Development of laser photodetachment technique using heated probe to eliminate the effect of probe surface ablation phenomena

Shin Kajita, Shinichiro Kado, Atsushi Okamoto, Satoru Tanaka

Research output: Contribution to journalReview articlepeer-review

6 Citations (Scopus)

Abstract

The characteristics of the phenomena caused by laser irradiation to an electrostatic probe in plasmas are studied to avoid the disturbance of the laser photodetachment signals for negative ion density measurement. In helium-hydrogen and hydrogen-methane plasmas, a probe surface ablation phenomenon was observed as an anomalous excess electron current in response to the laser irradiation to the electrostatic probe, while the phenomenon was not observed in pure hydrogen plasmas. Contaminations of the probe surface appear to be the mechanism causing the ablation phenomena. In order to clean the probe surface, a filament-type heated probe, which is the same type of conventional emissive probe, is applied to the laser photodetachment technique. When the surface is cleaned by heating the probe, the ablation phenomenon disappears, and the negative ion density can be evaluated at a sufficiently high laser pulse energy to saturate the photodetachment rate of negative ions. The method developed in this paper is useful for the measurement of negative ion density in plasmas where the probe surface is easily contaminated.

Original languageEnglish
Pages (from-to)8661-8666
Number of pages6
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume44
Issue number12
DOIs
Publication statusPublished - 2005 Dec 8

Keywords

  • Filament-type heated probe
  • Laser photodetachment
  • MAP-II
  • Negative ion
  • Surface ablation

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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