4 Internal transport barrier
To ensure that the plasma-generated "bootstrap" current dominates over the pulsed inductive current, we need to produce regions of very high pressure gradient by reducing the size of turbulent eddies inside the plasma. This simulation shows a poloidal cross-section of an idealized circular plasma in terms of its electric potential, which gives an estimate of the magnitude of turbulence. At a particular radius, a strong radial gradient in the plasma rotation arises - this sheared rotation breaks up the turbulent eddies, stabilizing them. The annular ring where turbulence appears stabilized acts as an internal transport barrier that improves heat and particle confinement.