Abstract

At the University of California, Santa Barbara (UCSB), a 6-MV electrostatic accelerator with beam recovery¹ is used for driving free-electron lasers (FELs).² The acceleration scheme produces long electron pulses. As a consequence, the FEL generates radiation with a very narrow frequency bandwidth of the order of 10^-8.³ For high-intensity levels such a narrowband radiation can act as an undulator for a second-stage FEL. The idea of a two-stage FEL was first put forward in 1979⁴ and is now being implemented in an experiment presently under way at UCSB.

© 1986 Optical Society of America