Observation of Time-Domain Modulation of Free-Electron-Laser Pulsesudby Multipeaked Electron-Energy Spectrum

摘要

We present the experimental demonstration of a new scheme for the generation of ultrashort pulseudtrains based on free-electron-laser (FEL) emission from a multipeaked electron energy distribution.udTwo electron beamlets with energy difference larger than the FEL parameter have been generated byudilluminating the cathode with two ps-spaced laser pulses, followed by a rotation of the longitudinal phaseudspace by velocity bunching in the linac. The resulting self-amplified spontaneous emission FEL radiation,udmeasured through frequency-resolved optical gating diagnostics, reveals a double-peaked spectrum and audtemporally modulated pulse structure.