Rapid formation of dielectric surface flashover due to pulsed high power microwave excitation

J. Foster, S. Beeson, M. Thomas, J. Krile, H. Krompholz, A. Neuber

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

High power microwave (HPM) dielectric surface flashover can be rapidly induced by providing breakdown initiating electrons in the high field region. An experimental setup utilizing a 2.85 GHz HPM source to produce a 4.5 MW, 3 μs pulse is used for studying HPM surface flashover in various atmospheric conditions. If flashover is to occur rapidly in an HPM system, it is desirable to provide a readily available source of electrons while keeping insertion loss at a minimum. The experimental results presented in this paper utilize a continuous UV source (up to 0.3 mW/cm2) to provide photo-emitted seed electrons from the dielectric surface. Similarly, electrons were provided through the process of field emission by using metallic points deposited on the surface. Initial experiments utilizing 0.2 mm2 aluminum points with a spatial density of 25/cm2 have increased the apparent effective electric field by a factor of ∼1.5 while keeping the insertion loss low (<0.01 dB). The field enhancements have sharply reduced the delay time for surface flashover. For an environment consisting of air at 2.07×104 Pa (155 Torr), for instance, the delay time is reduced from 455 ns to 101 ns. Two radioactive sources were also used in an attempt to provide seed electrons in the high field regions. Presented in this paper is a comparison of various field-enhancing geometries and how they relate to flashover development along with an analysis of time resolved imaging and an explanation of experimental results with radioactive materials.

Original languageEnglish
Article number5976082
Pages (from-to)964-970
Number of pages7
JournalIEEE Transactions on Dielectrics and Electrical Insulation
Volume18
Issue number4
DOIs
StatePublished - Aug 2011

Keywords

  • HPM
  • Microwave discharges
  • dielectric breakdown
  • statistics of breakdown

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