Generation of initial closed flux surface by ECH at conventional aspect ratio of R/a 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R/a3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 an initial closed flux surface by electron cyclotron heating at a conventional aspect ratio of R/a 3 has been investigated on LATE and further tested on the JT-60U tokamak. In both experiments, plasma currents are initiated and increased by ECH under steady external fields composed of a toroidal field and a weak vertical field. In LATE experiments, a movable inboard limiter is used to change the aspect ratio of plasmas up to R/a 3. The results show that the formation of an initial closed flux surface is still possible up to R/a 3 while higher decay indices 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 configuration having a high decay index.