High-charge ultrashort electron bunch generation by an energy chirping cell-attached rf electron gun and its measurement using a transverse deflecting cavity

Ultrashort electron bunches are becoming increasingly important for applications such as free-electron lasers, time-resolved electron diffraction/microscopy, and advanced accelerator concepts. We report femtosecond electron bunch generation with a unique rf gun and its precise measurement using a transverse deflecting cavity. A bunch length of 323±13 fs with 120 pC (∼7.5×10^{8} electrons) was achieved at a distance of just 3 m from the cathode. A longitudinal phase space distribution was also achieved, and we successfully experimentally confirmed the linearly energy chirped electron bunch generation and self-compression by the velocity difference