Pauli Center Blackboard Seminar

# X-ray Free-Electron Lasers: novel experiments and challenges for theory

## by Massimo Altarelli (XFEL)

Thursday, May 19, 2016 from to (Europe/Berlin)
at DESY Hamburg ( Sem. room 2 )
 Description X-ray Free-Electron Lasers, based on linear electron accelerators, are introducing a revolution in X-ray physics. Compared to the storage ring based sources, they open the possibility of generating very short pulses (of order 10 fs and even less), with extraordinary peak brilliance (108 and more times larger), and close to full transverse coherence. This introduces a wide range of new possibilities including, among others: the exploration of the time dependence of atomic and molecular processes, e.g. chemical reactions; the investigation of the mechanisms and the fundamental limits to the speed with which the magnetization can be erased and re-written in ferromagnetic materials; the emergence of appreciable non-linear optics phenomena, well known in the visible range since the laser invention, in the X-ray range of wavelengths. In this talk, I shall very briefly describe the key principles leading to the performance of Xray lasers, illustrate some examples of problems and phenomena addressed by the new experiments, and the challenges that their interpretation, in my view, poses to condensed-matter theory.