Results of the variable toroidal field ripple experiments in JET
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*
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.