🧲 Superconducting Solenoid: Field, Hoop Stress and NbTi Critical Margin (2D)

Half cross-section of a thick superconducting solenoid whose current is ramped up. Set the inner radius, thickness and length of the winding, the current density, the temperature and the share of superconductor, and see the field in the bore and on the winding, the outward magnetic stress, how close the winding is to its critical current and the current at which it would quench. The Fabry field formula, the long-solenoid limit, the critical margin and the hoop stress are checked with four in-page numerical checks.