THE PHASE CONTRAST METHOD AS A DIAGNOSTIC FOR PLASMA DENSITY FLUCTUATIONS
The spatial characteristics of broadband plasma turbulence (f < 1 MHz) were investigated by correlating two detectors viewing separate chords. Figure 4 shows the poloidal crosscorrelation as a function of detector separation for three typical frequencies. We found that about 50% of the spectral energy is associated with wavenumbers below 2 rad/cm, which are below the resolution capabilities of most existing scattering diagnostics. Using synchronous detection, the system has revealed driven waves during Alfven Wave heating at 2.5 MHz in TCA. Figure 5 shows the amplitude as a function of minor radius. The amplitude is peaked where natural plasma resonances are excited. The slope of the phase relative to the RF generator, Fig. 6, reveals that the wave propagates radially inwards and has a wavelength of about 4 cm, corresponding to the Kinetic Alfven Wave, which is excited at the resonance layers by a process of mode conversion.
Bibliographic Reference: 11TH INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES, TIRRENIA-PISA (ITALY), OCT. 20-24, 1986 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32552 ORA
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Record Number: 1989125059300 / Last updated on: 1987-11-01
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