Improved performance of low current hollow cathode by inserted emitter core. (January 2023)

• Record Type: Journal Article
• Authors: Li, Fan; Meng, Tianhang; Ning, Zhongxi; Li, Chenying; Han, Ao; Li, Yingting; Yu, Daren
• Is Part Of: Vacuum. Volume 207(2023)
• Publication Date: 2023-01
• Subjects: Hollow cathode -- Core structure emitter -- Low current -- Electron emission; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2022.111492
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Hollow cathode is a common electron source, of whom the flow rate and power consumption affect the overall performance of electric propulsion systems, especially the low-power systems. Aiming at the current problems of low current hollow cathode (0.15–1A), such as discharge instabilities, narrow self-sustaining margin and high power consumption, an emitter structure with an inserted core was designed in this paper. The cathode inserted another core emitter into the cylindrical emitter cavity. Compared with the traditional design, the core structure could greatly reduce the discharge power consumption (5 W), the minimum self-sustaining current (0.15A), and the flow consumption (0.07sccm). By measuring the plume parameters and the emitter temperature, a gap between thermionic emission and required current was discovered at low-current discharge. The improved performance was attributed to the enhanced thermionic emission of the inserted core by its higher temperature due to lower thermal loss, and by enhanced Schottky effect due to emersion in high density plasma. At this moment, the lifetime of the core was insufficient and more careful optimization is needed on the location and length of the core. Highlights: The highlights of the submitted manuscript. 1) A new type of 1Hz level oscillation was discovered on the hollow cathode, which was driven by the depletion of thermionic emission when decreasing the discharge current to the lower limit of self-sustain. 2) A new emitter structure was proposed-- adding a core to the emitter cavity. The core structure could significantly restrain the 1 Hz-level oscillation and broaden the self-sustain margin to as low as 0.1A and 0.07sccm. 3) Non-uniform stacks of piled-up Ba- and Al- compounds were discovered on the depleted BaO core, which implied that intensified plasma-enhanced redeposition would happen at the lifetime end and speed up the failure.