A new two-dimensional Thomson scattering measurement (2-D TS) system has been developed using multiple reflections and time-of-flight (TOF) of laser light. Its new ideas of our 2-D TS system are (1) to reflect YAG laser light for multiple times to cover the whole r − z plane of the ST (Spherical Tokamak) plasma, and (2) to reduce the number of polychromators and detectors using the time delay of the scattered light along the laser beam. We measured for the first time, Rayleigh scattering light signals with 50 ns time difference from two measurement points using a single detector, demonstrating the basic principle of the 2-D Thomson scattering system.

Two-Dimensional Thomson Scattering Measurement (2-D TS) was designed using multiple reflections and the time-of-flight of laser light. This new approach enable us to measure the r(radial)-z(axial) profiles of electron temperature and density. In this approach, (1) multiple reflections of YAG laser light are used to cover the whole r-z plane of the ST (Spherical Tokamak) plasma, and (2) the time delay of the scattered light along the laser beam is arbitrarily arranged by adjusting the multiply reflected laser light path in order to reduce the necessary number of detectors. Rayleigh scattering lights were observed successfully at two measurement points, suggesting that the basic principle of the 2-D Thomson scattering system functions effectively as a new extension of LIDAR (LIght Detection And Ranging) Thomson scattering system.