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Experimental Characterization of Plasma Heating with Beating Electrostatic Waves

Abstract

The heating of ions in a magnetized plasma by two electrostatic waves whose frequencies differ by the ion cyclotron frequency is experimentally and analytically characterized. An analytical model is presented for the power absorption by the two waves, and it is shown that the two-wave process will yield superior heating to a single electrostatic wave only in the event that the total wave energy density exceeds a threshold value. An experimental investigation of the increase in ion temperature as a function of the fraction of total energy density in one of the propagating modes subsequently reveals that for a low temperature plasma, heating with a single electrostatic wave is superior to employing two beating electrostatic waves. This result is consistent with the analytical prediction that the available wave energy density in the experiment is below the required threshold for the superiority of the two-wave process.