Reconnection bifurcation in Tokamaks

An ergodic magnetic limiter has been proposed to control the plasma-wall interactions in tokamaks. This apparatus generates resonant magnetic fields that interact with the equilibrium field, causing a selective destruction of magnetic surfaces. In this work, a numerical study of magnetic islands induced by a magnetic limiter in a large-aspect ratio tokamak with non-monotonic safety factor profiles is performed using a symplectic non-twist mapping. The dominant resonance leads to dimerized island chains and reconnection. The main bifurcation associated with this transition and the onset of global chaos is identified.