Time-resolved measurements of equilibrium profiles in MST

Based on the high-speed, three-wave, far-infrared polarimeter-interferometer measurement of $B_{pol}$ profiles and external coil measurements of $B_{tave}$ and $B_{tw}$, a new method is developed to derive $B_{tor}$ and other equilibrium profiles (J$_{//}$ and q) with high time resolution. Using Faraday's law, the inductive electric field (E$_{//})$ profile is also deduced from the temporal derivatives of the time-resolved magnetic field profiles. The derived $B(0)$ values have excellent agreement with direct measurements using a Motional Stark Effect (MSE) diagnostic. Evolution of equilibrium profiles during single sawtooth events in MST, both the slow linear ramp and crash phases, are presented. Profile scaling with plasma current I$_{p}$ and reversal parameter F is also explored. MHD stability is tested from the spatial gradients of the $J_{//}$ and q profiles, and correlation with fluctuation mode amplitude is investigated. Future improvements to equilibrium reconstruction are expected by measuring $B_{tor}$(r,t) directly via Cotton-Mouton interferometry.