Analysis of the effect of keeper working conditions on hollow cathode performance

Hollow cathodes are widely used in electric thrusters due to their high emission electron density and low maintained voltage. The hollow cathode performance may significantly change under different keeper working conditions. In this study, a series of ground experiments were carried out to study the effects of the keeper current and the distance between keeper and cathode top on the emission characteristics and plume structure of the hollow cathode. The experimental results show that the working state of the keeper electronic circuit is less likely to be disturbed by the anode electronic circuit when the ratio of keeper current to anode current rises up. The plasma potential does not always rise up with the emission current in the far-field (>6 cm) when the keeper current is not high (<3 A). The extend of the distance between keeper and cathode top forms a high obstacle to the anode electronic circuit, this obstacle not only causes an increase of anode voltage, but also leads to a significant discharge instability of hollow cathode. In this case, a higher keeper current and xenon flow rate are required to keep a stable working state of hollow cathodes. The experimental results contribute to research on the discharge instability mechanism of hollow cathodes and provide useful information for instructing hollow cathode design.