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.
`equiv`(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.
`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_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.
`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.
`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 this curve has stellarator symmetry.
`x_idx`	arrays of indices for each parameter in concatenated array.