Time-and energy-resolved d-He fusion reactions have been measured to Infer the energy of the d or He minority Ions heated near their cyclotron frequency by the magnetosonlc fast wave. The average energy of the reacting J He ions during J He minority heating Is in the range of 100-400 keV, as deduced from the magnitude of the reaction rate, its decay time, and the energy spread of the proton reaction products. The observed reaction rate and its scaling with wave power and electron density and

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... perature are In qualitative agreement with a radial reaction rate model using the minority distribution predicted from quasilinear velocity space diffusion. Oscillations in the reaction rate are observed concurrent with sawtooth and m=2 MHD activity in the plasma.