Re-generable Field Emission Cathodes
A significant challenge in scaling micro-propulsion devices up to 100s of Watts as well as scaling macro devices down to sub-kiloWatt level is the lack of a compatible neutralizer technology in the meso scale. Sub-kiloWatt EP systems require cathode technology that can produce sufficient current while consuming little or no gas or power. The most promising technology for meso-scale neutralizers is field emission. In field emission, electrons are extracted directly from a cold bulk solid material by an intense applied electric field at the solid-vacuum interface with no gas flow and no heating required. While many methods have been proposed to incorporate field-emission neutralizers in EP systems, the inherent fragility of the technology?specifically the reliance on solid structures with nanometer-radius tips?ensures that device failure due to tip degradation will be a near certainty for any application depending on field emission cathodes. The goal of research proposed here is to develop arrays of field-emission neutralizers for use in sub-1-kW EP that eliminate tip degradation not through attempts to minimize tip wear, but instead by incorporating self-assembling nanostructures that can repeatedly re-generate damaged emitter tips in space and fully restore the functionality of a damaged or degraded device.
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