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Related Experiment Videos

Dispersion interferometer using modulation amplitudes on LHD (invited).

T Akiyama1, R Yasuhara1, K Kawahata1

  • 1National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292, Japan.

The Review of Scientific Instruments
|November 29, 2014
PubMed
Summary
This summary is machine-generated.

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A new CO2 laser dispersion interferometer for the Large Helical Device eliminates the need for vibration compensation. This advanced system accurately measures electron density, overcoming previous limitations in high-density plasma diagnostics.

Area of Science:

  • Plasma physics
  • Interferometry
  • Fusion energy research

Background:

  • Dispersion interferometers are typically insensitive to mechanical vibrations.
  • Conventional dispersion interferometers can suffer from measurement errors due to intensity variations.
  • The Large Helical Device (LHD) requires precise plasma diagnostics.

Purpose of the Study:

  • To develop and validate a CO2 laser dispersion interferometer for the LHD.
  • To improve measurement accuracy by addressing intensity variation issues.
  • To achieve reliable electron density measurements without vibration compensation.

Main Methods:

  • Utilized a CO2 laser dispersion interferometer with phase modulations.
  • Implemented a novel phase extraction method using modulation amplitudes.

Related Experiment Videos

  • Employed a sampling rate of approximately 100 kHz for high-density measurements.

    • Main Results:

    • Achieved phase variation measurements within ±2 × 10^17 m^-3 without vibration compensation.
    • Demonstrated good agreement between the dispersion interferometer and a far-infrared laser interferometer.
    • Successfully overcame fringe jump errors in densities up to 1.5 × 10^20 m^-3.

    Conclusions:

    • The developed CO2 laser dispersion interferometer is effective for plasma diagnostics on the LHD.
    • The new phase extraction method enhances accuracy and reliability.
    • The system provides a robust solution for measuring electron density across a wide range.