Equilibrium reconstructions of reversed-shear discharges based on motional Stark effect measurements

Internal magnetic field measurements are now routinely made in tokamak discharges with a motional Stark effect polarimeter. Using these measurements, free-boundary equilibrium reconstructions of the temporal evolution of tokamak discharges can be made. The variational moments equilibrium code (VMEC) has been upgraded with an improved plasma boundary positioning algorithm and an improved spline representation of the pressure and q profiles. The uncertainty of the reconstruction is assessed for discharges with reversed magnetic shear where q(0)≫q min>1.