Speaker
Hiroyuki Tobari
(Naka Fusion Institution)
Description
Design and manufacturing of DC 1 MV components have progressed for the ITER neutral beam injector.
A multi-conductor DC 1 MV transmission line (TL) which can transmit five-different voltages of 200 kV step simultaneously has been manufactured and tested. The TL is a gas insulation tube with SF6 gas of 0.6 MPa. A layout of those conductors inside the tube was designed through electric field analysis to suppress electric field concentration lower than 20 kV/mm. A high voltage insulation test of the TL at DC 1200 kV for 1 hour has been successfully performed.
Cooling water supply system with insulation of DC 1 MV is also developed. A pure hot water feeding channel of 180 °C to the 1 MV potential is required to enhance the negative ion production in the ion source. A resistivity of the pure water decreases with an increase of the temperature. Low resistivity around 180 °C could result in a high leak current which causes further joule heating, however, the resistivity of hot water over 100 °C was unknown and the system cannot be designed. Thus, the resistivity of pure water up to 180 °C was experimentally investigated. As a result, high-temperature water channel with 10 mm diameter of insulation tubes was designed where a temperature rise is confirmed as small as 7 °C.
All conductors and tubes are introduced into the vacuum through the high voltage (HV) bushing. Those are electrostatically shielded with five-layered coaxial electrode called as electrostatic screen. Through an experimental study on vacuum insulation, a scaling of voltage holding capability of multi-layered electrodes on the surface area was obtained. Based on the scaling, the HV bushing with five electrostatic screens was designed and manufactured, and voltage holding at 240 kV in each gap was successfully achieved.
Co-authors
Atsushi Kojima
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Haruhiko Yamakana
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Hiroyuki Tobari
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Kazuhiro Watanabe
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Masaya Hanada
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Masayuki Dairaku
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Mieko Kashiwagi
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Naoki Shibata
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Naotaka Umeda
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Tetsuya Maejima
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
Yuki Oda
(Naka Fusion Institution, Japan Atomic Energy Agency, Mukouyama 801-1, Naka-shi, Ibaraki, Japan)
