Radial Transport & Confinement

Across the field, particles and heat diffuse outward; classical and neoclassical processes, plus field errors, set how well the central cell holds.

Losing plasma sideways

End loss along the field is the mirror's headline confinement problem, but plasma also diffuses across the field, radially outward to the wall. Classical diffusion from Coulomb collisions sets a floor; non-axisymmetric field components (resonant and neoclassical transport) and turbulence can raise the actual rate well above it.

In tandem mirrors the radial electric field — the same ambipolar potential that plugs the ends — also drives plasma rotation. Sheared rotation can suppress turbulence and improve radial confinement, linking the plug physics to cross-field losses. But non-axisymmetric anchor coils introduce field ripple that opens neoclassical transport channels.

The net picture

Radial and axial losses together set the central-cell confinement time that must satisfy the power balance. The design assumes rotation-improved radial confinement; confirming that at burner parameters, alongside the end-loss physics, is part of what the program must demonstrate.

The link between the plug potential and radial rotation means the burner cannot separate its axial and radial confinement problems — improving one through the electric field changes the other. This coupling is a feature when the rotation suppresses turbulence and a risk when field errors from the anchors open transport channels, and the net outcome at design parameters is not yet measured.

• Cross-field diffusion adds to end loss
• Field ripple opens neoclassical transport
• Sheared rotation (from E-field) can suppress turbulence
• Sets the central-cell confinement time