Generation of few-femtosecond relativistic electron bunches for 4-D imaging

The goal of this project is to generate electron bunches and to realize single shot time-resolved electron diffraction with them. The required relativistic electrons have few-fs temporal resolution, which is two orders of magnitude shorter than the resolution of present state-of-the-art techniques. In ultrafast electron diffraction the duration of the electron pulses and therefore the resolution is limited by space charge broadening to a few 100 fs. We apply laser-driven electron acceleration to generate a probe in laser pump-electron probe diffraction experiments. The few-fs bunch length of the electrons in our case is not elongated by space charge effects due to the relativistic energies about 1-10 MeV. Although the electrons might need energy bandwidth and divergence filtering or reshaping by for example quadrupole permanent magnet lenses and slits to reach the stringent conditions of electron diffraction as mrad diffraction angle with still 10⁵-10⁶ particles. One of the first realizations of electron diffraction experiments using a fast process on the one-fs time scale might deliver information about electron bunch duration either.

Well characterized relativistic electron pulses and their application to electron diffraction open the way toward 4-D imaging with atomic spatial and temporal resolution.