Non-Maxwellian electron energy probability functions in the plume of a SPT-100 Hall thruster

Giono, Gabriel; Guðmundsson, Jón Tómas; Ivchenko, Nickolay; Mazouffre, S.; Dannenmayer, Käthe; Loubère, D; Popelier, Lara; Merino, Mario; Olentšenko, G

doi:10.1088/1361-6595/aaa06b

Cited by 15 publications

(16 citation statements)

References 26 publications

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“…A cylindrical single Langmuir probe was used to determine the electron properties in the cathode plume on the axis 4,39,40 . The probe collection part is a 0.15 mm in diameter and 2 mm in length tungsten wire.…”

Section: Ion and Electron Properties A Diagnosticsmentioning

confidence: 99%

Anode geometry influence on LaB6 cathode discharge characteristics

et al. 2019

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The characterization of an electric propulsion device cathode is performed in the so-called diode configuration with an external anode. The anode acts as a physical boundary for the cathode plasma discharge; therefore, it influences cathode operation and performances. In this study, four different anodes—namely, a disk, a plate, a long cylinder, and a short cylinder—have been used with a flat disk LaB6 emitter 5 A-class cathode to examine the anode geometry impact on cathode discharge properties. Current–voltage curves, discharge oscillations, electron parameters, and ion velocities have been measured for currents in the 2 A to 12 A range and xenon mass flow rates varied from 0.4 mg/s to 1 mg/s with a fixed cathode-to-anode distance. The set of results clearly supports the fact that the anode geometry strongly influences the cathode characteristics both at the macroscopic and the microscopic scale.

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Section: Ion and Electron Properties A Diagnosticsmentioning

confidence: 99%

Anode geometry influence on LaB6 cathode discharge characteristics

et al. 2019

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“…A particle-based formulation of unmagnetized paraxial plumes led to similar results [69]. Plume cooling has been verified experimentally in EPTs [70][71][72] and in HETs [73,74]; still, detecting experimentally the temperature anisotropy continues to be challenging.…”

Section: D-axial Kinetic Model Of a Paraxial Plumementioning

confidence: 79%

Using electron fluid models to analyze plasma thruster discharges

Ahedo

2023

J Electr Propuls

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Fluid models of the slow-dynamics of magnetized, weakly-collisional electrons lead to build computationally-affordable, long-time simulations of plasma discharges in Hall-effect and electrodeless plasma thrusters. This paper discusses the main assumptions and techniques used in 1D to 3D electron fluid models, and some examples illustrate their capabilities. Critical aspects of these fluid models are the expressions for the pressure tensor, the heat flux vector, the plasma-wall fluxes, and the high-frequency-averaged electron transport and heating caused by plasma waves, generated either by turbulence or external irradiation. The different orders of magnitude of the three scalar momentum equations characterize the electron anisotropic transport. Central points of the discussion are: the role of electron inertia, magnetically-aligned meshes versus Cartesian-type ones, the use of a thermalized potential and the infinite mobility limit, the existence of convective-type heat fluxes, and the modeling of the Debye sheath, and wall fluxes. Plasma plume models present their own peculiarities, related to anomalous parallel cooling and heat flux closures, the matching of finite plume domains with quiescent infinity, and solving fully collisionless expansions. Solutions of two 1D electron kinetic models are used to derive kinetically-consistent fluid models and compare them with more conventional ones.

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“…We finally propose to fit the I-V curves with the q-Weibull cdf, shown in Eq. (15). It is important to note that this cdf is related to the EEPF through a second derivative, this is analyzed in Appendix C.…”

Section: Using the Q-weibull Distribution Function: Plasma Potential ...mentioning

confidence: 99%

“…Druyvesteyn has proved [11] that the second derivative of the probe current I(V) is related to the EEDF. After Druyvesteyn's work, measurements made with different probes, plasma conditions and positions of the probe inside the plasma chamber have shown that many EEDF are not Maxwellians [10,1,12,13,14,15,16]. In this line of development, Bi-Maxwellian, Druyvesteyn and Bi-Druyvesteyn distributions have been proposed to analyze plasma parameters as shown in Refs.…”

Section: Introductionmentioning

confidence: 99%

New procedure to estimate plasma parameters through the q-Weibull distribution by using a Langmuir probe in a cold plasma

Gonzalez

González

Soler

et al. 2022

Plasma Res. Express

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We describe a procedure to obtain the plasma parameters from the {\bf I-V} Langmuir curve by using the Druyvesteyn equation. We propose to include two new parameters, $q$ and $r$, to the usual plasma parameters: plasma potential ($V_p$), floating potential ($V_f$), electron density ($n$), and electron temperature ($T$). These new parameters can be particularly useful to represent non-Maxwellian distributions. The procedure is based on the fit of the {\bf I-V} Langmuir curve with the $q$-Weibull distribution function, and is motivated by recent works which use the $q$-exponential distribution function derived from Tsallis statistics. We obtain the usual plasma parameters employing three techniques: the numerical differentiation using Savitzky Golay (SG) filters, the $q$-exponential distribution function, and the $q$-Weibull distribution function. We explain the limitations of the $q$-exponential function, where the experimental data $V>V_p$ needs to be trimmed beforehand, and this results in a lower accuracy compared to the numerical differentiation with SG. To overcome this difficulty, the $q$-Weibull function is introduced as a natural generalization to the $q$-exponential distribution, and it has greater flexibility in order to represent the concavity change around $V_p$. We apply this procedure to analyze the measurements corresponding to a nitrogen $N_2$ cold plasma obtained by using a single Langmuir probe located at different heights from the cathode. We show that the $q$ parameter has a very stable numerical value with the height. This work may contribute to clarify some advantages and limitations of the use of non-extensive statistics in plasma diagnostics, but the physical interpretation of the non-extensive parameters in plasma physics remains not fully clarified, and requires further research.

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Non-Maxwellian electron energy probability functions in the plume of a SPT-100 Hall thruster

Cited by 15 publications

References 26 publications

Anode geometry influence on LaB6 cathode discharge characteristics

Anode geometry influence on LaB6 cathode discharge characteristics

Using electron fluid models to analyze plasma thruster discharges

New procedure to estimate plasma parameters through the q-Weibull distribution by using a Langmuir probe in a cold plasma

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