Determining the resistivity profile of a toroidal plasma using Integrated Data Analysis

The resistivity profile of a toroidally-confined plasma, one of the governing parameters of nonlinear MHD dynamics, is determined from a synthesis of measurements of the electron temperature, density, impurity density, and soft-x-ray emission profiles. In particular, corrections to the Spitzer resistivity due to non-uniform ion effective charge (Z_eff) are comparable to neoclassical corrections due to trapped particle effects. The Z_eff profile arises from the transport of highly-charged ions from the core to the mid-radius by either thermal screening (enhanced confinement) or magnetic stochasticity (standard plasmas). A self-consistent Integrated Data Analysis framework incorporates both the local information of charge exchange impurity density measurements and Thomson Scattering measurements with non-local information like neutral beam attenuation and line-integrated soft-x-ray brightness from impurity emission. The resulting resistivity profile and confidence intervals provide required information for validating nonlinear MHD simulations that predict the scaling of magnetic fluctuations and stochasticity due to resistive tearing instabilities with Lundquist number.