| 1. |
- Hau-Riege, S. P., et al.
(författare)
-
Wavelength dependence of the damage threshold of inorganic materials under extreme-ultraviolet free-electron-laser irradiation
- 2009
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 95:11, s. 111104-111104-3
-
Tidskriftsartikel (refereegranskat)abstract
- We exposed bulk SiC and films of SiC and B4C to single 25 fs long free-electron-laser pulses with wavelengths between 13.5 and 32 nm. The materials are candidates for x-ray free-electron laser optics. We found that the threshold for surface-damage of the bulk SiC samples exceeds the fluence required for thermal melting at all wavelengths. The damage threshold of the film sample shows a strong wavelength dependence. For wavelengths of 13.5 and 21.7 nm, the damage threshold is equal to or exceeds the melting threshold, whereas at 32 nm the damage threshold falls below the melting threshold.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Hau-Riege, S. P., et al.
(författare)
-
Damage threshold of inorganic solids under free-electron-laser irradiation at 32.5 nm wavelength
- 2007
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:17, s. 173128-
-
Tidskriftsartikel (refereegranskat)abstract
- Samples of B4C, amorphous C, chemical-vapor-deposition-diamond C, Si, and SiC were exposed to single 25 fs long pulses of 32.5 nm free-electron-laser radiation at fluences of up to 2.2 J/cm(2). The samples were chosen as candidate materials for x-ray free-electron-laser optics. It was found that the threshold for surface damage is on the order of the fluence required for thermal melting. For larger fluences, the crater depths correspond to temperatures on the order of the critical temperature, suggesting that the craters are formed by two-phase vaporization.
|
|
| 5. |
- Chalupsky, J., et al.
(författare)
-
Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic molecular solids
- 2007
-
Ingår i: Optics Express. - 1094-4087. ; 15:10, s. 6036-6043
-
Tidskriftsartikel (refereegranskat)abstract
- A linear accelerator based source of coherent radiation, FLASH (Free-electron LASer in Hamburg) provides ultra-intense femtosecond radiation pulses at wavelengths from the extreme ultraviolet (XUV; lambda< 100nm) to the soft X-ray (SXR; lambda<30nm) spectral regions. 25-fs pulses of 32-nm FLASH radiation were used to determine the ablation parameters of PMMA - poly ( methyl methacrylate). Under these irradiation conditions the attenuation length and ablation threshold were found to be (56.9 +/- 7.5) nm and similar to 2 mJ center dot cm(-2), respectively. For a second wavelength of 21.7 nm, the PMMA ablation was utilized to image the transverse intensity distribution within the focused beam at mu m resolution by a method developed here.
|
|
| 6. |
- Chalupsky, J, et al.
(författare)
-
Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses
- 2009
-
Ingår i: Optics Express. - 1094-4087. ; 17:1, s. 208-217
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first observation of single-shot soft x-ray laser induced desorption occurring below the ablation threshold in a thin layer of poly ( methyl methacrylate) - PMMA. Irradiated by the focused beam from the Free-electron LASer in Hamburg ( FLASH) at 21.7nm, the samples have been investigated by atomic-force microscope (AFM) enabling the visualization of mild surface modifications caused by the desorption. A model describing non-thermal desorption and ablation has been developed and used to analyze single-shot imprints in PMMA. An intermediate regime of materials removal has been found, confirming model predictions. We also report below-threshold multiple-shot desorption of PMMA induced by high-order harmonics (HOH) at 32nm. Short-time exposure imprints provide sufficient information about transverse beam profile in HOH's tight focus whereas long-time exposed PMMA exhibits radiation-initiated surface hardening making the beam profile measurement infeasible. (C) 2008 Optical Society of America
|
|
| 7. |
- Chapman, Henry N, et al.
(författare)
-
Femtosecond time-delay X-ray holography
- 2007
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 448:7154, s. 676-679
-
Tidskriftsartikel (refereegranskat)abstract
- Extremely intense and ultrafast X-ray pulses from free-electron lasers offer unique opportunities to study fundamental aspects of complex transient phenomena in materials. Ultrafast time-resolved methods usually require highly synchronized pulses to initiate a transition and then probe it after a precisely defined time delay. In the X-ray regime, these methods are challenging because they require complex optical systems and diagnostics. Here we propose and apply a simple holographic measurement scheme, inspired by Newton's 'dusty mirror' experiment1, to monitor the X-ray-induced explosion of microscopic objects. The sample is placed near an X-ray mirror; after the pulse traverses the sample, triggering the reaction, it is reflected back onto the sample by the mirror to probe this reaction. The delay is encoded in the resulting diffraction pattern to an accuracy of one femtosecond, and the structural change is holographically recorded with high resolution. We apply the technique to monitor the dynamics of polystyrene spheres in intense free-electron-laser pulses, and observe an explosion occurring well after the initial pulse. Our results support the notion that X-ray flash imaging2, 3 can be used to achieve high resolution, beyond radiation damage limits for biological samples4. With upcoming ultrafast X-ray sources we will be able to explore the three-dimensional dynamics of materials at the timescale of atomic motion.
|
|
| 8. |
|
|
| 9. |
- Hau-Riege, S. P., et al.
(författare)
-
Soft-x-ray free-electron-laser interaction with materials
- 2007
-
Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 76:4, s. 046403-
-
Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray free-electron lasers have enabled materials studies in which structural information is obtained faster than the relevant probe-induced damage mechanisms. We present a continuum model to describe the damage process based on hot-dense plasma theory, which includes a description of the energy deposition in the samples, the subsequent dynamics of the sample, and the detector signal. We compared the model predictions with experimental data and mostly found reasonable agreement. In view of future free-electron-laser performance, the model was also used to predict damage dynamics of samples and optical elements at shorter wavelengths and larger photon fluences than currently available.
|
|
| 10. |
|
|
