Biomedical subjects

S Bielawski

Publications and source records attributed to S Bielawski.

9 recordsLinked to original sources

PubMed2005

Advection-induced spectrotemporal defects in a free-electron laser.

We evidence numerically and experimentally that advection can induce spectrotemporal defects in a system presenting a localized structure. Those defects in the spectrum are associated with the breakings induced by the drift of the localized solution. The results are based on simulations and experiments performed on the super-ACO free-electron laser. However, we show that this instability can be generalized using a real Ginzburg-Landau equation with (i) advection and (ii) a finite-size supercritical region.

Journal Article↗

PubMed2004

Suppression of the pulsed regimes appearing in free-electron lasers using feedback control of an unstable stationary state.

We show that the pulsed regimes observed in free-electron lasers (FELs) can be suppressed using feedback control. By applying tiny parameter perturbations, the feedback allows to keep the systems onto a stationary state that is naturally existing in phase space, but is usually inaccessible because of its unstable nature. We test this method numerically on a master equation derived from the classical iterative model. Then we present the experimental results obtained on the super-ACO FEL. This method is in principle directly applicable to the other free-electron lasers, whose instabilities have a dynamical (deterministic) origin.

Journal Article↗

PubMed1996