Experimental observations of mode-converted ion cyclotron waves in a tokamak plasma by phase contrast imaging

The process of mode conversion, whereby an externally launched electromagnetic wave converts into a shorter wavelength mode(s) in a thermal plasma near a resonance in the index of refraction, is particularly important in a multi-ion species plasma near the ion cyclotron frequency. Using phase contrast imaging techniques (PCI), mode-converted electromagnetic ion cyclotron waves have been detected for the first time in the Alcator C-Mod tokamak near the H-He-3 ion-ion hybrid resonance region during high power rf heating experiments. The results agree with theoretical predictions.