnetically enhanced hollow cathode thrusters (MHCT), plume distortion and deflection often occur under multi-parameter coupling, potentially affecting plume symmetry and thrust-vector stability. Therefore, rapid steady-state plume diagnosis under different operating conditions and reliable parameter-selection strategies are needed. In this work, a physically constrained three-dimensional plume reconstruction method is proposed based on multispectral imaging and a distribution surrogate model. A parametric plume distribution is constructed using prior physical information, and the electron temperature and electron density fields are reconstructed through residual optimization coupled with a xenon collisional-radiative model and line-of-sight projection. The reconstructed plume-core morphology shows good agreement with the multispectral observations and probe-based validation data. Using this method, the projected plume eccentricity and divergence characteristics are analyzed under different voltage and keeper-current conditions. Based on the reconstructed spatial evolution, a plume-symmetry regulation map is established to identify operating conditions with reduced plume-core displacement and acceptable divergence. The proposed method provides a non-intrusive diagnostic and parameter-selection approach for evaluating steady-state plume asymmetry in compact electric propulsion systems.