Greenwald Density Limit

An empirical ceiling on tokamak plasma density set by current and size.

The Greenwald limit is an empirical maximum density, proportional to plasma current divided by minor-radius area, above which tokamaks tend to disrupt. Operating below it is a standard design constraint.

HYPERION's density is chosen to sit within the Greenwald limit; the burner, being a mirror, is not subject to it and instead operates at a design density of 2.6e20 m^-3.

The Greenwald limit is one of the most robust empirical boundaries in tokamak physics, scaling with plasma current over minor-radius area. Operating below it is a firm constraint for the breeder; the burner, being a linear mirror, is not subject to it and instead operates at its design density set by the fuel trajectory.