中国物理B ›› 2009, Vol. 18 ›› Issue (8): 3367-3372.doi: 10.1088/1674-1056/18/8/041

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Plasma characterization on carbon fiber cathode by spectroscopic diagnostics

刘列, 李立民, 徐启福, 苌磊, 文建春   

  1. College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China
  • 收稿日期:2008-12-05 修回日期:2009-02-09 出版日期:2009-08-20 发布日期:2009-08-20
  • 基金资助:
    Project supported by the National High Technology Research and Development Program of China.

Plasma characterization on carbon fiber cathode by spectroscopic diagnostics

Liu Lie(刘列), Li Li-Min(李立民)† and , Xu Qi-Fu(徐启福), Chang Lei(苌磊), and Wen Jian-Chun(文建春)   

  1. College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China
  • Received:2008-12-05 Revised:2009-02-09 Online:2009-08-20 Published:2009-08-20
  • Supported by:
    Project supported by the National High Technology Research and Development Program of China.

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摘要： This paper mainly investigates plasma characterization on carbon fiber cathodes with and without cesium iodide (CsI) coating powered by a ～300~ns, ～ 200~kV accelerating pulse. It was found that the CsI layers can not only improve the diode voltage, but also maintain a stable perveance. This indicates a slowly changed diode gap or a low cathode plasma expansion velocity. By spectroscopic diagnostics, in the vicinity of the cathode surface the average plasma density and temperature were found to be ～ 3× 1014~cm-3 and ～ 5~eV, respectively, for an electron current density of ～ 40~A/cm2. Furthermore, there exists a multicomponent plasma expansion toward the anode. The plasma expansion velocity, corresponding to the carbon and hydrogen ions, is estimated to be ～ 1.5~cm/μ s. Most notably, Cs spectroscopic line was obtained only at the distance ≤ 0.5~mm from the cathode surface. Carbon and hydrogen ions are obtained up to the distance of 2.5~mm from the cathode surface. Cs ions almost remain at the vicinity of the cathode surface. These results show that the addition of CsI enables a slow cathode plasma expansion toward the anode, providing a positive prospect for developing long-pulse electron beam sources.

Abstract: This paper mainly investigates plasma characterization on carbon fiber cathodes with and without cesium iodide (CsI) coating powered by a ～300 ns, ～200 kV accelerating pulse. It was found that the CsI layers can not only improve the diode voltage, but also maintain a stable perveance. This indicates a slowly changed diode gap or a low cathode plasma expansion velocity. By spectroscopic diagnostics, in the vicinity of the cathode surface the average plasma density and temperature were found to be ～3×1014 cm-3 and ～5 eV, respectively, for an electron current density of ～40 A/cm2. Furthermore, there exists a multicomponent plasma expansion toward the anode. The plasma expansion velocity, corresponding to the carbon and hydrogen ions, is estimated to be ～1.5 cm/μs. Most notably, Cs spectroscopic line was obtained only at the distance ≤ 0.5 mm from the cathode surface. Carbon and hydrogen ions are obtained up to the distance of 2.5 mm from the cathode surface. Cs ions almost remain at the vicinity of the cathode surface. These results show that the addition of CsI enables a slow cathode plasma expansion toward the anode, providing a positive prospect for developing long-pulse electron beam sources.

Key words: cold cathode, spectroscopic diagnostics, CsI coating, plasma expansion

中图分类号:  (Plasma diagnostic techniques and instrumentation)

  • 52.70.-m
52.50.Dg (Plasma sources) 52.75.Fk (Magnetohydrodynamic generators and thermionic convertors; plasma diodes)