1. Background magnetic field and holding coil simulation
By Michael Worcester

2. Background magnetic field data
The z and y components of the magnetic field were simulated at points along a yz plane.

3. Fitting an equation B_z as a function of z and y
Using field data from points, a polynomial expression for the magnetic field as a function of position was fitted.
Fitted with Matlab’s cftool function.
B_z as a function of z and y
B_y as a function of z and y

4. Using the equation
The equation was entered into Comsol Multiphysics 5.1 so that the background field could be simulated along with the DC holding coil fields.

5. DC Holding Coils
Constructed with Comsol’s helix geometry and multi-turn coil function.

6. Current objectives Simulating the electrical resistivity of Nb-Ti.
Optimizing the geometry of the holding coils for field uniformity and size.