VMEC

The three-dimensional Variational Moments Equilibrium Code (VMEC) minimizes the energy functional

$W=\int _{\omega _{p}}{\left({\frac {1}{2\mu _{0}}}B^{2}+p\right)dV}$

over the toroidal domain ω_p. The solution is obtained in flux co-ordinates (s, θ, ζ), related to the cylindrical co-ordinates (R, φ, Z) by

$R=\sum {R_{mn}(s)\cos(m\theta -n\zeta )}$

$Z=\sum {Z_{mn}(s)\sin(m\theta -n\zeta )}$

The code assumes nested flux surfaces.

Implementations of the code

The code is being used at:

• IPP-Garching, Germany
• NIFS, Japan
• LNF, Spain

Enhancements / extensions of the code

• DIAGNO, to calculate the response of magnetic diagnostics
• MFBE
• STELLOPT