Nonlinear stability limit in high b tokamaks
نویسندگان
چکیده
Linearly unstable high b tokamak equilibria are shown to be nonlinearly stabilized by an axisymmetric flow containing both toroidal and poloidal components. As fingers of hot plasma produced by pressure driven ballooning instabilities start to convect out towards the bounding wall, an axisymmetric flow is self-consistently generated and opposes the growth of the fingers, maintaining confinement. However, as b increases the growth rate of the fingers increases until there is insufficient time for the developing axisymmetric flow to halt their rapid progress to the wall, and confinement is lost. The ultimate stability of a tokamak plasma is determined by a nonlinear stability limit in b . © 2000 American Institute of Physics. @S1070-664X~00!00304-9#
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