Basic Study of Two‐Dimensional Thomson Scattering Measurement by Multiple Reflections and Time‐of‐Flight of Laser Beam

Abstract

SUMMARY A novel two‐dimensional Thomson scattering (TS) measurement system has been developed by adopting the time‐of‐flight (TOF) difference in the signals scattered from three parallel laser beams formed by multiple reflections. New ideas are: (1) a YAG laser beam is reflected by 6 mirrors so that it covers the whole r–z plane of a spherical Tokamak (ST) plasma; (2) the observation position is determined by the time delay of the scattered light, which helps to significantly reduce the necessary numbers of spectrometers and detectors. Using a TS‐4 torus plasma merging device. we successfully measured the electron temperature at nine points, demonstrating the basic theory of this novel TS system.

Design and development of a single-laser 2D Thomson scattering measurement system for TS-6 merging tokamak/magnetic reconnection experiments

“…Therefore, 2D (𝑚 × 𝑛 points) measurement is realized by only a single laser and as many polychromators as in 1D (𝑚 points) measurement. Electron temperature at 3 × 3 points was already measured in TS-4 experiments of our laboratory [6]. However, the resolution was insufficient to discuss physics because the laser paths were restricted to the position of three sets of windows.…”