Development of a rf negative-ion source for ITER neutral beam injection

• Published in: Review of scientific instruments 2006-03, Vol.77 (3), p.03A519-03A519-3
• Main Authors: McNeely, P., Falter, H.-D., Fantz, U., Franzen, P., Fröschle, M., Heinemann, B., Kraus, W., Martens, Ch, Riedl, R., Speth, E.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANIONS; CURRENT DENSITY; DEUTERIUM IONS; ELECTRONS; HYDROGEN IONS; ION SOURCES; ITER TOKAMAK; OPERATION; PLASMA BEAM INJECTION; PULSES; TEST FACILITIES
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.2166246

The development at IPP of a large-area rf source for negative hydrogen ions, an official EFDA task agreement, aims to demonstrate ITER-relevant source parameters. This implies a current density of 20 mA cm − 2 accelerated D − at a source-filling pressure of < 0.3 Pa , an electron to ion ratio of < 1 , and for pulse lengths of up to 1 h . The principle suitability concerning current density, pressure, and electron content has been demonstrated with the test facility Bavarian Test Machine for Negative Ions but with only small extraction area ( 70 cm 2 ) and for pulse length of < 6 s . The further development concentrates now on long pulse operation at the test stand Multi-Ampere Negative Ion Test Unit (MANITU), which became operational this spring. For source size extension from 70 to 1000 cm 2 MANITU and a third test facility, currently under development, called RADI will be used. This article will report on the latest results of the work in progress. A critical issue for ITER is reliable source operation at high current densities. Therefore the procedure used to obtain in a reproducible manner source operation at the ITER target values will be detailed and discussed.