  Single Helical Axis (SHAx) configurations are emerging as the natural state
for high current reversed field pinch (RFP) plasmas. These states feature the
presence of transport barriers in the core plasma. Here we present a method for
computing the equilibrium magnetic surfaces for these states in the force-free
approximation, which has been implemented in the SHEq code. The method is based
on the superposition of a zeroth order axisymmetric equilibrium and of a first
order helical perturbation computed according to Newcomb's equation
supplemented with edge magnetic field measurements. The mapping of the measured
electron temperature profiles, soft X-ray emission and interferometric density
measurements on the computed magnetic surfaces demonstrates the quality of the
equilibrium reconstruction. The procedure for computing flux surface averages
is illustrated, and applied to the evaluation of the thermal conductivity
profile. The consistency of the evaluated equilibria with Ohm's law is also
discussed.
