Currently holding the position of Scientific Director of European XFEL, my main research interests are in the field of ultrafast x-ray science. This activity was started in 2001 following the involvement with FEL sources and their scientific applications.
Initially we aimed at studying ultrafast time-dependent processes in solid-state photochemistry using ultrashort pulse x-ray sources, like the ESRF, SPPS at SLAC, laser–based laboratory sources, FLASH, and also LCLS. Particularly interesting were photoinduced phase transitions (M. Messerschmidt et al., J. Phys. Chem. A114, 7677 (2010)) and photo-induced irreversible reactions (G. Busse et al., Faraday Discuss. 122, 105 (2002)).
With the availability of highly intense and ultrashort FEL pulses at FLASH and LCLS, but also the availability of high power optical lasers installed next to an FEL instrument, the emphasis of activities shifted towards the investigation of ultrafast dynamics in the regime of condensed matter under extreme conditions. In this area several milestone experiments were carried out using FLASH, LCLS and more recently SACLA. These experiments provided new observations of the interaction of intense x-ray pulses with matter (B. Nagler et al., Nature Phys. 5, 693 (2009)) and of the dynamics of excited matter following absorption of energetic photons (R.R. Fäustlin et al., Phys. Rev. Lett. 104,125002 (2010)), but also investigated the properties of dense, extreme matter states (C. Brown et al., Sci. Rep., DOI: 10.1038/srep05214, (2014)).
A significant aspect of this work has been the development of new instrumentation for FEL experiments and of new FEL techniques (I. Grguras et al., Nature Phot. 6, 852 (2012), J. Gaudin et al., Sci. Rep., DOI: 10.1038/srep04724,(2014), Th. Tschentscher et al., Appl. Sci. 7, 592 (2017)).