I know that a toroidal plasma current is an essential feature on tokamaks as it creates the poloidal magnetic field essential to avoid separation between negative and positive charges.
The current is created inducing a magnetic field with an increasing current applied to a central coil which in turn induces a current in the plasma.
My question is how to keep the current for long experiments (such as ITER project)? One can go from a minimum value on the central coil (even better maximum negative value) to a maximum value, but that is the limitation. What are the options there?