Conditioning of carbon fiber cathodes in UHV-sealed tubes at 200 A/cm 2

Jonathan M. Parson, Curtis F. Lynn, John J. Mankowski, Magne Kristiansen, Andreas A. Neuber, James C. Dickens

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


This paper presents a study on outgassing and electrical conditioning for three carbon fiber cathode types in a vacuum-sealed, high-power microwave virtual-cathode-oscillator (vircator) that operates in the low 10-9 torr pressure regime. The three cathode types consist of a bare bimodal fiber structure, a bare unimodal fiber structure, and a cesium-iodide coated bimodal fiber structure with identical fiber coverage of 2% by area with a surface area of ~20 cm2. The electrodes are cleaned by a 1.2 kW, argon/oxygen microwave plasma prior to complete vircator assembly, followed by a 300 °C bake-out for 72 h. Each cathode was pulsed in a single pulse operation by an 80 J, low inductance Marx generator with an approximate pulsewidth of 100 ns full-width at half-maximum for 10 000 current pulses. The data presented includes individual gas constituents, high-speed intensified charge coupled device (ICCD) imaging, and voltage and current waveforms. The conditioning process resulted in a gas load reduction of ~80% overall, with the indication that the bare bimodal fiber structure performed the best as diode power increased throughout the experiment, while the power decreased for the other tested cathode types. 0018-9456

Original languageEnglish
Article number6847740
Pages (from-to)2007-2014
Number of pages8
JournalIEEE Transactions on Plasma Science
Issue number8
StatePublished - Aug 2014


  • Carbon fiber
  • cathodes
  • electron beam
  • electron emission
  • electron sources
  • high power microwave generation
  • virtual-cathode-oscillator (Vircator)


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