Magnetic topology and guiding centre drift orbits in a reversed shear tokamak

The magnetic topology and particle drift orbits are analysed in a monotonic q profile and in a reversed shear TEXTOR equilibrium that is subject to a magnetic perturbation driven by the Dynamic Ergodic Divertor (DED). The main results prove that there exists a transport barrier for magnetic field lines and for circulating particles in the reversed shear case when the DED is applied. This transport barrier occurs near the surface of minimum q value where the KAM theory may be invalid. Moreover, it should be noted that trapped particles are lost due to the presence of ripple and that the DED does not affect their trajectories. To analyse magnetic topology, a symplectic perturbed map is used and the guiding centre orbits are evaluated in Boozer co-ordinates.