| 1. |
- Pearce, Neil E, et al.
(författare)
-
IARC Monographs : 40 Years of Evaluating Carcinogenic Hazards to Humans
- 2015
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Ingår i: Journal of Environmental Health Perspectives. - : Environmental Health Perspectives. - 0091-6765 .- 1552-9924. ; 123:6, s. 507-514
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Recently the International Agency for Research on Cancer (IARC) Programme for the Evaluation of Carcinogenic Risks to Humans has been criticized for several of its evaluations, and also the approach used to perform these evaluations. Some critics have claimed that IARC Working Groups' failures to recognize study weaknesses and biases of Working Group members have led to inappropriate classification of a number of agents as carcinogenic to humans.OBJECTIVES: The authors of this paper are scientists from various disciplines relevant to the identification and hazard evaluation of human carcinogens. We have examined here criticisms of the IARC classification process to determine the validity of these concerns. We review the history of IARC evaluations and describe how the IARC evaluations are performed.DISCUSSION: We conclude that these recent criticisms are unconvincing. The procedures employed by IARC to assemble Working Groups of scientists from the various discipline and the techniques followed to review the literature and perform hazard assessment of various agents provide a balanced evaluation and an appropriate indication of the weight of the evidence. Some disagreement by individual scientists to some evaluations is not evidence of process failure. The review process has been modified over time and will undoubtedly be altered in the future to improve the process. Any process can in theory be improved, and we would support continued review and improvement of the IARC processes. This does not mean, however, that the current procedures are flawed.CONCLUSIONS: The IARC Monographs have made, and continue to make, major contributions to the scientific underpinning for societal actions to improve the public's health.
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| 2. |
- Berglund, M., et al.
(författare)
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Compact water-window transmission X-ray microscopy
- 2000
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 197, s. 268-273
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate sub-100 nm resolution water-window soft X-ray full-field transmission microscopy with a compact system. The microscope operates at lambda = 3.37 nm and is based on a 100 Hz table-top regenerative debris-free droplet-target laser-plasma X-ray source in combination with normal-incidence multilayer condenser optics for sample illumination. High-spatial-resolution imaging is performed with a 7.3% efficiency nickel zone plate and a 1024 x 1024 pixel CCD detector. Images of dry test samples are recorded with exposure times of a few minutes and show features smaller than 60 nm.
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| 3. |
- Hansson, B. A. M., et al.
(författare)
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A liquid-xenon-jet laser-plasma X-ray and EUV source
- 2000
-
Ingår i: Microelectronic Engineering. - 0167-9317 .- 1873-5568. ; 53:04-jan, s. 667-670
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Tidskriftsartikel (refereegranskat)abstract
- We describe a laser-plasma soft-x-ray source based on a cryogenic-xenon liquid-jet target. The source is suitable for extreme ultraviolet (EUV) projection lithography and proximity x-ray lithography (PXL). Absolute calibrated spectra in the 1-2 nm range and uncalibrated spectra in the 9-15 nm range are obtained using a free-standing transmission grating and a CCD-detector.
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| 4. |
- Hansson, B. A. M., et al.
(författare)
-
Characterisation of a liquid-xenon jet laser-plasma extreme-ultraviolet source
- 2004
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 75:6, s. 2122-2129
-
Tidskriftsartikel (refereegranskat)abstract
- A liquid-xenon-jet laser-plasma source for extreme-ultraviolet (EUV) and soft-x-ray generation has been characterized. Being a source candidate for EUV lithography (EUVL), we especially focus on parameters important for the integration of the source in EUVL systems. The deep-ultraviolet (DUV) out-of-band radiation (=120–400 nm) was quantified, to within a factor of two, using a flying-circus tool together with a transmission-grating spectrograph resulting in a total DUV conversion efficiency (CE) of ~0.33%/2sr. The size and the shape of the xenon plasma was investigated using an in-band-only EUV microscope, based on a spherical Mo/Si multilayer mirror and a charge-coupled device detector. Scalability of the source size from 20–270 µm full width at half maximum was shown. The maximum repetition-rate sustainable by the liquid-xenon-jet target was simulated by a double-pulse experiment indicating feasibility of >17 kHz operation. The xenon-ion energy distribution from the plasma was determined in a time-of-flight experiment with a Faraday-cup detector showing the presence of multi-kilo-electron-volt ions. Sputtering of silicon witness plates exposed to the plasma was observed, while a xenon background of >1 mbar was shown to eliminate the sputtering. It is concluded that the source has potential to meet the requirements of future EUVL systems.
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| 5. |
- Hemberg, O., et al.
(författare)
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Stability of droplet-target laser-plasma soft x-ray sources
- 2000
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 88:9, s. 5421-5425
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Tidskriftsartikel (refereegranskat)abstract
- The spatial stability of microscopic target droplets used for laser-plasma soft x-ray generation in vacuum is investigated. A long-term drift in drop position is characterized with an ultrafast laser-diode imaging system. The drift is experimentally and theoretically shown to be due to a temperature-induced increase in target-liquid viscosity as a result of evaporation. Finally, the drift is compensated for and stable, long-term unattended operation of the source is demonstrated with an automatic phase-delay drop-to-laser synchronizing system. This is important for future compact lithography and microscopy systems.
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| 6. |
- Hertz, Hans M., et al.
(författare)
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Electron-Impact Liquid-Metal-Jet Hard x-Ray Sources
- 2014
-
Ingår i: Comprehensive Biomedical Physics. - : Elsevier. - 9780444536327 ; , s. 91-109
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The power and brightness of electron-impact microfocus x-ray sources have long been limited by thermal damage in the target. This is a major constraint for a wide range of biomedical applications, from imaging to diffraction. Here, we describe the development of an x-ray microfocus source based on a new target concept, the liquid-metal jet (LMJ). The regenerative nature of this target allows for significantly higher e-beam power density than on conventional targets, resulting in this source showing promise for >. 100. × higher brightness than state-of-the-art sources. We first discuss the basic physics of the two important subsystems of the source, LMJ in vacuum and focused electron-beam systems, and then describe the properties of several versions of the source, from early prototypes to the first LMJ sources now reaching the market. Finally, we review some early applications of the source for biomedical imaging and diffraction.
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| 7. |
- Hertz, Hans M., et al.
(författare)
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Laboratory x-ray micro imaging : Sources, optics, systems and applications
- 2009
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
-
Tidskriftsartikel (refereegranskat)abstract
- We summarize the recent progress in laboratory-scale soft and hard x-ray micro imaging in Stockholm. Our soft x-ray work is based on liquid-jet laser-plasma sources which are combined with diffractive and multilayer optics to form laboratory x-ray microscopes. In the hard x-ray regime the imaging is based on a liquid-metal-jet electron-impact source which provides the necessary coherence to allow phase-contrast imaging with high fidelity.
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| 8. |
- Hertz, Hans M., et al.
(författare)
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Liquid-jet laser-plasma X-ray sources for microscopy and lithography
- 2001
-
Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 11:PR2, s. 389-396
-
Tidskriftsartikel (refereegranskat)abstract
- We review the development of compact laser-plasma soft x-ray sources based on microscopic liquid-drop or liquid-jet targets. It is shown that such sources provide practically debris-free, high-flux operation at water-window and EUV wavelengths. This regenerative and solid-density target system holds promise for the generation of high-average power using high-repetition-rate lasers. Application of the source to compact x-ray microscopy, multi layer-op tics characterization and EUV lithography is briefly discussed.
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| 9. |
- Legall, H., et al.
(författare)
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A compact laboratory transmission X-ray microscope for the water window
- 2013
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 463:1, s. 012013-
-
Tidskriftsartikel (refereegranskat)abstract
- In the water window (2.2-4.4 nm) the attenuation of radiation in water is significantly smaller than in organic material. Therefore, intact biological specimen (e.g. cells) can be investigated in their natural environment. In order to make this technique accessible to users in a laboratory environment a Full-Field Laboratory Transmission X-ray Microscope (L-TXM) has been developed. The L-TXM is operated with a nitrogen laser plasma source employing an InnoSlab high power laser system for plasma generation. For microscopy the Ly α emission of highly ionized nitrogen at 2.48 nm is used. A laser plasma brightness of 5 × 1011 photons/(s × sr × μm2 in line at 2.48 nm) at a laser power of 70 W is demonstrated. In combination with a state-of-the-art Cr/V multilayer condenser mirror the sample is illuminated with 106 photons/(μm2 × s). Using objective zone plates 35-40 nm lines can be resolved with exposure times < 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. These exposure times enable cryo tomography in a laboratory environment.
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| 10. |
- Legall, H., et al.
(författare)
-
Compact X-ray microscope for the water window based on a high brightness laser plasma source
- 2012
-
Ingår i: Optics Express. - 1094-4087. ; 20:16, s. 18362-18369
-
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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| 11. |
- Lundström, Ulf, et al.
(författare)
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X-ray phase-contrast CO2 angiography for sub-10 mu m vessel imaging
- 2012
-
Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 57:22, s. 7431-7441
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray in-line phase contrast has recently been combined with CO2 angiography for high-resolution small-animal vascular imaging at low radiation dose. In this paper we further investigate the potential and limitations of this method and demonstrate observation of vessels down to 8 mu m in diameter, considerably smaller than the 60 mu m previously reported. Our in-line phase-contrast imaging system is based on a liquid-metal-jet-anode x-ray source and utilizes free-space propagation to convert phase shifts, caused by refractive index variations, into intensity differences. Enhanced refractive index variations are obtained through injection of CO2 gas into the vascular system to replace the blood. We show rat-kidney images with blood vessels down to 27 mu m in diameter and mouse-ear images with vessels down to 8 mu m. The minimum size of observable blood vessels is found to be limited by the penetration of gas into the vascular system and the signal-to-noise ratio, i.e. the allowed dose. The diameters of vessels being gas-filled depend on the gas pressure and follow a simple model based on surface tension. A theoretical signal-to-noise comparison shows that this method requires 1000 times less radiation dose than conventional iodine-based absorption contrast for observing sub-50 mu m vessels.
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| 12. |
- Eriksson, Fredrik, et al.
(författare)
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14.5% near-normal incidence reflectance of Cr/Sc x-ray multilayer mirrors for the water window
- 2003
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 28:24, s. 2494-2496
-
Tidskriftsartikel (refereegranskat)abstract
- Cr/Sc multilayer mirrors, synthesized by ion-assisted magnetron sputter deposition, are proved to have a high near-normal reflectivity of R = 14.5% at a grazing angle of 87.5degrees measured at the wavelength A = 3.11 nm, which is an improvement of more than 31% compared with previously published results. Elastic recoil detection analyses show that the mirrors contained as much as 15 at. % of N and traces of C and O. Soft x-ray reflectivity simulations reveal interface widths of sigma = 0.34 nm and an exceptionally small layer thickness drift of similar to1.6 X 10(-5) nm/multilayer period throughout the stack. Simulations show that a reflectivity of R = 25.6% is attainable if impurities and layer thickness drift can be eliminated. The abrupt interfaces are achieved with ion assistance with a low ion energy of 24 eV and high ion-to-metal flux ratios of 7.1 and 23.1 during Cr and Se sputter deposition, respectively. In addition, a near-normal incidence reflectivity of 5.5% for the C VI emission line (lambda = 3.374 nm) from a laser plasma source was verified.
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| 13. |
- Hansson, Björn A. M., et al.
(författare)
-
Improved emission uniformity from a liquid-jet laser-plasma extreme-ultraviolet source
- 2004
-
Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 43:29, s. 5452-5457
-
Tidskriftsartikel (refereegranskat)abstract
- Many modern compact soft-x-ray and extreme-ultraviolet (EUV) imaging systems operate with small fields of view and therefore benefit from the use of small high-brightness sources. Such systems include water-window microscopes and ELTV lithography tools. We show that the photon losses in such systems can be minimized while uniformity of object-plane illumination is maintained by controlled scanning of the source. The improved collection efficiency is demonstrated both theoretically and experimentally for a scanned laser-plasma source compared with static sources. A prospective aerial image microscope and a liquid-xenon-jet laser-plasma source are offered as examples of modem imaging tools that may benefit from such scanning of the source.
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| 14. |
- Hansson, B. A. M., et al.
(författare)
-
Liquid-jet laser-plasma extreme ultraviolet sources : from droplets to filaments
- 2004
-
Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 37:23, s. 3233-3243
-
Tidskriftsartikel (refereegranskat)abstract
- The laser plasma is one of the major contenders as a high-power source for future high-volume-manufacturing extreme ultraviolet lithography systems. Such laser-plasma sources require a target system that allows high-repetition-rate operation with low debris and manageable thermal load at the required high laser power. In this paper, we review the development of the liquid-jet target laser plasmas, from droplets to filaments, with special emphasis on its applicability for high-power extreme ultraviolet generation. We focus on two target systems, the liquid-xenon-jet and the liquid-tin-jet.
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| 15. |
- Hansson, B. A. M., et al.
(författare)
-
Liquid-xenon-jet LPP source
- 2006
-
Ingår i: EUV Sources for Lithography. - : SPIE - International Society for Optical Engineering. - 9780819480712 ; , s. 619-647
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 16. |
- Johansson, G. A., et al.
(författare)
-
Compact soft x-ray reflectometer based on a line-emitting laser-plasma source
- 2001
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 72:1, s. 58-62
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a compact soft x-ray reflectometer for in-house characterization of water-window multilayer optics. The instrument is based on a line-emitting, liquid-jet, laser-plasma source in combination with angular scanning of the studied multilayer optics. With a proper choice of target liquid and thin-film filters, one or a few lines of well-defined wavelength dominate the spectrum and multilayer periods are measured with an accuracy of 0.003 nm using a multi-line calibration procedure. Absolute reflectivity may also be estimated with the instrument. The typical measurement time is currently 10 min. Although the principles of the reflectometer may be used in the entire soft x-ray and extreme ultraviolet range, the current instrument is primarily directed towards normal-incidence multilayer optics for water-window x-ray microscopy, and is thus demonstrated on W/B4C multilayers for this wavelength range.
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| 17. |
- Larsson, Daniel H., et al.
(författare)
-
Small-animal tomography with a liquid-metal-jet x-ray source
- 2012
-
Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE - International Society for Optical Engineering. - 9780819489623 ; , s. 83130N-
-
Konferensbidrag (refereegranskat)abstract
- X-ray tomography of small animals is an important tool for medical research. For high-resolution x-ray imaging of few-cm-thick samples such as, e.g., mice, high-brightness x-ray sources with energies in the few-10-keV range are required. In this paper we perform the first small-animal imaging and tomography experiments using liquid-metal-jet-anode x-ray sources. This type of source shows promise to increase the brightness of microfocus x-ray systems, but present sources are typically optimized for an energy of 9 keV. Here we describe the details of a high-brightness 24-keV electron-impact laboratory microfocus x-ray source based on continuous operation of a heated liquid-In/Ga-jet anode. The source normally operates with 40 W of electron-beam power focused onto the metal jet, producing a 7×7 μm 2 FWHM x-ray spot. The peak spectral brightness is 4 × 10 9 photons/( s × mm 2 × mrad 2 × 0.1%BW) at the 24.2 keV In K α line. We use the new In/Ga source and an existing Ga/In/Sn source for high-resolution imaging and tomography of mice.
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| 18. |
- Thuering, T., et al.
(författare)
-
X-ray grating interferometry with a liquid-metal-jet source
- 2013
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 103:9, s. 091105-
-
Tidskriftsartikel (refereegranskat)abstract
- A liquid-metal-jet X-ray tube is used in an X-ray phase-contrast microscope based on a Talbot type grating interferometer. With a focal spot size in the range of a few microns and a photon flux of similar to 10(12) photons/s x sr, the brightness of such a source is approximately one order of magnitude higher than for a conventional microfocus source. For comparison, a standard microfocus source was used with the same grating interferometer, showing significantly increased visibility for the liquid-metal-jet arrangement. Together with the increased flux, this results in improved signal-to-noise ratio.
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| 19. |
- Tuohimaa, Tomi, et al.
(författare)
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A microfocus x-ray source based on a nonmetal liquid-jet anode
- 2008
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:23, s. 233509-1-233509-3
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate stable operation of a nonmetallic anode in an electron-impact x-ray source. A high-brightness electron beam is focused on a similar to 70 m/s speed, similar to 10 mu m diameter methanol jet producing stable x-ray emission with peak spectral brightness at similar to 5.4 x 10(5) photons/(s x mu m(2) x sr x 0.1% BW). The jet is fully evaporated in the interaction point. The shape of a simulated spectrum using Monte Carlo methods shows good agreement with experimental data, and the theoretical brightness values give an upper limit for the achievable x-ray emission from jets with very high velocities. Using this anode concept, all compounds and elements found in liquid form are potentially usable for x-ray generation.
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| 20. |
- Vogt, Ulrich, et al.
(författare)
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Towards Soft X-Ray Phase-Sensitive Imaging with Diffractive Optical Elements
- 2006
-
Ingår i: Proc. 8th International Conference X-ray Microscopy. ; , s. 91-93
-
Konferensbidrag (refereegranskat)abstract
- In this contribution we present the first diffractive optical elements for soft x-ray differential interference contrast microscopy.Due to an improved calculation method the nanofabrication accuracy of these optics is the same as for comparable normal zoneplate optics with the same outermost zone width. Different diffractive optical elements were fabricated with outermost zone widthof 100 nm, different spot separation directions and different phase relations between the two spots. The optics were successfullyused in experiments both at the synchrotron radiation based TWINMIC microscope and at the Stockholm compact liquid-nitrogenlaser-plasma source based microscope.
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| 21. |
- Wiklund, Martin, et al.
(författare)
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Ultrasonic enrichment of microspheres for ultrasensitive biomedical analysis in confocal laser-scanning fluorescence detection
- 2004
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:2, s. 1242-1248
-
Tidskriftsartikel (refereegranskat)abstract
- An ultrasonic particle concentrator based on a standing-wave hemispherical resonator is combined with confocal laser-scanning fluorescence detection. The goal is to perform ultrasensitive biomedical analysis by concentration of biologically active microspheres. The standing-wave resonator consists of a 4 MHz focusing ultrasonic transducer combined with the optically transparent plastic bottom of a disposable 96-well microplate platform. The ultrasonic particle concentrator collects suspended microspheres into dense, single-layer aggregates at well-defined positions in the sample vessel of the microplate, and the fluorescence from the aggregates is detected by the confocal laser-scanning system. The biochemical properties of the system are investigated using a microsphere-based human thyroid stimulating hormone assay.
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| 22. |
- Wiklund, Martin, et al.
(författare)
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Ultrasonic standing wave manipulation technology integrated into a dielectrophoretic chip
- 2006
-
Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 6:12, s. 1537-1544
-
Tidskriftsartikel (refereegranskat)abstract
- Several cell-based biological applications in microfluidic systems require simultaneous high-throughput and individual handling of cells or other bioparticles. Available chip-based tools for contactless manipulation are designed for either high-precision handling of individual particles, or high-throughput handling of ensembles of particles. In order to simultaneously perform both, we have combined two manipulation technologies based on ultrasonic standing waves (USWs) and dielectrophoresis (DEP) in a microfluidic chip. The principle is based on the competition between long-range ultrasonic forces, short-range dielcctrophoretic forces and viscous drag forces from the fluid flow. The ultrasound is coupled into the microchannel resonator by an external transducer with a refractive element placed on top of the chip, thereby allowing transmission light microscopy to continuously monitor the biological process. The DEP manipulation is generated by an electric field between co-planar microelectrodes placed on the bottom surface of the fluid channel. We demonstrate flexible and gentle elementary manipulation functions by the use of USWs and linear or curved DEP deflector elements that can be used in high-throughput biotechnology applications of individual cells.
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| 23. |
- Zanette, I., et al.
(författare)
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Speckle-Based X-Ray Phase-Contrast and Dark-Field Imaging with a Laboratory Source
- 2014
-
Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 112:25, s. 253903-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the observation and application of near-field speckles with a laboratory x-ray source. The detection of speckles is possible thanks to the enhanced brilliance properties of the used liquid-metal-jet source, and opens the way to a range of new applications in laboratory-based coherent x-ray imaging. Here, we use the speckle pattern for multimodal imaging of demonstrator objects. Moreover, we introduce algorithms for phase and dark-field imaging using speckle tracking, and we show that they yield superior results with respect to existing methods.
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| 24. |
- Zanette, I., et al.
(författare)
-
X-ray microtomography using correlation of near-field speckles for material characterization
- 2015
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:41, s. 12569-12573
-
Tidskriftsartikel (refereegranskat)abstract
- Nondestructive microscale investigation of objects is an invaluable tool in life and materials sciences. Currently, such investigation is mainly performed with X-ray laboratory systems, which are based on absorption-contrast imaging and cannot access the information carried by the phase of the X-ray waves. The phase signal is, nevertheless, of great value in X-ray imaging as it is complementary to the absorption information and in general more sensitive to visualize features with small density differences. Synchrotron facilities, which deliver a beam of high brilliance and high coherence, provide the ideal condition to develop such advanced phase-sensitive methods, but their access is limited. Here we show how a small modification of a laboratory setup yields simultaneously quantitative and 3D absorption and phase images of the object. This single-shot method is based on correlation of X-ray near-field speckles and represents a significant broadening of the capabilities of laboratory- based X-ray tomography.
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| 25. |
- Zhou, Tunhe, et al.
(författare)
-
Comparison of propagation-and grating-based x-ray phase-contrast imaging techniques with a liquid-metal-jet source
- 2014
-
Ingår i: Medical Imaging 2014. - : SPIE - International Society for Optical Engineering. - 9780819498267 ; , s. 903353-
-
Konferensbidrag (refereegranskat)abstract
- X-ray phase-contrast imaging has been developed as an alternative to conventional absorption imaging, partly for its dose advantage over absorption imaging at high resolution. Grating-based imaging (GBI) and propagation-based imaging (PBI) are two phase-contrast techniques used with polychromatic laboratory sources. We compare the two methods by experiments and simulations with respect to required dose. A simulation method based on the projection approximation is designed and verified with experiments. A comparison based on simulations of the doses required for detection of an object with respect to its diameter is presented, showing that for monochromatic radiation, there is a dose advantage for PBI for small features but an advantage for GBI at larger features. However, GBI suffers more from the introduction of polychromatic radiation, in this case so much that PBI gives lower dose for all investigated feature sizes. Furthermore, we present and compare experimental images of biomedical samples. While those support the dose advantage of PBI, they also highlight the GBI advantage of quantitative reconstruction of multimaterial samples. For all experiments a liquid-metal-jet source was used. Liquid-metal-jet sources are a promising option for laboratory-based phase-contrast imaging due to the relatively high brightness and small spot size.
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| 26. |
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| 27. |
- Bertilson, Michael C., et al.
(författare)
-
Zone plate efficiency measurements with a laser-plasma source
- 2007
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Ingår i: Advances in X-Ray/EUV Optics and Components II. - : SPIE. - 9780819468536 ; , s. F7050-F7050
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate a compact instrument for rapid and accurate measurements of the absolute and local efficiency of soft x-ray zone plates in the water window [M. Bertilson, et al, Rev. Sci. Instrum 78, 026103 (2007)]. The arrangement is based on a new single-line lambda = 2.88 nm liquid-nitrogen-jet laser-plasma source. The versatility of the instrument enables micro and condenser zone plates with focal lengths in the range from similar to 200 mu m to similar to 100 mm to be measured. We demonstrate an accurate local efficiency map of a in-house fabricated micro zone plate. Furthermore, we show how this compact instrument allows rapid feedback to the fabrication process which is important for future improvements.
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| 28. |
- Bertilson, Michael, et al.
(författare)
-
Compact high-resolution differential interference contrast soft x-ray microscopy
- 2008
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:064104
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 29. |
- Bertilson, Michael, et al.
(författare)
-
High-resolution computed tomography with a compact soft x-ray microscope
- 2009
-
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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| 30. |
- Bertilson, Michael, et al.
(författare)
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Laboratory Soft X-Ray Cryo Tomography
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- X-rays allow quantitative high-spatial-resolution three-dimensional (3D) imaging of intact unstained cells. Such 3D imaging is provided by soft x-ray lens-based methods (water-window cryo tomography) and hard x-ray lens-less methods (coherent diffraction imaging) are emerging. However, both methods rely on high-brightness synchrotron-radiation sources, which limit the accessibility of a wider scientific community. Here we show 3D water-window cryo tomography with a laboratory-source-based microscope arrangement. The system relies on a λ=2.48-nm liquid-jet laser-plasma source, normal- incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate imaging of intact unstained yeast, protozoan parasites and mammalian cells. 3D images show noise-limited features close to ~100 nm and intra-cellular structure is classified based on the local absorption coefficient. A comprehensive theoretical model of the tomographic imaging system allows optimization of system parameters and a quantitative estimate of the 3D imaging accuracy. The model includes issues such as non-geometric projections of the thick samples and stray light, and is applicable to laboratory as well as synchrotron-based x-ray microscopes. The model shows that laboratory x-ray cryo tomography will allow quantitative 3D imaging with ~30-nm (half-period) resolution over a full 5 µm object.
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| 31. |
- Bertilson, Michael, et al.
(författare)
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Laboratory soft-x-ray microscope for cryotomography of biological specimens
- 2011
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 36:14, s. 2728-2730
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Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a lambda = 2.48nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to similar to 100nm.
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| 32. |
- 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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| 33. |
- Birch, Jens, et al.
(författare)
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Recent advances in ion-assisted growth of Cr/Sc multilayer X-ray mirrors for the water window
- 2002
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 68:3, s. 275-282
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Tidskriftsartikel (refereegranskat)abstract
- Cr/Sc multilayer X-ray mirrors intended for normal incidence reflection in the water window wavelength range, lambda=[2.4-4.4 nm], have been grown by ion-assisted sputter deposition and characterized using soft and hard X-ray reflectivity. By extracting low-energy ions, with energies, E-ion, ranging from 9 to 113 eV and with ion-to-metal flux ratios, Phi, between 0.76 and 23.1, from the sputtering plasma to the growing film, the nano-structure of the multilayer interfaces could be modified. A significantly increased soft X-ray reflectivity, using lambda = 3.374 nm, for Cr/Sc multilayers with layer thicknesses in the range 0.4-2.8 nm, was obtained when high ion-to-metal flux ratios, Phi(Cr) = 7.1 and Phi(Sc) = 23.1, and low energy ions, E-ion = 9eV, were used. An experimental reflectivity of 5.5% was obtained at 76degrees for a multilayer with 400 bi-layers. Simulations of the reflectivity data showed that the interface widths are < 0.425 nm. It could be concluded that roughness of low spatial frequency is reduced at lower ion energies than the high spatial frequency which was eliminated at the expense of intermixing at the interfaces at higher ion energies. The predicted performance of normal incidence multilayer mirrors grown at optimum conditions and designed for lambda = 3.374 and 3.115 nm indicates possible reflectivities of 6.5% and 14%, respectively.
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| 34. |
- Burvall, Anna, et al.
(författare)
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Phase retrieval in X-ray phase-contrast imaging suitable for tomography
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:11, s. 10359-10376
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Tidskriftsartikel (refereegranskat)abstract
- In-line phase-contrast X-ray imaging provides images where both absorption and refraction contribute. For quantitative analysis of these images, the phase needs to be retrieved numerically. There are many phase-retrieval methods available. Those suitable for phase-contrast tomography, i.e., non-iterative phase-retrieval methods that use only one image at each projection angle, all follow the same pattern though derived in different ways. We outline this pattern and use it to compare the methods to each other, considering only phase-retrieval performance and not the additional effects of tomographic reconstruction. We also outline derivations, approximations and assumptions, and show which methods are similar or identical and how they relate to each other. A simple scheme for choosing reconstruction method is presented, and numerical phase-retrieval performed for all methods.
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| 35. |
- Burvall, Anna, et al.
(författare)
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Phase-retrieval methods with applications in composite-material tomography
- 2013
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Ingår i: 11th International Conference On X-Ray Microscopy (XRM2012). - : Institute of Physics Publishing (IOPP). ; , s. 012015-
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Konferensbidrag (refereegranskat)abstract
- In-line phase-contrast x-ray imaging is emerging as a method for observing small details when the contrast in absorption x-ray imaging is low. It gives images with strong edge enhancement, and phase retrieval is necessary to obtain quantitative thickness information. In particular for tomography, clarity can be enhanced by phase retrieval, as here demonstrated on a 3D-weave reinforced composite material. Seven suitable phase-retrieval methods are identified and integrated into a single method, where each version is marked by variations in particular steps. The general method and its variations are outlined and a comparison shows which methods are most suitable in different situations.
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| 36. |
- Chubarova, Elena, et al.
(författare)
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Platinum zone plates for hard X-ray applications
- 2011
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 88:10, s. 3123-3126
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Tidskriftsartikel (refereegranskat)abstract
- We describe the fabrication and evaluation of platinum zone plates for 5–12 kV X-ray imaging and focusing. These nano-scale circular periodic structures are fabricated by filling an e-beam generated mold with Pt in an electroplating process. The plating recipe is described. The resulting zone plates, having outer zone widths of 100 and 50 nm, show good uniformity and high aspect ratio. Their diffraction efficiencies are 50–70% of the theoretical, as measured at the European Synchrotron Radiation Facility. Platinum shows promise to become an attractive alternative to present hard X-ray zone plate materials due to its nano-structuring properties and the potential for zone-plate operation at higher temperatures.
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| 37. |
- de Groot, J., et al.
(författare)
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Capillary nozzles for liquid-jet laser-plasma x-ray sources
- 2003
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 74:8, s. 3881-3882
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Tidskriftsartikel (refereegranskat)abstract
- We describe a method to fabricate tapered glass nozzles suitable for liquid-jet-target generation in laser-plasma soft x-ray and extreme ultraviolet sources. In the method, a tapered nozzle is formed as an integral part of a flexible capillary glass tubing. The method makes use of inert materials, extending the possible choice of target liquids compared to current nozzles. It also provides flexibility as regards nozzle diameter and pressure, thereby allowing optimization of the target size and extending the range of applicability for the liquid-jet-target laser plasmas.
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| 38. |
- de Groot, J., et al.
(författare)
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Improved liquid-jet laser-plasma source for X-ray microscopy
- 2003
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 104, s. 121-122
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Tidskriftsartikel (refereegranskat)abstract
- We increase the x-ray flux from a liquid-jet laser-plasma x-ray source by optimizing the target geometry. A new nozzle fabrication method allows us to produce stable microscopic liquid jets with a wide range of diameters. The improved x-ray flux is demonstrated by optimizing the diameter of an ethanol liquid-jet for our 3 ns, square=532 nm Nd:YAG laser and measuring the flux at the square=3.37 rim C VI emission line. Preliminary data suggest that the x-ray flux can be increased by more than a factor of 4 compared to previous experiments. The goal is to significantly reduce the exposure time of our laser-plasma-based compact x-ray microscope by improving the source.
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| 39. |
- de Groot, J., et al.
(författare)
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Target optimization of a water-window liquid-jet laser-plasma source
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 94:6, s. 3717-3721
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Tidskriftsartikel (refereegranskat)abstract
- We optimize the water-window x-ray flux and debris deposition for a liquid-jet laser plasma source by varying both the target diameter and the jet material. For two target liquids, methanol and ethanol, measurements of the lambda = 3.37 nm C vi x-ray flux and the debris deposition rates are presented as function of the jet diameter. It is shown that the effective carbon debris deposition is more than I order of magnitude smaller for methanol, while the x-ray flux is reduced only similar to40%. The reduction in carbon debris deposition may be explained by reactive ion etching by oxygen from the plasma. Thus, the methanol water-window source may be operated at a 5-10X higher flux without increasing the debris deposition. The optimization potentially allows a reduction of the exposure time of compact soft x-ray microscopy or other water-window applications based on such sources without increasing damage to sensitive x-ray optics.
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| 40. |
- Eriksson, Fredrik, et al.
(författare)
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Enhanced soft x-ray reflectivity of Cr/Sc multilayers by ion-assisted sputter deposition
- 2002
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Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 41:11, s. 2903-2909
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Tidskriftsartikel (refereegranskat)abstract
- Cr/Sc multilayers have been grown on Si substrates using dc magnetron sputtering. The multilayers are intended as condenser mirrors in a soft x-ray microscope operating at the wavelength 3.374 nm. They were designed for normal reflection of the first and second orders, with multilayer periods of 1.692 and 3.381 nm, and layer thickness ratios of 0,471 and 0.237, respectively. At-wavelength soft-x-ray reflectivity measurements were carried out using a reflectometer with a compact soft-x-ray laser-plasma source. The multilayers were irradiated during growth with Ar ions, varying both in energy (9 to 113 eV) and flux, in order to stimulate the adatom mobility and improve the interface flatness. It was found that to obtain a maximum soft x-ray reflectivity with a low flux (Cr=0.76, Sc=2.5) of Ar ions a rather high energy of 53 eV was required, Such energy also caused intermixing of the layers. By the use of a solenoid surrounding the substrate, the arriving ion-to-metal flux ratio could be increased 10 times and the required ion energy could be decreased. A high flux (Cr=7.1, Sc=23.1) of low-energy (9 eV) Ar ions yielded the most favorable growth condition, limiting the intermixing with a subsistent good surface flatness.
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| 41. |
- Fogelqvist, Emelie, et al.
(författare)
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Stability of liquid-nitrogen-jet laser-plasma targets
- 2015
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 118:17
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Tidskriftsartikel (refereegranskat)abstract
- Microscopic jets of cryogenic substances such as liquid nitrogen are important regenerative high-density targets for high-repetition rate, high-brightness laser-plasma soft x-ray sources. When operated in vacuum such liquid jets exhibit several non-classical instabilities that negatively influence the x-ray source's spatial and temporal stability, yield, and brightness, parameters that all are important for applications such as water-window microscopy. In the present paper, we investigate liquid-nitrogen jets with a flash-illumination imaging system that allows for a quantitative stability analysis with high spatial and temporal resolution. Direct and indirect consequences of evaporation are identified as the key reasons for the observed instabilities. Operating the jets in an approximately 100 mbar ambient atmosphere counteracts the effects of evaporation and produces highly stable liquid nitrogen jets. For operation in vacuum, which is necessary for the laser plasmas, we improve the stability by introducing an external radiative heating element. The method significantly extends the distance from the nozzle that can be used for liquid-jet laser plasmas, which is of importance for high-average-power applications. Finally, we show that laser-plasma operation with the heating-element-stabilized jet shows improved short-term and long-term temporal stability in its water-window x-ray emission.
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| 42. |
- Fogelqvist, Emelie, et al.
(författare)
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The Stockholm laboratory cryo x-ray microscope : towards cell-cell interaction studies
- 2013
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Ingår i: 11th International Conference On X-Ray Microscopy (XRM2012). - : Institute of Physics (IOP). ; , s. 012054-
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Konferensbidrag (refereegranskat)abstract
- We describe recent improvements in the Stockholm laboratory x-ray microscope and the first experiments aiming towards studies of cell-cell interaction. The shorter exposure time due to a higher brightness laser-plasma source will become of large importance for tomography while the reproducible cryo preparation of few-cell samples is essential for the interaction studies.
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| 43. |
- Hansson, Björn, et al.
(författare)
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Stabilization of liquified-inert-gas jets for laser-plasma generation
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:8, s. 4432-4437
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the hydrodynamic properties of liquified-inert-gas jets in a vacuum with a special emphasis on their stability. Such jets have applications as targets for laser-plasma generation of soft-x-ray and extreme-ultraviolet (EUV) radiation. An important example is the liquid-xenon-jet laser-plasma source, one of the source candidates for EUV lithography. A simple hydrodynamic model in not sufficient to explain experimental observations of jet stability. Evaporation-induced cooling explains observed in-flight freezing of the jet and may be a key factor influencing jet stability. It is shown how the jet stability, and, thus, the stability of the laser-plasma x-ray and EUV emission, are improved by applying localized heating to the tip of the jet-generating nozzle.
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| 44. |
- Hemberg, Oskar, et al.
(författare)
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A Liquid-Metal-Jet Anode X-Ray Tube
- 2004
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Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 43:7, s. 1682-1688
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Tidskriftsartikel (refereegranskat)abstract
- We describe a novel electron-impact x-ray source based on a high-speed liquid-metal-jet anode. Thermal power load calculations indicate that this new anode concept potentially could increase the achievable brightness in compact electron-impact x-ray sources by more than a factor 100 compared to current state-of-the-art rotating-anode or microfocus sources. A first, successful, low-power proof-of-principle experiment is described and the feasibility of scaling to high-brightness and high-power operation is discussed. Some possible applications that would benefit from such an increase in brightness are also briefly
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| 45. |
- Hemberg, Oscar, et al.
(författare)
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High-brightness liquid-metal-jet x-ray tube
- 2011
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Ingår i: Acta Crystallographica Section A. - : International Union of Crystallography. - 2053-2733. ; 67, s. C257-C257
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 46. |
- Hemberg, Oscar, et al.
(författare)
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The liquid-metal-jet anode x-ray source
- 2004
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Ingår i: Proceedings of The International Society for Optical Engineering. - : SPIE. ; , s. 421-431
-
Konferensbidrag (refereegranskat)abstract
- We introduce a novel electron-impact x-ray source based on a high-speed liquid-metal-jet anode. Basic thermal power load calculations indicate that this new anode concept potentially could increase the achievable brightness in compact electron-impact x-ray sources by more than a factor 100 compared to current state-of-the-art rotating-anode or microfocus sources. A first, successful, low-power proof-of-principle experiment is described and the feasibility of scaling to high-brightness and high-power operation is discussed. Some possible applications that would benefit from such an increase in brightness are also briefly described.
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| 47. |
- Hertz, Hans M., et al.
(författare)
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Laboratory x-ray fluorescence tomography for high-resolution nanoparticle bio-imaging
- 2014
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 39:9, s. 2790-2793
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that nanoparticle x-ray fluorescence computed tomography in mouse-sized objects can be performed with very high spatial resolution at acceptable dose and exposure times with a compact laboratory system. The method relies on the combination of the 24 keV line-emission from a high-brightness liquid-metal-jet x-ray source, pencil-beam-forming x-ray optics, photon-counting energy-dispersive detection, and carefully matched (Mo) nanoparticles. Phantom experiments and simulations show that the arrangement significantly reduces Compton background and allows 100 mu m detail imaging at dose and exposure times compatible with small-animal experiments. The method provides a possible path to in vivo molecular x-ray imaging at sub-100 mu m resolution in mice.
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| 48. |
- Hertz, Hans M., et al.
(författare)
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Laboratory X-ray micro- and nano-imaging
- 2009
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Ingår i: Frontiers in Optics (FiO) 2009. - Washington, D.C. : Optical Society of America. - 9781557528780
-
Konferensbidrag (refereegranskat)abstract
- We summarize recent progress in laboratory x-ray imaging systems based on compact high-brightness liquid-jet sources, including <25 nm soft x-ray zone-plate microscopy and <10 μm (lens-free) hard x-ray phase-contrast imaging.
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| 49. |
- Hertz, Hans M., et al.
(författare)
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Laboratory X-ray microscopy for high-resolution imaging of environmental colloid structure
- 2012
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Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 329:SI, s. 26-31
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 50. |
- Hertz, Hans M., et al.
(författare)
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Propagation-based phase-contrast imaging with laboratory sources
- 2016
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Ingår i: Optics InfoBase Conference Papers. - Washington, D.C. : OSA - The Optical Society. - 9781943580095
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Konferensbidrag (refereegranskat)abstract
- We demonstrate that propagation-based phase-contrast x-ray imaging with state-of-the art laboratory microfocus sources allows imaging of thick biomedical objects with very high spatial resolution.
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