desc.magnetic_fields.field_line_integrate

class desc.magnetic_fields.field_line_integrate(r0, z0, phis, field, params=None, source_grid=None, rtol=1e-08, atol=1e-08, max_steps=None, min_step_size=1e-08, solver=Tsit5(), bounds_R=(0, inf), bounds_Z=(-inf, inf), chunk_size=None, bs_chunk_size=None, options=None, return_aux=False)Source

Trace field lines by integration, using diffrax package.

Parameters:

  • r0 (array-like) – initial starting coordinates for r,z on phi=phis[0] plane

  • z0 (array-like) – initial starting coordinates for r,z on phi=phis[0] plane

  • phis (array-like) – geometric toroidal angle values to output r,z at. Can be strictly increasing or decreasing, but must be monotonic.

  • field (MagneticField) – source of magnetic field to integrate

  • params (dict, optional) – parameters passed to field

  • source_grid (Grid, optional) – Collocation points used to discretize source field.

  • rtol (float) – relative and absolute tolerances for PID stepsize controller. Not used if stepsize_controller is provided.

  • atol (float) – relative and absolute tolerances for PID stepsize controller. Not used if stepsize_controller is provided.

  • max_steps (int) – maximum number of steps for the integration. Defaults to abs((phis[-1] - phis[0]) * 1000)

  • min_step_size (float) – minimum step size (in phi) that the integration can take. default is 1e-8

  • solver (diffrax.Solver) – diffrax Solver object to use in integration, defaults to Tsit5(), a RK45 explicit solver

  • bounds_R (tuple of (float,float), optional) – R bounds for field line integration bounding box. Trajectories that leave this box will be stopped, and NaN returned for points outside the box. Defaults to (0, np.inf)

  • bounds_Z (tuple of (float,float), optional) – Z bounds for field line integration bounding box. Trajectories that leave this box will be stopped, and NaN returned for points outside the box. Defaults to (-np.inf, np.inf)

  • chunk_size (int or None) – Chunk of field lines to trace at once. If None, traces all at once. Defaults to None.

  • bs_chunk_size (int or None) – Chunk size to use when evaluating Biot-Savart for the magnetic field. If None, evaluates all the source grid points at once. Defaults to None.

  • options (dict, optional) – Additional arguments to pass to the diffrax diffeqsolve.

  • return_aux (bool, optional) – Whether to return auxiliary information from the integrator. If True, will return a tuple (r, z, aux) where aux consists stats and result from diffrax.diffeqsolve. Defaults to False.

Returns:

r, z (ndarray) – arrays of r and z coordinates of the field line, corresponding to the input phis