Ion-beam extraction with single hole extractor from multiantenna rf ion source in NIFS
- National Institute for Fusion Science, Toki 509-5292 (Japan)
A new multiantenna system for large area radio-frequency H{sup -} ion source using a filamentless ion source was tested to extract ions from dense plasmas with high rf input power. A 1/6 scale large helical device ion source was equipped inside a plasma chamber with four linear antenna rods. Positive-ion extraction with a single hole extractor was studied in detail, while a negative one only showed preliminary results. The positive-ion current density of 34 mA/cm{sup 2} to the collector plate was achieved with a new multiantenna after optimization of the antenna number and source gas pressure, where the number of the antennae was 2 with {approx}36 kW of rf input power and with a gas pressure of {approx}0.1 Pa with H{sub 2}. If the external magnetic filter optimized for negative-ion production in the multifilament discharge source is taken off, the current density is estimated to reach about 120 mA/cm{sup 2}. This corresponded closely to the value measured with a Langmuir probe near the center. Two antennae appear to be required to generate uniform plasmas as well as dense plasmas in the present size of the 35x35 cm{sup 2} source. A negative-ion current density of 0.3 mA/cm{sup 2} to the collector plate was detected with hydrogen without optimization. This multiantenna rf ion source is expected to be adaptable advantageously to large area positive- and negative-ion sources, owing to not only a filamentless source but also potentially due to uniform plasmas as well as probable low-electron-temperature plasmas, compared to that with a one-turn coil system.
- OSTI ID:
- 20779063
- Journal Information:
- Review of Scientific Instruments, Vol. 77, Issue 3; Conference: 11. international conference on ion sources, Caen (France), 12-16 Sep 2005; Other Information: DOI: 10.1063/1.2165772; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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