An Integral Equation Approach to a Free Boundary Problem in Magnetic Confinement Fusion

Evan Toler, Courant Institute of Mathematical Sciences
MCS Seminar Graphic

To design and control magnetic confinement fusion reactors, one must compute the geometry of the confined plasma at equilibrium. In this talk, I present a new method for solving this free-boundary problem through integral equations and PDE-constrained optimization. I detail a formulation of the equilibrium equations that couples the Grad-Shafranov equation for the interior magnetic field with an integral equation for the exterior vacuum field. I introduce high order numerical methods for solving the associated integral equation, including a novel application of the Kapur-Rokhlin quadrature rule for singular integrals in axisymmetric magnetic confinement systems. Finally, I frame the coupled equations in the larger PDE-constrained optimization framework and discuss gradient descent methods for the optimization iteration.