| 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. |
- Nelson, A. J., et al.
(författare)
-
Soft x-ray free electron laser microfocus for exploring matter under extreme conditions
- 2009
-
Ingår i: Optics Express. - 1094-4087. ; 17:20, s. 18271-18278
-
Tidskriftsartikel (refereegranskat)abstract
- We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: lambda = 13.5 nm, pulse length 15 fs, pulse energy 10-40 mu J, 5Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled six-axis gimbal. Beam imprints on poly(methyl methacrylate) -PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of <= 1 mu m. Observations were correlated with simulations of best focus to provide further relevant information.
|
|
| 3. |
- 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
|
|
