Probe Measurements in a Negative Ion Plasma

Itsuo Ishikawa, Satoru Iizuka, Rikizo Hatakeyama, Noriyoshi Sato

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


A plasma with negative ions (negative ion plasma), which is generated by introducing a small amount of SF6 gas into a surface ionized plasma (e.g., Q-machine plasma), is investigated by electrostatic probe measurements. A theoretical analysis has been made by considering the presence of a negative ion sheath (NIS) in addition to the usual positive ion sheath (PIS), where the thermal velocity of negative ions is less than that of positive ions and the electron number density ne is much less than the positive ion n+. The ratios of saturation current of electrons and negative ions to that of positive ions, which are experimentally obtained by probe measurements, suggest that the sheath has a property of the change from PIS to NIS at the ratio of electron to positive-ion number densities ne/n+ below 10-2.

Original languageEnglish
Pages (from-to)158-162
Number of pages5
Journaljournal of the physical society of japan
Issue number1
Publication statusPublished - 1998 Jan


  • Electrostatic probe
  • Negative ion plasma
  • Positive and negative ion sheath
  • Saturation current ratio

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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