ABSTRACT
The free electron laser (FEL) amplifier uses an intense, relativistic beam of electrons to amplify a copropagating laser beam as they both pass through a long, periodic undulator field. This chapter discusses the FEL physics and technology with emphasis on topics that are most relevant to inertial confinement fusion (ICF) application. The goal of an ICF driver is the placement of high energy density on a target. During amplification, conventional lasers must expand the light beam to many square meters to prevent damage of material. Few electron accelerators have the potential for delivering the current and energy of the beam required for ICF. The beam current of 20 kA at 1 GeV eliminates Van de Graaff and pulseline accelerators, but ICF also requires a pulse length of about 15 nsec. The electron trajectories through the undulator determine the character of the FEL interaction. As the electrons “wiggle” through the undulator, they are coupled to the transverse electromagnetic laser beam.
