Insights from Collisional-Radiative Models of Neutral and Singly Ionized Xenon in Hall Thrusters

Chaplin, Vernon H.; Johnson, L. K.; Lobbia, Robert B.; Konopliv, Mary; Simka, Timothy; Wirz, Richard E.

doi:10.2514/1.b38676

Cited by 6 publications

(7 citation statements)

References 38 publications

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“…This may introduce some error, especially in the high-density regions. However, it has been shown that including photon absorption in the neutral xenon CR model led to a less than ten percent change in results for over the full range of Hall thruster-relevant parameters [14], and the impact for xenon ions is expected to be similar. We also acknowledge that there is some uncertainty in the cross sections.…”

Section: Discussionmentioning

confidence: 99%

“…A CR model for singly-charged xenon ions has recently been developed by JPL and compared with experiments [14,15].…”

Section: Xe II Cr Modelmentioning

confidence: 99%

“…This CR model can be used to calculate the source and sink frequencies for each xenon ion excited state, which when combined with the fluid equations, can be used to calculate the velocity of the metastable state ions used in LIF. The structure of this CR model is more thoroughly discussed in Chaplin et al [14], with the relevant information and equations given here. The model assumes the plasma is optically thin.…”

Section: Xe II Cr Modelmentioning

confidence: 99%

“…Although transitions to the ground state will be significantly absorbed, the transition rate to the ground state from the main non-metastable state explored in this paper is only about one tenth of the total decay rate to other excited states. We calculated the optical thickness of the plasma for the two dominant decay paths at the middle of the acceleration region in HERMeS to be ≪1 using equation (15) of [14]. Therefore, we expect minimal re-absorption.…”

Section: Xe II Cr Modelmentioning

confidence: 99%

“…Therefore, the objective of this paper is to assess the accuracy of using the metastable ion state velocity as representative of the ground state ion velocity. The Xe II collisional-radiative (CR) model recently developed by JPL [14,15] is augmented with one-dimensional ion continuity and momentum equations in order to calculate the metastable ion velocity for a given set of plasma parameters, and therefore answer this question. The approach is to choose a thruster with spatially resolved plasma parameters known from validated discharge simulations.…”

Section: Introductionmentioning

confidence: 99%

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Accuracy of using metastable state measurements in laser-induced fluorescence diagnostics of xenon ion velocity in Hall thrusters

Konopliv

Chaplin

Johnson

et al. 2023

Plasma Sources Sci. Technol.

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Laser-induced ﬂuorescence (LIF) measurements of singly-charged xenon ion velocities in Hall thrusters typically target metastable states due to lack of available laser technology for exciting the ground state. The measured velocity distribution of these metastable ions are assumed to reﬂect the ground state ion behavior. However, this assumption has not been experimentally veriﬁed. To investigate the accuracy of this assumption, a recently developed xenon ion (Xe II) collisional-radiative (CR) model is combined with a 1D ﬂuid model for ions, using plasma parameters from higher ﬁdelity simulations of each thruster, to calculate the metastable and ground state ion velocities as a function of position along the channel centerline. For the HERMeS and SPT-100 thruster channel centerlines, diﬀerences up to 0.2 km/s were observed between the metastable and ground state ion velocities. While both the ground state ions and metastable state ions experience the same acceleration by the electric ﬁeld, these small velocity diﬀerences arise because ionization directly into these states from the slower neutral ground state can reduce their mean velocities by diﬀerent amounts. Therefore, the velocity discrepancy may be larger for thrusters with lower propellant utilization eﬃciency and higher neutral density. For example, diﬀerences up to 1.5 km/s were calculated on the HET-P70 thruster channel centerline. Note that although the creation of slow ions can inﬂuence the mean velocity, the most probable velocity should be unaﬀected by these processes.

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Section: Discussionmentioning

confidence: 99%

“…A CR model for singly-charged xenon ions has recently been developed by JPL and compared with experiments [14,15].…”

Section: Xe II Cr Modelmentioning

confidence: 99%

Section: Xe II Cr Modelmentioning

confidence: 99%

Section: Xe II Cr Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Accuracy of using metastable state measurements in laser-induced fluorescence diagnostics of xenon ion velocity in Hall thrusters

Konopliv

Chaplin

Johnson

et al. 2023

Plasma Sources Sci. Technol.

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An optical emission spectroscopy method for determining the electron temperature and density in low-temperature xenon plasma by using a collisional-radiative model considering the hyperfine structure of emission line into metastable state

Wang,

Zhu

2023

Spectrochimica Acta Part B: Atomic Spectroscopy

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Azimuthal ion dynamics at the inner pole of an axisymmetric Hall thruster

Roberts,

Chaplin,

Jorns

2024

Physics of Plasmas

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The azimuthal dynamics of ions along the inner pole of a Hall thruster with a centrally mounted cathode and a magnetic shielding topography are experimentally investigated. A time-averaged laser-induced fluorescence diagnostic is implemented to characterize the azimuthal ion velocity distribution, and its moments are computed numerically to infer bulk rotation speed and ion temperature. It is found that the time-averaged ion swirl velocity grows to 2 km/s in the near-pole region, and the cathode ions exhibit ion temperatures in the azimuthal direction approaching 8 eV. Both of these quantities exceed the speeds and temperatures anticipated from classical acceleration and heating. Time-resolved laser-induced fluorescence is then employed to investigate the role of plasma fluctuations in driving the time-averaged ion properties. Semicoherent fluctuations at 90 kHz are observed in the ion velocity distribution and its associated moments. These oscillations are correlated with the gradient-driven anti-drift wave, which propagates azimuthally in the near-field cathode plume. Quasilinear theory is used to construct a 1D model for acceleration and heating of the ion population as a result of the anti-drift mode. This approach demonstrates qualitative agreement with the time-averaged ion velocity and temperature, suggesting that the anti-drift mode may be a dominant driver of azimuthal ion acceleration and heating in front of the cathode keeper and the inner half of the inner front pole cover. These results are discussed in terms of their relevance to the erosion of thruster surfaces in the near-field cathode plume.

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Insights from Collisional-Radiative Models of Neutral and Singly Ionized Xenon in Hall Thrusters

Cited by 6 publications

References 38 publications

Accuracy of using metastable state measurements in laser-induced fluorescence diagnostics of xenon ion velocity in Hall thrusters

Accuracy of using metastable state measurements in laser-induced fluorescence diagnostics of xenon ion velocity in Hall thrusters

An optical emission spectroscopy method for determining the electron temperature and density in low-temperature xenon plasma by using a collisional-radiative model considering the hyperfine structure of emission line into metastable state

Azimuthal ion dynamics at the inner pole of an axisymmetric Hall thruster

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