Effects of Roughening Insulator Surface on Charging and Flashover Characteristics of a Long Glass Insulator in Vacuum

Yamamoto, Osamu; Satoh, Takehiro; Hayashi, Hirotaka; Hamada, Shoji; Kobayashi, Tetsuo; Omura, Hiroshi; Morii, Hiroshi

doi:10.1541/ieejfms.126.769

Cited by 4 publications

(2 citation statements)

References 20 publications

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“…Recently, the method of roughening an insulator surface was found to be effective in the wide range of insulating distances between a few hundreds of ptm to 50 mm [8] and even for ac voltage excitations [7]. In the future, we intend to work on the practical application of these research results to the development of more compact and reliable equipment.…”

Section: Effect Of the Spacer Shapementioning

confidence: 98%

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Depression of Insulator Charging in Vacuum by Partial Mechanical Processing

Yamamoto

Markon

Morii

et al. 2006

2006 International Symposium on Discharges and Electrical Insulation in Vacuum

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This paper describes experimental results on surface charging of partially mechanically processed insulators in vacuum. The charging phenomena were observed when insulators were exposed to a ramped dc voltage, by using a capacitive probe embedded in the cathode. First, we examined a partially roughened cylindrical insulator. The height of the roughened surface measured from the cathode, was varied while keeping the total length of the insulator constant. Second, in the same way, we examined a cylindrical insulator having a truncated conical frustum or a chamfer at its cathode-side end. Based on these experiments we have proved that the partial mechanical processing is effective for suppressing insulator charging in vacuum.

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Section: Effect Of the Spacer Shapementioning

confidence: 98%

“…However, since such insulators have inevitably large volume, it obstructs the compactness. On the other hand, roughening the insulator surface is also effective to prevent the surface from charging [6,7,8]. In this case, the cost for roughening the entire surface may be high when the insulator is large.…”

Section: Introductionmentioning

confidence: 99%

Depression of Insulator Charging in Vacuum by Partial Mechanical Processing

Yamamoto

Markon

Morii

et al. 2006

2006 International Symposium on Discharges and Electrical Insulation in Vacuum

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View full text Add to dashboard Cite

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Construction of microgrooves on the surface of alumina ceramic insulator to enhance its flashover strength

et al. 2020

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The fabrication method of grooves on the surface of alumina and their influence on the surface flashover characteristics of the alumina insulator were studied in this paper. To prepare grooves with a regular surface structure, the UV laser was applied to carve grooves on the surface of alumina ceramic, and dilute hydrochloric acid was used to corrode and remove the residual materials produced in the laser carving process. By adjusting the laser parameters, periodic grooves were prepared on the surface of a cylindrical alumina insulator with a groove depth of 60 µm and a groove width of approximately 50 µm on the laser spinning carving platform. Then, alumina insulators with different periods were prepared, and their vacuum surface flashover voltages were tested on a short pulsed high-voltage test platform. The test results indicated that the flashover voltages of the alumina insulators with laser carved periodic grooves were increased over 200%, and the improvement did not change much with the groove periods. A further study of the groove parameters showed that several grooves fabricated on the cathode end of the insulators were able to improve the flashover voltage of the alumina insulator to the voltage-withstand level of the fully grooved insulators.

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Effect of insulator surface conditioning on the pinch dynamics and x-ray production of a Ne-filled dense plasma focus

Housley

Hahn

Narkis

et al. 2021

Journal of Applied Physics

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The dense plasma focus (DPF) can be an intense source of x rays, wherein the insulator sleeve strongly dictates the electrical breakdown, which subsequently affects the formation of a plasma sheath and a collapse phase. Experiments on a 25 kJ DPF (operated at 4.4 kJ) are carried out to demonstrate the influence of insulator surface morphology on the pinch structure, dynamics, and x-ray yield using a Ne fill. Two borosilicate insulators are directly compared, one with a smooth finish and the other machined with four circumferential grooves traversing the perimeter of the exterior insulator surface. Comparisons are made through same-shot imaging diagnostics of the evolving plasma sheath during breakdown, rundown, and at the pinch in addition to the time-resolved measurements of emitted x rays via filtered photodiodes. The presence of structures on the insulator sleeve reduces x-ray production across all fill pressures by a factor of 2.8 ± 2.4 on average and reduces the highest x ray producing shots by a factor of 5.5 ± 1.8. Observations of sheath asymmetry and inhomogeneity at lift-off are observed and correlated with subsequent observations of off-axis radial collapse. Taken together, this suggests that local variations in the insulator surface decrease the spatial uniformity of the sheath, leading to an azimuthally asymmetric focus, reduced electron densities, and, ultimately, degraded x-ray production.

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Effects of Roughening Insulator Surface on Charging and Flashover Characteristics of a Long Glass Insulator in Vacuum

Cited by 4 publications

References 20 publications

Depression of Insulator Charging in Vacuum by Partial Mechanical Processing

Depression of Insulator Charging in Vacuum by Partial Mechanical Processing

Construction of microgrooves on the surface of alumina ceramic insulator to enhance its flashover strength

Effect of insulator surface conditioning on the pinch dynamics and x-ray production of a Ne-filled dense plasma focus

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