Regenerable Field Emission Cathodes: Surface Morphology and Performance

摘要: This paper reports on a field-emission cathode for use in electric propulsion that has the potential very long lifetime due to its ability be regenerated when emitter tip(s) become damaged. The field-emitting tips were formedby applying an ion-extracting heated indium-coated tungsten needle, knownas liquidmetal ion source. liquid-metal source was then cooled, freezing solid nanotip at apex. When modified subjected electron-extracting potentials, stable and long-lived electron emission observed. first goal of this investigation operate quench currents from 1 30 A acquiremicrographs surfacemorphology as function current quench.Micrographs quenched revealed Taylor-cone-shaped structures. Some emitters exhibited multiple nanoprotrusions tapered surface microscale Taylor cone, which capable electronfield emission.The secondgoal investigationwas compare regenerablefield emitterswith single-needle field emitters. Each type used obtain vacuum chamber pressure 10 8 Torr, exposed increased pressure, up 5 observe how they could sustain emission. In all cases, regenerable lasted 10s hours longer it demonstrated would eventually permanently fail, whereas repaired became