Design of magnetic nozzle for an advanced RF thruster

Summary form only given, as follows. Summary form only given. The aim of the magnetic nozzle in this study is for converting plasma pressure into directed flow, thereby providing thrust for plasma propulsion. The detachment of the particle flow from the magnetic field line must be highly directed, otherwise the thruster efficiency will be low. The ion detachment is basically due to ion inertia, but electrons frozen in the magnetic field reduces the ion detachment efficiency due to the ambipolar E-field arising perpendicular to the B-field although calculated single ion trajectories are shown to be highly directed. To investigate the electron effect and thus the ambipolar E-field effect on ion detachment, numerical simulation using a particle-in-cell (PIC) code and the fluid approach was attempted. All this considered, the design of a new-type magnetic nozzle was performed to investigate the curvature effect on plasma detachment. With the designed nozzle consisting of two coils of different radii and opposite current direction, the magnetic field curvature can be continuously changed by varying the outer coil current. The PIC code simulation and the fluid model show that the highly directed ion detachment can be obtained with the new design, whereas the plasma is highly constrained to the magnetic field in a conventional, slowly curving magnetic nozzle.