Numerical Simulations of Ion Thruster Accelerator Grid Erosion

Brophy, John R.; Katz, Ira; Polk, James E.; Anderson, John R.

doi:10.2514/6.2002-4261

Cited by 17 publications

(4 citation statements)

References 12 publications

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“…That is, when a single ion with a particular energy bombards the grid surface, it will produce a certain number of atoms or sputtering, and the unit is / n ion or / g ion. The amount of sputtering yield is calculated by the preset number of iterations, and sputtering yield is calculated according to the fitting formula given by Rosenberg, Brophy and Yim et al [22][23][24].…”

Section: R E F Ref Erefmentioning

confidence: 99%

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

Sun

Long

Guo

et al. 2023

Plasma Sci. Technol.

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In view of the high cost caused by the 1:1 lifetime verification test of ion thrusters, the lifetime acceleration test should be considered. This paper uses PIC-MCC (Particle-in-Cell Monte-Carlo Collision) method to analyze the five failure factors that lead to the failure of the accelerator grid of 30cm diameter ion thruster under the working mode of 5kW. Meanwhile, the acceleration stress levels corresponding to different failure factors are obtained. The results show that background pressure has the highest stress level on the grids erosion. The accelerator grid aperture’s mass sputtering rate under rated vacuum degree (1×10-4Pa) of 5kW work mode is 8.78 times that of the baseline vacuum degree (1×10-6Pa), and the mass sputtering rate under worse vacuum degree (5×10-3Pa) is 5.08 times that of 1×10-4Pa. The other four failure factors, namely, voltage of the accelerator grid, upstream plasma density, the screen grid voltage and mass utilization efficiency, the mass sputtering rate of the accelerator grid hole is 2.32, 2.67, 1.98 and 2.51 times that of baseline condition, respectively. The ion sputtering results of two 30cm diameter ion thrusters (both installed with new grids assembly) after working for 1000h show that the mass sputtering rate of the accelerator grid hole under vacuum condition of 5×10-3Pa is 4.54 times of that under the condition of 1×10-4Pa, and the comparison error between simulation results and test results of acceleration stress is about 10%. In the subsequent ion thruster lifetime verification, the working vacuum degree can be adjusted according to the acceleration stress level of background pressure, so as to shorten the test time and reduce the test cost.

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Section: R E F Ref Erefmentioning

confidence: 99%

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

Sun

Long

Guo

et al. 2023

Plasma Sci. Technol.

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“…The distribution of ion density in the upstream region of the grids is an important boundary condition for obtaining the ion extraction characteristics using the numerical calculation method. Some references [7,9] have indicated that an overperveance condition and an under-perveance condition occur when the upstream plasma density is at a higher level and a lower level, respectively. as equation (4), which only changes the density of the different particle types.…”

Section: Ion Density In the Upstream Of The Gridsmentioning

confidence: 99%

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

Sun¹,

Jia²,

Huang³

et al. 2018

Plasma Sci. Technol.

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In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process, a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 kW operation mode. Meanwhile, the fluid simulation method and particle-in-cell-Monte Carlo collision (PIC-MCC) method are adopted to simulate the ion extraction process according to the previous test results. The numerical calculation results are verified by the ion thruster performance test. The results show that after about 1.2 h operation, the hot gap between the screen grid and the accelerator grid reduce to 0.25-0.3 mm, while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium, and the hot gap is almost unchanged. In addition, the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value. Fluid simulation results show that the plasma density of the screen grid is in the range 6×10 17-6×10 18 m 13 and displays a parabolic characteristic, while the electron temperature gradually increases along the axial direction. The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant. Meanwhile, the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap. The ion beam current has optimal perveance status without thermal deformation, and the intercepted current of the accelerator grid and the decelerator grid are 3.65 mA and 6.26 mA, respectively. Furthermore, under the effect of thermal deformation, the ion beam current has over-perveance status, and the intercepted current of the accelerator grid and the decelerator grid are 10.46 mA and 18.24 mA, respectively. Performance test results indicate that the breakdown times increase obviously. The intercepted current of the accelerator grid and the decelerator grid increases to 13 mA and 16.5 mA, respectively, due to the change in the hot gap after 1.5 h operation. The numerical calculation results are well consistent with performance test results, and the error comes mainly from the test uncertainty of the hot gap.

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“…ions tend along single ion trajectory paths [15]. Therefore, for a beam flatness based on the ion flux of ions of all charges we use…”

Section: Beam Flatness (Grid Performance and Utilization)mentioning

confidence: 99%

“…Performance effects due to double ion content. Double ions typically hurt thruster performance since they require nearly twice the electron energy to create as single ions, accelerate wear mechanisms and deliver reduced thruster per unit of ion current [15,17,18]. Consequently, discharge chambers should be designed to minimize double ionization to avoid these performance losses.…”

Section: Beam Flatness (Grid Performance and Utilization)mentioning

confidence: 99%

Effects of magnetic field topography on ion thruster discharge performance

Wirz¹,

Goebel²

2008

Plasma Sources Sci. Technol.

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Traditional magnetic field design techniques for dc ion thrusters typically focus on closing a sufficiently high maximum closed magnetic contour, B cc , inside the discharge chamber. In this study, detailed computational analysis of several modified NSTAR thruster 3-ring and 4-ring magnetic field geometries reveals that the magnetic field line shape as well as B cc determines important aspects of dc ion thruster performance (i.e. propellant efficiency, beam flatness and double ion content). The DC-ION ion thruster model results show that the baseline NSTAR configuration traps the primary electrons on-axis, which leads to the high on-axis plasma density peak and high double ion content observed in experimental measurements. These

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Numerical Simulations of Ion Thruster Accelerator Grid Erosion

Cited by 17 publications

References 12 publications

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

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

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

Effects of magnetic field topography on ion thruster discharge performance

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