Chaotic magnetic field lines in a Tokamak with resonant helical windings

We use a Hamiltonian description for magnetic field lines in a large aspect ratio Tokamak for describing the effect of resonant helical windings in a perturbative way, taking into account the toroidal correction. We consider the formation of chains of primary (main and satellites) and secondary islands, analysing their interactions to describe the generation of chaotic magnetic field lines within a portion of the plasma column. This chaotic structure is responsible for disruptive instabilities that may spoil plasma confinement in the Tokamak. Results are compared with numerical integration of magnetic field line equations.