Spectrum response and analysis of 77 GHz band collective Thomson scattering diagnostic for bulk and fast ions in LHD plasmas: Paper

M. Nishiura, S. Kubo, K. Tanaka, R. Seki, S. Ogasawara, T. Shimozuma, K. Okada, S. Kobayashi, T. Mutoh, K. Kawahata, T. Watari, LHD Experiment Group, T. Saito, Y. Tatematsu, Søren Bang Korsholm, Mirko Salewski

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

A collective Thomson scattering (CTS) diagnostic was developed and used to measure the bulk and fast ions originating from 180 keV neutral beams in the Large Helical Device (LHD). Electromagnetic waves from a gyrotron at 77 GHz with 1 MW power output function as both the probe and electron cyclotron heating beam. To clarify the diagnostic applicability of the gyrotron in the 77 GHz frequency band, we investigated the dependence of the probe and receiver beam trajectories in plasmas with high electron densities of (4–5) × 1019 m−3 and low electron densities of (1–2) × 1019 m−3. At high density, a stray radiation component was observed in the CTS spectrum whereas it was negligibly small at low density. The CTS spectrum was measured and analysed after the in situ beam alignment using a beam scan. Qualitatively, the CTS spectrogram shows consistent response to ion temperatures of 1–2 keV for electron densities of (1–2) × 1019 m−3 and electron temperatures of 2–4 keV. The measured CTS spectrum shows an asymmetric shape at the foot of the bulk-ion region during the injection of 180 keV fast ions. This shape is explained by the fast-ion distribution in the velocity space (v‖, v⊥) based on Monte Carlo simulation results. The analysis method of the CTS spectra is used to evaluate the ion temperature and fast-ion velocity distribution from the measured CTS data.
Original languageEnglish
JournalNuclear Fusion
Volume54
Issue number2
Pages (from-to)023006
ISSN0029-5515
DOIs
Publication statusPublished - 2014

Keywords

  • Nuclear fusion
  • Collective Thomson scattering
  • Fast ions
  • Bulk ions
  • Plasma diagnostics

Fingerprint Dive into the research topics of 'Spectrum response and analysis of 77 GHz band collective Thomson scattering diagnostic for bulk and fast ions in LHD plasmas: Paper'. Together they form a unique fingerprint.

Cite this