Generation of initial closed flux surface by ECH at a conventional aspect ratio of / 3; Experiments on the LATE device and JT-60U tokamak

コンベンショナルなアスペクト比/3でのECHによる閉磁気面の形成; LATE装置とJT-60Uトカマクにおける実験

打田 正樹*; 前川 孝*; 田中 仁*; 井手 俊介; 高瀬 雄一*; 渡辺 文武*; 西 誠司*

Uchida, Masaki*; Maekawa, Takashi*; Tanaka, Hitoshi*; Ide, Shunsuke; Takase, Yuichi*; Watanabe, Fumitake*; Nishi, Seiji*

Generation of initial closed flux surfaces by electron cyclotron heating at a conventional aspect ratio of / 3 has been investigated on the Low Aspect ratio Torus Experiment (LATE) device and further tested on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) Tokamak. In both experiments, a plasma current is initiated and increased by ECH under steady external fields composed of a toroidal field and a weak vertical field. In the LATE experiments, a movable inboard limiter is used to change the aspect ratio of plasmas up to / 3. The results show that the formation of closed flux surfaces is still possible up to / 3 while higher decay indexes of vertical field are required as the aspect ratio increases. Similar current start-up discharges have been performed on JT-60U, and a plasma current is initiated and increased up to 20 kA under a vertical field having a high decay index.