PLASMA ROTATION IN A RIPPLED-FIELD TOKAMAK

A theory is developed for plasma rotation in a rippled-field tokamak u nder the conditions corresponding to the banana regime. This rotation is assumed to be governed by the longitudinal plasma viscosity. The lo ngitudinal fast-ion beam, which is present in experiments on fast-neut ral injection, is incorporated. The solution of the drift kinetic equa tion for the circulating ions is derived with allowance for the field ripple. Using this solution, it is possible to calculate the contribut ion that both the circulating ions and the ions trapped in the local r ipple well make to the poloidal and toroidal viscous forces. The previ ous understanding of the role played by locally trapped ions in the pr oblem of plasma rotation is revised. Attention is drawn to the dominan t influence of the frictional forces due to collisions between the cir culating and locally trapped ions in the problem of toroidal viscosity . The expressions for the stationary values of the poloidal and toroid al velocities of the plasma are obtained. This approach is used to exp lain the experimentally observed reduction in toroidal plasma velocity caused by the ripple-depth growth.