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Title: Negative ion production and beam extraction processes in a large ion source (invited)

Recent research results on negative-ion-rich plasmas in a large negative ion source have been reviewed. Spatial density and flow distributions of negative hydrogen ions (H{sup −}) and positive hydrogen ions together with those of electrons are investigated with a 4-pin probe and a photodetachment (PD) signal of a Langmuir probe. The PD signal is converted to local H{sup −} density from signal calibration to a scanning cavity ring down PD measurement. Introduction of Cs changes the slope of plasma potential local distribution depending upon the plasma grid bias. A higher electron density H{sub 2} plasma locally shields the bias potential and behaves like a metallic free electron gas. On the other hand, the bias and extraction electric fields penetrate in a Cs-seeded electronegative plasma even when the electron density is similar. Electrons are transported by the penetrated electric fields from the driver region along and across the filter and electron deflection magnetic fields. Plasma ions exhibited a completely different response against the penetration of electric fields.
Authors:
; ; ; ; ; ;  [1] ;  [2] ; ;  [1] ;  [3] ;  [4] ; ;  [5] ; ; ; ; ;  [6] ;  [7]
  1. National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan)
  2. (Japan)
  3. The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa 240-0193 (Japan)
  4. Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)
  5. Division of Quantum Science and Engineering, Hokkaido University, Sapporo 060-8628 (Japan)
  6. Plasma Engineering Group, Consorzio RFX, Corso Stati Uniti 4, 35127 Padova (Italy)
  7. Max-Planck-Institut für Plasmaphysik, Bereich ITER-Technologie und -Diagnostik/N-NBI Boltzmannstr. 2, 85748 Garching (Germany)
Publication Date:
OSTI Identifier:
22483042
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 87; Journal Issue: 2; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ANIONS; BEAM EXTRACTION; CALIBRATION; ELECTRIC FIELDS; ELECTRON DENSITY; ELECTRON GAS; HYDROGEN IONS; LANGMUIR PROBE; MAGNETIC FIELDS; PLASMA; PLASMA POTENTIAL; SIGNALS