Measurement of Whistler-like Waves in the Madison Symmetric Torus (MST) Tokamak Plasma*

Experiments and simulations show Whistler waves can be driven by runaway electrons, RE, which in a predator-prey fashions stabilize these RE. High frequency magnetic fluctuation measured in MST reveal multiple coherent modes.. Multipole single-turn coils are used to measure magnetic fluctuation and wave number spectra. Whistler-like magnetic fluctuations up to 3.4 GHz have been observed. Magnetic fluctuation and x-ray intensity in the range of 5 to 100 keV show a strong correlation. Both signals show alternating bands of high and low activities. The highest frequency measured is 3.4 GHz in the range of the local electron cyclotron frequency, 3.4 GHz. The amplitude of this mode is modulated at about 200 MHz. A new high frequency probe that measures the parallel and perpendicular fluctuation simultaneously is used to determine the wave polarization.. Using two-point correlation method, and are measured. Signals are digitized at 12.5 GHz with 5 GHz bandwidth. The target Plasma has , , , -2. The fluctuation amplitude of these frequency lines decrease with increased density and are absent at 0.4x10¹³ cm^-3.. The polarization, wave numbers, and other properties of these waves will be discussed

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