Laboratoire de Physique Théorique
Toulouse - UMR 5152

The intensity of an electromagnetic wave interacting self-consistently with a beam of charged particles, as in a Free Electron Laser, displays large oscillations due to an aggregate of particles, called the macro-particle. This clustering can be interpreted in terms of regular structures (KAM tori) in a low-dimensionnal phase-space. We propose a strategy to stabilize the intensity of the wave by re-shaping the macro-particle. As parameters of an additional perturbation are varied, bifurcations occur in the system which modify the topology of phase-space, yielding drastic effects on the modification of the self-consistent dynamics, especially of the macro-particle. We show how to obtain an appropriate tuning of the parameters which is able to strongly decrease the oscillations of the intensity without reducing its mean-value.