Speaker
Kenji Saito
(Department of Helical Plasma Research)
Description
The transmission line is one of the most important parts among the ion cyclotron range of frequencies (ICRF) heating devices. In the case of unwanted troubles on the line, immediate power-off is necessary for the protection of the line and for safety. In the Large Helical Device (LHD), though the causes were unclear, several troubles such as melting sometimes occurred on the line between the Final Power Amplifier (FPA) and the impedance matching device. The impedance matching device is located in the LHD hall because the shorter distance between the ICRF antenna and the matching device is better for reducing the power loss. As a result, a long distance of more than 100 m between the FPA and the impedance matching device is necessary. Therefore, it will be difficult to check the whole line temperature with IR cameras. Moreover, it is difficult to recognize the fault by the reflection power since the matching device reduces the reflection.
For these reasons, we developed the fault detection system for the ICRF transmission line in LHD by applying the Scattering Matrix Arc Detection System (SMAD) technique in the JET ITER-like ICRF antenna. Three signals are combined with power combiners so that the combined signal is zero. Balancing must be maintained with arbitral output impedance. Adjustment of phase shifters and attenuators is done by changing the output impedance with the matching device. If the three signals are not balanced, the combined signal is not zero. In this case, there is a fault somewhere in the transmission line since the S-matrix has been changed, and the ICRF power must be turned off immediately. The fault detection system will be operated in the next ICRF heating experiments.
Co-authors
Kamio Shuji
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
Kasahara Hiroshi
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
Kenji Saito
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
Mutoh Takashi
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
Nomura Goro
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
Seki Ryosuke
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
Seki Tetsuo
(Department of Helical Plasma Research, National Institute for Fusion Science, Toki-shi Gifu, Japan)
