  A special surface discharge is proposed based on the multi-anode electrode
geometry. Instead of the traditional surface flashover of creepage on the
insulator surface between the electrodes, a surface discharge with one of the
electrodes being placed far away from the insulator is achieved in this paper.
The unique electric field distribution due to the multi-anode electrode
geometry has a significant influence on the discharge process of the surface
discharge. It changes the generation and propagation process of the plasma,
forming a plasma plume contributes to the propulsion performance of the
thruster. Through theoretical analysis of the obtained plume data, it is
indicated that the ablative pulsed plasma thruster based on multi-anode
electrode geometry (short for multi-anode APPT) promotes the internal pressure
of the plasma jet during its propagation and significantly increases the
density and energy of charged particles. The discharge phenomena manifest that
the multi-anode APPT and the helix-coil multi-anode APPT effectively increase
the intensity of the plasma plume. Through electron density spatial
distribution measurement, it has been found that the helix-coil multi-anode
APPT increases the density of plasma in the axial direction to more than 4
times of the conventional coaxial APPT and reduces the electron density in
other directions. In the propulsion test, it has been demonstrated that the
multi-anode APPT and the helix-coil multi-anode APPT have better performance in
terms of the impulse bit and the thrust-to-power ratio. In addition, it is also
identified that the pinch effect will be enhanced with the increase of
discharge power and the propulsion performance is promoted more distinctly. The
multi-anode APPT and the helixcoil multi-anode APPT have been proved to have
potential application advantage in the field of micro-satellite propulsion.
