Electron cyclotron emission measurements by means of a grating polychromator on the large helical device

P. C. De Vries, K. Kawahata, Y. Nagayama, S. Inagaki, H. Sasao, Y. Ito

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The electron cyclotron emission (ECE) spectrum at the large helical device (LHD) is measured by a 14-channel grating polychromator. During standard operation, the polychromator monitors second harmonic frequencies (100-150 GHz). At sufficient high density, the second harmonic X-mode polarisation is optically thick and can be used to determine the temperature profile. However, the large magnetic field shear in LHD affects the ECE polarisation. This effect has been studied numerically. The wave polarisation was found to rotate in the laboratory frame. Eperiments have been carried out by means of a polarisation rotator in the diagnostic waveguide system, which confirmed the calculations. By a proper setting of the polarisation rotator, the rotation can be corrected and pure X-mode is detected. Temperature profiles have been measured successfully by the polychromator.

Original languageEnglish
Pages (from-to)185-191
Number of pages7
JournalFusion Engineering and Design
Issue number1-4
Publication statusPublished - Jan 1 2001
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Nuclear Energy and Engineering
  • Materials Science(all)
  • Mechanical Engineering

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