Anomalous Wave Energy Deposition in the Beginning Phases of Wave Injection in JT-60U Lower Hybrid Current Drive Experiments

An anomalous phenomenon of wave energy deposition and its evolution were noticed in the beginning phases of lower hybrid wave injection in JT-60U experiments. It was found that the driven currents are always formed in the central region of the plasma column in the first several hundred milliseconds of the wave pulses, no matter what N|| spectrum of the waves is. Then the driven current profile will change to their normal situation gradually, which depends on N|| spectrum closely.