Domain overview
How magnetic confinement holds a burning plasma
Original Fusenergy explanation, framed against public technical references. Educational, not engineering or investment advice.
Magnetic confinement uses strong, carefully shaped magnetic fields to keep charged plasma particles spiralling along field lines and away from material walls. The tokamak — an axisymmetric torus combining a toroidal field from external coils with a poloidal field from plasma current — is the most developed configuration and the basis of ITER and most private tokamak ventures. The stellarator achieves the same twisted field entirely with external coils, trading manufacturing complexity for intrinsically steady-state, disruption-free operation, as demonstrated on Wendelstein 7-X.
The engineering centre of gravity is the magnet system. High-field superconducting coils — low-temperature Nb₃Sn as in ITER, or high-temperature REBCO tapes that let newer designs reach higher field in a smaller machine — store enormous energy and must be protected against quench, where a small normal-conducting spot can dump that energy destructively. Coil shape, magnetic shear, and the bootstrap self-driven current all feed into whether a device can run continuously rather than in pulses.
The plasma boundary is where power meets hardware: the divertor channels exhaust heat and helium ash to a target that must survive steady heat fluxes comparable to a rocket nozzle. Across the ten topics — tokamak and spherical-tokamak geometry, stellarator optimization, superconducting coils, quench protection, divertors, steady-state operation, and field-reversed configurations — the six lenses let you judge which confinement claims are physics records and which are integrated, sustainable operating points.
Tokamaks and stellarators
Tokamaks lead on confinement performance but rely on plasma current and face disruptions; optimized stellarators run steady-state without that current at the cost of intricate 3D coils.
High-field superconducting magnets
Nb₃Sn and HTS REBCO coils set machine size and cost. Higher field shrinks the device for a given performance but sharpens the quench-protection and structural-load challenge.
Steady-state and the divertor
Continuous operation needs non-inductive current drive and a divertor that survives the exhaust heat and particle load without eroding too fast — often the limiting subsystem.