Unified Ideal Stability Limits for Advanced Tokamak and Spherical Torus Plasmas
Authors: J.E. Menard, M.G. Bell, R.E. Bell, D.A. Gates, S.M. Kaye, B.P. LeBlanc, S.A. Sabbagh, E.D. Fredrickson, S.C. Jardin, R. Maingi, J. Manickam, D. Mueller, M. Ono, F. Paoletti, Y.-K.M. Peng, V. Soukhanovskii, D. Stutman, E.J. Synakowski, and the NSTX Research Team
Date of PPPL Report: February 2003
Ideal magnetohydrodynamic stability limits of shaped tokamak plasmas with high bootstrap fraction are systematically determined as a function of plasma aspect ratio. For plasmas with and without wall stabilization of external kink modes, the computed limits are well described by distinct and nearly invariant values of a normalized beta parameter utilizing the total magnetic field energy density inside the plasma. Stability limit data from the low aspect ratio National Spherical Torus Experiment is compared to these theoretical limits and indicates that ideal nonrotating plasma no-wall beta limits have been exceeded in regimes with sufficiently high cylindrical safety factor. These results could impact the choice of aspect ratio in future fusion power plants.