Here is a look at the new enhanced extractor design for the next AIS-ILIS1 ionic liquid electrospray thruster iteration. The slit width has been decreased significantly, while introducing a flare at the emitter corners to keep field enhancement higher across the emitter length and lower at the sharp corners of the emitter.
Due to the sharp corner of the ridge emitter ends, field enhancement is naturally highest at this point for uniform extractor aperture size and distance. Because of this, emission will normally start at the corner, which has been observed in both ignition tests so far. However, I want emission to occur along the length of the ridge. If the field is too high at the edges, or there is even slight misalignment, it is possible for the corner to act more as a point emitter, causing emission to be concentrated in this small area. By keeping the aperture very narrow and widely flaring out at the corners, I hope to minimize or even eliminate turn-on and emission at the corners so that emission occurs evenly across the length instead. This is actually a rather unusual design for slit emitters I have not seen. However, most slit based electrospray has been based on cesium channel FEEP, where corner enhancement is not as large of an issue.