Improved chopping of a lithium beam for plasma edge diagnostic at ASDEX Upgrade

Journal Article · Wed Feb 15 00:00:00 EST 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3682003· OSTI ID:22063790

Willensdorfer, M; Aumayr, F ^[1]; Wolfrum, E; Fischer, R; Schweinzer, J; Sertoli, M; Sieglin, B ^[2]; Veres, G ^[3]

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1. Institute of Applied Physics, Vienna University of Technology, Association EURATOM-OeAW, A-1040 Vienna (Austria)
2. Max-Planck-Institut fuer Plasmaphysik, Association EURATOM, D-85748 Garching (Germany)
3. KFKI-RMKI, Association EURATOM, Pf. 49, H-1525 Budapest (Hungary)

The lithium beam diagnostic at ASDEX Upgrade routinely delivers electron density profiles in the plasma edge by lithium beam impact excitation spectroscopy. An accurate background subtraction requires a periodically chopped lithium beam. A new, improved chopping system was developed and installed. It involves a voltage modulation for the extractor electrode and the beam deflection plates. The modulation of the extractor electrode reduces the unused portion of lithium ions and improves the stability of the beam with respect to its position. Furthermore, the data indicate an extended emitter lifetime. The extractor chopping was also found to be insensitive to sparks. The deflection chopping experiments demonstrated beam chopping in the kilohertz range. The significantly higher modulation frequency of the deflection chopping improves background subtraction of fast transient events. It allows a more accurate density measurements in the scrape off layer during impurity injections and edge localized modes.

• OSTI ID: 22063790
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 2; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ASDEX TOKAMAK
BEAM EXTRACTION
BEAM PULSERS
EDGE LOCALIZED MODES
ELECTRODES
ELECTRON DENSITY
ION BEAMS
LITHIUM
LITHIUM IONS
MODULATION
PLASMA DIAGNOSTICS
PLASMA IMPURITIES
PLASMA SCRAPE-OFF LAYER
SPECTROSCOPY