Tuesday, Oct. 9th，at 3pm given by Dr. Zhu Caoxiang of Princeton Plasma Physics Laboratory.
Title: Development of the FOCUS code for designing stellarator coils.
Dr. Zhu Caoxiang (朱曹祥）
Princeton Plasma Physics Laboratory, Princeton, NJ 08543
Abstract: Finding an easy-to-build coil set has been a critical issue for stellarator design for decades. Conventional approaches assume a toroidal ‘winding’ surface. We present a new method to design stellarator coils. The new coil design code, FOCUS, represents coils as arbitrary, closed, one-dimensional curves embedded in three-dimensional space. The target function to be minimized consists of multiple physical requirements and engineering constraints. By differentiating the first and second order derivatives of the target function with respect to coil parameters, FOCUS uses gradient-based and Hessian-based minimization algorithms to optimize the coils, fast and robustly. FOCUS has been applied to design modular/helical/RMP coils for stellarator and tokamak configurations. With analytically calculated Hessian, FOCUS can also use the eigenvalues of the Hessian matrix for determining the error field sensitivity to coil deviations. The sensitivities could provide information to avoid dominant coil misalignments and simplify coil designs for stellarators.