Single-stage gradient-based stellarator coil design: optimization for quasi-symmetry on surfaces

We will present a single-stage approach to optimize current-carrying coils to produce quasisymmetric vacuum magnetic fields on surfaces. First, we describe a new technique to compute magnetic surfaces in Boozer coordinates. Then, we optimize for quasisymmetry on these surfaces. Use gradient-based optimization methods, we can directly optimize the coils to favor quasisymmetry on surfaces. We will present numerical results that demonstrate the performance of this approach.