Density Fluctuations in the JFT-2M H-Mode Plasma Measured by Using a New Analysis Method Microwave Reflectometry

Density fluctuations in JFr-2M tokamak are investigated by a microwave reflectometer using the new complex amplitude analysis (K. Shinohara et al., Jpn. J. Appl. Phys. 36, 7367 (1997)). A coherent spectral peak in the fluctuation spectrum is found during the H'-mode which is defined as the H-mode with degraded confinement. It seems that the amplitude of the coherent fluctuation would not directly determine the confinement from the comparison between a plasma with co-injection of the neutral beam and a plasma with counter-injection. It is also found that high frequency fluctuations ( > 500 kHz) during the H-mode are larger than those during the L-mode. We discuss such complex roles of the fluctuation spectrum to the confinement based on the data obtained by this measurement.