Ellipticity

Sketch of tokamak geometry

The ellipticity refers to the shape of the poloidal cross section of the Last Closed Flux surface or separatrix of a tokamak.

Assuming:

• R_max is the maximum value of R along the LCFS or separatrix.
• R_min is the minimum value of R along the LCFS or separatrix.
• Z_max is the maximum value of Z along the LCFS or separatrix.
• Z_min is the minimum value of Z along the LCFS or separatrix.
• a is the minor radius of the plasma, defined as (R_max - R_min)/2.

The ellipticity is then defined as follows:

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \kappa = (Z_{max}-Z_{min})/2a}

See also

• Triangularity
• Toroidal coordinates
• Effective plasma radius