| 1. |
- Bertilson, Michael, et al.
(författare)
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High-resolution computed tomography with a compact soft x-ray microscope
- 2009
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Ingår i: Optics Express. - 1094-4087. ; 17:13, s. 11057-11065
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Tidskriftsartikel (refereegranskat)abstract
- Computed tomography based on high-resolution soft x-ray microscopy utilizes the natural contrast for biological specimens provided by the water window (lambda = 2.4 - 4.4 nm) and the high resolving power of zone plate objectives. It is capable of revealing the 3D structure of biological specimens at sub-visible-microscopic resolution. To date, the technique has only been available at synchrotron-based microscopes, which limits the researchers access. In the present paper we demonstrate high-resolution soft x-ray tomography with a laboratory zone-plate-based soft x-ray microscope. The specimen, a diatom mounted on a glass capillary, was reconstructed from a tilt series of 53 images covering 180 using a filtered back projection algorithm. The resolution of the tomogram was estimated to a half period of 140 nm using a differential-phase-residual method. Cryo-fixation, increased source brightness and extended-depth-of-focus objectives are important for pushing the resolution of compact systems for biological samples.
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| 2. |
- Bertilson, Michael, et al.
(författare)
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Numerical model for tomographic image formation in transmission x-ray microscopy
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:12, s. 11578-11583
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Tidskriftsartikel (refereegranskat)abstract
- We present a numerical image-formation model for investigating the influence of partial coherence, sample thickness and depth-of-focus on the accuracy of tomographic reconstructions in transmission x-ray microscopes. The model combines wave propagation through the object by finite difference techniques with Fourier methods. We include a ray-tracing model to analyse the origin of detrimental stray light in zone plate-based x-ray microscopes. These models allow optimization of x-ray microscopy systems for quantitative tomographic imaging of thick objects. Results show that both the depth-of-focus and the reconstructed local absorption coefficient are highly dependent on the degree of coherence of the optical system.
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| 3. |
- Björling, Alexander, et al.
(författare)
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Ptychographic characterization of a coherent nanofocused X-ray beam
- 2020
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 28:4, s. 5069-5076
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Tidskriftsartikel (refereegranskat)abstract
- The NanoMAX hard X-ray nanoprobe is the first beamline to take full advantage of the diffraction-limited storage ring at the MAX IV synchrotron and delivers a high coherent photon flux for applications in diffraction and imaging. Here, we characterize its coherent and focused beam using ptychographic analysis. We derive beam profiles in the energy range 6-22 keV and estimate the coherent flux based on a probe mode decomposition approach.
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| 4. |
- Legall, H., et al.
(författare)
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Compact X-ray microscope for the water window based on a high brightness laser plasma source
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:16, s. 18362-18369
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Tidskriftsartikel (refereegranskat)abstract
- We present a laser plasma based x-ray microscope for the water window employing a high-average power laser system for plasma generation. At 90 W laser power a brightness of 7.4 x 10(11) photons/(s x sr x mu m(2)) was measured for the nitrogen Ly alpha line emission at 2.478 nm. Using a multilayer condenser mirror with 0.3 % reflectivity 10(6) photons/(mu m(2) x s) were obtained in the object plane. Microscopy performed at a laser power of 60 W resolves 40 nm lines with an exposure time of 60 s. The exposure time can be further reduced to 20 s by the use of new multilayer condenser optics and operating the laser at its full power of 130 W.
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| 5. |
- Selin, Mårten, et al.
(författare)
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3D simulation of the image formation in soft x-ray microscopes
- 2014
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 22:25, s. 30756-30768
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Tidskriftsartikel (refereegranskat)abstract
- In water-window soft x-ray microscopy the studied object is typically larger than the depth of focus and the sample illumination is often partially coherent. This blurs out-of-focus features and may introduce considerable fringing. Understanding the influence of these phenomena on the image formation is therefore important when interpreting experimental data. Here we present a wave-propagation model operating in 3D for simulating the image formation of thick objects in partially coherent soft x-ray microscopes. The model is compared with present simulation methods as well as with experiments. The results show that our model predicts the image formation of transmission soft x-ray microscopes more accurately than previous models.
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| 6. |
- Uhlén, Fredrik, et al.
(författare)
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Damage investigation on tungsten and diamond diffractive optics at a hard x-ray free-electron laser
- 2013
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Ingår i: Optics Express. - : Optical Society America. - 1094-4087. ; 21:7, s. 8051-8061
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Tidskriftsartikel (refereegranskat)abstract
- Focusing hard x-ray free-electron laser radiation with extremely high fluence sets stringent demands on the x-ray optics. Any material placed in an intense x-ray beam is at risk of being damaged. Therefore, it is crucial to find the damage thresholds for focusing optics. In this paper we report experimental results of exposing tungsten and diamond diffractive optics to a prefocused 8.2 keV free-electron laser beam in order to find damage threshold fluence levels. Tungsten nanostructures were damaged at fluence levels above 500 mJ/cm(2). The damage was of mechanical character, caused by thermal stress variations. Diamond nanostructures were affected at a fluence of 59 000 mJ/cm(2). For fluence levels above this, a significant graphitization process was initiated. Scanning Electron Microscopy (SEM) and mu-Raman analysis were used to analyze exposed nanostructures.
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| 7. |
- Vogt, Ulrich, et al.
(författare)
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Moiré method for nanometer instability investigation of scanning hard x-ray microscopes
- 2017
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:11, s. 12188-12194
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Tidskriftsartikel (refereegranskat)abstract
- We present a Moiré method that can be used to investigate positional instabilities in a scanning hard x-ray microscope with nanometer precision. The development of diffractionlimited storage rings offering highly-brilliant synchrotron radiation and improvements of nanofocusing x-ray optics paves the way towards 3D nanotomography with 10 nm resolution or below. However, this trend demands improved designs of x-ray microscope instruments which should offer few-nm beam stabilities with respect to the sample. Our technique can measure the position of optics and sample stage relative to each other in the two directions perpendicular to the beam propagation in a scanning x-ray microscope using simple optical components and visible light. The usefulness of the method was proven by measuring short and long term instabilities of a zone-plate-optics-based prototype microscope. We think it can become an important tool for the characterization of scanning x-ray microscopes, especially prior to experiments with an actual x-ray beam.
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| 8. |
- von Hofsten, Olof, et al.
(författare)
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Theoretical development of a high-resolution differential-interference-contrast optic for x-ray microscopy
- 2008
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Ingår i: Optics Express. - 1094-4087. ; 16:2, s. 1132-1141
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the theoretical background and development of a differential-interference contrast (DIC) x-ray optic is presented. The single-element optic is capable of high-resolution phase contrast imaging and is compatible with compact sources. It is shown that an understanding of the coherence requirements in this type of imaging is imperative and is explained in detail. The optic is capable of a wavefront separation equal to the resolution of the optic which places only minor constraints on the object illumination.
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| 9. |
- Åstrand, Mattias, et al.
(författare)
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Adaptive multi-beam X-ray ptychography
- 2024
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 32:13, s. 22771-22780
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Tidskriftsartikel (refereegranskat)abstract
- Ptychography has evolved as an important method for nanoscale X-ray imaging with synchrotron radiation. Recently, it has been proposed to work with multiple beams in parallel. The main advantage of so-called multi-beam ptychography is that larger areas can be imaged much faster than with a conventional single beam scan. We introduce adaptive multi-beam ptychography performed with two Fresnel zone plates, placed one behind the other. In contrast to previous demonstrations of multi-beam ptychography, our optical scheme allows for adapting the spatial beam separation to the needs of the sample under investigation, relaxes thickness requirements on zone plates and is straightforward to implement. Moreover, it is simple to switch between single and multi-beam illumination during the same experiment. This opens the possibility of combining large and fast overview scans with detailed imaging of certain regions of interests.
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