The effect of segmented electrodes on the plasma plume and breathing oscillations in a wall-less Hall thruster

In the absence of channel walls bounding the plasma, a wall-less Hall thruster [1] is a promising configuration with both a potentially longer lifetime and easier scalability than conventional Hall thrusters. Because the ion acceleration takes place in the fringing magnetic field with a strong axial component, the operation of a typical wall-less thruster is characterized by a large beam divergence of the plasma flow, which reduces the thrust. In this work, the addition of biased segmented electrodes to the wall-less thruster is shown to control the plume divergence and large amplitude breathing oscillations of the discharge current commonly associated with ionization instability. For example, the segmented electrode placed outside the anode narrows the plasma plume and suppress the oscillations [2], while the central segmented electrode broadens the plasma plume, while reducing the ion energy spread [3]. In this work, we will discuss possible physical mechanisms responsible for these effects.

[1] J. Simmonds and Y. Raitses, J. Appl. Phys. 130, 093302 (2021)

[2] J. Simmonds and Y. Raitses, Appl. Phys. Lett. 119, 213501 (2021)

[3] J. Simmonds and Y. Raitses, IEPC-2022-395, International Electric Propulsion Conference, June 2022