Effects of extractor axial position on porous ionic liquid Ion source performance

Abstract

A porous-media type, passively-fed, single emitter ionic liquid ion source electrospray thruster with variable extractor electrode to emitter axial distance was tested. Plume current-voltage curves and extractor current-voltage curves were measured for extractor to emitter distances from -0.1 mm (below emitter apex) to +0.5 mm (above emitter apex). After onset, the formation of a secondary and tertiary emission site was identified via step change in current and shift in current-voltage slope. Results show a linear increase in onset voltage with increasing emitter-extractor distance and a reduction in slope of the plume current to applied voltage curve, with extractor positions below the emitter having the highest current to voltage slope.Temporally-resolved plume current and extractor current behaviour in the onset voltage region was also examined. A time delay between applied potential and plume current emission of 0.48s at the initial onset voltage of 2070 V decreased to zero after 2160 V when the extractor was co-planar with the emitter tip. This ΔV_t between first delayed emission and immediate emission remained constant as the extractor was moved downstream of the emitter.

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