Characterization of acceleration zone shifting in an anode-layer-type Hall thruster RAIJIN66

The location of the ion acceleration zone has been known to affect the performance and lifetime of a Hall thruster. Herein, the magnetic field in the anode-layer-type Hall thruster RAIJIN66 was designed to shift the acceleration zone downstream beyond the discharge channel exit. To examine the effectiveness of the design concept, plasma diagnosis using an emissive probe was conducted to obtain a one-dimensional plasma profile on the channel centerline. In addition, a two-dimensional potential profile was obtained to observe the effects of the presheath on the shifted potential structure. The results proved that the acceleration zone was pushed downstream along with the shifted magnetic field. With increasing discharge voltage, the axial length of the acceleration zone contracted at around the peak of the radial magnetic flux density. The ion current density lost to the guard-ring was estimated to be 9.9 mA/cm², which is comparable to the current density from the magnetically shielded stationary plasma thrusters. Furthermore, the measured two-dimensional potential distribution revealed the existence of a structure that attracted ions to the wall.