Surface discharge related properties of fiberglass reinforced plastic insulator for use in neutral beam injector of JT-60U

JT-60のNBI用FRP絶縁材の沿面放電特性

山納 康*; 高橋 昌宏*; 小林 信一*; 花田 磨砂也; 池田 佳隆

Yamano, Yasushi*; Takahashi, Masahiro*; Kobayashi, Shinichi*; Hanada, Masaya; Ikeda, Yoshitaka

JT-60Uの500keV負イオンNBIでは半径1.8m,長さ0.315mのFRP絶遠管を3個用いた3段加速構造を有している。これまでの結果、ビーム引出しがない場合でも耐電圧は460kV以下であり、その原因の1つとして、FRPの沿面放電が考えられる。本研究は、FRPの抵抗,2次電子放出率,カソードルミネッセンス,電子脱離ガスに関する測定結果を報告する。

The JT-60U negative-ion-based NBI was designed to have 3-stage electrostatic accelerators with total accelerating voltage of 500kV. In order to hold such high voltage, three Fiberglass Reinforced Plastic (FRP) insulators of 1.8 m inner diameter and 31.5 cm height are used. Currently the hold-off voltage capability of 3-stage FRP insulators has been typically limited to 460 kV without beam acceleration. One of the possible reason is a surface discharges on the FRP insulators. This paper describes measurement results of surface resistivity and volume resistivity under vacuum and atmospheric conditions, secondary electron emission (SEE) characteristics and cathodoluminescence under some keV electron beam irradiation, gas analysis desorbed from the FRP insulator under irradiation of some keV-electron beam were also analyzed.