THE LOS ALAMOS FREE-ELECTRON LASER (FEL) RF SYSlEM*

The FEL rf system was designed for 3.6-MW rf pulses from two klystrons to drive two linacs and one deflection cavity at 1300 MHz. Two 108.33-MHz subhar-monic buncher cavities and one fundamental buncher were also built, each powered by a 5-kW amplifier. A single phase-coherent source drives the various ampli-fiers as well as the grid of the electron gun, which is pulsed at 21.67 MHz. The initial buncher system did not work as well as expected, and the first linac tank required more t-f power than anticipated. The lioht output was extremely sensitive to amplitude and phase errors. More powerful klystrons were developed and installed. and a method was discovered for oper-ating a single subharmonic buncher and allowing the first linac to complete the bunching process. Thi