Non-linear evolution of RFX-mod tokamak equilibria during L-H transition including 3D wall effects

The achievement of an ELMy Ohmic H-mode regime was the aim of executing shaped tokamak discharges [1] in the RFX-mod experiment (R = 2.0 m, a = 0.46 m). In recent experiments, tokamak D-shaped upper single null plasmas with edge polarized electrode have been successfully achieved in order to induce the L-H transition [2]. Several experimental parameters (such as first wall conditioning, number and position of X-points, plasma shape and plasma dynamics) can play a key role in the transition by modifying the power threshold. In particular, a careful control of the magnetic configuration is necessary; this has been achieved by using a plasma shape feedback controller [3] designed on the basis of the CREATE_L linearized plasma response model [4]. The new experimental data give the opportunity of a further development in the electromagnetic modeling of the non-linear evolution of a plasma discharge. 3D volumetric effects of the passive conducting structures can be taken into account by using the evolutionary equilibrium code CarMa0NL [5] which solves the non-linear Grad-Shafranov equation. The effects of plasma global parameters variations on the equilibrium configuration can also be described by the tool. The evolution of the magnetic field at the sensor positions will be computed under different assumptions and their comparison with the available magnetic measurements will also be presented in the paper to validate the model.