Structural eddy current effects on plasma equilibrium and current induction in the IGNTEX experiment

In the IGNITEX (Fusion Ignition Experiment) device, the plasma is surrounded by massive conducting material composed of several layers. From inside to outside, the layers may be categorized as: first wall-vacuum vessel, poloidal-field magnet system, inner toroidal-field magnet region with slits, and an outer homogeneous toroidal-field magnet region divided into twelve sectors. The 2-D finite-element program PROTEUS is used to study current induction and plasma equilibrium throughout the ignition discharge. Some modifications of the original code PROTEUS which permit the study of compact plasmas with strong wall coupling are described. The structure layers are simulated either as diffusive or as a set of electric circuits properly connected. Different resistivity models are considered. The calculations presented show that the flux swing produced by the poloidal-field (PF) coil system is enough to induce over 12 MA of plasma current and that a sequence of equilibrium configurations with elliptical cross sections can be obtained by properly choosing the waveforms of the PF system currents throughout the discharge of 10 s