non-inductive current drive is sustaining 📝plasma current by waves, beams, or 📝bootstrap current instead of induction — the route to steady-state tokamaks.
Its near-neighbor is 📝inductive current drive, the default transformer action of the 📝central solenoid, and the two differ on exactly one axis: duration. Induction ends when the solenoid's flux swing runs out; non-inductive methods have no such clock. The main techniques are neutral beams, whose fast injected ions drag current as they circulate; radio-frequency waves — lower hybrid, electron cyclotron, and ion cyclotron — launched asymmetrically so they push electrons preferentially in one toroidal direction; and the bootstrap current the 📝plasma generates spontaneously from its own pressure gradients, which costs no external power at all.
The stakes are economic as much as physical. A 📝Tokamak that must stop to recharge its solenoid delivers power in pulses, and cyclic operation fatigues components built to last decades. Fully non-inductive operation — typically a large bootstrap fraction topped up by external 📝current drive — is therefore the route to a continuously running power plant, with the recirculating power spent driving current weighed directly against the plant's net electric output.