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Phase-Contrast and High-Resolution Optics for X-Ray Microscopy
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

X-ray microscopy is a well-established technique for nanoscale imaging. Zone plates are used as microscope objectives and provide high resolution, approaching 10 nm, currently limited by fabrication issues. This Thesis presents zone plate optics that achieve either high resolution or phase contrast in x-ray microscopy. The high-resolution optics use high orders of the zone plate, which alleviates the demands on fabrication, and the phase-contrast optics are single-element diffractive optical elements that produce contrast by Zernike or differential-interference contrast methods. The advantage of phase contrast in x-ray microscopy is shorter exposure times, and is crucial in the hard x-ray regime. Microscopy in the absorption‑contrast region of the water-window (2.34 - 4.37 nm) also benefits from these optics. The development of the optics for a laboratory soft x-ray microscope spans from theoretical and numerical analysis of coherence and stray light to experimental implementation and testing. The laboratory microscope uses laser-produced plasma-sources in the water-window and is unique in its design and performance. It will be shown that the laboratory microscope in its current form is a user-oriented and stable instrument, and has been used in a number of applications. The implementation of a cryogenic sample stage for tomographic imaging of biological samples in their natural environment has enabled applications in biology, and 3D x-ray microscopy of cells was performed for the first time with a laboratory instrument.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , x, 61 p.
Series
Trita-FYS, ISSN 0280-316X ; 72
Keyword [en]
Microscopy, X-ray optics, X-ray microscopy, Soft X-ray physics
National Category
Atom and Molecular Physics and Optics Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-26781ISBN: 978-91-7415-834-2 (print)OAI: oai:DiVA.org:kth-26781DiVA: diva2:372702
Public defence
2010-12-17, FD5, Roslagstullsbacken 21, Stockholm, 15:42 (English)
Opponent
Supervisors
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-26 Last updated: 2010-11-30Bibliographically approved
List of papers
1. Simulation of partially coherent image formation in a compact soft x-ray microscope
Open this publication in new window or tab >>Simulation of partially coherent image formation in a compact soft x-ray microscope
2007 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 107, no 8, 604-609 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we describe a numerical method of simulating two-dimensional images in a compact soft X-ray microscope using partially coherent illumination considerations. The work was motivated by recent test object images obtained by the latest generation inhouse compact soft X-ray microscope, which showed diffraction-like artifacts not observed previously. The numerical model approximates the condenser zone plate as a secondary incoherent source represented by individually coherent but mutually incoherent source points, each giving rise to a separate image. A final image is obtained by adding up all the individual source point contributions. The results are compared with the microscope images and show qualitative agreement, indicating that the observed effects are caused by partially coherent illumination.

Keyword
Image formation; Partial coherence; X-ray microscopy; Zone plates; Computer simulation; Light sources; Mathematical models; X ray diffraction; X ray microscopes; Incoherent sources; Partial coherence; X ray microscopy; Zone plates; Image processing; article; diffraction; illumination; image analysis; mathematical model; microscopy; qualitative analysis; separation technique; simulation; X ray analysis
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-7020 (URN)10.1016/j.ultramic.2006.12.001 (DOI)000246937000006 ()2-s2.0-34247139671 (Scopus ID)
Note
QC 20100820. Uppdaterad från In press till Published 20100820.Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2017-12-14Bibliographically approved
2. Theoretical development of a high-resolution differential-interference-contrast optic for x-ray microscopy
Open this publication in new window or tab >>Theoretical development of a high-resolution differential-interference-contrast optic for x-ray microscopy
2008 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 2, 1132-1141 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
phase-contrast
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-17274 (URN)10.1364/OE.16.001132 (DOI)000252479700064 ()2-s2.0-38549088419 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Compact high-resolution differential interference contrast soft x-ray microscopy
Open this publication in new window or tab >>Compact high-resolution differential interference contrast soft x-ray microscopy
Show others...
2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 064104Article in journal (Refereed) Published
Abstract [en]

We demonstrate high-resolution x-ray differential interference contrast (DIC) in a compact soft x-ray microscope. Phase contrast imaging is enabled by the use of a diffractive optical element objective which is matched to the coherence conditions in the microscope setup. The performance of the diffractive optical element objective is evaluated in comparison with a normal zone plate by imaging of a nickel siemens star pattern and linear grating test objects. Images obtained with the DIC optic exhibit typical DIC enhancement in addition to the normal absorption contrast. Contrast transfer functions based on modulation measurements in the obtained images show that the DIC optic gives a significant increase in contrast without reducing the spatial resolution. The phase contrast operation mode now available for our compact soft x-ray microscope will be a useful tool for future studies of samples with low absorption contrast.

Keyword
diffractive optical-elements, zone plates, phase-contrast, fabrication, condenser
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-9811 (URN)10.1063/1.2842422 (DOI)000253237900123 ()2-s2.0-39349084101 (Scopus ID)
Note
QC 20100728Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-12-14Bibliographically approved
4. Compact Zernike phase contrast x-ray microscopy using a single-element optic
Open this publication in new window or tab >>Compact Zernike phase contrast x-ray microscopy using a single-element optic
Show others...
2008 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 33, no 9, 932-934 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate Zernike phase contrast in a compact soft x-ray microscope using a single-element optic. The optic is a combined imaging zone plate and a Zernike phase plate and does not require any additional alignment or components. Contrast is increased and inversed in an image of a test object using the Zernike zone plate. This type of optic may be implemented into any existing x-ray microscope where phase contrast is of interest.

Keyword
spatial-resolution, zone plates
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:kth:diva-17561 (URN)000256166900014 ()2-s2.0-44949260817 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
5. High-resolution computed tomography with a compact soft x-ray microscope
Open this publication in new window or tab >>High-resolution computed tomography with a compact soft x-ray microscope
Show others...
2009 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 13, 11057-11065 p.Article in journal (Refereed) Published
Abstract [en]

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.

Identifiers
urn:nbn:se:kth:diva-18584 (URN)000267761100066 ()2-s2.0-67649271251 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. Sub-25-nm laboratory x-ray microscopy using a compound Fresnel zone plate
Open this publication in new window or tab >>Sub-25-nm laboratory x-ray microscopy using a compound Fresnel zone plate
Show others...
2009 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 17, 2631-2633 p.Article in journal (Refereed) Published
Abstract [en]

Improving the resolution in x-ray microscopes is of high priority to enable future applications in nanoscience. However, high-resolution zone-plate optics often have low efficiency, which makes implementation in laboratory microscopes difficult. We present a laboratory x-ray microscope based on a compound zone plate. The compound zone plate utilizes multiple diffraction orders to achieve high resolution while maintaining reasonable efficiency. We analyze the illumination conditions necessary for this type of optics in order to suppress stray light and demonstrate microscopic imaging resolving 25 nm features.

Keyword
resolution
Identifiers
urn:nbn:se:kth:diva-18788 (URN)000270114400031 ()2-s2.0-69549105762 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
7. High-resolution computed tomography with a compact soft x-ray microscope
Open this publication in new window or tab >>High-resolution computed tomography with a compact soft x-ray microscope
Show others...
2009 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 13, 11057-11065 p.Article in journal (Refereed) Published
Abstract [en]

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.

Identifiers
urn:nbn:se:kth:diva-18584 (URN)000267761100066 ()2-s2.0-67649271251 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
8. Laboratory X-ray microscopy for high-resolution imaging of environmental colloid structure
Open this publication in new window or tab >>Laboratory X-ray microscopy for high-resolution imaging of environmental colloid structure
Show others...
2012 (English)In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 329, no SI, 26-31 p.Article in journal (Refereed) Published
Abstract [en]

Transmission X-ray microscopy is a uniquely suited technique for studies of environmental colloids since it allows imaging in aqueous media with high spatial resolution, presently down to the 20 nm range. Such nanoscale morphological description of these high-specific-surface-area compounds show promise for improved understanding of soils, sediments or groundwater aquifers. However, present high-quality X-ray microscopes are located at synchrotron radiation facilities resulting in limited applicability and accessibility for colloid scientists. Here we investigate the applicability of a laboratory-scale transmission X-ray microscope for studies of colloids of the environment. The microscope is based on a laser-plasma source in combination with multilayer and zone plate optics. Samples are held at atmospheric pressure in their natural wet state. We show images revealing the nano-scale morphology of the clay nontronite, soils such as chernozem and luvisol, and the mineral hematite, an iron oxide. Comparative studies of dried substances clearly show the need for imaging in the wet state. The image quality approaches that of synchrotron-based microscopes, albeit at longer exposure times. Stereo imaging is investigated as a means for giving 3D information with shorter exposure times than tomography requires. Finally the future development of the laboratory X-ray microscope is discussed, especially with regard to the reduction of exposure times.

Keyword
X-ray microscopy, Laser plasma, Diffractive optics, Laboratory scale, environmental colloids, soils
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-26952 (URN)10.1016/j.chemgeo.2011.07.012 (DOI)000310125000005 ()2-s2.0-84866508020 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20121127

Available from: 2010-11-30 Created: 2010-11-30 Last updated: 2017-12-12Bibliographically approved

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  • Other locale
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