Magnetohydrodynamic equilibrium and the stability of tokamak and reversed-field pinch systems with 3D helical cores

W.A. Cooper, J.P. Graves, O. Sauter, D. Terranova, M. Gobbin, L. Marrelli, P. Martin, I. Predebon

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Abstract

Bifurcated magnetohydrodynamic (MHD) equilibrium states are computed for ITER hybrid scenario and RFX-mod SHAx configurations with very flat or reversed core magnetic shear conditions. In the ITER studies, the minimum inverse rotational transform qmin is near unity, while for RFX-mod it is 1/8. Two equilibrium states are obtained: one is axisymmetric, the other displays a 3D helical core. In tokamak devices, the structure resembles a saturated ideal MHD internal kink mode. In the reversed-field pinch, the structure is seven-fold toroidally periodic. The equilibrium magnetic field spectrum in the Boozer coordinate frame is calculated in both the ITER and RFX-mod configurations and the implications are discussed. The RFX-mod equilibria are strongly unstable to external ideal MHD kink modes, which become stabilized with a closely fitting conducting shell when the equilibrium state has a weak reversed core shear. It is marginally unstable with a monotonic q-profile. Unstable modes are driven by the Ohmic current, with pressure and Pfirsch-Schlüter currents having a very weak effect. The external kink mode spectrum is dominated by coupled m = 1, n = 6 and m = 2, n = 13 Fourier components, which revert to m = 1, n = 8 and m = 2, n = 15 terms with a conducting wall in proximity to the plasma-vacuum interface. © 2011 IOP Publishing Ltd.
Original languageEnglish
Article number084001
Pages (from-to)-
JournalPlasma Physics and Controlled Fusion
Volume53
Issue number8
DOIs
Publication statusPublished - Aug 2011
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

Cite this

Cooper, W. A., Graves, J. P., Sauter, O., Terranova, D., Gobbin, M., Marrelli, L., ... Predebon, I. (2011). Magnetohydrodynamic equilibrium and the stability of tokamak and reversed-field pinch systems with 3D helical cores. Plasma Physics and Controlled Fusion, 53(8), -. [084001]. https://doi.org/10.1088/0741-3335/53/8/084001