Study of microchannel structures for measuring emission conductance of indium field emission electric propulsion micro-thrusters

Surface morphology of emitting tip has a significant effect on performance of Liquid-Metal Ion Sources. In this paper, fabrication technics of dynamic micro-electrochemical etching was employed to realize micro-grooves processing of emitting tip surfaces at different depths by regulating roughening time and voltage frequency. Through field emission experiments of indium Field Emission Electric Propulsion micro-thruster, we measured volt–ampere characteristic curves of a batch of emitters with different microchannel structures. By a normalization method, the effect of inconsistency of apex radius between different tips on volt–ampere characteristics was eliminated, and influence law of surface roughness on emission conductance was revealed more clearly. The test results were found to be consistent with the current–voltage characteristics which was deduced from microchannel model based on a semi-cylindrical shape. This study presents an approach for pre-estimating and optimizing the emission conductance through assessment of emitter surface roughness and substantiates the method's viability.