Equilibrium evaluation for Wendelstein 7-X experiment programs in the first divertor phase

Abstract Wendelstein 7-X (W7-X) is a modular advanced stellarator, which successfully went into operation in December 2015 at the Max-Planck-Institut fur 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.