desc.coils.initialize_saddle_coils

class desc.coils.initialize_saddle_coils(eq, num_coils, r_over_a=0.5, offset=2.0, position='outer')Source

Initialize a CoilSet of saddle coils for stage 2 optimization.

The coils will be planar, circular coils positioned around the plasma without linking it, and aligned such that the normal to the coil points towards the magnetic axis. The currents will be initialized to zero.

The coils will be FourierPlanarCoil with N=0, if another type is desired use coilset.to_FourierXYZ(N=10), coilset.to_SplineXYZ() etc.

Parameters:

  • eq (Equilibrium) – Stage 1 equilibrium the coils are being optimized for.

  • num_coils (int) – Number of coils to create per field period. For stellarator symmetric equilibria, this will be the number of coils per half-period.

  • r_over_a (float) – Minor radius of the coils, in units of equilibrium minor radius.

  • offset (float) – Distance from coil to magnetic axis, in units of equilibrium minor radius. Note that for strongly shaped equilibria this may need to be large to avoid having the coils intersect the plasma.

  • position ({"outer", "inner", "top", "bottom"}) – Placement of coils relative to plasma. “outer” will place coils on the outboard side, “inner” on the inboard side, “top” will place coils above the plasma, “bottom” will place them below.

Returns:

coilset (CoilSet of FourierPlanarCoil) – Planar coils centered on magnetic axis, with appropriate symmetry.