Plasma Beta (β) and Beta-N

The ratio of plasma pressure to magnetic pressure; higher beta means a more economical machine.

Beta is the ratio of the plasma's thermal pressure to the pressure of the confining magnetic field. It is an efficiency metric: a machine that holds more plasma pressure per tesla of field is cheaper to build. The normalised form β_N removes size and field to compare configurations.

HYPERION is designed at β_N = 1.532 — comfortably within the no-wall stability limits observed on spherical tokamaks such as NSTX. Its low aspect ratio is what lets it hold high beta.