| 1. |
- Allaf Navirian, Hengameh, et al.
(författare)
-
Acoustically driven ferroelastic domain switching observed by time-resolved x-ray diffraction
- 2010
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 81:2
-
Tidskriftsartikel (refereegranskat)abstract
- Domain polarization switching in potassium dihydrogen phosphate (KH2PO4, KDP) induced by a propagating strain wave has been observed with time-resolved x-ray diffraction. A pulsed electric field with amplitude of 6 kV/cm and duration of 1 mu s was applied along the crystallographic c axis. The field-induced strain waves emanating from the sample surfaces are the result of the converse piezoelectric effect. In the center of the probed surface two waves interfered constructively inducing ferroelastic domain switching, in the absence of an external electric field, at a delay of 3 mu s, corresponding to acoustic propagation at a velocity found to be 1500 m/s.
|
|
| 2. |
- Burza, Matthias, et al.
(författare)
-
Dispersion and monochromatization of x-rays using a beryllium prism
- 2015
-
Ingår i: Optics Express. - 1094-4087. ; 23:2, s. 620-627
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate experimentally and numerically that an x-ray prism made of beryllium can be used to disperse and monochromatize x-rays. A polished beryllium cuboid was employed as refractive and dispersive optics. The results of a proof-of-principle experiment and methods of performance optimization are presented. The spatial separation of undulator harmonics and their subsequent selection using a slit are described. A numerical study, assuming realistic beam and beamline parameters, suggests that undulator harmonics can be spatially separated in the range from 3 keV to beyond 20 keV, while maintaining throughput above 50%. Refractive optics is particularly suitable for low-repetition-rate sources such as free-electron lasers and other LINAC-based short-pulse sources. (C) 2015 Optical Society of America
|
|
| 3. |
- Enquist, Henrik, et al.
(författare)
-
FemtoMAX - An X-ray beamline for structural dynamics at the short-pulse facility of MAX IV
- 2018
-
Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 25:2, s. 570-579
-
Tidskriftsartikel (refereegranskat)abstract
- The FemtoMAX beamline facilitates studies of the structural dynamics of materials. Such studies are of fundamental importance for key scientific problems related to programming materials using light, enabling new storage media and new manufacturing techniques, obtaining sustainable energy by mimicking photosynthesis, and gleaning insights into chemical and biological functional dynamics. The FemtoMAX beamline utilizes the MAX IV linear accelerator as an electron source. The photon bursts have a pulse length of 100fs, which is on the timescale of molecular vibrations, and have wavelengths matching interatomic distances (Å). The uniqueness of the beamline has called for special beamline components. This paper presents the beamline design including ultrasensitive X-ray beam-position monitors based on thin Ce:YAG screens, efficient harmonic separators and novel timing tools.The FemtoMAX beamline facilitates studies of the structural dynamics of materials on the femtosecond timescale. The first commissioning results are presented.
|
|
| 4. |
- Enquist, Henrik, et al.
(författare)
-
Subpicosecond hard x-ray streak camera using single-photon counting.
- 2010
-
Ingår i: Optics Letters. - 1539-4794. ; 35:19, s. 3219-3221
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed and characterized a hard x-ray accumulating streak camera that achieves subpicosecond time resolution by using single-photon counting. A high repetition rate of 2 kHz was achieved by use of a readout camera with built-in image processing capabilities. The effects of sweep jitter were removed by using a UV timing reference. The use of single-photon counting allows the camera to reach a high quantum efficiency by not limiting the divergence of the photoelectrons.
|
|
| 5. |
- Gaudin, J., et al.
(författare)
-
Time-resolved investigation of nanometer scale deformations induced by a high flux x-ray beam
- 2011
-
Ingår i: Optics Express. - 1094-4087. ; 19:16, s. 15516-15524
-
Tidskriftsartikel (refereegranskat)abstract
- We present results of a time-resolved pump-probe experiment where a Si sample was exposed to an intense 15 keV beam and its surface monitored by measuring the wavefront deformation of a reflected optical laser probe beam. By reconstructing and back propagating the wavefront, the deformed surface can be retrieved for each time step. The dynamics of the heat bump, build-up and relaxation, is followed with a spatial resolution in the nanometer range. The results are interpreted taking into account results of finite element method simulations. Due to its robustness and simplicity this method should find further developments at new x-ray light sources (FEL) or be used to gain understanding on thermo-dynamical behavior of highly excited materials. (C) 2011 Optical Society of America
|
|
| 6. |
- Gyan, D. S., et al.
(författare)
-
Low-temperature nanoscale heat transport in a gadolinium iron garnet heterostructure probed by ultrafast x-ray diffraction
- 2022
-
Ingår i: Structural Dynamics-Us. - : AIP Publishing. - 2329-7778. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- Time-resolved x-ray diffraction has been used to measure the low-temperature thermal transport properties of a Pt/Gd3Fe5O12//Gd3Ga5O12 metal/oxide heterostructure relevant to applications in spin caloritronics. A pulsed femtosecond optical signal produces a rapid temperature rise in the Pt layer, followed by heat transport into the Gd3Fe5O12 (GdIG) thin film and the Gd3Ga5O12 (GGG) substrate. The time dependence of x-ray diffraction from the GdIG layer was tracked using an accelerator-based femtosecond x-ray source. The ultrafast diffraction measurements probed the intensity of the GdIG (1 -1 2) x-ray reflection in a grazing-incidence x-ray diffraction geometry. The comparison of the variation of the diffracted x-ray intensity with a model including heat transport and the temperature dependence of the GdIG lattice parameter allows the thermal conductance of the Pt/GdIG and GdIG//GGG interfaces to be determined. Complementary synchrotron x-ray diffraction studies of the low-temperature thermal expansion properties of the GdIG layer provide a precise calibration of the temperature dependence of the GdIG lattice parameter. The interfacial thermal conductance of the Pt/GdIG and GdIG//GGG interfaces determined from the time-resolved diffraction study is of the same order of magnitude as previous reports for metal/oxide and epitaxial dielectric interfaces. The thermal parameters of the Pt/GdIG//GGG heterostructure will aid in the design and implementation of thermal transport devices and nanostructures. (C) 2022 Author(s).
|
|
| 7. |
- Harb, Maher, et al.
(författare)
-
Picosecond dynamics of laser-induced strain in graphite
- 2011
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 84:4
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the use of grazing-incidence time-resolved x-ray diffraction to investigate the evolution of strain in natural graphite excited by femtosecond-laser pulses in the fluence range of 6-35 mJ/cm(2). Strains corresponding to up to similar to 2.8% c-axis expansion were observed. We show that the experimental data is in good agreement with calculations based on the Thomsen strain model in conjunction with dynamical diffraction theory. Furthermore we find no evidence of nonthermal lattice expansion as reported in recent ultrafast electron-diffraction studies of laser-excited graphite conducted under comparable excitation conditions.
|
|
| 8. |
- Harb, Maher, et al.
(författare)
-
The c-axis thermal conductivity of graphite film of nanometer thickness measured by time resolved X-ray diffraction
- 2012
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:23
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the use of time resolved X-ray diffraction to measure the dynamics of strain in laser-excited graphite film of nanometer thickness, obtained by chemical vapour deposition (CVD). Heat transport in the CVD film is simulated with a 1-dimensional heat diffusion model. We find the experimental data to be consistent with a c-axis thermal conductivity of similar to 0.7 Wm(-1) K-1. This value is four orders of magnitude lower than the thermal conductivity in-plane, confirming recent theoretical calculations of the thermal conductivity of multilayer graphene. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769214]
|
|
| 9. |
- Jensen, Maja, 1978, et al.
(författare)
-
High-resolution macromolecular crystallography at the FemtoMAX beamline with time-over-threshold photon detection
- 2021
-
Ingår i: Journal of Synchrotron Radiation. - 1600-5775 .- 0909-0495. ; 28, s. 64-70
-
Tidskriftsartikel (refereegranskat)abstract
- Protein dynamics contribute to protein function on different time scales. Ultrafast X-ray diffraction snapshots can visualize the location and amplitude of atom displacements after perturbation. Since amplitudes of ultrafast motions are small, high-quality X-ray diffraction data is necessary for detection. Diffraction from bovine trypsin crystals using single femtosecond X-ray pulses was recorded at FemtoMAX, which is a versatile beamline of the MAX IV synchrotron. The time-over-threshold detection made it possible that single photons are distinguishable even under short-pulse low-repetition-rate conditions. The diffraction data quality from FemtoMAX beamline enables atomic resolution investigation of protein structures. This evaluation is based on the shape of the Wilson plot, cumulative intensity distribution compared with theoretical distribution, I/σ, Rmerge /Rmeas and CC1/2 statistics versus resolution. The FemtoMAX beamline provides an interesting alternative to X-ray free-electron lasers when studying reversible processes in protein crystals.
|
|
| 10. |
- Jurgilaitis, Andrius, et al.
(författare)
-
Measurements of light absorption efficiency in InSb nanowires
- 2014
-
Ingår i: Structural Dynamics. - : AIP Publishing. - 2329-7778. ; 1:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report on measurements of the light absorption efficiency of InSb nanowires. The absorbed 70 fs light pulse generates carriers, which equilibrate with the lattice via electron-phonon coupling. The increase in lattice temperature is manifested as a strain that can be measured with X-ray diffraction. The diffracted X-ray signal from the excited sample was measured using a streak camera. The amount of absorbed light was deduced by comparing X-ray diffraction measurements with simulations. It was found that 3.0(6)% of the radiation incident on the sample was absorbed by the nanowires, which cover 2.5% of the sample. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
|
|
| 11. |
- Jurgilaitis, Andrius
(författare)
-
Picosecond X-ray Diffraction Studies of Bulk and Nanostructure Materials
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fast phenomena occurring after laser excitation were studied using time-resolved X-ray diffraction (TXRD). In most experiments, a femtosecond laser pulse was used to excite the sample, and X-rays were used as a probe. The X-ray diffraction technique was used to study bulk semiconductor samples, molten liquids, ferro-electric domain switching in potassium dihydrogen phosphate (KDP), and strain propagation in graphite and semiconductor nanowires. When a laser pulse is absorbed by a solid, a wide range of phase transitions and phenomena can be induced. If the laser fluence is high enough to melt the material, repetitive illumination will create periodic structures on the surface of the sample. This effect was studied using static X-ray diffraction, and it was shown that the effect is important if liquid scattering experiments are carried out on molten samples using the laser in repetitive mode. When the laser fluence is too low to cause sample melting, coherent acoustic phonons can be excited, and this effect was studied in semiconductor nanowires. The time resolution of the synchrotron light source is defined by the length of the electron bunch in the storage ring, and is typically 50-300 ps. In order to achieve higher time resolution, short X-ray pulses, such as those at the SLS, or fast detectors, such as the streak cameras available at MAX-lab can be used. X-ray diffraction is a very sensitive technique for the study of structures, since X-ray photons scatter from all the electrons in the sample. Scattered X-rays can be used to recreate the atomic structure in the sample. In TXRD the sample is perturbed and subsequently probed after a certain delay, giving a snapshot of the structure at a given time. Several images can be merged providing a real-time movie of the structural changes. This was achieved with nanosecond time resolution at MAX-lab, when a laser-created liquid was studied. The development of a sub-picosecond, hard X-ray streak camera was one of the prerequisites for many of the studies presented in this thesis. This detector was used to study the acoustic vibrations in InSb nanowires. Oscillations with a period of 30-70 ps were recorded, and were attributed to acoustic phonons in the semiconductor nanowire. A dramatic decrease in the velocity of acoustic waves was also observed in these structures.
|
|
| 12. |
- Jurgilaitis, Andrius, et al.
(författare)
-
Time-Resolved X-ray Diffraction Investigation of the Modified Phonon Dispersion in InSb Nanowires
- 2014
-
Ingår i: Nano letters (Print). - Washington, DC : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 14:2, s. 541-546
-
Tidskriftsartikel (refereegranskat)abstract
- The modified phonon dispersion is of importance for understanding the origin of the reduced heat conductivity in nanowires. We have measured the phonon dispersion for 50 nm diameter InSb (111) nanowires using time-resolved X-ray diffraction. By comparing the sound speed of the bulk (3880 m/s) and that of a classical thin rod (3600 m/s) to our measurement (2880 m/s), we conclude that the origin of the reduced sound speed and thereby to the reduced heat conductivity is that the C44 elastic constant is reduced by 35% compared to the bulk material. © 2014 American Chemical Society.
|
|
| 13. |
- Jurgilaitis, Andrius, et al.
(författare)
-
Time resolved X-ray studies in semiconductor nanostructures
- 2012
-
Ingår i: 2012 Conference on Lasers and Electro-Optics (Cleo). - 9781557529336
-
Konferensbidrag (refereegranskat)abstract
- Time resolved X-ray diffraction has been used to study acoustic oscillations in InAs/Sb nanowires with diameters of 80 nm and 40 nm in order to determine the speed of sound in the wires.
|
|
| 14. |
- Jurgilaitis, Andrius, et al.
(författare)
-
X-ray diffraction from the ripple structures created by femtosecond laser pulses
- 2010
-
Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 100:1, s. 105-112
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the investigation and characterization of the laser-induced surface structure on an asymmetrically cut InSb crystal. We describe diffraction from the ripple surface and present a theoretical model that can be used to simulate X-ray energy scans. The asymmetrically cut InSb sample was irradiated with short-pulse radiation centred at 800 nm, with fluences ranging from 10 to 80 mJ/cm(2). The irradiated sample surface profile was investigated using optical and atomic force microscopy. We have investigated how laser-induced ripples influence the possibility of studying repetitive melting of solids using X-ray diffraction. The main effects arise from variations in local asymmetry angles, which reduce the attenuation length and increase the X-ray diffraction efficiency.
|
|
| 15. |
- Nüske, Ralf, et al.
(författare)
-
Picosecond time-resolved x-ray refectivity of a laser-heated amorphous carbon film
- 2011
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:10
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate thin film x-ray reflectivity measurements with picosecond time resolution. Amorphous carbon films with a thickness of 46 nm were excited with laser pulses characterized by 100 fs duration, a wavelength of 800 nm, and a fluence of 70 mJ/cm(2). The laser-induced stress caused a rapid expansion of the thin film followed by a relaxation of the film thickness as heat diffused into the silicon substrate. We were able to measure changes in film thickness as small as 0.2 nm. The relaxation dynamics are consistent with a model which accounts for carrier-enhanced substrate heat diffusivity. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562967]
|
|
| 16. |
- Nüske, Ralf, et al.
(författare)
-
Time-resolved x-ray scattering from laser-molten indium antimonide.
- 2010
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 81:1
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a concept to study transient liquids with picosecond time-resolved x-ray scattering in a high-repetition-rate configuration. Femtosecond laser excitation of crystalline indium antimonide (InSb) induces ultrafast melting, which leads to a loss of the long-range order. The remaining local correlations of the liquid result in broad x-ray diffraction rings, which are measured as a function of delay time. After 2 ns the liquid structure factor shows close agreement with that of equilibrated liquid InSb. The measured decay of the liquid scattering intensity corresponds to the resolidification rate of 1 m/s in InSb.
|
|
| 17. |
- Nüske, Ralf, et al.
(författare)
-
Transforming graphite to nanoscale diamonds by a femtosecond laser pulse
- 2012
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:4
-
Tidskriftsartikel (refereegranskat)abstract
- Formation of cubic diamond from graphite following irradiation by a single, intense, ultra-short laser pulse has been observed. Highly oriented pyrolytic graphite (HOPG) samples were irradiated by a 100 fs pulse with a center wavelength of 800 nm. Following laser exposure, the HOPG samples were studied using Raman spectroscopy of the sample surface. In the laser-irradiated areas, nanoscale cubic diamond crystals have been formed. The exposed areas were also studied using grazing incidence x-ray powder diffraction showing a restacking of planes from hexagonal graphite to rhombohedral graphite. (C) 2012 American Institute of Physics. [doi:10.1063/1.3678190]
|
|
| 18. |
- Persson, Anna, et al.
(författare)
-
Real-time observation of coherent acoustic phonons generated by an acoustically mismatched optoacoustic transducer using x-ray diffraction
- 2015
-
Ingår i: Applied Physics Reviews. - New York : AIP Publishing. - 1931-9401. ; 118:18
-
Tidskriftsartikel (refereegranskat)abstract
- The spectrum of laser-generated acoustic phonons in indium antimonide coated with a thin nickel film has been studied using time-resolved x-ray diffraction. Strain pulses that can be considered to be built up from coherent phonons were generated in the nickel film by absorption of short laser pulses. Acoustic reflections at the Ni-InSb interface leads to interference that strongly modifies the resulting phonon spectrum. The study was performed with high momentum transfer resolution together with high time resolution. This was achieved by using a third-generation synchrotron radiation source that provided a high-brightness beam and an ultrafast x-ray streak camera to obtain a temporal resolution of 10 ps. We also carried out simulations, using commercial finite element software packages and on-line dynamic diffraction tools. Using these tools, it is possible to calculate the time-resolved x-ray reflectivity from these complicated strain shapes. The acoustic pulses have a peak strain amplitude close to 1%, and we investigated the possibility to use this device as an x-ray switch. At a bright source optimized for hard x-ray generation, the low reflectivity may be an acceptable trade-off to obtain a pulse duration that is more than an order of magnitude shorter. (C) 2015 Author(s).
|
|
