Direct observation of betatron oscillations in a laser-plasma electron acceleratorY. Glinec1, J. Faure1, A. Lifschitz1, J. M. Vieira2, R A. Fonseca2, L. O. Silva2 and V. Malka1
1 Laboratoire d'Optique Appliquée, ENSTA, UMR 7639, CNRS, École Polytechnique - 91761 Palaiseau, France
2 GoLP/Centro de Física dos Plasmas, Instituto Superior Técnico - 1049-001 Lisboa, Portugal
received 7 December 2007; accepted in final form 18 January 2008; published March 2008
published online 20 February 2008
During experiments performed on a laser-plasma-based accelerator, correlation of the electron output angle with the electron energy has been observed. These spectral oscillations of the electron beam centroid are attributed to betatron oscillations of the electron beam during its propagation. An analytical model for betatron oscillations including constant longitudinal acceleration is described and used to validate the scenario and retrieve physical parameters. The oscillations can arise from an off-axis injection of the electrons, which can be reproduced using an asymmetric laser intensity profile in Particle-In-Cell (PIC) simulations. This study emphasizes the influence of non-ideal interaction conditions inherent to experiments.
41.75.Jv - Laser-driven acceleration.
52.35.-g - Waves, oscillations, and instabilities in plasmas and intense beams.
52.38.Kd - Laser-plasma acceleration of electrons and ions.
© EPLA 2008