Energy and particle losses due to abnormal transport in magnetic confinement devices (tokamak) are still a serious obstacle to controlled thermonuclear fusion. Even modest changes in containment properties can drastically change the energy amplification factor. The French laboratory CPT worked on a new model (computer code) to improve targeted mixing by adding a suitable perturbation to the ideal flow. The induced chaotic advection exhibits two remarkable properties which do not hold in the case of a generic perturbation: Particles remain trapped within a specific domain bounded by two oscillatingbarriers (suppression of chaotic transport along the channel), and the stochastic sea seems to cover this whole bounded domain (enhancement of mixing within the rolls).