Plasma and Fusion Research
Volume 5, S2102 (2010)
Regular Articles
- National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
Abstract
Optical emission in a negative hydrogen ion source for the Large Helical Device Neutral Beam Injector (LHD-NBI) has been measured to investigate the behavior of Cs. Two optical sight lines exist parallel to the plasma grid, in the discharge area and in the magnetic filter area near the plasma grid. In the discharge area, the spectrum intensity from Cs+ ions is considerably increased during 20 s of the beam extraction. This indicates a considerable increase in the Cs+ density inside the plasma due to the impact of back-streaming H+ ions. A strong neutral Cs spectrum is observed in the magnetic filter area, where the electron density is lower than in the discharge area. The rate of increase of neutral Cs is much enhanced after t = 30 s, probably because the Cs adsorbed on the cooled region inside the arc chamber evaporates because its temperature increases during the long pulse discharge.
Keywords
neutral beam injector, negative ion source, cesium, arc discharge
Full Text
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This paper may be cited as follows:
Katsunori IKEDA, Kenichi NAGAOKA, Yasuhiko TAKEIRI, Katsuyoshi TSUMORI, Masaki OSAKABE, Haruhisa NAKANO and Osamu KANEKO, Plasma Fusion Res. 5, S2102 (2010).