Multi-frequency electron cyclotron heating and current drive

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Double frequency electron cyclotron heating (ECH) was tested in the WT-3 tokamak to demonstrate the effects of multi frequency ECH. A 56GHz ECH system has been illustrated in WT-3. A new 48GHz ECH system is installed. A prototype of a 48GHz, 200kW, 30msec pulse gyrotoron was developed for the new ECH system.Double frequency (56 and 48GHz) ECH is applied to ohmic heating or lower hybrid current drive (LHCD) plasmas in WT-3. A notable effect of double frequency ECH can be observed in LHCD plasmas. In the case of single frequency ECH, the central electron temperature TィイD2e0ィエD2 increases up to about 600eV by 48GHz ECH and up to about 550eV by 56GHz ECH from original TィイD2e0ィエD2 of about 350eV when the 2nd harmonic resonance layer is localized near plasma center. In the case of double frequency ECH, 56GHz 2nd harmonic resonance layer is localized near plasma center and 48GHz 2nd harmonic resonance is near half of the minor radius in the low field size. TィイD2e0ィエD2 increases up to about 800eV. The effect of double frequency ECH is clear but the mechanism has not yet been cleared. The further study is required.