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Review of Scientific Instruments / Volume 83 / Issue 2 / ARTICLES / Nuclear Physics, Fusion and Plasmas

Rev. Sci. Instrum. 83, 023501 (2012); http://dx.doi.org/10.1063/1.3682003 (7 pages)

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

M. Willensdorfer1, E. Wolfrum2, R. Fischer2, J. Schweinzer2, M. Sertoli2, B. Sieglin2, G. Veres3, F. Aumayr1, and the ASDEX Upgrade Team2

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

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(Received 27 September 2011; accepted 9 January 2012; published online 6 February 2012)

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.

© 2012 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. CHOPPING SYSTEM OF THE LITHIUM BEAM DIAGNOSTIC
  3. PERFORMANCE OF THE NEW SYSTEMS
    1. Rising edges
    2. Chopping via extraction
    3. Comparison to chopping via deflection
  4. EXPERIMENTAL RESULTS IN ASDEX UPGRADE
    1. Experimental spectra
    2. Argon gas injection
    3. Edge localized modes
  5. CONCLUSIONS

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KEYWORDS, PACS, and IPC

Keywords

beam choppers, electrodes, lithium, plasma boundary layers, plasma density, plasma diagnostics, plasma impurities, plasma instability, sparks

PACS

  • 52.70.Nc

    Particle measurements

  • 52.40.Hf

    Plasma-material interactions; boundary layer effects

  • 52.25.Vy

    Impurities in plasmas

  • 52.35.Qz

    Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

  • 52.80.Mg

    Arcs; sparks; lightning; atmospheric electricity

International Patent Classification (IPC)

  • H01T

    Spark gaps; Overvoltage arresters using spark gaps; Sparking plugs; Corona devices; Generating ions to be introduced into non-enclosed gases

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.3682003

PUBLICATION DATA

ISSN

0034-6748 (print)  
1089-7623 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

For access to fully linked references, you need to log in.
    I. Pusztai, G. Pokol, D. Dunai, D. Refy, G. Por, G. Anda, S. Zoletnik, and J. Schweinzer, Rev. Sci. Instrum. 80, 083502 (2009)RSINAK000080000008083502000001.

    D. Thomas, Rev. Sci. Instrum. 74, 1541–1546 (2003)RSINAK000074000003001541000001.

    M. Brix, D. Dodt, A. Korotkov, P. Morgan, D. Dunai, R. Fischer, A. Meigs, I. Nedzelskiy, J. Schweinzer, J. Vince, S. Zoletnik, and JET-EFDA Contributers, Rev. Sci. Instrum. 81, 10D733 (2010)RSINAK00008100001010D733000001.

    E. Wolfrum, F. Aumayr, D. Wutte, H. Winter, E. Hintz, D. Rusbuldt, and R. Schorn, Rev. Sci. Instrum. 64, 2285–2292 (1993)RSINAK000064000008002285000001.

    E. Wolfrum, J. Schweinzer, M. Reich, L. Horton, and ASDEX Upgrade Team, Rev. Sci. Instrum. 77, 033507 (2006)RSINAK000077000003033507000001.

    D. Dunai, S. Zoletnik, J. Sarkozi, and A. Field, Rev. Sci. Instrum. 81, 103503 (2010)RSINAK000081000010103503000001.

    S. Zoletnik, G. Petravich, A. Bencze, M. Berta, S. Fiedler, K. McCormick, J. Schweinzer, and W7-AS Team, Rev. Sci. Instrum. 76, 073504 (2005)RSINAK000076000007073504000001.


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