Plasma geometry and current profile identification on ASDEX Upgrade using an integrated equilibrium generation and interpretation system

The identification of ideal MHD equilibrium states on a tokamak is the starting point for interpreting any diagnostic data dependent on knowledge of the flux surface geometry. The method of Function Parameterization (FP) starts with the Monte Carlo generation of a simulated equilibrium database, regression analysis of which yields simple functional representations of plasma geometry whose arguments are information-rich, uncorrelated linear com- binations of simulated diagnostic signals. Once calculated, these FP expressions can be rapidly evaluated using experimental data. FP using magnetic data is in routine realtime use on ASDEX Upgrade for plasma position and shape control and has been applied to diagnostic design studies for ITER. An extension to FP using MSE data has recently been developed for realtime identification and control of the current profile on ASDEX Upgrade. Post- discharge interpretive equilibrium solutions are generated by the CLISTE code, which best fits a set of specified diagnostic data. CLISTE can include kinetic data and poloidal halo currents in the scrape-off layer as constraints on the equilibrium solution, a valuable feature which has been applied to ELM analysis. The code has recently been extended to interpret dB=dt data from magnetics and dγ=dt data from MSE to yield a best fit solution to the time derivative of the Grad-Shafranov equation Δ ∂ ψ=∂ t = 2π μ0R∂ jφ=∂ t. The ∂ ψ=∂ t solution is used to calculate the flux surface averaged profile hE Bi which can be used to calculate current drive from auxiliary heating methods via the equation hj Biaux: heating =hj Biequil σhE Bih j Biboot wherehj Biboot is calculated from kinetic profiles and neoclassical theory and hj Biequil is an equilibrium output. This technique is applied here to analyse current profile modification by off-axis NBI on ASDEX Upgrade.