Characterization of a heaterless 60 A hollow cathode on krypton and argon

Abstract We present a steady-state current-voltage (IV) characterization of a heaterless version of the 9 kW-class H9 Hall thruster cathode. This work was conducted at Georgia Tech’s High-Power Electric Propulsion Laboratory (HPEPL) at operational background pressures of 0.22–0.70 µTorr on krypton and 0.11–0.24 µTorr on argon, with a base pressure of 9.1 × 10 − 8 Torr. The characterization mapped steady-state voltage behavior from 5 to 45 A of discharge current on krypton and 5 to 30 A on argon (with paired magnetized and unmagnetized data over 5 to 35 A on krypton and 5 to 20 A on argon), in both magnetized and unmagnetized configurations. The magnetized configuration produced a higher discharge voltage than the unmagnetized configuration at every paired (current, flow) operating point on both propellants. On krypton, the magnetized-unmagnetized voltage gap ranged from near zero at the highest cathode flow and lowest current to + 39.6 V (+ 148%) at 30 A and 12.39 sccm. On argon, the gap ranged from + 6.0 V at 15 A and 12.39 sccm to + 67.5 V (+ 159%) at 20 A and 15.89 sccm. In both cases, the gap widened with discharge current and narrowed with cathode flow. These results verify reproducible ignition at every tested flow rate, confirm uninterrupted steady-state heaterless operation on krypton and argon, and quantify how the applied magnetic field shifts the steady-state operating point at fixed discharge current. The key finding is that the applied magnetic field increases the steady-state discharge voltage at fixed current rather than reducing it, and the effect is systematically larger on argon than on krypton at matched operating conditions.