Designs for an infrared free-electron laser based on gyrotron-powered electromagnetic wigglers

The possibility of developing gyrotron-powered electromagnetic wiggler free-electron laser (FEL) oscillators is of considerable interest for reducing the electron energy required for operation in the infrared spectrum. This paper considers the design of a 10.6 μm electromagnetic wiggler FEL experiment based on the University of California at Santa Barbara (UCSB) 6 MeV electrostatic accelerator. Both waveguide and quasioptical wiggler resonator configurations are considered. A prescription for optimizing the gain of a waveguide electromagnetic wiggler FEL is derived and the nonlinear regime is treated by relating the electromagnetic wiggler FEL equations-of-motion to the “universal” normalized FEL equations. Point designs are given showing accelerator, gyrotron, and output parameters for 10.6 μm Proof-of-Principle FEE experiments based on both waveguide gyrotron and quasioptical gyrotron wigglers. Designs are given for both a 5- and a 2-A FEL electron beam