desc.equilibrium.Equilibrium.to_sfl

Equilibrium.to_sfl(L=None, M=None, N=None, L_grid=None, M_grid=None, N_grid=None, rcond=None, copy=False)

Transform this equilibrium to use straight field line coordinates.

Uses a least squares fit to find FourierZernike coefficients of R, Z, Rb, Zb with respect to the straight field line coordinates, rather than the boundary coordinates. The new lambda value will be zero.

NOTE: Though the converted equilibrium will have the same flux surfaces, the force balance error will likely be higher than the original equilibrium.

Parameters:

  • L (int, optional) – radial resolution to use for SFL equilibrium. Default = 1.5*eq.L

  • M (int, optional) – poloidal resolution to use for SFL equilibrium. Default = 1.5*eq.M

  • N (int, optional) – toroidal resolution to use for SFL equilibrium. Default = 1.5*eq.N

  • L_grid (int, optional) – radial spatial resolution to use for fit to new basis. Default = 2*L

  • M_grid (int, optional) – poloidal spatial resolution to use for fit to new basis. Default = 2*M

  • N_grid (int, optional) – toroidal spatial resolution to use for fit to new basis. Default = 2*N

  • rcond (float, optional) – cutoff for small singular values in least squares fit.

  • copy (bool, optional) – Whether to update the existing equilibrium or make a copy (Default).

Returns:

eq_sfl (Equilibrium) – Equilibrium transformed to a straight field line coordinate representation.