Triangularity

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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[1]:

  • Rmax is the maximum value of R along the LCFS or separatrix.
  • Rmin is the minimum value of R along the LCFS or separatrix.
  • Rgeo is the geometric major radius, defined as (Rmax + Rmin)/2.
  • a is the minor radius of the plasma, defined as (Rmax - Rmin)/2.
  • Rupper is the major radius of the highest vertical point of the LCFS or separatrix.
  • Rlower is the major radius of the lowest vertical point of the LCFS or separatrix.

The upper triangularity is then defined as follows:

$ \delta_{upper} = (R_{geo}-R_{upper})/a $

and similar for δlower. The overall triangularity is defined as the mean of δupper and δlower.

See also

References

  1. T.C. Luce, Plasma Phys. Control. Fusion 55 (2013) 095009