Bootstrap current and quasi-symmetry in reactor-size stellarators

The impact of the bootstrap current (BC) has become an important issue in the modeling of quasi-symmetric stellarator devices. Magnetohydrodynamic equilibria have been calculated with self-consistent BC in the collisionless l/nu regime for characteristic quasi-symmetric configurations: a three-period quasi-axisymmetric and a four-period quasi-helically symmetric stellarator. The relationship between magnetic geometry and BC is shown along with its effect on the equilibrium when beta is increased. The relevance of the nonsymmetric modes is also investigated for both configurations. In each case, the effect on stability has been studied.