Non-singular computation of magnetic field created by 3D distributed plasma current density

Computation of 3D magnetic field inside and nearby of 3D current carrying plasma is presented. Non-singular, accurate and “fast” (a few seconds on laptop with moderate dense 3D grid) method, based on numerical solution to a few 3D Poisson’s equations, is used. The 3D magnetic solver “ELSOME” was developed and aligned with plasma and vessel geometry and parameters typical for plasma shots in the C-2W device [1]. Although FRC plasmas and currents are mainly designed to be axisymmetric, some physics models naturally bring 3D effects. Any unstable mode with mode number greater than 0 produces 3D current perturbation, which can be transformed into 3D magnetic field (MF) perturbation with help of ELSOME. Non-axisymmetric fast ion current, due to the finite number of neutral beams on each injection plane, generates 3D MF perturbations, which can be computed by ELSOME too. We will discuss possible implementations of ELSOME to improve plasma operations, including some 3D diagnostic effects also. Details of the 3D magnetic model and the solver will be presented too.

[1] H. Gota et al., Nucl. Fusion 59, 112009 (2019).