Computation of Tokamak Equilibria With Steady Flow

At present controlled therm onuclear fusion research is close to dem onstrating the feasibility of a fusion reactor. Three large tokam ak devices, TFTR , JE T , and JT-60, aim at break-even. These experiments are diagnosed and controlled by utiliz­ ing codes which are based on various plasma models. M acroscopic models describing equilibri­ um , stability and transport are am ong the most im portant ones. Neglecting flow and assuming isotropic pressure yields the well-known GradSchlüter-Shafranov equation. Ideal M H D stability of these configurations is considered a necessary condition for successful operation of a tokam ak. M ost transport models also neglect flow in the basic equilibrium . However, to achieve adequate sim ulation, the flows should be taken into ac­ count. T hat flows are present can be seen from the definition o f the current in the two-fluid model, j = e n ( v ' v e) = e n u (n being density and v the velocity). Furtherm ore, dissipative models require a flow for toroidal equilibria. Pfirsch-Schlüter diffusion sustains such a pressure-driven flow. If viscosity is included, the neoclassical flows nearly follow the observed behaviour. H eating power in the form o f neutral-beam injection substantially increases the plasm a tem perature. Depending mainly on the injection angle, this beam injection