Local heating induced by Coherent Harmonic Generation on electron beam dynamics in storage ring

¹  DSM/DREACM/SPAM, CEA Saclay - 91191 Gif-sur-Yvette, France
²  Synchrotron SOLEIL - Saint Aubin, BP 34, 91192 Gif-sur-Yvette, France
³  RIKEN SPring-8 Harima - Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan
⁴  UVSOR Facility, Institute for Molecular Science - Okazaki 444-8585, Japan
⁵  Nagoya University - Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
⁶  JASRI SPring-8 - Kouto 1-1-1, Sayo, Hyogo 679-5198, Japan

Received: 1 August 2007
Accepted: 30 November 2007

Abstract

We investigate the dynamical response of an electron bunch in a storage ring to a brief and intense excitation of an external laser. We present a model that simulates the evolution of the electronic distribution in the Coherent Harmonic Generation (CHG) configuration: the energy exchange between photons and electrons occurs within an undulator magnetic field, and further leads to a coherent radiation process. Using those simulations and experimental results on the UVSOR-II CHG free electron laser, we demonstrate that the electronic distribution reaches an equilibrium regime thanks to energy spread relaxation in between two laser injections. We also show that saturation is driven by laser-induced local heating, leading to global effect over the whole bunch.