Calculation of the poloidal ambipolar field in a stellarator and its effect on transport

The portion Phi1 of the ambipolar potential Phi which produces an electric field in the flux surfaces of a stellarator is self-consistently calculated, and its effect on stellarator transport at low collisionality is considered. The effect is small in a parameter delta/sub h/, which is proportional to the square root of the ripple amplitude, epsilon/sub h/. However, since delta/sub h/ can be an appreciable fraction of 1 for realistic parameters, the effect of Phi1 on transport can also be appreciable. Whether the effect is harmful or beneficial to confinement depends on the degree of pressure anisotropy and on the sign of p/sub perpendicular/-p/sub parallel/