Modelling and experimental validation of RFX-mod Tokamak shaped discharges

A general procedure for computing plasma equilibria through the CREATE-L code has been applied to RFX-mod shaped tokamak discharges in order to produce very accurate models with respect to experimental data. It involves the solution of a constrained non-linear minimization problem to estimate the CREATE-L free parameters by using an iterative scheme trying to minimize the discrepancy between the poloidal magnetic field experimentally measured by pick-up coils and the one simulated by the model. The procedure has been applied considering eleven experimental shots spanning the whole range of poloidal beta achieved in the RFX-mod tokamak. A preliminary sensitivity analysis showed a non-negligible dependence of static equilibria on variations of the total plasma current with respect to the measurement provided by Rogowski coils. Thus, the total plasma current has been set as an additional degree of freedom in the minimization problem assuming values between the Rogowski measurement and the value of the discrete line integral of the poloidal magnetic field measured by the pick-up coils. In all cases under analysis, the iterative procedure showed that the most accurate equilibrium is obtained with a plasma current higher than the Rogowski measurement but lower than the pick-up coils line integral.