(IT/P7-5) -1 MV DC UHV Power Supply for ITER NBI

K. Watanabe1), M. Yamamoto1), J. Takemoto1), Y. Yamashita2), M. Dairaku1), M. Kashiwagi1), M. Taniguchi1), H. Tobari1), N. Umeda1), K. Sakamoto1), T. Inoue1)
1) Japan Atomic Energy Agency, Naka, Japan
2) Hitachi Ltd., Hitachi, Japan

Abstract.  A dc -1 MV ultra high voltage (UHV) power supply system is required for the ITER neutral beam injector (NBI) to accelerate negative ion beams up to the energy of 1 MeV with the beam current of 40 A for 3600 s. Domestic Agency of Japan (JADA) and Domestic Agency of EU (EUDA) have agreed the procurement sharing for the ITER NBI power supply system. JADA contributes procurement of dc - 1 MV ultra-high voltage (UHV) components such as a - 1 MV dc generator, a transmission line and a - 1 MV insulating transformer. The dc UHV insulation is essential issue for the system, because dc long pulse insulation is different from conventional ac insulation. Voltage sharing is changed from capacitive distribution to resistive one by dc long pulse applying. Electric field distribution for multi-layer (oil/paper composites) insulation structure of the transformer has been studied by simulation for the long pulse operation up to 3600 s. The insulating structure has been designed and the overall dimensions of the dc UHV components have been finalized. In order to realize a stable NBI system, a surge energy suppression system is also essential to protect the accelerator from electric breakdowns. JADA contributes to provide an effective surge suppression system composed of a core snubber and resistors. Input energy from the power supply to the accelerator can be reduced to less than 20 joule which is smaller than design criteria of 50 joule at 1 MV breakdown. From these studies, JADA is ready for procurement arrangement for the UHV components.

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