Establishment of Cross-Polarization Scattering Method for Measurement of Internal Magnetic-Field Fluctuations in Plasmas

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1)During the period of this research project, a cross-polarization scattering diagnostic system with frequency of 8-18 GHz has been fabricated and applied to the central-cell plasma of the GAMMA 10 tandem mirror in order to measure internal magnetic-field fluctuations. The system utilized dual-polarized horns as a transmitter and a receiver that enabled the simultaneous measurement of the CPS and reflectometry, The density and magnetic fluctuations of the waves were evaluated from both the CPS and reflectometry.2)The CPS diagnostic system and reflectometer were applied to the measurement of electromagnetic plasma waves in the ion cyclotron range of frequencies (ICRF) and low-frequency drift-wave mode.i)The fluctuations associated with ICRF waves were observed to investigate the physics of the wave absorption of RF heating power and the excitation of an Alfven ion cyclotron (AIC) instability. The fluctuation-induced transport due to the AIC mode was evaluated from the end-loss flux and … More temperature of electrons during the excitation of the AIC mode.ii)As the plasma beta and temperature anisotropy increased. the amplitude of the AIC mode became large . and the discrete modes appeared. The adjacent MG modes coupled to excite another low-frequency wave that caused the saturation of the plasma beta.iii)The wavelet transform was applied to the analyses of the CPS and reflectometry signals. The wavelet time-frequency spectrum and cross-correlation function allowed us to estimate the rotation speed of the low-frequency waves (-3 km./s) in the ExB direction, and the propagation speed (-1000 km/s) of the AIC modes from the center towards the magnetic plugs.iv)The k -omega) spectra of the low-frequency wave (< 40 kHz) were obtained from the angular distribution of the scattered waves. From the ridge of the k -omega spectra the.dispersion relation of the electromagnetic drift wave was confirmed for the first time.4)Computational study on the CPS of electromagnetic waves produced by magnetic fluctuations was performed. It was shown that the peak frequencies in the spectral signals of the mode-converted waves were determined from the Bragg resonance condition in the wave number between the incident wave, scattered wave, and magnetic fluctuations for relatively short-wavelength localized magnetic fluctuations. Less