Effect of the Magnetic Field on the Plasma Plume of the Cylindrical Hall Thruster with Permanent Magnets

Abstract

A low power miniaturized cylindrical Hall thruster with permanent magnets (CHTpm) was operated with and without the magnetic shield. The magnetic field outside the thruster channel is shown to play a critical role in the formation of an unusual halo shape of the plasma flow from CHTpm without the magnetic shield. It is suggested that this result is applicable for other types of permanent magnet cylindrical thrusters, including diverge-cusp field (DCF) and HEMP thrusters. For the CHTpm, the use of a magnetic shield allows to restore a conic shape of the plasma plume, which is typical for conventional annular Hall thrusters and cylindrical Hall thrusters with electromagnets, and to reduce the plasma plume divergence.

Hollow Plume Mitigation of a High-Efficiency Multistage Plasma Thruster

“…The team at PPPL implemented a low-carbon steel shield onto their CHT with permanent magnets (CHTpm) and observed excellent results. [20,19] Results of the shielded CHTpm experiments showed plume change from the hollow shape into a typical conical type with maximum ion current along the centerline, along with a narrowing of the plume. [19,7] The shield configuration and experimental results of the CHT testing is in Figure 3.5.…”

“…[19] Since there is a strong radial magnetic field in this region, the ions are accelerated off at angles rather than straight up the centerline of the thruster. [20,19,7] In order to mitigate this hollow plume issue, a magnetic shield will be im-plemented on the HEMPT with the goal of reducing the outer magnetic field and restoring a conical shape to the plume. The team at PPPL implemented a low-carbon steel shield onto their CHT with permanent magnets (CHTpm) and observed excellent results.…”

“…Other plasma thrusters, such as cylindrical Hall-thrusters (CHT's) and diverging cusped field thrusters (DCFT's) have a similar issue. [5,20,19] The DCF magnet design was inspired by the PPM system used in the HEMPT, therefore it experiences some of the same types of issues. [5] The CHT with permanent magnets had a cusped magnetic field near the exit of the ceramic channel, similar to that seen in the HEMPT.…”

“…[5] The CHT with permanent magnets had a cusped magnetic field near the exit of the ceramic channel, similar to that seen in the HEMPT. [20,7] In-depth investigation has been done at the Princeton Plasma Physics Laboratory (PPPL) into the effect of this outer magnetic field on plume shape for the CHT. These investigations have shown that the strong magnetic field outside the thruster is actually a significant area of ion acceleration;…”

Divergent Plume Reduction of a High-Efficiency Multistage Plasma Thruster

“…This same material was used by the PPPL to mitigate a hollow plume in a CHT [11]. Also, it was provided by Dr. Goebel for Scott's thesis and some material was left over.…”