Results of the variable toroidal field ripple experiments in JET

JETにおけるトロイダル磁場リップル変化実験の結果

Saibene, G.*; McDonald, D. C.*; Beurskens, M.*; Salmi, A.*; Lonnroth, J. S.*; Parail, V.*; de Vries, P.*; Andrew, Y.*; Budny, R.*; Boboc, A.*; Coffey, I.*; la Luna, E. de.*; Loarte, A.*; Lomas, P. J.*; Gerasimov, S.*; Giroud, C.*; Hobirk, J.*; Hotchin, S.*; Johnson, T.*; Lescure, C.*; Nunes, I.*; 大山 直幸; Riccardo, V.*; 浦野 創; JET-EFDA Contributors*

Saibene, G.*; McDonald, D. C.*; Beurskens, M.*; Salmi, A.*; Lonnroth, J. S.*; Parail, V.*; de Vries, P.*; Andrew, Y.*; Budny, R.*; Boboc, A.*; Coffey, I.*; la Luna, E. de.*; Loarte, A.*; Lomas, P. J.*; Gerasimov, S.*; Giroud, C.*; Hobirk, J.*; Hotchin, S.*; Johnson, T.*; Lescure, C.*; Nunes, I.*; Oyama, Naoyuki; Riccardo, V.*; Urano, Hajime; JET-EFDA Contributors*

本発表は0.08%から約1%までトロイダル磁場リップルの振幅を変化できるJETにおけるリップル実験の結果を報告するものである。リップルがペデスタルとコアプラズマに与える影響をq=33.6のELMy Hモードプラズマで測定した。Hモード特性の変化は明確であるが、閉じ込め性能が劣化する物理機構は明確でない。プラズマ密度の減少や閉じ込め性能劣化は0.5%程度のリップルで観測されるが、その閾値はプラズマパラメータで変化する。リップルはペデスタル圧力とELMにも影響を与える。また、プラズマ回転もリップルの影響を強く受ける。

This paper describes the results of dedicated experiments carried out in JET, where H-mode plasmas properties were studied for varying levels of toroidal field ripple, in the range from 0.08% (natural for JET) up to 1%. The experiments were carried out in the ELMy H-mode regime with q =3 to 3.6, to investigate the effect of on pedestal and core properties of the plasma. These experiments show that toroidal field ripple has a clear effect on H-mode properties, although the physics mechanisms at the root of the reduced energy confinement with have not been identified unambiguously. Plasma density pump out and reduction of the global energy confinement is found for 0.5%, but the magnitude of this effect depends on plasma parameters. Ripple may also affect pedestal pressure, as well as size and frequency of ELMs. Plasma toroidal rotation was also strongly affected by ripple.