Generation of Double-Decker Femtosecond Electron Beams in a Photoinjector

Femtosecond electron beams are practical sources in the pump-probe experiment for studies of ultrafast physical/chemical reactions in materials, in which a femtosecond electron bunch is used as a pump source and a mode-locked ultrashort laser light is used as a probe source. The synchronized time jitter between the electron beam and the laser light limits the time resolution in the experiment. In order to reduce the time jitter, a new concept of synchronized double-decker electron beams generation in a photo-injector was proposed. The double electron beams were observed in a photocathode RF gun by injecting two laser beams which produced with a picosecond laser. The double electron beams were compressed into 380 fs in rms with a phase-space rotation technique in magnetic fields. The beams, which one is used as a pump source and another is used as a probe source, are expected for ultrafast reaction studies on femtosecond scale.