Characterization of a Heaterless Hollow Cathode

Vekselman, V.; Krasik, Ya. E.; Gleizer, S.; Gurovich, V. Tz.; Warshavsky, A.; Rabinovich, L.

doi:10.2514/1.b34628

Cited by 33 publications

(19 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[4][5][6][7][8][9] Depending on the technological application, HC high current discharge is ignited and sustained by different electron emission mechanisms, namely, field, secondary, photo, or thermionic emission, or a combination of these electron emission mechanisms. The HCs driven by thermionic emission are used in applications related to electric propulsion; [4][5][6][7][8][9] we will consider only this type of HC below.…”

Section: Introductionmentioning

confidence: 99%

Influence of Xe2+ ions on the micro-hollow cathode discharge driven by thermionic emission

2014

Self Cite

View full text Add to dashboard Cite

The influence of Xe 2 þ dimer ions and excited Xe* atoms on the hollow cathode discharge driven by electron thermionic emission is studied using two-dimensional Particle-in-Cell Monte Carlo Collisions modeling. A comparison with the results of two-component (electrons and Xe þ ions) plasma modeling showed that the presence of the Xe 2 þ dimer ions and excited Xe* atoms in the plasma affects the plasma parameters (density, potential, and ion fluxes toward the cathode). The influence of Xe 2 þ ions and Xe* atoms on the plasma sheath parameters, such as thickness and the ion velocity at the sheath edge, is analyzed. V C 2014 AIP Publishing LLC. [http://dx.

show abstract

Section: Introductionmentioning

confidence: 99%

Influence of Xe2+ ions on the micro-hollow cathode discharge driven by thermionic emission

2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…In this work, we present evidence from three plasma scenarios without magnetic fields where different sheath structures are accurately described by either extreme emission electron sheaths, ion trapping in the SCL dip, or standard SCL theory. Measurements were made as follows: (1) In a low pressure discharge (discharge voltage V D = 45 V, current I D = 1.37 A) with a thermionic hollow cathode [22], the filament floated negatively or at φ P ; (2) Inside a 10-cm-diameter, 50-60 W ferromagnetic inductively coupled plasma source [25,26], the filament floated positively; (3) Placed several cm from the anode in the plume of a 2.6-cm-diameter, unmagnetized Hall thruster (V D = 50 V, I D = 1.37 A) with flowing electrons, ions, and neutrals [23,24], filaments remained negative. The studied plasmas are stable, homogeneous across measurement scale lengths, and well-characterized by Langmuir probe measurements.…”

mentioning

confidence: 99%

Floating potential of emitting surfaces in plasmas with respect to the space potential

Kraus

Raitses

2018

Physics of Plasmas

View full text Add to dashboard Cite

The potential difference between a floating emitting surface and the plasma surrounding it has been described by several sheath models, including the space-charge-limited sheath, the electron sheath with high emission current, and the inverse sheath produced by charge-exchange ion trapping. Our measurements reveal that each of these models has its own regime of validity. We determine the potential of an emissive filament relative to the plasma potential, emphasizing variations in emitted current density and neutral particle density. The potential of a filament in a diffuse plasma is first shown to vanish, consistent with the electron sheath model and increasing electron emission. In a denser plasma with ample neutral pressure, the floating filament potential is positive, as predicted by a derived ion trapping condition. Lastly, the filament floated negatively in a third plasma, where flowing ions and electrons and nonnegligible electric fields may have disrupted ion trapping. Depending on the regime chosen, emitting surfaces can float positively or negatively with respect to the plasma potential.Any solid surface in contact with a plasma is surrounded by the sheath, a potential structure that controls particle and energy transport between the plasma and the surface [1]. Sheath structure is complicated when the surface emits an electron current, which can be caused by impinging radiation or plasma particles. Emissive sheaths are present in divertors [2] and scrape-off layers [3] in magnetic fusion devices, around dust grains in laboratory [4] and astrophysical [5] plasmas, around satellites [6], in RF plasma processing devices [7] and around plasma probes [8]. In all of these cases, the interplay between emitted and background plasmas determines the structure of sheath that forms. Predicting which structure exists is essential for understanding the heat and charge flux to the surface.A surface emits a normalized currentĴ = J emit /J e in a background electron current J e . WhenĴ = 0, mobile plasma electrons charge the surface negatively so that its potential is negative with respect to the plasma potential φ P (in this work, all surface potentials called positive r/r 0 −3 −2 −1 0 ∆φ [V] T e [eV] (a)

show abstract

“…Most of the HCs that are presently used in electric propulsion are driven by the thermionic electron emission from emitters heated up to temperatures exceeding 1000 K and having a work function in the range of 1.3-2.5 eV. [1][2][3][4][5][6] At the beginning of the HC operation, an external heater is used to heat the emitter to a temperature sufficient for thermionic emission of electrons, which produce the plasma inside the HC. This plasma supplies ions that are accelerated toward the emitter, mainly inside the sheath formed between the plasma and emitter.…”

Section: Introductionmentioning

confidence: 99%

“…This cylinder in its turn is placed coaxially inside a so-called keeper, which is kept at a floating potential during the steady state operation of the HC. 1,4 The main purposes of the keeper are to facilitate the turning on of the HC discharge, maintain the cathode temperature, and protect the emitter from the interaction of relatively high-energy ions that might limit the HC lifetime. 1 These high-energy ions (up to several tens of eV) are generated in the gap between the keeper and anode.…”

Section: Introductionmentioning

confidence: 99%

Influence of the floating potential on micro-hollow cathode operation

2015

Self Cite

View full text Add to dashboard Cite

The influence of a keeper electrode with a floating potential on the operation of a micro-hollow cathode is studied using the two-dimensional particle-in-cell Monte Carlo collisions model. The floating potential is determined self-consistently, taking into account the electron and ion charges collected by the keeper and the potential induced by the plasma non-compensated space charge. It is shown that the parameters of the micro-hollow cathode operation vary significantly, according to whether the keeper potential is floating or has a specified constant value. V

show abstract

Characterization of a Heaterless Hollow Cathode

Cited by 33 publications

References 21 publications

Influence of Xe2+ ions on the micro-hollow cathode discharge driven by thermionic emission

Influence of Xe2+ ions on the micro-hollow cathode discharge driven by thermionic emission

Floating potential of emitting surfaces in plasmas with respect to the space potential

Influence of the floating potential on micro-hollow cathode operation

Contact Info

Product

Resources

About