The new X-Ray Free Electron Laser (SwissFEL) facility at PSI has produced its first FEL light at 4.1 nm and will deliver 20 fsec pulses of coherent x-rays in the wavelength range 0.1 to 7 nm, with extremely high peak brightness. These characteristics will provide opportunities for new experiments in chemistry, solid state physics, biology and materials science. The Aramis hard x-ray FEL branch...
Time-resolved X-ray spectroscopy is a versatile tool for investigating both electronic and structural dynamics in functional chemical systems. By measuring both the X-ray absorption and X-ray emission signals simultaneously we obtain information on both the occupied and unoccupied electronic states of the sample, as well as structural information from both the near-edge and Extended X-ray...
Ultra-short, ultra-bright X-ray pulses from Free Electron Lasers are a viable tool for observing diffraction from two-dimensional (2D) crystals, unlike synchrotron-based data collection, extending the possibilities of structural determinations in membrane proteins.
Using serial diffraction frames from bacteriorhodopsin 2D crystals we extended the resolution limit of zero-tilt data to 4 A...
SwissFEL, like other SASE-based x-ray FEL facilities, requires the monitoring of the photon spectrum (photon energy and intensity) on a shot-to-shot basis for machine optimization and for experiments. In order to cover the Hard X-ray range variations (4-15keV) for the Aramis beamline, the Photon Single Shot Spectrometer has been designed to measure the spectrum with high resolution over the...
ACHIP is an international collaboration, funded by the Gordon and Betty Moore Foundation, whose goal is to demonstrate that laser-driven accelerator on a chip can be integrated to fully build an accelerator based on dielectric structures.
PSI will provide access to the high brightness electron beam of SwissFEL to test structures, approaches and methods towards achieving the final goal of the...
The next hard X-ray line (2025-2029) at SwissFEL, Porthos, is planned to further extend the photon energy of Aramis, reaching wavelength down to 0.03 nm. Harmonic lasing and inter-undulator chicanes will be implemented to meet this target. Nevertheless the undulator period length must decrease to 10 mm while the K value has to increase to 2.4 with a vacuum gap above 4 mm. These parameters...
The soft X-ray line of SwissFEL, Athos, is designed to extend the present capability of the existing FEL facilities. Several new operating modes will be tested to allow greater control over the bandwidth, pulse length and synchronisation. After a brief overview of the entire facility, the layout of the Athos line will be presented and the new operating modes described in detail: starting from...
Here I give an overview of some applications of femtosecond time-resolved x-ray methods to study the out-of-equilibrium dynamics of materials. Non-equilibrium pathways represent a novel means of manipulating order parameters, but in order to effectively understand and use these pathways we need experimental means to "see" the dynamics associated with these order parameters. X-rays offer some...
Ultrafast demagnetization is a long standing problem of solid state physics, as the transfer of angular momentum on the femtosecond time scale is not understood.
Spin and time resolved photoemission experiments are able to separate the different aspects of spin dynamics: Close to the Fermi energy, we observe an initial loss of the spin polarization. This is caused by the initial spin flips as...
We report a new route to manipulate the electronic properties of a material via vibrational excitation. Using the LCLS free electron laser we investigate the dynamics of the charge order in a manganite film following resonant excitation of a phonon mode to large amplitude. Combining our experimental results with ab initio calculation, we find that the direct nonlinear coupling between the...
The planned SwissFEL ATHOS beamline features all necessary parameters for femtosecond time-resolved experiments in magnetism using x-ray absorption spectroscopy and circular dichroism: intense fs soft x-ray pulses with linear and circular polarization.
An exemplary measurement investigates spin currents between two magnetic films separated by a spacer layer: the upper, fs laser pulse excited...
Sn2P2Se6 is a ferroelectric semiconductor with interesting structural properties. In the temperature range between 193 and 221 K, just above the Curie-Temperature, an incommensurate phase emerges. This permanent structural modulation is believed to be the result of two coupled frozen phonon modes.
In our experiment, we photoexcite the material and probe this structural modulation using...
We used ultrashort x-ray pulses to monitor the structural dynamics associated with the charge density wave (CDW)-state in K0.3MoO3 after photoexcitation. In a first experiment the response to different excitation fluences was investigated. Starting in a regime of coherent oscillations, increasing the excitation fluence leads to a complete melting of the ordered state. Remarkably, a further...
Ultrafast optical control of correlation-induced order parameters in complex materials is a key challenge en route to new functional materials. Here we employ above-bandgap femtosecond pulses with various wavelenghts to excite EuTiO$_3$ out of its low-temperature antiferrodistortive equilibrium phase. Monitoring the subsequent transient intensity of distortion-induced superlattice reflections...
