Greenwald Fraction

How close a plasma runs to its empirical density limit.

The Greenwald fraction is the operating density divided by the Greenwald limit. Running well below 1 is conservative; approaching it raises disruption risk. HYPERION is designed within the limit.

The Greenwald fraction — operating density over the empirical limit — is a compact measure of how aggressively a tokamak is running. Well below one is conservative; approaching one raises disruption risk. HYPERION is designed within the limit, while the burner is free of it entirely.