MODE-LOCKED FREE-ELECTRON LASER-OSCILLATOR

In this experiment we observe emission of a single RF macropulse from a mode-locked FEL oscillator. The FEL employs a continuous electron beam and operates in the microwave regime. The amplitude mode-locking is achieved by modulating the attenuation of the FEL ring cavity at its round-trip frequency (approximately 27 MHz). The observed RF macropulse consists of short RF micropulses. Their period (approximately 37 ns) is determined by the modulating frequency, and their width is comparable to the slippage time (approximately 3 ns). Examples of experimental results of amplitude mode-locked FEL signals are presented for coaxial-line and waveguide cavity sections.