The role of outgassing in surface flashover under vacuum

Neuber, A.; Butcher, M.; Krompholz, H.; Hatfield, L.L.; Kristiansen, M.

doi:10.1109/27.901239

Cited by 122 publications

(48 citation statements)

References 6 publications

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“…Finally, the surface flashover occurs due to desorption of adsorbed gas from solid dielectrics or vaporization of a surface layer from solid insulator and metal materials etc. [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Impulse surface flashover development associated with transient charging by explosive electron emission in vacuum

Nakano

Kojima

Tsuchiya

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

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Surface discharge on solid insulator in vacuum, which is one of the most significant issues under high electric field, prevents the development of higher voltage vacuum circuit breakers and vacuum interrupters. To clarify the mechanism of the surface discharge in vacuum, charge activities on solid insulators in the development process of the surface discharge should be investigated. By using electrostatic probes behind the alumina dielectrics and measuring fast-framing images of the surface discharge, in the present paper, we clarified that the impulse surface flashover starts in developing with explosive electron emission (EEE) on cathode, which is specific phenomenon on the electron emission site exploding due to extreme field emission current density. Experimental results revealed the characteristics of transient charging by EEE in the surface flash over development as follows: (1) the probe current due to EEE increases with the EEE inception electric field on the cathode, and also depends on the work function of the cathode material, (2) the transient charge distribution on the alumina dielectrics is determined by the EEE spot on the cathode, (3) EEE occurs several times due to the erosion and the regeneration of electron emission sites. (4) the successive EEE makes the transient charge distribution smooth on the alumina dielectrics.

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“…Finally, the surface flashover occurs due to desorption of adsorbed gas from solid dielectrics or vaporization of a surface layer from solid insulator and metal materials etc. [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Impulse surface flashover development associated with transient charging by explosive electron emission in vacuum

Nakano

Kojima

Tsuchiya

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

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“…5 In addition, on the basis of Ref. 4, the phase 1 of flashover process under steady voltage excitation could be separated into two stages, including phase 1(a) which means SSEE process and phase 1(b) which means general SEEA, as shown in Fig. 3.…”

Section: Theoretical Analysis On Ssee and Related Surface Charginmentioning

confidence: 99%

“…[1][2][3] It is generally considered that the flashover process in vacuum can be divided into four distinct phases, i.e., (phase 0) the field electron emission (FEE) from cathode triple junction (CTJ); (phase 1) subsequently, the development of secondary electron emission avalanche (SEEA) on dielectric surface; (phase 2) which is accompanied by a local pressure buildup due to electron stimulated outgassing and dust impurities; and (phase 3) finally, followed by gaseous ionization and breakdown. 2,4 In our recent research, a kind of particular optical emission phenomena, i.e., the cathode-like luminescence (CLL) from insulator surface under steady voltage excitation in vacuum has been reported, 5 as shown in Fig. 1.…”

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confidence: 99%

Theoretical and simulation research on self-stabilizing secondary electron emission process across solid dielectrics in vacuum

Zhan

Huang

et al. 2013

Journal of Applied Physics

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Recently, the cathode-like luminescence phenomena are observed from the surface of solid dielectrics under steady-state high voltage excitation in vacuum, which is closely related to the self-stabilizing secondary electron emission (SSEE) occurring on insulator surface. In this paper, the theoretical analysis about surface charging based on the SSEE is made, and a one-dimensional Mont Carlo simulation on surface charge accumulation under DC voltage excitation is provided. The results reveal that surface charging process can be divided into three stages including initial accumulation, fast multiplication, and final stable stage. In the final stage, the SSEE phenomena are achieved and surface charges are invariable and reach up to a stable distribution. The simulated stable surface charge distribution is consistent with the theoretical deduction results, which confirms the existence of SSEE process.

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“…The surface discharge in vacuum can be influenced by many factors such as charging on solid dielectrics [7][8][9], electric field distribution [10], insulator materials [11,12], and adsorption gas [12][13][14] etc. Generally, the surface discharge event in vacuum is considered to be a process that starts with the electron emission from the metal cathode (not only the cathode triple junction but also the center shield and/or the relaxation ring of the VI), giving rise to a secondary electron emission avalanche (SEEA) due to the collision of the emitted electrons from the dielectrics, and ends with the flashover occurring in the desorbed surface gas layer [15].…”

Section: Introductionmentioning

confidence: 99%

Pre-discharge and flashover characteristics of impulse surface discharge in vacuum

Nakano

Kojima

Hayakawa

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

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Surface discharge on solid insulators is one of the significant issues in the development of vacuum circuit breakers (VCB) and vacuum interrupters (VI).We measured the charge activity on alumina dielectrics in vacuum through ultra-high speed and high sensitivity optical measurements. We identified the existence of charge activity with a small light emission on alumina dielectrics before the surface flashover development process, and defined this as a "pre-discharge" and measured its characteristics. We classified the charge activities into three processes: (1) pre-discharge, (2) surface flashover initiation, and (3) surface flashover expansion, in the development of surface discharge in vacuum. Utilizing this classification, we found that the surface predischarge in vacuum is generated by the electron emission from the cathode, and the subsequent flashover initiates with a steep increase in current and develops with the distortion of the electric field due to transiently-formed charging on the alumina dielectrics in vacuum.

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The role of outgassing in surface flashover under vacuum

Cited by 122 publications

References 6 publications

Impulse surface flashover development associated with transient charging by explosive electron emission in vacuum

Impulse surface flashover development associated with transient charging by explosive electron emission in vacuum

Theoretical and simulation research on self-stabilizing secondary electron emission process across solid dielectrics in vacuum

Pre-discharge and flashover characteristics of impulse surface discharge in vacuum

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