Internal transport barrier triggering by rational magnetic flux surfaces in tokamaks

E. Joffrin, C.D. Challis, G.D. Conway, X. Garbet, A. Gude, S. Günter, N.C. Hawkes, T.C. Hender, D.F. Howell, G.T.A. Huysmans, E. Lazzaro, P. Maget, M. Marachek, A.G. Peeters, S.D. Pinches, S.E. Sharapov

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The formation of internal transport barriers (ITBs) has been experimentally associated with the presence of rational q surfaces in both JET and ASDEX Upgrade. The triggering mechanisms are related to the occurrence of magnetohydrodynamic (MHD) instabilities such as mode coupling and fishbone activity. These events could locally modify the poloidal velocity and increase transiently the shearing rate to values comparable with the linear growth rate of ion temperature gradient modes. For JET reversed magnetic shear scenarios, ITB emergence occurs preferentially when the minimum q reaches an integral value. In this case, transport effects localized in the vicinity of zero magnetic shear and close to rational q values may be at the origin of ITB formation. The role of rational q surfaces in ITB triggering stresses the importance of q profile control for an advanced tokamak scenario and could assist in substantially lowering the access power to these scenarios in next step facilities.
Original languageEnglish
Pages (from-to)1167 - 1174
Number of pages8
JournalNuclear Fusion
Issue number10
Publication statusPublished - Oct 2003
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Joffrin, E., Challis, C. D., Conway, G. D., Garbet, X., Gude, A., Günter, S., Hawkes, N. C., Hender, T. C., Howell, D. F., Huysmans, G. T. A., Lazzaro, E., Maget, P., Marachek, M., Peeters, A. G., Pinches, S. D., & Sharapov, S. E. (2003). Internal transport barrier triggering by rational magnetic flux surfaces in tokamaks. Nuclear Fusion, 43(10), 1167 - 1174.