Workflow

Scalar Potential Transfer Coil Design

Prepare COMSOL model (by hand)

1. Make new model. Add the following physics interfaces:
   • Magnetic fields, no currents
   • Magnetic fields, no currents 2
   • Magnetic fields
   • Magnetic fields, no currents 3
2. Build geometry. Needs the following features:
   • "fiducial sphere": the inner sample volume over which the field will be optimized.
   • "Coil surface": flat-faced surface (does not have to be convex) where coils will go.
3. Assign physics as follows:
   • MFNC: World outside the coil surface
   • MFNC2: Everything inside the coil surface
   • MF: Everything
   • MFNC3: Fiducial sphere only.
     • Solve for Reduced Field, with background field <mf.Hx, mf.Hy, mf.Hz>
4. Add a study with another stationary solver.
   • Enable MFNC and MFNC2 on Study 1
   • Enable MF' and MFNC3onStudy 2`
5. Label planar surfaces for solver
6. Do you have keep-out zones (e.g. penetrations)? To prevent wires from going through the keep-out zone, you'll need for the scalar potential to be constant on that boundary element. Here's one prescription that you'll have to repeat for each penetration:
   1. Add annular region around no-go zone itself.
   2. Add two surface probes, each pointing to the annulus. One needs to evaluate the integrated average of Vm <Vm>and the other needs to calculate <Vm2>.
   3. In MFNC and MFNC2 add a Magnetic Scalar Potential constraint to the penetration, and set Vm=bnd1, where you've adjusted the index to whatever your boundary probe is called.
   4. Assign a zero magnetic flux boundary condition to the annulus.
7. Add a table to the solutions branch.
8. Add a surface integral to the results: More Derived Values > Surface Integration
9. Assign a scalar potential to the coil surface for both MFNC and MFNC2.
10. Run Study 1. Make sure mesh is satisfactory, make sure solution (Vm-Vm2 here) is roughly what you expect.
11. Compact History.
12. Save model as Matlab file.