| 1. |
- 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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| 2. |
- 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
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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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| 3. |
- Hertz, Hans M., et al.
(författare)
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Laboratory x-ray micro imaging : Sources, optics, systems and applications
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
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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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| 4. |
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| 5. |
- Lindblom, Magnus, et al.
(författare)
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High-resolution differential-interference-contrast x-ray zone plates : Design and Fabrication
- 2007
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 62:6-7, s. 539-543
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Tidskriftsartikel (refereegranskat)abstract
- Differential interference contrast is a potentially powerful technique for contrast enhancement in soft X-ray microscopy. We describe the design and fabrication of single-element diffractive optical elements suitable as objectives for high-resolution differential interference contrast microscopy in the water-window spectral range. A one-dimensional pattern calculation followed by an extension to two dimensions results in a pattern resolution of 1 nm, which is well below fabrication accuracy. The same fabrication process as for normal zone plates is applicable, but special care must be taken when converting the calculated pattern to a code for e-beam lithography.
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| 6. |
- Lindén, Martin, et al.
(författare)
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Force generation in small ensembles of Brownian motors
- 2006
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Ingår i: Physical Review E. - 1539-3755. ; 74:2, s. 021908-1-021908-8
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Tidskriftsartikel (refereegranskat)abstract
- The motility of certain gram-negative bacteria is mediated by retraction of type IV pili surface filaments, which are essential for infectivity. The retraction is powered by a strong molecular motor protein, PilT, producing very high forces that can exceed 150 pN. The molecular details of the motor mechanism are still largely unknown, while other features have been identified, such as the ring-shaped protein structure of the PilT motor. The surprisingly high forces generated by the PilT system motivate a model investigation of the generation of large forces in molecular motors. We propose a simple model, involving a small ensemble of motor subunits interacting through the deformations on a circular backbone with finite stiffness. The model describes the motor subunits in terms of diffusing particles in an asymmetric, time-dependent binding potential (flashing ratchet potential), roughly corresponding to the ATP hydrolysis cycle. We compute force-velocity relations in a subset of the parameter space and explore how the maximum force (stall force) is determined by stiffness, binding strength, ensemble size, and degree of asymmetry. We identify two qualitatively different regimes of operation depending on the relation between ensemble size and asymmetry. In the transition between these two regimes, the stall force depends nonlinearly on the number of motor subunits. Compared to its constituents without interactions, we find higher efficiency and qualitatively different force-velocity relations. The model captures several of the qualitative features obtained in experiments on pilus retraction forces, such as roughly constant velocity at low applied forces and insensitivity in the stall force to changes in the ATP concentration.
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| 7. |
- Otendal, Mikael, et al.
(författare)
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Microscopic High-Speed Liquid-Metal Jets in Vacuum
- 2005
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Ingår i: Experiments in Fluids. - : Springer Science and Business Media LLC. - 0723-4864 .- 1432-1114. ; 39, s. 799-804
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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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| 8. |
- Otendal, Mikael, et al.
(författare)
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Stability and debris in high-brightness liquid-metal-jet-anode microfocus x-ray sources
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:2, s. 026102-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the x-ray spot stability and the debris emission in liquid-metal-jet anode electron-impact x-ray sources operating in the 10-100 W microfocus regime. The x-ray spot size is 15-23 mu m in diameter and the electron-beam power density is up to similar to 210 kW/mm(2), an order of magnitude higher than for conventional microfocus sources. In the power range of the investigation the source is stable in terms of spot size and position. The debris emission rate increases exponentially with the applied electron-beam power but may be reduced by combining larger and faster target jets with smaller e-beam foci and by mitigation schemes. It is concluded that the investigated factors will not limit the performance and function of liquid-metal-jet-anode electron-impact microfocus sources when operating in this high-brightness regime.
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| 9. |
- Otendal, Mikael, et al.
(författare)
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Status of the liquid-metal-jet-anode electron-impact x-ray source
- 2004
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Ingår i: X-RAY SOURCES AND OPTICS. - BELLINGHAM : SPIE-INT SOC OPTICAL ENGINEERING. - 0819454753 ; , s. 57-63
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Konferensbidrag (refereegranskat)abstract
- We have demonstrated a new electron-impact hard-x-ray source based on a liquid-metal-jet anode in a proof-of-principle experiment. Initial calculations show that this new anode concept potentially allows a >100x increase in source brightness compared to today's compact hard-x-ray sources. In this paper we report on the scale up of the system to medium electron-beam power resulting in a brightness comparable to current state-of-the-art sources. The upgraded system combines a similar to20-mum diameter liquid-tin jet operating at similar to60 m/s with a 50 kV, 600 W electron beam focused to similar to150 mum FWHM. We describe the properties of the current system, experimental results, as well as a brief discussion of key issues for future high-power scaling.
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| 10. |
- Tuohimaa, Tomi, et al.
(författare)
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A microfocus x-ray source based on a nonmetal liquid-jet anode
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:23, s. 233509-1-233509-3
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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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| 11. |
- Tuohimaa, Tomi, et al.
(författare)
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High-intensity electron beam for liquid-metal-jet anode hard x-ray generation
- 2005
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5918
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Tidskriftsartikel (refereegranskat)abstract
- We report on our progress towards the experimental realization of a liquid-metal-jet-anode x-ray source with high brightness. We have previously shown that this electron-impact source has potential for very high x-ray brightness by combining small-spot high-flux operation of the electron beam with high-speed operation of the regenerative liquid-metal-jet anode. In the present paper we review the system and describe theoretical calculations for improving the 50 kV, 600 W electron-beam focussing to ∼30 μm spot size. With such a system the power density on the liquid-metal-jet would be ∼400 kW/mm 2, i.e., more than an order of magnitude higher than the power density on a state-of-the-art rotating anode.
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| 12. |
- Tuohimaa, Tomi, 1974-
(författare)
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Liquid-Jet-Target Microfocus X-Ray Sources : Electron Guns, Optics and Phase-Contrast Imaging
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This Thesis describes the development of an electron-impact microfocus x-ray source and its application for phase-contrast imaging. The source is based on a novel, liquid-jet target concept. Stable and continuous operation can be achieved at substantially higher electron-beam power densities than conventional solid target based systems. The maximum x-ray brightness can potentially be increased by a factor of 10-1000, which would provide significantly improved performance in applications such as imaging. In order to reach the high x-ray brightness, comparable performance from the electron gun is needed. A LaB6-cathode-based electron gun is analyzed in terms of achievable e-beam brightness and beam quality and is found capable to deliver power densities in the 10-100 MW/mm2 range using optimized electro-optics. A proof-of-principle microfocus source has been developed. Experiments show that the liquid-metal-jet target can be operated at more than an order of magnitude higher e-beam power densities than modern solid-metal targets. This brightness enhancement has been utilized to acquire in-line phase-contrast images of weakly absorbing objects. The source potentially enables the application of high-resolution phase-contrast x-ray imaging with short exposure times in clinics and laboratories. Different liquid-jet-target materials have been tested. The Sn-jet (Ka=25.3 keV) could be suitable for mammography, whereas the Ga-jet ((Ka=9.2 keV) may be utilized for x-ray diffraction studies. In addition, a non-metallic methanol jet has been the demonstrated in stable x-ray operation. All materials and compounds found in liquid form can, thus, potentially be used for electron-impact liquid-jet-target x-ray generation. Scaling to higher e-beam power density and x-ray brightness levels is discussed and is determined to be feasible. Potential difficulties, such as debris emission and instabilities of the x-ray emission spot, are investigated in some detail. Larger and/or faster jets could overcome the present limitations because of their inherently higher heat load capacities. Dynamic-similarity experiments show that liquid jets can in principle be operated in a stable manner at much higher speeds than previously shown.
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| 13. |
- Tuohimaa, Tomi, et al.
(författare)
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Phase-contrast x-ray imaging with a liquid-metal-jet-anode microfocus source
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:7, s. 074104-
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Tidskriftsartikel (refereegranskat)abstract
- Phase-contrast methods increase contrast, detail, and selectivity in x-ray imaging. Present compact x-ray sources do not provide the necessary spatial coherence with sufficient power to allow the laboratory-scale high-resolution phase-contrast imaging with adequate exposure times. In this letter, the authors demonstrate phase-contrast imaging with few-micron detail employing a compact similar to 6.5 mu m spot liquid-metal-jet-anode high-brightness microfocus source. The 40 W source is operated at more than ten times higher electron-beam power density than present microfocus sources and is shown to provide sufficient spatial coherence as well as scalability to high power, thereby enabling the application of phase-contrast x-ray imaging with short exposure times in clinics and laboratories.
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| 14. |
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| 15. |
- Vogt, Ulrich, et al.
(författare)
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Single-optical-element soft-x-ray interferometry with a laser-plasma x-ray source
- 2005
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 30:15, s. 2167-
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Tidskriftsartikel (refereegranskat)abstract
- We report on a compact interferometer for the water-window soft-x-ray range that is suitable for operation with laser-plasma sources. The interferometer consists of a single diffractive optical element that focuses impinging x rays to two focal spots. The light from these two secondary sources forms the interference pattern. The interferometer was operated with a liquid-nitrogen jet laser-plasma source at lambda = 2.88 nm. Scalar wave-field propagation was used to simulate the interference pattern, showing good correspondence between theoretical and experimental results. The diffractive optical element can simultaneously be used as an imaging optic, and we demonstrate soft-x-ray microscopy with interferometric contrast enhancement of a phase object.
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| 16. |
- Vogt, Ulrich, et al.
(författare)
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Towards Soft X-Ray Phase-Sensitive Imaging with Diffractive Optical Elements
- 2006
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Ingår i: Proc. 8th International Conference X-ray Microscopy. ; , s. 91-93
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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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