def test_biotsavart_coil_current_taylortest(self):
coil0 = get_coil()
current0 = 1e4
coil1 = get_coil(perturb=True)
current1 = 1e3
bs = BiotSavart([coil0, coil1], [current0, current1])
points = np.asarray(
17 * [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]])
bs.set_points(points)
B = bs.B()
J = bs.dB_by_dX()
H = bs.d2B_by_dXdX()
dB = bs.dB_by_dcoilcurrents()
dJ = bs.d2B_by_dXdcoilcurrents()
dH = bs.d3B_by_dXdXdcoilcurrents()
h = 1.
bs.currents_optim[0].set_dofs(1e4 + h)
bs.invalidate_cache()
Bp = bs.B()
Jp = bs.dB_by_dX()
Hp = bs.d2B_by_dXdX()
bs.currents_optim[0].set_dofs(1e4 - h)
bs.invalidate_cache()
Bm = bs.B()
Jm = bs.dB_by_dX()
Hm = bs.d2B_by_dXdX()
dB_approx = (Bp - Bm) / (2 * h)
dJ_approx = (Jp - Jm) / (2 * h)
dH_approx = (Hp - Hm) / (2 * h)
assert np.linalg.norm(dB[0] - dB_approx) < 1e-15
assert np.linalg.norm(dJ[0] - dJ_approx) < 1e-15
assert np.linalg.norm(dH[0] - dH_approx) < 1e-13
def test_dB_by_dcoilcoeff_reverse_taylortest(self):
np.random.seed(1)
coil = get_coil()
bs = BiotSavart([coil], [1e4])
points = np.asarray(
17 * [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]])
points += 0.001 * (np.random.rand(*points.shape) - 0.5)
bs.set_points(points)
coil_dofs = np.asarray(coil.get_dofs())
B = bs.B()
J0 = np.sum(B**2)
dJ = bs.B_vjp(B)
h = 1e-2 * np.random.rand(len(coil_dofs)).reshape(coil_dofs.shape)
dJ_dh = 2 * np.sum(dJ[0] * h)
err = 1e6
for i in range(5, 10):
eps = 0.5**i
coil.set_dofs(coil_dofs + eps * h)
bs.clear_cached_properties()
Bh = bs.B()
Jh = np.sum(Bh**2)
deriv_est = (Jh - J0) / eps
err_new = np.linalg.norm(deriv_est - dJ_dh)
assert err_new < 0.55 * err
err = err_new
def stdBonAxis(self):
bs = BiotSavart(self.coils, self.currents)
bs.set_points(self.axis.gamma())
Bfield = bs.B()
devBstrength = [
sqrt(dot(Bfieldi, Bfieldi)) - self.stel.B0 for Bfieldi in Bfield
]
return std(devBstrength)
def test_helicalcoil_Bfield(self):
point = [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]]
field = [[-0.00101961, 0.20767292, -0.00224908]]
derivative = [[[0.47545098, 0.01847397, 1.10223595],
[0.01847426, -2.66700072, 0.01849548],
[1.10237535, 0.01847085, 2.19154973]]]
coils = [CurveHelical(100, 2, 5, 2, 1., 0.3) for i in range(2)]
coils[0].set_dofs(np.concatenate(([0, 0], [0, 0])))
coils[1].set_dofs(np.concatenate(([np.pi / 2, 0], [0, 0])))
currents = [-3.07e5, 3.07e5]
Bhelical = BiotSavart(coils, currents)
Bhelical.set_points(point)
assert np.allclose(Bhelical.B(), field)
assert np.allclose(Bhelical.dB_by_dX(), derivative)
def test_biotsavart_B_is_curlA(self):
coil = get_coil()
bs = BiotSavart([coil], [1e4])
points = np.asarray(
17 * [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]])
bs.set_points(points)
B, dA_by_dX = bs.B(), bs.dA_by_dX()
curlA1 = dA_by_dX[:, 1, 2] - dA_by_dX[:, 2, 1]
curlA2 = dA_by_dX[:, 2, 0] - dA_by_dX[:, 0, 2]
curlA3 = dA_by_dX[:, 0, 1] - dA_by_dX[:, 1, 0]
curlA = np.concatenate(
(curlA1[:, None], curlA2[:, None], curlA3[:, None]), axis=1)
err = np.max(np.abs(curlA - B))
assert err < 1e-14
def subtest_biotsavart_dBdX_taylortest(self, idx):
coil = get_coil()
bs = BiotSavart([coil], [1e4])
points = np.asarray(
17 * [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]])
points += 0.001 * (np.random.rand(*points.shape) - 0.5)
bs.set_points(points)
B0 = bs.B()[idx]
dB = bs.dB_by_dX()[idx]
for direction in [
np.asarray((1., 0, 0)),
np.asarray((0, 1., 0)),
np.asarray((0, 0, 1.))
]:
deriv = dB.T.dot(direction)
err = 1e6
for i in range(5, 10):
eps = 0.5**i
bs.set_points(points + eps * direction)
Beps = bs.B()[idx]
deriv_est = (Beps - B0) / (eps)
new_err = np.linalg.norm(deriv - deriv_est)
assert new_err < 0.55 * err
err = new_err
def test_sum_Bfields(self):
pointVar = 1e-1
npoints = 20
points = np.asarray(
npoints * [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]])
points += pointVar * (np.random.rand(*points.shape) - 0.5)
# Set up helical field
coils = [CurveHelical(101, 2, 5, 2, 1., 0.3) for i in range(2)]
coils[0].set_dofs(np.concatenate(([np.pi / 2, 0], [0, 0])))
coils[1].set_dofs(np.concatenate(([0, 0], [0, 0])))
currents = [-2.1e5, 2.1e5]
Bhelical = BiotSavart(coils, currents)
# Set up toroidal fields
Btoroidal1 = ToroidalField(1., 1.)
Btoroidal2 = ToroidalField(1.2, 0.1)
# Set up sum of the three in two different ways
Btotal1 = MagneticFieldSum([Bhelical, Btoroidal1, Btoroidal2])
Btotal2 = Bhelical + Btoroidal1 + Btoroidal2
Btotal3 = Btoroidal1 + Btoroidal2
# Evaluate at a given point
Bhelical.set_points(points)
Btoroidal1.set_points(points)
Btoroidal2.set_points(points)
Btotal1.set_points(points)
Btotal2.set_points(points)
Btotal3.set_points(points)
# Verify
assert np.allclose(Btotal1.B(), Btotal2.B())
assert np.allclose(Bhelical.B() + Btoroidal1.B() + Btoroidal2.B(),
Btotal1.B())
assert np.allclose(Btotal1.dB_by_dX(), Btotal2.dB_by_dX())
assert np.allclose(
Bhelical.dB_by_dX() + Btoroidal1.dB_by_dX() +
Btoroidal2.dB_by_dX(), Btotal1.dB_by_dX())
assert np.allclose(Btoroidal1.d2B_by_dXdX() + Btoroidal2.d2B_by_dXdX(),
Btotal3.d2B_by_dXdX())
assert np.allclose(Btoroidal1.A() + Btoroidal2.A(), Btotal3.A())
assert np.allclose(Btoroidal1.dA_by_dX() + Btoroidal2.dA_by_dX(),
Btotal3.dA_by_dX())
assert np.allclose(Btoroidal1.d2A_by_dXdX() + Btoroidal2.d2A_by_dXdX(),
Btotal3.d2A_by_dXdX())
def CoilsBonAxis(axis, qvfilename, NFP):
from axisOptFuncs import importCoils, getFourierCurve, plot_stellarator
from simsopt.geo.biotsavart import BiotSavart
from numpy import sqrt, dot
import matplotlib.pyplot as plt
_, current = importCoils("coils." + qvfilename)
outputFile = qvfilename + "_coil_coeffs.dat"
coils, currents = getFourierCurve(outputFile, current)
print("Look at resulting coils")
plot_stellarator("coils_FOURIER_", qvfilename, coils, NFP, axis,
"quasisymmetry_out." + qvfilename + ".nc")
print("Plot on-axis B from these coils")
bs = BiotSavart(coils, currents)
bs.set_points(axis.gamma())
Bfield = bs.B()
Bstrength = [sqrt(dot(Bfieldi, Bfieldi)) for Bfieldi in Bfield]
plt.figure()
plt.plot(Bstrength)
plt.xlabel('phi')
plt.ylabel('B')
plt.savefig("Bonaxis" + qvfilename + '.pdf',
bbox_inches='tight',
pad_inches=0)
def test_circularcoil_Bfield(self):
current = 1.2e7
radius = 1.12345
center = [0.12345, 0.6789, 1.23456]
pointVar = 1e-1
npoints = 1
## verify the field at the center of a coil in the xy plane
Bfield = CircularCoil(I=current, r0=radius)
points = np.array([[1e-10, 0, 0.]])
Bfield.set_points(points)
assert np.allclose(Bfield.B(),
[[0, 0, current / 1e7 * 2 * np.pi / radius]])
# Verify that divergence is zero
dB1_by_dX = Bfield.dB_by_dX()
assert np.allclose(
dB1_by_dX[:, 0, 0] + dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints)))
# Verify that, as a vacuum field, grad B=grad grad phi so that grad_i B_j = grad_j B_i
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(dB1_by_dX, transpGradB1)
### compare to biosavart(circular_coil)
## at these points
points = np.asarray(
npoints * [[-1.41513202e-03, 8.99999382e-01, -3.14473221e-04]])
points += pointVar * (np.random.rand(*points.shape) - 0.5)
## verify with a x^2+z^2=radius^2 circular coil
normal = [np.pi / 2, 0]
coils = [CurveXYZFourier(300, 1)]
coils[0].set_dofs(
[center[0], radius, 0., center[1], 0., 0., center[2], 0., radius])
Bcircular = BiotSavart(coils, [current])
Bfield = CircularCoil(I=current,
r0=radius,
normal=normal,
center=center)
Bfield.set_points(points)
Bcircular.set_points(points)
dB1_by_dX = Bfield.dB_by_dX()
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(Bfield.B(), Bcircular.B())
assert np.allclose(Bfield.dB_by_dX(), Bcircular.dB_by_dX())
assert np.allclose(
dB1_by_dX[:, 0, 0] + dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints)))
assert np.allclose(dB1_by_dX, transpGradB1)
# use normal = [0, 1, 0]
normal = [0, 1, 0]
coils = [CurveXYZFourier(300, 1)]
coils[0].set_dofs(
[center[0], radius, 0., center[1], 0., 0., center[2], 0., radius])
Bcircular = BiotSavart(coils, [current])
Bfield = CircularCoil(I=current,
r0=radius,
normal=normal,
center=center)
Bfield.set_points(points)
Bcircular.set_points(points)
dB1_by_dX = Bfield.dB_by_dX()
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(Bfield.B(), Bcircular.B())
assert np.allclose(Bfield.dB_by_dX(), Bcircular.dB_by_dX())
assert np.allclose(
dB1_by_dX[:, 0, 0] + dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints)))
assert np.allclose(dB1_by_dX, transpGradB1)
## verify with a y^2+z^2=radius^2 circular coil
normal = [np.pi / 2, np.pi / 2]
coils = [CurveXYZFourier(300, 1)]
coils[0].set_dofs(
[center[0], 0, 0., center[1], radius, 0., center[2], 0., radius])
Bcircular = BiotSavart(coils, [current])
Bfield = CircularCoil(I=current,
r0=radius,
normal=normal,
center=center)
Bfield.set_points(points)
Bcircular.set_points(points)
dB1_by_dX = Bfield.dB_by_dX()
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(Bfield.B(), Bcircular.B())
assert np.allclose(Bfield.dB_by_dX(), Bcircular.dB_by_dX())
assert np.allclose(dB1_by_dX[:, 0, 0] +
dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints))) # divergence
assert np.allclose(dB1_by_dX, transpGradB1) # symmetry of the gradient
Bfield.set_points([[0.1, 0.2, 0.3]])
Afield = Bfield.A()
assert np.allclose(Afield, [[0, 5.15786, -2.643056]])
# use normal=[1,0,0]
normal = [1, 0, 0]
coils = [CurveXYZFourier(300, 1)]
coils[0].set_dofs(
[center[0], 0, 0., center[1], radius, 0., center[2], 0., radius])
Bcircular = BiotSavart(coils, [current])
Bfield = CircularCoil(I=current,
r0=radius,
normal=normal,
center=center)
Bfield.set_points(points)
Bcircular.set_points(points)
dB1_by_dX = Bfield.dB_by_dX()
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(Bfield.B(), Bcircular.B())
assert np.allclose(Bfield.dB_by_dX(), Bcircular.dB_by_dX())
assert np.allclose(dB1_by_dX[:, 0, 0] +
dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints))) # divergence
assert np.allclose(dB1_by_dX, transpGradB1) # symmetry of the gradient
## verify with a x^2+y^2=radius^2 circular coil
center = [0, 0, 0]
normal = [0, 0]
coils = [CurveXYZFourier(300, 1)]
coils[0].set_dofs(
[center[0], 0, radius, center[1], radius, 0., center[2], 0., 0.])
Bcircular = BiotSavart(coils, [current])
coils2 = [CurveRZFourier(300, 1, 1, True)]
coils2[0].set_dofs([radius, 0, 0])
Bcircular2 = BiotSavart(coils, [current])
Bfield = CircularCoil(I=current,
r0=radius,
normal=normal,
center=center)
Bfield.set_points(points)
Bcircular.set_points(points)
Bcircular2.set_points(points)
dB1_by_dX = Bfield.dB_by_dX()
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(Bfield.B(), Bcircular.B())
assert np.allclose(Bfield.B(), Bcircular2.B())
assert np.allclose(Bfield.dB_by_dX(), Bcircular.dB_by_dX())
assert np.allclose(Bfield.dB_by_dX(), Bcircular2.dB_by_dX())
assert np.allclose(dB1_by_dX[:, 0, 0] +
dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints))) # divergence
assert np.allclose(dB1_by_dX, transpGradB1) # symmetry of the gradient
# use normal = [0, 0, 1]
center = [0, 0, 0]
normal = [0, 0, 1]
coils = [CurveXYZFourier(300, 1)]
coils[0].set_dofs(
[center[0], 0, radius, center[1], radius, 0., center[2], 0., 0.])
Bcircular = BiotSavart(coils, [current])
coils2 = [CurveRZFourier(300, 1, 1, True)]
coils2[0].set_dofs([radius, 0, 0])
Bcircular2 = BiotSavart(coils, [current])
Bfield = CircularCoil(I=current,
r0=radius,
normal=normal,
center=center)
Bfield.set_points(points)
Bcircular.set_points(points)
Bcircular2.set_points(points)
dB1_by_dX = Bfield.dB_by_dX()
transpGradB1 = [dBdx.T for dBdx in dB1_by_dX]
assert np.allclose(Bfield.B(), Bcircular.B())
assert np.allclose(Bfield.B(), Bcircular2.B())
assert np.allclose(Bfield.dB_by_dX(), Bcircular.dB_by_dX())
assert np.allclose(Bfield.dB_by_dX(), Bcircular2.dB_by_dX())
assert np.allclose(dB1_by_dX[:, 0, 0] +
dB1_by_dX[:, 1, 1] + dB1_by_dX[:, 2, 2],
np.zeros((npoints))) # divergence
assert np.allclose(dB1_by_dX, transpGradB1) # symmetry of the gradient
def BonAxis(self):
bs = BiotSavart(self.coils, self.currents)
bs.set_points(self.axis.gamma())
Bfield = bs.B()
Bstrength = [sqrt(dot(Bfieldi, Bfieldi)) for Bfieldi in Bfield]
return Bstrength