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ICRF Heating System in LHD

T. Mutoh, R. Kumazawa, T. Seki, K. Saito, H. Kasahara, F. Shimpo, G. Nomura, LHD Experiment Group

Fusion Science and Technology / Volume 58 / Number 1 / July-August 2010 / Pages 504-514

Chapter 10. Ion Cyclotron Range of Frequency Heating / Special Issue on Large Helical Device (LHD) /

A heating system for the Large Helical Device (LHD) based on the ion cyclotron range of frequencies (ICRF) heating is reviewed. Various physical and engineering issues were studied and solved to construct an effective and stable system for high-power, steady-state experiments in LHD. Successful results were achieved using six loop antennas. The physical design of the ICRF antenna was an important subject during the research and development phase. A single current strap antenna was adopted to maintain high coupling resistance. The antenna designed to conform to the LHD plasma shape provided effective plasma heating. Steady-state operation is one of the most important mission items of superconducting LHD device. Many ICRF components, including the transmitter, transmission line, impedance matching tuner, feedthrough ceramics, and antenna launcher, were developed and applied in long-pulse experiments. All components are water cooled to remove the heat loss during the operation. Especially, a liquid stub impedance tuner using dielectric liquid was developed and implemented for the first time in a plasma experiment. An antenna launcher was also designed with the ability to change its position during the steady-state operation. Steady-state operation for 54 min with an input energy of 1.6 GJ was achieved, the largest input energy on record for a toroidal plasma device.

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