The ecton mechanism of unipolar arcing in magnetic confinement fusion devices

Barengolts, S. A.; Mesyats, G.; Tsventoukh, M. M.

doi:10.1088/0029-5515/50/12/125004

Cited by 56 publications

(27 citation statements)

References 34 publications

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“…Next, the effects of the fuzzy layer thickness on the erosion processes were analysed. For spherically symmetric destruction of the surface, the radius of the crater formed due to Joule heating during the operation of a cathode spot cell is determined by the formula

r_{ex} = \sqrt{i_{c} false/ 2 π} {(t / \overset{true‾}{h})}^{1 false/ 4}

, where i c is the cell current . For sufficiently thick fuzzy layers, assuming that the cathode destruction rate dr ex / dt is equal to the velocity of the heat wave d ( αt ) 1/2 / dt , the radius of the crater formed due to Joule heating

r_{exi} = i_{c} false/ ((), 4 π \sqrt{α \overset{h}{true}})

can be estimated in this case, yielding r exi ≈ i c · 2.2 µm.…”

Section: Discussionmentioning

confidence: 99%

“…From a theoretical point of view, the arc ignition present on the fuzzy W surfaces under fusion‐relevant conditions has been explained by the ecton mechanism, which accounts for a cathode spot as an individual explosive electron emission cell, referred to as an ecton . The motion and erosion properties that depend on the fuzzy layer thickness were discussed using that theoretical basis .…”

Section: Introductionmentioning

confidence: 99%

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Ignition and erosion of materials by arcing in fusion‐relevant conditions

Hwangbo

Kajita

Barengolts

et al. 2018

Contributions to Plasma Physics

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This study investigated the characteristics of arcing initiated on nanostructured fuzzy tungsten (W) surfaces in helium (He) plasmas. Under the same He plasma conditions, the relationship between arc voltage and current was characterized as linear due to plasma resistance across the He plasma from the target surface to the plasma source. Properties of the erosion caused by arcing were investigated by focusing on two parameters: arc current and fuzzy layer thickness. The erosion per charge was significantly dependent on the thickness of the fuzzy layer but did not depend on the arc current. Sample surface analysis revealed that drastic changes in arc spot grouping features were accompanied by the fuzzy layer thickness variation. The ecton model indicated that the erosion as ions does not play a main role, but mechanical destruction by momentum transfer from the explosive electron emission centre to neighbouring nanowires seems to enhance the erosion greatly.

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r_{ex} = \sqrt{i_{c} false/ 2 π} {(t / \overset{true‾}{h})}^{1 false/ 4}

r_{exi} = i_{c} false/ ((), 4 π \sqrt{α \overset{h}{true}})

can be estimated in this case, yielding r exi ≈ i c · 2.2 µm.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ignition and erosion of materials by arcing in fusion‐relevant conditions

Hwangbo

Kajita

Barengolts

et al. 2018

Contributions to Plasma Physics

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“…The time cutoff is derived by the observation of smoothing of a surface, rather than crater formation, when the discharge pulse duration is less than 5 ns [94]. The lower limit of the length scale is found from the smallest macroparticles and crater sizes [118,119]. The ignition of cathode spots has much in common with high voltage electrical breakdown [92,120].…”

Section: Cathodic Arc Plasma Production With Emphasis On Pulsed Arcsmentioning

confidence: 99%

A review comparing cathodic arcs and high power impulse magnetron sputtering (HiPIMS)

Anders

2014

Surface and Coatings Technology

222

109

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High power impulse magnetron sputtering (HiPIMS) has been in the center of attention over the last years as it is an emerging physical vapor deposition (PVD) technology that combines advantages of magnetron sputtering with various forms of energetic deposition of films such as ion plating and cathodic arc plasma deposition. It should not come at a surprise that many extension and variations of HiPIMS make use, intentionally or unintentionally, of previously discovered approaches to film processing such as substrate surface preparation by metal ion sputtering and phased biasing for film texture and stress control. Therefore, in this review, an overview is given on some historical developments and features of cathodic arc and HiPIMS plasmas, showing commonalities and differences. To limit the scope, emphasis is put on plasma properties, as opposed to surveying the vast literature on specific film materials and their properties.

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“…The experimental results exhibited interesting and essential characteristics in grouping feature of arc spot cells. Earlier, we attempted to interpret the experimental results by considering the processes occurring during the operation of an individual cell of the cathode spot of a vacuum arc 19,20 in the context of the explosive-emission center (ecton) model of a cathode spot. 21 It has been shown that as a spot cell moves to a thick nanostructured layer, the size of the crater it leaves increases and its velocity decreases.…”

Section: Introductionmentioning

confidence: 99%

Arc spot grouping: An entanglement of arc spot cells

Kajita

Hwangbo

Ohno

et al. 2014

Journal of Applied Physics

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Articles you may be interested inA model of reaction field in gas-injected arc-in-water method to synthesize single-walled carbon nanohorns: Influence of water temperatureIn recent experiments, clear transitions in velocity and trail width of an arc spot initiated on nanostructured tungsten were observed on the boundary of the thick and thin nanostructured layer regions. The velocity of arc spot was significantly decreased on the thick nanostructured region. It was suggested that the grouping decreased the velocity of arc spot. In this study, we try to explain the phenomena using a simple random walk model that has properties of directionality and selfavoidance. And grouping feature was added by installing an attractive force between spot cells with dealing with multi-spots. It was revealed that an entanglement of arc spot cells decreased the spot velocity, and spot cells tend to stamp at the same location many times. V C 2014 AIP Publishing LLC.

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The ecton mechanism of unipolar arcing in magnetic confinement fusion devices

Cited by 56 publications

References 34 publications

Ignition and erosion of materials by arcing in fusion‐relevant conditions

Ignition and erosion of materials by arcing in fusion‐relevant conditions

A review comparing cathodic arcs and high power impulse magnetron sputtering (HiPIMS)

Arc spot grouping: An entanglement of arc spot cells

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