Femtosecond Single- Bunch Electron Linear Accelerator Based on a Photocathode Rf Gun

A femtosecond single-bunch electron linear accelerator based on a photocathode rf gun was developed in Osaka University for the study of radiation-induced ultrafast physical and chemical reactions. A 32 MeV single electron bunch with bunch length of 98 fs in rms was generated successfully with a magnet bunch compressor, and was used as pump source to study the electroninduced ultrafast reactions or phenomena by pulse radiolysis with a synchronized femtosecond laser (as a probe source). Moreover, in order to improve the time resolution and reduce the synchronized time jitter between the electron beam and the probe light, a new concept of synchronized double-decker electron beams generation in the linac was proposed. The double-decker electron beams were observed in the photocathode rf gun by injecting two laser beams which produced with a picosecond laser. The double electron beams were compressed into femtosecond by rotating the phase-space in magnetic fields.