inductive current drive is driving 📝plasma current by transformer action from the 📝central solenoid, and it is inherently pulsed.
The mechanism is a textbook transformer with one exotic winding. The central solenoid ramps its magnetic flux, the changing flux induces a toroidal electric field, and the 📝plasma — an excellent conductor — responds as the secondary circuit, carrying megaamperes of current. Every 📝Tokamak starts its current this way, and the same induced current delivers 📝ohmic heating as a byproduct. The method is simple, robust, and efficient, which is why it has anchored tokamak operation since the machine was invented.
Its defining limitation is duration. Induction works only while the solenoid's flux is changing, and a solenoid can swing its field only so far before it must reset; when the flux runs out, so does the current. Inductive operation therefore comes in pulses, and its near-neighbor — non-inductive 📝current drive by waves, beams, or the plasma's own 📝bootstrap current — exists precisely to escape that limit. Machine designs split on this axis: steady-state concepts minimize their reliance on the solenoid, while pulsed designs accept the duty cycle in exchange for induction's simplicity and efficiency.