Direct identification of magnetic surface by a differential double probe in JFT-2M

JFT-2Mにおける差動ダブルプローブによる磁気面の直接測定

上原 和也; 都筑 和泰; 雨宮 宏*; 永島 芳彦*; 星野 克道; 定本 嘉郎*

Uehara, Kazuya; Tsuzuki, Kazuhiro; Amemiya, Hiroshi*; Nagashima, Yoshihiko*; Hoshino, Katsumichi; Sadamoto, Yoshiro*

トカマクの磁気面位置を検知したデータが示される。バイアス電圧をかけられた段差のある2つのダブルプローブで、磁気面位置を移動させた時に、2つのダブルプローブの電流の差を読み取るとセパラトリックスの位置で変化が生じる。この値から、セパラトリックスの位置が推定され、磁気面コードとの違いを評価した。この値は同じプローブで測定した浮遊電位の揺動の相関とも比較され良い一致を示した。同時に、このプローブでイオン温度を測定した。

Data for detecting the magnetic flux surfaces at the edge plasma in tokamak are presented. When the magnetic surfaces are moved by the plasma jog, it is observed that a current increment appears in the two set of double probe whose front surfaces are shifted by a small distance and that the difference of these two currents through the differential amplifier giving a signal of the arrival of the separatrix also appears, where we refer the separatrix point as a typical position of the magnetic flux surfaces. It is confirmed that magnetic flux surfaces are located by a few cm outward from that calculated by the eqfit-code (EQFIT) and the absolute value of its deviation is identified. This identification is supported by the result of observation of the correlation of the floating potential fluctuation between two different points using one probe pin of the same differential double probe. The ion temperature and the space potential are observed by the another use of the differential double probe are modified following the estimated real magnetic surfaces positions.