Ultrafast Electron Diffraction
Present-day electron microscopy enables sub-Angstrom spatial resolution, i.e. a single atom may be resolved, but only at exposure times of the order of seconds. The time scale of atomic motion, however, can be as short as 100 fs. The next challenge is therefore to realize both atomic spatial and temporal resolution, i.e. 0.1 nm and 0.1 ps, thus enabling the study of structural dynamics at the shortest time scales. For reasons of process repeatability, reproducibility, and radiation damage considerations single-shot operation would be ideal. Because of stringent beam requirement single-shot, 100 fs electron microscopy is completely impossible. Electron diffraction, however, is much less demanding, requiring much less charge for recording a high-quality diffraction patter and only a modest beam quality. We have developed a setup for doing single-shot, 100 fs electron diffraction. Key ingredients are creation of waterbag bunches by femtosecond photoemission and compression of bunches (inversion of the Coulomb expansion) using the electromagnetic fields in a resonant 3 GHz cavity. The required RF and femtosecond synchronization technology was developed in previous relativistic accelerator projects. We are now working on the application of this new technique in solid state physics and (bio)molecular physics and chemistry in the framework of several collaborations, both within and outside TU/e. In parallel, we are working on the development of a laser-cooled, ultracold electron source, which at some point should replace the photocathode. The ultracold electron source should enable a dramatic increase in beam brightness, which possibly may lead to single-shot, femtosecond diffractive imaging, which up to now is the exclusive domain of the X-ray Free Electron Laser.
Keywords: Structural dynamics, atomic length and time scales, electron diffraction, X-ray Free Electron Lasers, femtosecond lasers.
People involved: The following people are or have been involved in this project:
|PhD student||Peter Pasmans, Wouter Engelen|
|Stefano Dal Conte|
|Former PhD students||Thijs van Oudheusden, Gabriel Taban|
|Former students||Arjan Klessens, Marloes van der Heijden|
|Technicians||Eddy Rietman, Jolanda van de Ven, Ad Kemper, Harry van Doorn, and Iman Koole|
|Staff members||Bas van der Geer, Marieke de Loos, and Jom Luiten|