Arc spot grouping: An entanglement of arc spot cells

Abstract

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.

In-situ plasma treatment of Cu surfaces for reducing the generation of vacuum arc breakdowns

“…A few breakdown spots are visible in the middle of this expanded white spot area. We note the irregular shape of these white spot area, resembling the random walk pattern observed for arc plasma 36 , and hence suggesting the origin of the white spot to be from the plasma surface interaction.…”

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

“…As found previously in Ref. [], spot grouping occurs, and the trajectory of the spot motion becomes entangled as shown in Figure g and h. As a result, the velocity of the spot motion decreases sharply, and a droplet fraction appears in the eroded cathode material, which can be clearly seen in Ref. [].…”

“…In Figure a and b, the branches have similar appearances that show narrow and complex zigzag structures, whereas the branches in Figure c and d become wider and more simplified as l fuzz increases. Enlarged features of the arc trails, shown in Figure e−h, illustrate that the broader branches are due to arc spot groupings in which the arc spots are entangled and behave as a group . In Figure e and f, single arc trails are visible, and the widths of the trails are ∼10 µm, which is consistent with previous reports .…”

A Simple Model of Distribution of Current Over Cathodes of Vacuum Circuit Breakers

“…Although k 1 and k 2 may also depend on other parameters, in particular, on the state of the cathode surface, the arc current, and the interelectrode gap [11], this dependence was not taken into account in the modeling reported in this work and it was set k 1 = 230 ms −1 T −1 , k 2 = 19 ms −1 ; values corresponding to CuCr cathodes at an arc current of 30 A [29]. Note that the above-mentioned values of the coefficients D, k 1 , and k 2 correspond to CuCr cathodes with the usual surface roughness; fine effects, like the effect of nanostructured layers [19], remain beyond the scope of this work.…”

“…A description of the motion of a cathode spot in terms of a standard probability distribution assumed for spot displacements has been developed in [17] and [18]. In [19], the Monte Carlo method is used to simulate the random walk of grouped spot cells, with the aim to describe velocity and trail width of arc spots on nanostructured tungsten cathode.…”