Confinement characteristics of the extended operation regime of KSTAR toward advanced scenarios

先進シナリオに向けたKSTAR拡大運転領域の閉じ込め特性

Na, Y. S.*; 鈴木 隆博; 井手 俊介; Mueller, D.*; Kim, J. H.*; 宮田 良明; Kim, S. H.*; Kim, H. S.*; Jeon, Y. M.*; Bae, Y. S.*; Jeong, J. H.*; Joung, M.*; Lee, S. G.*; Park, S. I.*; Kim, W. C.*; Oh, Y. K.*; Kwak, J. G.*; KSTAR Team*

Na, Y. S.*; Suzuki, Takahiro; Ide, Shunsuke; Mueller, D.*; Kim, J. H.*; Miyata, Yoshiaki; Kim, S. H.*; Kim, H. S.*; Jeon, Y. M.*; Bae, Y. S.*; Jeong, J. H.*; Joung, M.*; Lee, S. G.*; Park, S. I.*; Kim, W. C.*; Oh, Y. K.*; Kwak, J. G.*; KSTAR Team*

KSTARプロジェクトの重要な実験目標である先進シナリオ開発を開始した。プラズマ電流立ち上げ初期にダイバータ配位を形成し、その後に加熱を行いつつ電流を立ち上げることで先進シナリオに適した鋸歯状不安定性のないターゲットプラズマの生成に成功した。さらにこのプラズマに対して、高いポロイダルベータ値と自発電流割合を得て磁気シアを変化させるためにJET装置で用いられている「Ipオーバーシュート」法を適用した。これら一連のプラズマについて、平衡及び輸送と加熱・電流駆動を考慮した統合シミュレーションコードを用いて閉じ込めと輸送特性を調べた。プラズマ電流立ち上げ中の安全係数、電流立ち上げ後の閉じ込め特性、自発電流を含む非誘導駆動電流について議論する。また、これらのプラズマを他のトカマク装置で開発された先進シナリオと比較し、今後のKSTAR先進シナリオ開発の方向性も議論する。

Development of advanced scenarios, an important experimental goal for the KSTAR project, has just begun. Target plasmas were successfully produced using large bore plasma and early divertor formation which exhibit low internal inductance with low magnetic shear at the centre and no sawtooth instability. Auxilliary heating during the current rampup phase was employed to slow the inductive current diffusion to the centre of the plasma. With respect to hybrid scenario development, so-called "Ip-overshoot" method being used in JET is applied for tailoring magnetic shear at reduced plasma current for higher poloidal beta and bootstrap current fraction. The confinement characteristics of these scenarios are investigated. Transport modeling is performed self-consistently with an integrated simulation package incorporating plasma equilibrium, transport, heating and current drive. Firstly, the current rampup phase is simulated and its impact on the target q-profile is addressed. Secondly, energy confinement of flattop phases is discussed. In addition, the non-inductive current drive fraction including the bootstrap current fraction is calculated. Lastly, these scenarios are compared with advanced scenarios developed in other tokamak devices and future directions in achieving advanced regimes are discussed.