Persistent current
Poloidal field lines
Quench (resistive)
drag ring to rotate
This simulator models a toroidal superconducting coil that stores energy directly in its magnetic field — no chemical reaction, no moving parts, and (below its critical surface) essentially zero resistive loss. Drive a real charging voltage across the coil and watch the persistent current ramp via Faraday's law, track the stored energy climb as E = ½LI², and shrink the critical-current curve by raising the coil's temperature toward its 92 K transition point. Push the current past that shrinking critical curve and the coil genuinely quenches — flipping to a resistive state that dumps the stored energy as heat instead of returning it to the grid — exactly the failure mode SMES engineers design their protection systems around. Three linked panels show the coil ring itself, the live Ic(T) curve with the operating point marked, and a strip-chart history of current and stored energy.