Verification of a multiscale surface stress model near voids in copper under the load induced by external high electric field

Vigonski, Simon; Veske, Mihkel; Aabloo, Alvo; Djurabekova, Flyura; Zadin, Vahur

doi:10.1016/j.amc.2015.01.102

Cited by 5 publications

(8 citation statements)

References 30 publications

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“…30 However, the formation process of such protrusions in a metal subject to an electric field has not yet been adequately described theoretically or observed experimentally. 19,25,28,29 Our model, based on mobile dislocation density fluc- tuations (MDDF), 16 complements these previous models by proposing that surface features appear as a result of a critical increase in the mobile dislocation density ρ. According to this model, prior to breakdown, the mobile dislocation density is in a long-lived metastable state, fluctuating around a deterministically stable value ρ * .…”

Section: Introductionsupporting

confidence: 53%

“…This early stage evolution can nucleate consequent dynamics, which are described by other models. [25][26][27][28][29]53 In addition, the model defines some unique features of breakdown nucleation, which have not been directly treated by previous models. First, breakdown is a critical process, which develops within several tens of nanoseconds for parameter values around those of the nominal parameters, see Section VI.…”

Section: Discussionmentioning

confidence: 99%

“…Previous attempts to explain breakdown nucleation were centered around the formation of distinct protrusions leading to electric field enhancement, evidenced by increased dark currents. 28,29 The enhanced electric field can lead to heating, due to the current and field emission effects after a significant surface protrusion appears. 30 However, the formation process of such protrusions in a metal subject to an electric field has not yet been adequately described theoretically or observed experimentally.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the MDDF model describes the process up to the formation of surface deformations, while the subsequent processes of breakdown can be treated by the models previously mentioned. 19,25,28,29 This post-nucleation evolution is not discussed here, and may, as well, not be deterministic. Indeed, there are initial indications from microscopy and current measurements suggesting the existence of sub-breakdown events, which may be a result of critical transitions which did not develop into a full-blown breakdown.…”

Section: Introductionmentioning

confidence: 99%

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Theory of electric field breakdown nucleation due to mobile dislocations

Engelberg

Yashar

Ashkenazy

et al. 2019

Phys. Rev. Accel. Beams

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A model is described, in which electrical breakdown in high-voltage systems is caused by stochastic fluctuations of the mobile dislocation population in the cathode. In this model, the mobile dislocation density normally fluctuates, with a finite probability to undergo a critical transition due to the effects of the external field. It is suggested that once such a transition occurs, the mobile dislocation density will increase deterministically, leading to electrical breakdown. Model parametrization is achieved via microscopic analysis of OFHC Cu cathode samples from the CERN CLIC project, allowing the creation and depletion rates of mobile dislocations to be estimated as a function of the initial physical condition of the material and the applied electric field. We find analytical expressions for the mean breakdown time and quasistationary probability distribution of the mobile dislocation density, and verify these results by using a Gillespie algorithm. A least-squares algorithm is used to fit these results with available experimental data of the dependence of the breakdown rate on the applied strength of the electric field and on temperature. The effects of the variation of some of the assumptions of the physical model are considered, and a number of additional experiments to validate the model are proposed, which include examining the effects of the temperature and pulse length, as well as of a time-dependent electric field, on the breakdown rate. Finally, applications of the model are discussed, including the usage of the quasistatic probability distribution to predict breakdowns, and applying the predictions of the model to improve the conditioning process of the cathode material.

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Section: Introductionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Theory of electric field breakdown nucleation due to mobile dislocations

Engelberg

Yashar

Ashkenazy

et al. 2019

Phys. Rev. Accel. Beams

View full text Add to dashboard Cite

show abstract

“…This protrusion would then enhance the electric current on the surface, leading to heating and thus to plasma formation and arc nucleation. However, molecular dynamics and finite element simulations showed these processes occurring only at E 1 GV/m [11,12], significantly more than the observed BD fields, in the range of 100-200 MV/m [4,10]. It is well established that plasticity in metals close to the yield is controlled by stochastic dislocation reactions [13].…”

mentioning

confidence: 99%

Stochastic Model of Breakdown Nucleation under Intense Electric Fields

2018

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A plastic response due to dislocation activity under intense electric fields is proposed as a source of breakdown. A model is formulated based on stochastic multiplication and arrest under the stress generated by the field. A critical transition in the dislocation population is suggested as the cause of protrusion formation leading to subsequent arcing. The model is studied using Monte Carlo simulations and theoretical analysis, yielding a simplified dependence of the breakdown rates on the electric field. These agree with experimental observations of field and temperature breakdown dependencies.

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Simulations of surface stress effects in nanoscale single crystals

Zadin¹,

Veske²,

Vigonski³

et al. 2018

Modelling Simul. Mater. Sci. Eng.

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Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the surface and subsurface layers in the presence of high electric fields. Thermally activated processes, as well as plastic deformation caused by tensile stress due to an applied electric field, are usually not accessible by atomistic simulations because of long time needed for these processes to occur. On the other hand, finite element methods, able to describe the process of plastic deformations in materials at realistic stresses, do not include surface properties. The latter are particularly important for the problems where the surface plays crucial role in the studied process, as for instance, in case of plastic deformations at a nanovoid. In the current study by means of molecular dynamics and finite element simulations we analyse the stress distribution in single crystal copper containing a nanovoid buried deep under the surface. We have developed a methodology to incorporate the surface effects into the solid mechanics framework by utilizing elastic properties of crystals, pre-calculated using molecular dynamic simulations. The method leads to computationally efficient stress calculations and can be easily implemented in commercially available finite element software, making it an attractive analysis tool.

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Verification of a multiscale surface stress model near voids in copper under the load induced by external high electric field

Cited by 5 publications

References 30 publications

Theory of electric field breakdown nucleation due to mobile dislocations

Theory of electric field breakdown nucleation due to mobile dislocations

Stochastic Model of Breakdown Nucleation under Intense Electric Fields

Simulations of surface stress effects in nanoscale single crystals

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