Investigation of variable aperture on the performance and lifetime of ion thruster

Abstract

Beam flatness is an important parameter that determines the performance and the lifetime of a gridded ion thruster. To improve the beam flatness of the 30 cm (LIPS-300) ion thruster, variable aperture ion optics that adapts to the decreasing ion density as the radius increases is proposed. It is the ion optics that the screen grid surface is divided into several zones, where the aperture diameter in each zone is determined by the ion density and the electron temperature upstream of the screen grid. The beam current density in the central area is artificially reduced. A particle in cell-Monte Carlo collision model is applied in this work to investigating the effect of variable aperture on the perveance and the maximum beam current per aperture by simulating the extraction, focusing and acceleration processes of ions. Taking into account the engineering implementability, the screen grid surface is divided into four zones. The hole diameter in each zone is decreased from 1.95 mm to 1.8 mm, 1.9 mm, 1.8 mm and 1.7 mm, respectively. The simulation results show that the maximum ion density in the center area of grid is decreased by 10.6% and 6.99%, while it is increased by 6.49% and 22.3% in the edge region, respectively. The beam flatness of the variable aperture ion optics is improved from 0.69 to 0.88. The erosion rate is decreased by 31.9%, but the total beam current is also decreased by 7.15%. The simulation results can provide a valuable reference of the development of the ion thruster.

Numerical study of the radio-frequency biased accelerating system in ion thrusters

“…A typical two-grid RF biasing system has numerous apertures in two grids, and the accelerating plasma beam is ejected from these apertures. In order to investigate the ion optics deeply, we focus on the structure of a single set of grid apertures, which is commonly used when studying the accelerating grid system [12,30,31]. Figure 2 shows the geometry of the RF self-bias accelerating system for a single set of slit apertures that is also used in many studies [32][33][34], which is simulated in Cartesian coordinates, and the x and y coordinates refer to the axial and radial directions of the thruster.…”

Numerical study on variable aperture extraction grids of a titanium hydride cathodic vacuum arc ion source

“…As presented in figure 10, the first three kinds of grids are fixed aperture extraction grids with different aperture size to test the influence of aperture size to the beam uniformity. The later three kinds of grids are variable aperture extraction grids with large central apertures, which are different from the traditional variable aperture extraction grids with small apertures in the central and large aperture on the edge of grids [18,24]. Detailed parameters of these extraction grids are presented in table 3.…”

“…Another technical route is based on the fact that the plasma density is high in the middle and gradually decreases along the radial direction. Therefore, a grid with variable aperture can be designed that reduce the aperture in the central area of the grid, and gradually increase the aperture as it goes to the edge, so that the plasma density and aperture size are matched, thereby improving the beam uniformity [18]. Unfortunately, this method is not entirely applicable for the metallic hydride cathodic vacuum arc ion source since it will result in a large beam loss (> 50%) at the target position according to our simulated results.…”

Investigation into the thermal effect of the LIPS-200 ion thruster plume

“…Ion thrusters [1][2][3] have the potential to dramatically enhance the payload, prolong the service life and reduce the launching budget of spacecraft owing to their high specific impulse, low thrust, prolonged lifespan, and repeatable start-up etc, and have been successfully employed in missions concerning attitude control, station keeping, drag compensation, and deep space exploration. The implementation of electric propulsion technology on spacecraft will alter the plasma environment in the vicinity of the spacecraft owing to its special plume environment, resulting in a series of effects such as charged spacecraft surfaces, electromagnetic interference, and subsequent changes in the thermal properties of thermally sensitive surfaces.…”