High Power Experiment and Heat Load Evaluation of Transmission Line for the ECH/CD System in JT-60SA

Temperature rise of the waveguide transmission line for high-power long-pulse ECH/CD system has been evaluated experimentally using the dummy load transmission line in JT-60SA. It has been demonstrated that the waveguide components with the inner diameter of 60.3 mm are applicable for 1 MW/100 s transmission at 110/138 GHz required in JT-60SA. A newly developed pre-load installed in front of the dummy load reduced the temperature rise of the waveguide due to the reflection from the dummy load. With this pre-load, the temperature rise distribution in the 37 m-long test transmission line was measured to simulate the real transmission line condition for tokamak experiment. As a result of the high-power experiments, it has been clarified that the temperature of the waveguides close to miter-bends could be increased by approximately 120 K for 1 MW/100 s operation at 110 GHz, in the worst case, and it is marginal for the stable operation with the waveguides made of aluminum alloy. The heat loads on the waveguides have been evaluated as 23 kW/m2 for the worst case between miter bends, 12-23 kW/m2 within 4 m from miter bend and 4-12 kW/m2 for waveguide far from miter bends. The evaluated heat loads will be taken into account for the final design of the TL components and cooling for the JT-60SA ECH/CD system.