  The chaotic transport of charged particles in a turbulent electrostatic
potential sets the conditions of a severe limitation to the plasma confinement
in devices such as tokamaks. In this chapter, we consider the motion of
impurities driven by the ExB velocity where a strong magnetic field B (which
allows for the guiding center approximation) is uniform and constant, and a
turbulent electric field is obtained from models or from numerical fluid codes.
Hamiltonian dynamics rule the transport properties of these impurities.
Therefore a technique to reduce chaotic diffusion in Hamiltonian systems is
able to address the issue of reducing the radial transport of impurities under
some approximations. The general idea is to build barriers in phase space by a
small and apt modification of the Hamiltonian. We show numerically that such
perturbations are able to drastically reduce the diffusion of test-particles,
and we discuss the robustness of such additional modifications.
