Theoretical Modeling of Cathode Spot Phenomena

Beilis, I. I.

doi:10.1016/b978-081551375-9.50008-4

Cited by 69 publications

(129 citation statements)

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“…In this work, C a and n e have been estimated assuming T s = 4 × 10 3 K and the plasma pressure was set equal to 20 bar or 100 bar, which are values of the pressure of saturated copper vapor evaluated with the use of [16] for temperatures of 3.8 × 10 3 K and 4.6 ×10 3 K, respectively. Values of the temperature of plasma electrons given by different authors vary from about one to several electronvolts; for example, values of 4 −6 eV; 0.9 eV and 3.5 eV; 1 −6 eV are cited in, respectively, [17], p. 194; [15], p. 231; [12], p. 260. Since variations in T e strongly affect the ionization rate constant, the estimates of this work have been performed for T e varying between 1 and 6 eV.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Let us set U = 15 V, which is the near-cathode voltage drop in a vacuum arc on a copper cathode cited by most authors, e.g., [15], p. 229. Values of the temperature of the surface of a copper cathode inside a spot given by different authors are somewhere between 3.5×10 3 K and 5.5×10 3 K; for example, values of 3.7 × 10 3 K and 5.1 × 10 3 K are cited in [15], p. 231. In this work, C a and n e have been estimated assuming T s = 4 × 10 3 K and the plasma pressure was set equal to 20 bar or 100 bar, which are values of the pressure of saturated copper vapor evaluated with the use of [16] for temperatures of 3.8 × 10 3 K and 4.6 ×10 3 K, respectively.…”

Section: Discussionmentioning

confidence: 99%

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Space-charge sheath with ions accelerated into the plasma

Benilov¹

2010

J. Phys. D: Appl. Phys.

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To cite this version:M S Benilov. Space-charge sheath with ions accelerated into the plasma. Journal of Physics D: Applied Physics, IOP Publishing, 2010, 43 (17) The conventional model of near-cathode space-charge sheath with ions entering the sheath from the quasi-neutral plasma may be not applicable to discharges burning in cathode vapor, e.g., vacuum arcs, where ionization of emitted atoms may occur inside the sheath with some of the produced ions returning to the cathode and others moving into the plasma. In this connection, a simple model is considered of a sheath formed by electrons and positive ions injected into the sheath with a very low velocity and moving from the sheath into the plasma. It is shown that such sheath is possible provided that the sheath voltage is equal to or exceeds approximately 1.256kT e /e. This limitation is due to the space charge in the sheath and is in this sense analogous to the limitation of ion current in a vacuum diode expressed by the Child-Langmuir law. The ions leave a sheath and enter the plasma with a velocity equal to or exceeding approximately 1.585u B .

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Space-charge sheath with ions accelerated into the plasma

Benilov¹

2010

J. Phys. D: Appl. Phys.

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“…Much research, both theoretically [2][3][4][5][6][7] and experimentally [8][9][10][11][12][13][14] , has been done for decades to understand the spot phenomena that produce non-equilibrium plasmas containing multiply ion charge states. The plasma is mesosonic 15 , i.e., subsonic for electrons and supersonic for ions, with respect to the local ion sound velocity.…”

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confidence: 99%

Cathodic arcs: Fractal voltage and cohesive energy rule

Anders

Окс

Yushkov

2005

Applied Physics Letters

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The noise of the burning voltage of cathodic arcs in vacuum was analyzed for a range of cathode materials (C, Mg, Ti, V, Ni, Cu, Zr, Nb, Ag, Hf, Ta, W, Pt, Bi, and Si). Cathodic arcs were generated in a coaxial plasma source, and the voltage noise was measured with a broadband (250 MHz) measuring system. Each measurement of 50,000 points was analyzed by Fast Fourier Transform, revealing a power spectrum ~ 1/f 2 for all metals over several orders of magnitude of frequency f (brown noise). The absence of any characteristic time down to possible cutoffs at high frequencies supports a fractal model of cathode spots. Our preliminary research indicate that materials of high cohesive energy have a cutoff of self-similarity at 50 MHz while no cutoff could be found up to 100 MHz for non-refractory metals. The amplitude of colored noise scaled approximately linearly with the cathode's cohesive energy, which is another manifestation of the Cohesive Energy Rule. a) electronic address: aanders@lbl.gov LBNL-57025 1The plasma of cathodic vacuum arcs is produced at non-stationary cathode spots 1 . Much research, both theoretically 2-7 and experimentally [8][9][10][11][12][13][14] , has been done for decades to understand the spot phenomena that produce non-equilibrium plasmas containing multiply ion charge states. The plasma is mesosonic 15 ,i.e., subsonic for electrons and supersonic for ions, with respect to the local ion sound velocity. Difficulties in experimentation and modeling are associated with the spots' fast changes, small sizes, and extreme gradients of power density and particle densities. The formation of spot plasma is often described as a sequence of microexplosions, where cathode material transitions through various phases, from solid to liquid, non-ideal plasma and/or gas phases, finally turning into in a non-equilibrium, expanding, fully ion ionized plasma 6,16 .With improvement of experimental techniques, faster and smaller phenomena have been discovered. This becomes especially striking when the issue of current density is considered. As the apparent area of electron emission was found to be smaller than previously thought, the corresponding current density increased accordingly 17,18 . There were arguments what constitutes an electron-emitting site.In one extreme, electron emission should occur from areas much larger than the molten crater due to intense ion bombardment of the crater vicinity. On the other hand, the most relevant electron emission area might be smaller than the later visible crater because crater formation could be the result of the action of several spot fragments or cells.In order to make any useful statements on cathode processes and parameters of cathodic arc plasma, many researches decided to repeat measurements and average the measured data. For example, one can find data on average ion charge states 10,19 , average burning voltages 20,21 , average ion velocities 15 , or average ion velocity distribution functions 22 .All parameters fluctuate with large amplitude; in some cases up to...

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“…This work is an extension of the mentioned model and describes the formation of secondary ectons upon the interaction of a dense plasma with cathode surface microprotrusions. In the general case, the charge particle flow that closes onto a microprotrusion consists of three components: an ion flow and an electron flow from the plasma and a flow of emission electrons (Ecker, 1980;Hantzsche, 1995;Beilis, 1995). Each of these flows carries both an electric charge and an energy flux, forming a space charge zone at short distances from the cathode surface and giving rise to an electric field E c at the cathode.…”

Section: Initiation Of An Explosive Center Beneath the Plasma Of A Vamentioning

confidence: 99%

Numerical Simulation of the Fast Processes in a Vacuum Electrical Discharge

Uimanov¹

2011

Numerical Simulations - Applications, Examples and Theory

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Theoretical Modeling of Cathode Spot Phenomena

Cited by 69 publications

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Space-charge sheath with ions accelerated into the plasma

Space-charge sheath with ions accelerated into the plasma

Cathodic arcs: Fractal voltage and cohesive energy rule

Numerical Simulation of the Fast Processes in a Vacuum Electrical Discharge

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