Error Fields & Correction

Tiny imperfections in the magnets create error fields that can lock modes and trigger disruptions. Correction coils cancel them.

What

Small unwanted field asymmetries from imperfect coils

Risk

Can seed locked modes and disruptions

Fix

Dedicated correction coils

Also matters

Precision magnet assembly

Error fields are the small, unintended asymmetries in a tokamak's magnetic field that arise because no real magnet is perfectly built or aligned. Though tiny — parts in ten thousand — they can be surprisingly harmful: they can seed magnetic islands and "locked" modes that don't rotate away, and a locked mode is a common precursor to a disruption.

The remedy is a set of dedicated correction coils that generate a canceling field, tuned to null out the measured error. Managing error fields is part of the routine stability engineering of any high-performance tokamak, and for Kronos MetroVolt it is one of many small precision requirements — alongside careful magnet assembly — that keep the plasma clear of avoidable disruption triggers.