The multiampere negative hydrogen ion source has been developed in National Institute for Fusion Science (NIFS). The ion source is a volume-production type multicusp one with an extraction area of 25×25 cm2. It is found that high density negative hydrogen ions of more than 1 × 10 12 cm-3 are produced in the center of the arc chamber with a double magnetic filter configuration. A supply of a small amount of cesium vapor into the arc chamber has greatly enhanced the H- ion current and reduced the operation pressure. The H- ion current of 3.3 A has been extracted from a Cs-seeded plasma at the pressure of 0.9 Pa.
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