Dynamic RF power control for DIII-D ICH/fast wave operation

Thanks to the broadcast industry, high power transmitters between 10 MHz and 100 MHz in megawatts power range can be obtained at a reasonable price. Thus, we could take advantage of such development to use this frequency range for ion cyclotron and harmonics fast wave heating in the magnetic fusion energy research. Usually, antenna loading conditions can be fine tuned to meet the fusion plasma heating needs. However, the edge localized mode (ELM) during the plasma operation can cause up to 90% of RF power reflections when it appears at the antenna straps. In order to protect the transmitters, the whole transmitter system would shut down completely via crowbar under these conditions. This forceful shutdown can lead to unwanted wear and tear on the high voltage DC power supply system and impact the plasma operation due to the RF power interruption. In order to enable the transmitter to “ride” through the ELM induced high power reflections and avoid unwanted crowbar conditions, we can modify the transmitter power control and protective circuitry to accommodate the ELM´s perturbations.