Refined modeling of superconducting double helical coils using finite element analyses

Double helical coils are becoming more and more attractive for accelerator magnets and other applications. Conceptually, a sinusoidal modulation of the longitudinal position of the turns allows virtually any multipolar field to be produced and maximizes the effectiveness of the supplied ampere turns. Being intrinsically three-dimensional, the modeling of such structures is very complicated, and several approaches, with different degrees of complexity, can be used. In this paper we present various possibilities for solving the magnetostatic problem of a double helical coil, through both finite element analyses and direct integration of the Biot–Savart law, showing the limits and advantages of each solution and the corresponding information which can be derived. (paper)