Thermionic Emission Including Both Space Charge and Image Forces

Lin, T. P.; Eng, George

doi:10.21236/ada212732

Cited by 1 publication

(3 citation statements)

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“…Eqs. (42) and (43) describe the growth of the instability in the quasi-linear regime assuming the electron and ion distribution functions remain almost maxwellian. Therefore, it cannot describe the inherently kinetic instability saturation mechanisms [40].…”

Section: Streaming Instabilitiesmentioning

confidence: 99%

“…The approach used here is largely based on an existing model by Lin and Eng [42] with the addition of ions and of electrons coming from the plasma bulk.…”

Section: Hypothesesmentioning

confidence: 99%

“…We first express the density of an initially maxwellian population of electrons at wall temperature having to cross a potential barrier. Following the derivation presented by Lin and Eng [42], the following expression is obtained (see Eq. 8a in their article):…”

Section: Poisson's Equation In the Sheathmentioning

confidence: 99%

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Hollow cathode modeling: I. A coupled plasma thermal two-dimensional model

Sary¹,

Garrigues²,

Boeuf³

2017

Plasma Sources Sci. Technol.

130

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A two dimensional axisymmetric quasi-neutral fluid model of an emissive hollow cathode that includes neutral xenon, single charge ions and electrons has been developed. The gas discharge is coupled with a thermal model of the cathode into a self-consistent generic model applicable to any hollow cathode design. An exhaustive description of the model assumptions and governing equations is given. Boundary conditions for both the gas discharge and thermal model are clearly specified as well. A new emissive sheath model that is valid for any emissive material and in both space charge and thermionic emission limited regimes is introduced. Then, setting the emitter temperature to an experimentally measured profile, we compare simulation results of the plasma model to measurements available in the literature for NASA NSTAR barium oxide cathode. Qualitative discrepancies between simulation results and measurements are noted in the cathode plume regarding the simulated plasma potential. Motivated by experimental evidence supporting the occurrence of ion acoustic instabilities in the cathode plume, an enhanced model of electron transport in the plume is presented and its consequences analyzed. Using the obtained plasma model, simulated quantities in the plume are qualitatively comparable with measurements. Inside the cathode, the simulated plasma density agrees well with measurements and is within the ±50 % experimental uncertainty associated with these measurements. A comparison of simulation results of the full coupled cathode model for the NASA NSTAR cathode with experimental measurements is presented in a companion paper, as well as a physical analysis of the cathode behavior and a parametric study of the influence of the operating point and key design choices.

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Section: Streaming Instabilitiesmentioning

confidence: 99%

“…The approach used here is largely based on an existing model by Lin and Eng [42] with the addition of ions and of electrons coming from the plasma bulk.…”

Section: Hypothesesmentioning

confidence: 99%