| 1. |
|
|
| 2. |
|
|
| 3. |
- Finetti, P., et al.
(author)
-
Pulse duration of seeded free electron lasers
- 2017
-
In: Physical Review X. - 2160-3308. ; 7:2
-
Journal article (peer-reviewed)abstract
- The pulse duration, and, more generally, the temporal intensity profile of free-electron laser (FEL) pulses, is of utmost importance for exploring the new perspectives offered by FELs; it is a nontrivial experimental parameter that needs to be characterized. We measured the pulse shape of an extreme ultraviolet externally seeded FEL operating in high-gain harmonic generation mode. Two different methods based on the cross-correlation of the FEL pulses with an external optical laser were used. The two methods, one capable of single-shot performance, may both be implemented as online diagnostics in FEL facilities. The measurements were carried out at the seeded FEL facility FERMI. The FEL temporal pulse characteristics were measured and studied in a range of FEL wavelengths and machine settings, and they were compared to the predictions of a theoretical model. The measurements allowed a direct observation of the pulse lengthening and splitting at saturation, in agreement with the proposed theory.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Makita, M., et al.
(author)
-
Femtosecond phase-transition in hard x-ray excited bismuth
- 2019
-
In: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
-
Journal article (peer-reviewed)abstract
- The evolution of bismuth crystal structure upon excitation of its A(1g) phonon has been intensely studied with short pulse optical lasers. Here we present the first-time observation of a hard x-ray induced ultrafast phase transition in a bismuth single crystal at high intensities (similar to 10(14) W/cm(2)). The lattice evolution was followed using a recently demonstrated x-ray single-shot probing setup. The time evolution of the (111) Bragg peak intensity showed strong dependence on the excitation fluence. After exposure to a sufficiently intense x-ray pulse, the peak intensity dropped to zero within 300 fs, i.e. faster than one oscillation period of the A(1g) mode at room temperature. Our analysis indicates a nonthermal origin of a lattice disordering process, and excludes interpretations based on electron-ion equilibration process, or on thermodynamic heating process leading to plasma formation.
|
|
| 7. |
- Tachibana, T., et al.
(author)
-
Nanoplasma Formation by High Intensity Hard X-rays
- 2015
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
-
Journal article (peer-reviewed)abstract
- Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at similar to 5 keV. Our experiment was carried out at the SPring-8 Angstrom Compact free electron LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with the molecular dynamics tool XMDYN. We found that in this unprecedented wavelength regime nanoplasma formation is a highly indirect process. In the argon clusters investigated, nanoplasma is mainly formed through secondary electron cascading initiated by slow Auger electrons. Energy is distributed within the sample entirely through Auger processes and secondary electron cascading following photoabsorption, as in the hard x-ray regime there is no direct energy transfer from the field to the plasma. This plasma formation mechanism is specific to the hard-x-ray regime and may, thus, also be important for XFEL-based molecular imaging studies. In xenon clusters, photo-and Auger electrons contribute more significantly to the nanoplasma formation. Good agreement between experiment and simulations validates our modelling approach. This has wide-ranging implications for our ability to quantitatively predict the behavior of complex molecular systems irradiated by high-intensity hard x-rays.
|
|
| 8. |
- Wang, F, et al.
(author)
-
Coherent Diffraction of a Single Virus Particle : The Impact of a Water Layer on the Available Orientational Information
- 2011
-
In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1539-3755 .- 1550-2376. ; 83, s. 031907-1-031907-5
-
Journal article (peer-reviewed)abstract
- Coherent diffractive imaging using x-ray free-electron lasers (XFELs) may provide a unique opportunity for high-resolution structural analysis of single particles sprayed from an aqueous solution into the laser beam. As a result, diffraction images are measured from randomly oriented objects covered by a water layer. We analyze theoretically how the thickness of the covering water layer influences the structural and orientational information contained in the recorded diffraction images. This study has implications for planned experiments on single-particle imaging with XFELs.
|
|
| 9. |
|
|
| 10. |
|
|
