{'fraction_non_alphanumeric': 0.015372168284789644, 'fraction_numerical': 0.011326860841423949, 'mean_word_length': 5.093596059113301, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Regenerable Field Emission Cathode for Spacecraft Neutralization

This research investigates the discharge characteristics of a field emission cathode for use in electric propulsion that has the ability to be regenerated when the emitter tip becomes damaged. Emitter tip regeneration is achieved by taking advantage of Taylor cone formation from an operating liquid―metal ion source. Tip formation is accomplished by solidifying, or quenching, the ion-emitting cone to preserve the sharp protrusion so that it can then be used for electron emission. Electron emission I-V curves were taken after tips were formed by quenching the liquid―metal ion source at ion discharge currents ranging from 1 to 25 μA. Fowler―Nordheim modeling was then used to estimate the emitter tip radii of each quenched liquid―metal ion source. Results of the Fowler―Nordheim modeling were promising, showing the ability to regenerate tips and to control the features of the resulting tips by varying the ion current during the quench process. The set of experiments that are reported demonstrated the regeneration process of emitter tip radii ranging from approximately 30―45 nm from a tip quenched at 2 μA down to tip radii of 15―22 nm when quenched at 25 μA.