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Author(s):
A. Ando, Y. Takeiri, O. Kaneko, Y. Oka, M. Wada, and T. Kuroda
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Title:
Production of Negative Hydrogen Ions in a Large Multicusp Ion Source with Double-Magnetic Filter Configuration
Date of publication:
May 1992
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Key words:
negative ion source, H^- ion source, NBI, volume production, magnetic filter, photodetachment
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Abstract:
The production of the negative hydrogen ions in a large multicusp ion source has been investigated in a double-magnetic filter (DMF) configuration. In the DMF configuration, the energetic electrons are trapped by the mirror of a magnetic multicusp field, and only the thermal electrons are present in the center of the arc chamber. A large amount of H^- ions of more than 1 x 10^12 cm^-3 are produced in the center region. The electron current extracted with the H^- ions can be suppressed by a magnetic filter field in front of a plasma grid without affecting the H^- ion current. The experimental data obtained in the DMF configuration are compared with those obtained in a single-magnetic filter (SMF) configuration. In the SMF configuration, the energetic electrons are present in the center region, and the magnetic filter in front of a plasma grid reduces the electron density and temperature, which results in the reduction of the H^- ion current as well as the electron current. The extracted electron current and the optimum gas pressure for the H^- ion current are lower in the DMF configuration than those in the SMF configuration.
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