Computational and Experimental Study on the Discharge Model of a 20 Amperes Emission Current Hollow Cathode

Abstract

The discharge characteristics of hollow cathode directly affect the performance of thruster. In order to obtain the plasma parameters of the 20 A emission current hollow cathode, COMSOL software is used to simulate the potential distribution, neutral fluid distribution and plasma parameters of the cathode, then the test is carried out to verify the simulations. The results show that the fluid velocity in the emitter region is about 20 ms -1 and is uniform in the radial direction. The electron density throughout the cathode discharge zone is almost uniform within the range of 1.09 × 10 20 ~ 1.2 × 10 20 m -3 . The electron temperature increased from 2.8 to 4.9 eV throughout the cathode discharge zone. The electron collision frequency is in the order of 10 23 Hz. The test results show that the electron temperature is increased from 2.4 to 5.2 eV from outlet of the emitter region to the plume region, and which presents an opposite trend to the electron density. There is a small error between the test results and the simulation results, and this error is mainly caused by the flow boundary setting.

A study of grid failure mode drivers and methods for accelerated life testing of a 30 cm diameter ion thruster

“…The screen grid erosion is not obvious in the lifetime test of ion thrusters. The life test of the 30 cm diameter ion thruster conducted in LIP showed a slight change in the aperture and thickness of the screen grid after 6500 h of operation [13]. The structural failure of the accelerator grid is mainly due to the pits-and-grooves erosion caused by CEX ions sputtering, and the pits-and-grooves erosion around individual apertures will eventually wear through the accelerator grid, resulting in short with the screen grid by thin metal sputtering.…”

“…There are many factors that can cause electron backstreaming failure of the accelerator grid [6][7][8][9][10][11][12][13][14]. At present, it can be summarized that the test and the analysis results mainly include background pressure, the diameter of the grid hole, the voltage of the accelerator grid, upstream plasma density, the screen grid voltage, propellant flow rate, mass utilization efficiency, thickness of the accelerator grid and the screen grid, etc.…”

“…At present, the special lifetime acceleration verification of adjusting the background pressure in the vacuum chamber has not been carried out, but the simulation results can be verified through the performance test and life test of a 30 cm diameter ion thruster in different vacuum facilities. From 2017 to 2021, two 30 cm diameter ion thrusters (number M04 and M06, with newly installed grids) were, respectively, subjected to 1500 h and 6500 h verification tests in the vacuum facility numbered TS-7 and TS-7A (as shown in figure 12) of LIP [13,19]. The TS-7 vacuum facility is 3.8 m in diameter and 8 m in length, which can provide a vacuum level of 5 × 10 −3 Pa when the thruster is under 5 kW rated condition.…”