FREE-FIX code web page

Sample coil and plasma input 
for a FREE-FIX run


The calculation of an axisymmetric equilibrium for tokamak modeling is common task in plasma physics research. The main unknown of the problem is the magnetic poloidal flux ψ. The easiest approach is to assign the shape of the plasma and only solve the equilibrium problem in the plasma / closed-field-lines region (the "fixed-boundary approach"). However, one may also need the vacuum fields, i.e. the equilibrium in the open- field-lines region, requiring either coil currents or ψ on some closed curve outside the plasma to be assigned as input for an equilibrium code (the "free-boundary approach"). Going from one approach to the other is a textbook problem [S. Jardin, Computational Methods in Plasma Physics, Taylor & Francis, Boca Raton, FL, 2010.], involving the calculation of Green's functions and surface integrals in the plasma. However, no tools are readily available to perform this task. This is why the FREE-FIX code was developed. FREE-FIX computes a boundary condition for a free-boundary equilibrium given only the corresponding fixed-boundary equilibrium. An improvement to the standard textbook solution method, allowing for much faster calculations, was found and implemented in FREE-FIX.

References and support material:

A paper describing the code is in preparation. Details will be published as they become available.

FREE-FIX code user manual

FREE-FIX code source files

FREE-FIX sample runs

Contact: Luca Guazzotto, Auburn University

Copyright notes:

Any use of FREE-FIX should be acknowledged. Keeping Dr. Guazzotto informed of any use or development related to the code will be greatly appreciated.

last modified May 31 2016