A 3D MHD equilibrium description of nonlinearly saturated ideal external kink/peeling structures in tokamaks
Novel free boundary magnetohydrodynamic equilibrium states with spontaneous three-dimensional (3-D) deformations of the plasmaâvacuum interface are computed. The structures obtained look like saturated ideal external kink/peeling modes. Large edge pressure gradients yield toroidal mode number n = 1 distortions when the edge bootstrap current is large and higher n corrugations when this current is small. Linear ideal MHD stability analyses confirm the nonlinear saturated ideal kink equilibrium states produced and we can identify the PfirschâSchlÃ¼ter current as the main linear instability driving mechanism when the edge pressure gradient is large. The dominant non-axisymmetric component of this PfirschâSchlÃ¼ter current drives a near resonant helical parallel current density ribbon that aligns with the near vanishing magnetic shear region caused by the edge bootstrap current. This current ribbon is a manifestation of the outer mode previously found on JET (Solano 2010). We claim that the equilibrium corrugations describe structures that are commonly observed in quiescent H-mode tokamak discharges.
- URL: http://journals.cambridge.org/action/displayJournal?jid=PLA
- URL: https://crpplocal.epfl.ch/pinboard/jpapers/1503703.pdf
Record created on 2015-12-08, modified on 2016-08-09