Ideal MHD restricts both the current and the pressure which can be stably confined in a Tokamak. A pressure profile opthisation is carried out for a variety of equilibria, which include JET and INTOR-like plasmas, in order to obtain the maximun! p which can be stably confined at constant current. The current is limited to a value correspndinq to a safety factor slightly above 2 at the plasma surface. A simple scaling law is found that fits well all the cases and which predicts a linear rise of 3 with the current.

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Axisymmetric toroidal plasma equilibria with mass flows and anisotropic pressure are investigated. The equilibrium system is derived for a general functional form of the pressures, which includes both fluid models, such as the magnetohydrodynamic (MHD) and the double-adiabatic models, and Grad’s guiding center model [Proceedings of the Symposium on Electromagnetics and Fluid Dynamics of Gaseous Plasmas, edited by J. Fox (Polytechnic Inst. of Brooklyn, New York, 1961), p. 37]. This allows for detailed comparisons between the models and clarifies how the ‘‘first hyperbolic region,’’ occurring in fluid theory when the poloidal flow is of the order of the poloidal sound speed, can be eliminated in guiding center theory. In the case of a pure toroidal rotation, macroscopic equations of state are derived from the guiding center model, characterized by a parallel temperature that is constant on each magnetic surface and a perpendicular temperature that varies with the magnetic field. The outward centrifugal shifts of the magnetic axis and of the mass density profile, caused by toroidal rotation, are increased by anisotropy if p∥<p⊥ or decreased (and can even be inverted) if p∥>p⊥. In the guiding center model poloidal flow produces an inward shift of the density profile, in contrast with the MHD result.