Microwave magnetic field effects on high-power microwave window breakdown

David Hemmert, Andréas A. Neuber, James Dickens, Hermann Krompholz, L. L. Hatfield, Magne Kristiansen

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Microwave window breakdown in vacuum is investigated for an idealized geometry, where a dielectric slab is located in the center of a rectangular waveguide with its normal parallel to the microwave direction of propagation. An S-band resonant ring with a frequency of 2.85 GHz and a power of 60 MW is used. With field enhancement tips at the edges of the dielectric slab, the threshold power for breakdown is observed to be dependent on the direction of the microwaves; i.e., it is approximately 20% higher for the downstream side of the slab than it is for the upstream side. Simple trajectory calculations of secondary electrons in an RF field show a significant forward motion of electrons parallel to the direction of microwave propagation. Electrons participating in a saturated secondary avalanche on the upstream side are driven into the surface, and electrons on the downstream side are driven off the surface, because of the influence of the microwave magnetic field. In agreement with the standard model of dielectric surface flashover for dc conditions (saturated avalanche and electron-induced outgassing), the corresponding change in the surface charge density is expected to be proportional to the applied breakdown threshold electric field parallel to the surface.

Original languageEnglish
Pages (from-to)472-477
Number of pages6
JournalIEEE Transactions on Plasma Science
Volume28
Issue number3
DOIs
StatePublished - Jun 2000

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