Neoclassical Transport

The irreducible, geometry-driven leakage of heat and particles across the field.

Even a perfectly stable plasma loses heat by collisional transport enhanced by the torus geometry — neoclassical transport. It sets a floor below which confinement cannot fall; real machines usually lose more, via turbulence.

The bootstrap current is itself a neoclassical effect, which is why good confinement and self-driven current tend to come together.

Neoclassical transport is the irreducible collisional leakage enhanced by the torus geometry; real machines usually lose more, via turbulence, but it sets the theoretical floor. It is also the source of the bootstrap current, which is why good confinement and self-driven current tend to come together in a well-designed plasma.