Triangularity: Difference between revisions

Revision as of 11:00, 12 June 2014

Sketch of tokamak geometry, including separatrix

The triangularity refers to the shape of the poloidal cross section of the Last Closed Flux surface (LCFS) or separatrix of a tokamak. Assuming:

R₀ is the major radius of the midpoint of the 2 intersections of the LCFS or separatrix with the equatorial plane (Z = 0).
a is the minor radius of the plasma, defined as the radial difference between the 2 intersections of the LCFS or separatrix with the equatorial plane (Z = 0), divided by 2.
R_upper is the major radius of the highest vertical point of the LCFS.
R_lower is the major radius of the lowest vertical point of the LCFS.

The upper triangularity is then defined as follows:

\delta _{upper}=(R_{0}-R_{upper})/a

and similar for δ_lower. The overall triangularity is defined as the mean of δ_upper and δ_lower.

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 * ''R<sub>0</sub>'' is the major radius of the midpoint of the 2 intersections of the LCFS or separatrix with the equatorial plane (''Z'' = 0).
 * ''a'' is the minor radius of the plasma, defined as the radial difference between the 2 intersections of the LCFS or separatrix with the equatorial plane (''Z'' = 0), divided by 2.
-* ''R<sub>upper</sub>'' is the major radius of the upper X-point (in case it exists) or of the highest vertical point of the LCFS.
+* ''R<sub>upper</sub>'' is the major radius of the highest vertical point of the LCFS.
-* ''R<sub>lower</sub>'' is the major radius of the lower X-point (in case it exists) or of the lowest vertical point of the LCFS.
+* ''R<sub>lower</sub>'' is the major radius of the lowest vertical point of the LCFS.
 The upper triangularity is then defined as follows:
 :<math> \delta_{upper} = (R_0-R_{upper})/a</math>