Eur. Phys. J. D 59, 451-455 (2010)
https://doi.org/10.1140/epjd/e2010-00186-4

Remaining noise-induced spatiotemporal dynamics in a free electron laser stabilized by feedback control

¹ Laboratoire de Physique des Lasers, Atomes et Molécules, UMR CNRS 8523, Centre d'Études et de Recherches Lasers et Applications, FR CNRS 2416, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
² Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 34, 91192 Gif-sur-Yvette Cedex, France
³ Laboratoire de L'Accélérateur Linéaire, Université Paris-Sud 11, UMR 8607, Bâtiment 200, 91898 Orsay Cedex, France
⁴ UVSOR Facility, Institute for Molecular Science, 444-8585, Okazaki, Japan

Corresponding author: ^a christophe.szwaj@univ-lille1.fr

Received: 29 March 2010
Revised: 11 June 2010
Published online: 27 July 2010

Abstract

We investigate the efficiency of the pulsed regime stabilization by feedback control in a free electron laser (FEL) in oscillator configuration. We show that a hidden dynamics remains in the controlled FEL. Though not visible in the evolution of the pulse envelope, this dynamics affects the internal pulse shape evolution, and thus the FEL spectrum and coherence properties. The experimental results obtained on the UVSOR FEL are interpreted in the framework of a field master equation model. The stochastic nature of spontaneous emission is taken into account, and appears as an essential ingredient since the dynamics of the controlled structures is governed by noise like the other stable regimes of the FEL.