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• Bootstrap current was measured in all reference magnetic configurations of OP1.2a. • Experimental profiles can be reliably mapped with vacuum pre-calculated equilibria. • VMEC calculations show good agreement with Minerva and V3FIT reconstruction. Wendelstein 7-X (W7-X) is a modular advanced stellarator, which successfully went into operation in December 2015 at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany, and continued to thrive at the experimental campaign with the first divertor phase in August-December 2017. The nested magnetic surfaces in W7-X are created by a system of 3-D toroidally discrete coils, providing both toroidal and poloidal field components, and designed with the aim to create optimum equilibrium properties. The optimization criteria included the high quality of vacuum magnetic surfaces, good finite beta equilibrium and MHD-stability properties as well as a substantial reduction of the neoclassical transport and bootstrap current in comparison to classical stellarators. Equilibrium calculations, devoted to the analysis of the experiment programs dedicated to measure the bootstrap current, were performed with help of the Variational Moments Equilibrium Code, available as Wendelstein 7-X web service. Pressure profiles based on experimental data served as an input for calculations. The mapping of measurements using pre-calculated equilibria for different beta values has been analyzed. A comparison with reconstruction results obtained by means of the Minerva Framework, considering only experimental data of magnetics measurements, and the V3FIT code is presented. [ABSTRACT FROM AUTHOR]

Abstract: Wendelstein 7-X, currently under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany, is a modular advanced stellarator, combining the modular coil concept with optimised properties of the plasma. The magnet system of the machine consists of 50 non-planar and 20 planar superconducting coils which are arranged in five identical modules, forming a toroidal five-fold symmetric system. The majority of operational magnetic configurations will have rotational transform ι/2π =1 at the boundary. Such configurations are very sensitive to symmetry breaking perturbations, which are the consequence of imprecisely manufactured coils or assembly errors. To date, all 70 coils have been fabricated, and the first two half-modules of the machine have been assembled. The comparative analysis of manufactured winding packs and estimates of the corresponding level of magnetic field perturbation are presented. The dependency of the error fields on the coil assembly sequence is considered, as well as the impact of the first assembly errors. The influence of different construction uncertainties is discussed, and measures to minimise the magnetic field perturbation are suggested. [Copyright &y& Elsevier]