Effect of body bias on near-field electron behavior in a magnetically shielded Hall thruster

This work investigates the influence of thruster body bias on near-field electron behavior in a magnetically shielded Hall effect thruster (HET) through spatially resolved laser Thomson scattering diagnostics. Experiments were conducted on the 9 kW class H9 magnetically shielded HET operating at 40 A discharge current and 150 V discharge voltage on krypton propellant in the Georgia Tech Vacuum Test Facility 2. Three electrical configurations were examined: floating (body electrically isolated), cathode-tied (body at cathode potential, approximately −10.3 V relative to facility ground), and +2 V bias (body biased +2 V relative to ground). Spatially resolved measurements of electron density, electron temperature, and radial electron bulk velocity were obtained at up to 23 locations (a 15-point radial grid and up to eight axial stations along the cathode centerline) spanning the cathode near-field from the cathode centerline to the discharge channel centerline. A configuration-dependent spatial density inversion reveals distinct circuit topologies: at z/r0 = 0.029, cathode-tied elevates ne at the cathode centerline (4.4 × 1019 m−3) while exhibiting the lowest channel-centerline density (6.6 × 1017 m−3), whereas the +2 V configuration shows the opposite pattern (3.4 × 1019 and 9.0 × 1017 m−3, respectively). The +2 V configuration exhibits the lowest Te at the inner front pole cover, consistent with magnetization-limited, energy-selective electron collection. Electron pressure does not serve as a reliable proxy for electrostatic potential in this near-field region due to unmeasured anomalous transport terms.