desc.coils.FourierRZCoil

class desc.coils.FourierRZCoil(current=1, R_n=10, Z_n=0, modes_R=None, modes_Z=None, NFP=1, sym='auto', name='')Source

Coil parameterized by fourier series for R,Z in terms of toroidal angle phi.

Parameters:

• current (float) – current through coil, in Amperes

• R_n (array-like) – fourier coefficients for R, Z

• Z_n (array-like) – fourier coefficients for R, Z

• modes_R (array-like) – mode numbers associated with R_n. If not given defaults to [-n:n]

• modes_Z (array-like) – mode numbers associated with Z_n, defaults to modes_R

• NFP (int) – number of field periods

• sym (bool) – whether to enforce stellarator symmetry

• name (str) – name for this coil

Examples

from desc.coils import FourierRZCoil
from desc.grid import LinearGrid
import numpy as np

I = 10
mu0 = 4 * np.pi * 1e-7
R_coil = 10
# circular coil given by R(phi) = 10
coil = FourierRZCoil(
    current=I, R_n=R_coil, Z_n=0, modes_R=[0]
)
z0 = 10
field_evaluated = coil.compute_magnetic_field(
    np.array([[0, 0, 0], [0, 0, z0]]), basis="rpz"
)
np.testing.assert_allclose(
    field_evaluated[0, :], np.array([0, 0, mu0 * I / 2 / R_coil]), atol=1e-8
)
np.testing.assert_allclose(
    field_evaluated[1, :],
    np.array(
        [0, 0, mu0 * I / 2 * R_coil**2 / (R_coil**2 + z0**2) ** (3 / 2)]
    ),
    atol=1e-8,
)

Methods

change_resolution([N, NFP, sym])	Change the maximum toroidal resolution.
compute(names[, grid, params, transforms, ...])	Compute the quantity given by name on grid.
compute_Bnormal(surface[, eval_grid, ...])	Compute Bnormal from self on the given surface.
compute_magnetic_field(coords[, params, ...])	Compute magnetic field at a set of points.
copy([deepcopy])	Return a (deep)copy of this object.
eq(other)	Compare equivalence between DESC objects.
flip(normal)	Flip the curve about the plane with specified normal.
from_input_file(path)	Create a axis curve from Fourier coefficients in a DESC or VMEC input file.
get_coeffs(n)	Get Fourier coefficients for given mode number(s).
load(load_from[, file_format])	Initialize from file.
rotate([axis, angle])	Rotate the curve by a fixed angle about axis in xyz coordinates.
save(file_name[, file_format, file_mode])	Save the object.
save_BNORM_file(surface, fname[, basis_M, ...])	Create BNORM-style .txt file containing Bnormal Fourier coefficients.
set_coeffs(n[, R, Z])	Set specific Fourier coefficients.
to_FourierXYZ([N, grid, s, name])	Convert coil to FourierXYZCoil representation.
to_SplineXYZ([knots, grid, method, name])	Convert coil to SplineXYZCoil.
translate([displacement])	Translate the curve by a rigid displacement in x, y, z.

Attributes

N	Maximum mode number.
NFP	Number of field periods.
R_basis	Spectral basis for R_Fourier series.
R_n	Spectral coefficients for R.
Z_basis	Spectral basis for Z_Fourier series.
Z_n	Spectral coefficients for Z.
current	Current passing through the coil, in Amperes.
name	Name of the curve.
sym	Whether this curve has stellarator symmetry.