Plasma response model to resonant magnetic perturbations

Magnetically confined plasmas in tokamaks usually do not operate under equilibrium conditions and high temperature particles are transported to the reactor wall, causing its erosion. External resonant windings or coils can be used to generate a perturbative magnetic field that modifies particle transport near the plasma border. A pair of helical wires placed at the reactor external wall is used to create a resonant magnetic perturbation (RMP) capable of reducing the amount of particles colliding with the wall. However, the plasma is also affected by RMPs and it modifies the magnetic field lines. In this work, a semi-analytical model in polar toroidal coordinates was developed to study the plasma response, which has been modeled as a helical current sheet at the resonant surface with the condition that the total radial magnetic field vanishes at this surface. This condition is associated to the mitigation of magnetic islands around the resonant surface. Poincar\'{e} plots have shown that the plasma response regularizes the magnetic field lines around the resonant surface.