High power heating in the ion cyclotron range of frequencies in the Wisconsin Tokapole II

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Abstract
Fast wave heating at the second, third and fourth harmonics of the ion cyclotron resonance, and slow wave heating at the fundamental in a single ion species hydrogen plasma, are found to be in good agreement with warm plasma theory at RF power levels <or=130 kW. Ion heating is negligible off an eigenmode. Ion body temperatures are more than doubled to 75 eV from the 35 eV ohmically heated case with tails comprising 8% of the plasma at 320 eV. No deleterious effects except a non-disruptive 10% shortening of the discharge length caused by impurity influx are noted. A passive mode tracking technique allows approximately=40% increase in power deposition in a passing eigenmode over that of a fixed frequency RF source. Ion temperatures are limited by charge exchange due to the <50 eV central temperature and the small 13 cm radius current channel.