Abstract
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 $323\ifmmode\pm\else\textpm\fi{}13\text{ }\text{ }\mathrm{fs}$ with 120 pC ($\ensuremath{\sim}7.5\ifmmode\times\else\texttimes\fi{}{10}^{8}\text{ }\text{ }\mathrm{electrons}$) 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.
Highlights
Photocathode rf electron guns have become a promising electron source for generating high-brightness electron beams
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
Summary
Photocathode rf electron guns have become a promising electron source for generating high-brightness electron beams. The idea of adding an extra short cell was studied at University of California, Los Angeles [54], for improving the temporal resolution of UED The cavity structure such as the length of the short iris and the ECC was determined by iteration of modeling on SUPERFISH and beam tracking on GPT [49]. The electrons emitted from the photocathode are first accelerated up to approximately 4 MeV and the space charge effect is mitigated These relativistic electrons acquire a positive linear energy chirp at the adjacent ECC. Laser pulse energy [μJ] Laser pulse width [ps, rms] RF power to the gun [MW] RF pulse width [μs] Repetition rate [Hz] Electric field on cathode [MV=m] Beam energy [MeV]
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