Measurement of magnetic surfaces on the TJ-I U torsatron

Results of magnetic surface mapping experiments over the whole operational range of the TJ-I U torsatron are reported. A theoretical model of the coil sets that includes internal and external error fields has been developed. It accounts for the main experimental features of the magnetic surfaces measured in the different magnetic configurations: size and shape of the surfaces, magnetic axis position and rotational transform dependence on the coil currents