Transport barrier for the radial diffusion due to the E x B drift motion of guiding centers in cylindrical confinement geometry

We consider the radial transport of test particles due to the E x B drift motion in the guiding-center approximation. Using an explicit expression to modify the electrostatic potential, we show that it is possible to construct a transport barrier which suppresses radial transport. We propose an algorithm for the implementation of this local modification computed from an electrostatic potential known on a spatio-temporal grid. The number of particles which escape the inner region defined by the barrier measures the efficiency of the control. We show that the control is robust by showing a significant reduction in radial transport, when applied with a reduced number of probes aligned on a circle.