How superconducting materials that carry current with zero electrical resistance enable the powerful, persistent magnetic fields needed to confine a fusion plasma indefinitely.
A fusion reactor needs magnetic fields of 5–20 tesla sustained continuously for months or years. Conventional copper electromagnets at these field strengths would consume hundreds of megawatts of electrical power just to maintain the field — far exceeding the reactor’s output. Superconducting magnets carry current with zero resistance, consuming no power in steady state (only cryogenic cooling is needed).[1]
ITER uses the world’s largest superconducting magnet system: 18 toroidal field coils (Nb3Sn, ~12 T), 6 poloidal field coils (NbTi), a central solenoid (Nb3Sn, 13 T), and 18 correction coils. The stored magnetic energy is 41 GJ — equivalent to 10 tonnes of TNT. The Nb3Sn conductor alone required 100,000 km of superconducting strand.[2]
REBCO HTS magnets are being adopted by CFS (SPARC), Tokamak Energy (ST-HTS), Type One Energy, Proxima Fusion, and others. Key advantages: higher field (B4 scaling of fusion power), higher operating temperature (simpler cryogenics), and the potential for demountable joints enabling modular reactor assembly.[3]