Power Modulation System and Experiments of Lower Hybrid Wave on EAST

To satisfy various requirements of different physics experiments, a new power modulation method of the lower hybrid wave (LHW) has been developed in Experimental Advanced Superconducting Tokamak (EAST), including the development of a control source combining software and hardware. Such modulation system is realized by the main positive-intrinsic-negative diode switch located at the oscillator. The LHW modulation system has been installed and tested, demonstrating that the modulation parameters can be controlled flexibly. The maximal modulation frequency is about 10 kHz, which is limited by the hardware circuit speed. The system has been successfully used to study the influence of LHW on the performances of plasma. Under the modulation of LHW, strong mitigation of edge-localized modes (ELMs) has been observed, and ELM pace-making technique has been demonstrated. Further experimental studies with the modulation system will be continued in EAST.