Impact of toroidal and poloidal mode spectra on the control of non-axisymmetric fields in tokamaks

M.J. Lanctot, J.-K. Park, P. Piovesan, Y. Sun, R.J. Buttery, L. Frassinetti, B.A. Grierson, J.M. Hanson, S.R. Haskey, Y. In, Y.M. Jeon, R.J. La Haye, N.C. Logan, L. Marrelli, D.M. Orlov, C. Paz-Soldan, H.H. Wang, E.J. Strait

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In several tokamaks, non-axisymmetric magnetic field studies show that applied magnetic fields with a toroidal harmonic n = 2 can lead to disruptive n = 1 locked modes. In Ohmic plasmas, n = 2 magnetic reconnection thresholds in otherwise stable discharges are readily accessed at edge safety factors q ∼ 3, low density, and low rotation. Similar to previous studies with n = 1 fields, the thresholds are correlated with the "overlap" field computed with the IPEC code. The overlap field quantifies the plasma-mediated coupling of the external field to the resonant field. Remarkably, the "critical overlap fields" at which magnetic islands form are similar for applied n = 1 and 2 fields. The critical overlap field increases with plasma density and edge safety factor but is independent of the toroidal field. Poloidal harmonics m > nq dominate the drive for resonant fields while m 1 field control including the need for multiple rows of coils to control selected plasma parameters for specific functions (e.g., rotation control or ELM suppression).
Original languageEnglish
Article number056117
Pages (from-to)-
JournalPhysics of Plasmas
Issue number5
Publication statusPublished - 1 May 2017
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

Lanctot, M. J., Park, J-K., Piovesan, P., Sun, Y., Buttery, R. J., Frassinetti, L., Grierson, B. A., Hanson, J. M., Haskey, S. R., In, Y., Jeon, Y. M., La Haye, R. J., Logan, N. C., Marrelli, L., Orlov, D. M., Paz-Soldan, C., Wang, H. H., & Strait, E. J. (2017). Impact of toroidal and poloidal mode spectra on the control of non-axisymmetric fields in tokamaks. Physics of Plasmas, 24(5), -. [056117].