Article

Priorities of cathode and anode contaminations in triggering the short-pulsed voltage breakdown in vacuum

Institute of High Current Electronic, Russian Academy of Sciences, Moskva, Moscow, Russia
IEEE Transactions on Dielectrics and Electrical Insulation (Impact Factor: 1.28). 03/2006; 13(1):41 - 51. DOI: 10.1109/TDEI.2006.1593400
Source: IEEE Xplore

ABSTRACT

Modern theoretical notations on electrical breakdown in vacuum consider cathode triggering mechanisms to be most responsible on short-pulsed (<1 μs) breakdowns while anode mechanisms to be responsible in a part on DC and long-pulsed breakdowns. Following those notations, we tried to reveal conditions at which either mechanism steps aside to another one. The study involved several experimental techniques including the anode-probe surface scanning, pulsed electron-beam surface melting in vacuum for surface cleaning, and intentional dust particle contamination of electrode surfaces. Breakdown tests were performed using a pulser capable of producing 220 kV quasi-square pulses that were adjustable to ∼30 to 80 ns pulse length. Our experiments showed that cathode emission sites are responsible for breakdowns at relatively low hold-off fields. At higher electric fields of up to 1 MV/cm, the anode share in the mechanism of triggering breakdown becomes probably more significant than the cathode mechanism.

Download full-text

Full-text

Available from: Sergey Onischenko, Sep 08, 2015
  • Source
    • "The dc low-voltage arrangement is based on the anodeprobe scanning technique described recently elsewhere [5] in details. The essence of the method is based on idea that a plane electrode is rotated whilst a needle anode at dc positive potential scans a plane electrode along it radius at a certain distance to produce prebreakdown emission current from local places recognized as emission sites. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The paper is devoted to study of the mechanisms responsible for vacuum breakdown as a whole and the total voltage effect in particular. Experiments at DC and pulsed voltages were carried out. It has been shown that there is no manifestation of the total voltage effect at DC voltages up to 20 kV. The strong dependence of hold-off on anode temperature was recognized at DC voltages while pulsed hold-off turned out to be almost the same with heating the electrodes. This gives a basis to consider gas desorption as an insufficient factor in the initiation of pulsed breakdown. An attempt to enhance hold-off with electrostatic removing of loosely bound particles with assistance of electron flow from a thermionic cathode was undertaken in the work. The approach turned out to be ineffective.
    Full-text · Article · Jul 2007 · IEEE Transactions on Dielectrics and Electrical Insulation
  • Source
    • "13-0--[3 --a ----0 --.43 edge radius = 50 .Lm edge radius = 20 .Lm C. Pulsed breakdown ofbroad gaps The results are presented in Table 3 (reference data are available in Fig. 10 of [4]). Electrode heating affects vacuum insulation rather slightly except for the HC P protocol. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The paper is devoted to study of mechanisms responsible on vacuum breakdown as a whole and the total voltage effect in particular. Experiments at dc and pulsed voltages were carried out. It has been shown that there is no manifestation of the total voltage effect at dc voltages up to 20 kV. The strong dependence of hold-off on anode temperature was recognized at dc voltages while pulsed hold-off turned out to be almost the same with heating electrodes. This gives a basis to consider gas desorption as an insufficient factor in initiation of pulsed breakdown. An attempt to enhance hold-off with electrostatic removing of loosely bound particles with assistance of electron flow from a thermionic cathode was undertaken in the work. The approach tuned out to be ineffective
    Full-text · Conference Paper · Oct 2006
  • [Show abstract] [Hide abstract]
    ABSTRACT: An investigation of the HV vacuum breakdown between polished, powder coated, and e-beam treated 304L and 316L stainless steel electrodes is described. Tests were performed with 160 ns, 1-cos(ωt), and 260 ns flat-top voltage pulses of up to 500 kV. The high voltage hold-off for the 160 ns pulse was ∼130 kV/mm for 2 mm gaps for 80-mm diameter polished stainless steel electrodes, and 15% lower for 120-mm polished and e-beam treated electrodes. The longer 260 ns pulse gave 15% lower hold-off for 80-mm electrodes. These electrodes showed voltage hold-off that scaled as the square root of the gap between 0.5 and 7 mm. This total voltage effect has been interpreted in the past as due to accelerated particles. We analyze our data in terms of this mechanism and show that only nanoparticles of molecular size could be responsible. We also discuss how ions or background gas could affect the breakdown thresholds but existing models do not predict square root dependence. We test how extremely fine powers affect hold-off and show that contaminated surfaces have relatively constant reduced breakdown E-fields that intersect the clean-electrode voltage-dependent breakdown at critical gaps defined by the type and quantity of contamination. The hold-off was ∼55 and 65 kV/mm with copper powder on the cathode and anode for 2 to 6.5 mm gaps, respectively, and ∼95 and 75 kV/mm for talc powder on the cathode and anode for gaps <3.5 and 6.5 mm. Optical diagnostics show no difference in the light emission from clean and contaminated electrode breakdown arcs.
    No preview · Article · Mar 2006 · IEEE Transactions on Dielectrics and Electrical Insulation
Show more