EFFECT OF A MATCHED ELECTRON-BEAM ON HIGH-GAIN FREE-ELECTRON-LASER AMPLIFIER PERFORMANCE

It is commonly assumed that a matched electron beam optimizes free-ele ctron-laser performance. however, this assumption has not been proven for operation in the high-gain regime. We test this hypothesis for a s elf-amplified spontaneous emission configuration using a 3D multimode simulation. The gain length predicted for a matched beam is in good ag reement with analytic theory. Further, the simulation indicates that w hile the gain length is optimized for a matched beam the saturated pow er is nor necessarily optimized.