Global Numerical Model for the Assessment of the Effect of Geometry and Operation Conditions on Insert and Orifice Region Plasmas of a Thermionic Hollow Cathode Electron Source

Abstract

Thermionic hollow cathodes have been widely used in wide variety of areas such as spacecraft electric propulsion systems, material processing and lasers for more than half a century as efficient electron sources. Especially in electric propulsion systems, hollow cathodes are being used as electron sources for propellant ionization and ion beam neutralization. Moreover, it is also a promising candidate for utilization as a stand-alone propulsion system in microsatellites or nanosatellites due to its small physical size, low power consumption and ease of operation. On the other hand, the small geometry of the typical orificed hollow cathodes makes the plasma diagnostics difficult which is why numerical studies become important for understanding the driving physical processes behind their operation, and the effects of the geometry and the operation parameters on cathode performance. In this paper, a global numerical model for the insert and orifice plasma of a hollow cathode is presented where volume averaged plasma parameters are considered for both regions. The results of this study show that the developed model can be used for designing and sizing orificed hollow cathodes as comparisons with the results of experimental and other numerical studies are in good agreement with the ones obtained from the developed model.

Thermal Analysis and Testing of Different Designs of LaB6 Hollow Cathodes to Be Used in Electric Propulsion Applications

“…In each case, the inner surface of the LaB 6 insert is kept at 1500 • C, which is sustained by the self-heating mechanism of the cathode plasma. Heat transfer from the insert region plasma is important in determining the power needed for sustaining the self heating mechanism [19]. In order to simulate the interaction of the cathode with the support structure, the bottom surface of the cathode base part is kept at 400 • C. As the cathode operates in a high vacuum environment, convective heat transfer is neglected.…”

“…The electric field of the sheath accelerates the ions towards the emitter surface. Collision of the ions with the emitter surface provides a self heating mechanism [2,18,19]. The self heating mechanism adjusts the insert surface temperature according to the extracted electron current and sustains a plasma inside the cathode tube [20].…”

Solution of Orifice Hollow Cathode Plasma Model Equations by Means of Particle Swarm Optimization

“…Hall Effect Thrusters (HETs), Gridded Ion Thrusters (GITs), High Efficiency Multistage Plasma Thrusters (HEMPTs) [2]. A lot of computational tools, based on phenomenological models, also known as zero-dimensional (0D) or reduced-order models, aimed to predict OHCs' plasma properties and performances and useful to support their design, have been developed since '80s [3][4][5][6][7][8][9][10][11][12].…”

“…The equations that constitutes the most of the models presented in the open literature [5][6][7][9][10][11][12] are commonly iteratively solved to face with their own non-linear characteristic. Each author adopts a different approach.…”