Poloidal Field & Shaping Coils

Poloidal field coils position and shape the plasma — setting its elongation, triangularity, and vertical stability. They hold the Kronos NT shape.

Job

Position and shape the plasma cross-section

Set

Elongation, triangularity, vertical position

Kronos shape

κ = 2.56, δ = −0.30

Design tool

Free-boundary equilibrium (S03/S07)

The poloidal field (PF) coils are the ring-shaped magnets, above and below the plasma, that control its position and cross-sectional shape. By adjusting their currents, operators set the plasma's elongation and triangularity, hold it centered, and provide the fast feedback that prevents a vertical displacement event.

For Kronos MetroVolt the PF system is what physically maintains the conserved δ = −0.30 negative-triangularity shape and the κ = 2.56 elongation that define the design. The required coil set and its control authority come out of the free-boundary equilibrium calculations (S03, S07), which solve the self-consistent balance of plasma and coil currents that fixes the plasma's actual shape.