Impact of self-consistent bootstrap current on the magnetic structure of W7-X

The impact of self-consistent bootstrap current on the magnetic structure of equilibria in computational studies of the W7-X stellarator is examined. While one of the criteria in designing W7-X was the minimization of the bootstrap current, at finite-$\beta$ there will likely still be some residual bootstrap current. Even a small bootstrap current can change the rotational transform profile and thus, change the magnetic configuration, especially in the edge region. In this work, free-boundary equilibria for the W7-X coil configuration have been obtained at a range of $\beta$ values and the bootstrap current has been calculated for each. An optimization is underway to obtain equilibria with self-consistent bootstrap current (i.e., where the plasma current is solely from the bootstrap current). The impact of both finite-$\beta$ and bootstrap currents on the magnetic structure in the edge will then be examined using the SIESTA code [Hirshman, {\it et al.}, Phys. Plasmas {\bf 18}, 062504 (2011)].