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 the 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.
compute_magnetic_vector_potential(coords[, ...])	Compute magnetic vector potential at a set of points.
copy([deepcopy])	Return a (deep)copy of this object.
equiv(other)	Compare equivalence between DESC objects.
flip([normal])	Flip the curve about the plane with specified normal in X,Y,Z coordinates.
from_input_file(path, **kwargs)	Create a axis curve from Fourier coefficients in a DESC or VMEC input file.
from_values(current, coords[, N, NFP, ...])	Fit coordinates to FourierRZCoil representation.
get_coeffs(n)	Get Fourier coefficients for given mode number(s).
load(load_from[, file_format])	Initialize from file.
pack_params(p)	Convert a dictionary of parameters into a single array.
rotate([axis, angle])	Rotate the curve by a fixed angle about axis in X,Y,Z 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.
save_mgrid(path, Rmin, Rmax, Zmin, Zmax[, ...])	Save the magnetic field to an mgrid NetCDF file in "raw" format.
set_coeffs(n[, R, Z])	Set specific Fourier coefficients.
to_FourierPlanar([N, grid, basis, name])	Convert Coil to FourierPlanarCoil representation.
to_FourierRZ([N, grid, NFP, sym, name])	Convert Coil to FourierRZCoil representation.
to_FourierXY([N, grid, s, basis, name])	Convert Coil to FourierXYCoil representation.
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 coordinates.
unpack_params(x)	Convert a single array of concatenated parameters into a dictionary.

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.
dim_x	total number of optimizable parameters.
dimensions	dictionary of integers of sizes of each optimizable parameter.
name	Name of the curve.
num_coils	Number of coils.
optimizable_params	string names of parameters that have been declared optimizable.
params_dict	dictionary of arrays of optimizable parameters.
rotmat	Rotation matrix of curve in X, Y, Z.
shift	Displacement of curve in X, Y, Z.
sym	Whether or not the curve is stellarator symmetric.
x_idx	arrays of indices for each parameter in concatenated array.