Global model of a radio-frequency ion thruster based on a holistic treatment of electron and ion density profiles

Reeh, Andreas; Probst, Uwe; Klar, Peter J.

doi:10.1140/epjd/e2019-100002-3

Cited by 12 publications

(7 citation statements)

References 18 publications

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“…For the present thruster no critical fraction of charge-exchange ions has been observed so far when simulating comparable operational points. 15 Small currents, a low mass flow and a reasonable background pressure in the 10 −5 mbar range support this behavior.…”

Section: A Thruster Setup / Beam Characterizationmentioning

confidence: 73%

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster

Buntrock

Volkmar

Hannemann

2021

Review of Scientific Instruments

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The goal of this work was the setup of an electric propulsion (EP) sputtering test section as a feasibility study for ground-based sputter testing of spacecraft materials with a radio-frequency ion thruster (RIT). Such experiments deliver valuable data which are scarce but highly desired to model EP-based space missions, for example with SPIS (Spacecraft Plasma Interaction System), in order to predict the performance and lifetime of spacecraft components. This study assessed if sufficient testing conditions can be met to produce reliable experimental material data in the future. Therefore, the thruster was operated at ion energies of 1.5 keV and 1.8 keV, and a quartz crystal microbalance (QCM) was installed to detect sputter deposition rates. Molybdenum (Mo) and silver (Ag) were chosen as sputter targets. Wafer substrates served as a passive sampling method to characterize the composition of sputtered material by Rutherford Backscattering Spectrometry (RBS). Additionally, sputtering simulations matching the experimental conditions were conducted with the software SDTrimSP. We obtained comparable experimental and computational data, as measured sputter deposition rates lie within the simulated order of magnitude and to some extent show the predicted angular dependence. Analysis of deposited sputter material revealed the formation of metal oxides which requires a future adaption of the material specific QCM settings. Furthermore, the cooling system of the QCM sensor head was not sufficient, limiting the comparability of results.

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Section: A Thruster Setup / Beam Characterizationmentioning

confidence: 73%

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster

Buntrock

Volkmar

Hannemann

2021

Review of Scientific Instruments

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“…The radial length of the parallel-plane electrodes is set to be the same as that of the simulation domain of the ion optics, and L p is equal to l e . The value of d up should be longer than the thickness of the sheath upstream of SG to correctly resolve the upstream sheath [28], so d up ⩾ 20λ D where λ D = √ ε 0 T e /(en p ) is the Debye length, n p is the plasma density and T e is the electron temperature [29,33].…”

Section: Model Setup and Simulation Methodsmentioning

confidence: 99%

On the space-charge effects in the beam extraction process of ion thrusters: the roles of compensating electrons and changing beam radius

Zhang

et al. 2023

Plasma Sources Sci. Technol.

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Space-charge effects limit the beam-extraction capability of the ion optics and thus hindering the miniaturization and other performance improvements of ion thrusters. This paper numerically studies the space-charge effects in ion optics using hybrid and full particle-in-cell (PIC) simulations and proposes a modified Child-Langmuir (CL) law. As the injected current increases, the parallel-plane electrode system which corresponds to the classical CL law will reach an unstable and oscillatory state, while the ion optics system remains stable because the electrons from the bulk plasma will compensate for the space-charge effects. Furthermore, the radial expansion of ion beam and the loss of ions on the grids can counteract the space-charge effects when the injected current increases. In general, the space-charge effects in ion optics are self-consistently adjusted by the compensating electrons and the variation of the beam radius. Accordingly, we identify a region in ion optics where generally no electrons exist to exclude the influence of electron compensation, and then we modify the CL law of this region by taking into account the effect of the change in the beam radius. We validate the modified CL law and demonstrate its effectiveness in predicting the operating points of the ion optics, such as the perveance-limit point.

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“…B and C are the functions of the sheath thickness t s since equation ( 10) is derived based on the assumption that the electric field at the sheath edge is zero. Assuming that the sheath thickness t s is approximately 20λ D [15,25] where λ D = ε 0 T e /(en e ) area where the divergence angles drop significantly with the increase of n p . It can be seen that F m will always be higher than D when γ o ∈ [0, 1] and n p > n p,max , which corresponds to the potential distributions shown in figure 5(b) and proves that the ion optics cannot match with the density higher than n p,max .…”

Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

“…Some earlier works tried to simulate the formation of the upstream sheath or even presheath self-consistently [20,21], but it was proved by Li and Sun [22] that the local model of ion optics can only describe a given sheath and is unable to form the presheath. Therefore, the simulations of positive ion extraction were more effective in the investigations of the beam characteristics and grid erosion [11,[23][24][25] or the ion dynamics in the sheath field [4,10]. Consequently, the structure particularity of the ion optics makes it difficult for experiments and simulations to analyze the detailed sheath characteristics and the mechanism of its effect on beam divergence.…”

Section: Introductionmentioning

confidence: 99%

Numerical and theoretical modeling of the sheath upstream of ion optics: sheath structure transition and its effect on the beam divergence

Li¹,

Yuan²,

Yang³

et al. 2021

Plasma Sources Sci. Technol.

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The grasp of the sheath characteristics is fundamental to evaluate the extraction capabilities of ion optics and accommodate the wide application of ion sources. A one-dimensional theoretical model is developed to investigate the sheath upstream of ion optics as well as the matching relation between the ion optics and plasma, by simplifying and decomposing the Poisson's equation at the outer surface and centerline of the grid aperture. The one-dimensional model is validated by 2D3V hybrid simulations which are also applied to visualize the sheath structure and ion beam divergence. With the increase of plasma density, it is found that the upstream sheath will transform gradually into a sheath near the plate electrode at first and then enter the screen aperture with a sheath edge approximately paralleling to the meniscus. Accordingly, the structure of the upstream sheath can be classified into four kinds which correspond to different beam divergence. The structure transition of the upstream sheath reflects the interaction between the extraction field and plasma, and the ion optics is considered to work at the matching point when the plasma is relatively balanced with the extraction field. Around the matching point, a small beam divergence angle can be achieved without the occurrence of over-perveance. Then a matching model is proposed based on the characteristics of the potential distribution at the matching point. It is verified to be effective of the model for quickly analyzing the ion beam divergence characteristics and determining an ideal operating range of the ion optics.

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Global model of a radio-frequency ion thruster based on a holistic treatment of electron and ion density profiles

Cited by 12 publications

References 18 publications

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster

Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster

On the space-charge effects in the beam extraction process of ion thrusters: the roles of compensating electrons and changing beam radius

Numerical and theoretical modeling of the sheath upstream of ion optics: sheath structure transition and its effect on the beam divergence

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