| 1. |
- Cederström, Björn, 1973-
(författare)
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A multi-prism lens for hard X-Rays
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes a new type of refractive lens for hardx-rays. It is shown that a linear array of prisms, slightlyinclined with respect to the optical axis, will form a linefocus at a certain distance from the lens. Hence, the namemulti-prism lens. These lenses are free from sphericalaberration and are similar to planar parabolic compoundrefractive lenses in terms of performance. However, theydistinguish themselves in that only planar surfaces need to befabricated. A special feature is that the focal length can beeasily varied by adjusting the inclination angle. Theoretical calculations, based on geometrical and physicaloptics, are used to characterize the lenses. Aberrations arediscussed, as well as the sensitivity to fabricationimperfections, and insufficient flatness is identified as apotential problem. Ray-tracing is used to test theapproximations and assumptions used in the theory. Applicationsin x-ray microscopy and mammography are discussed. Lenses have been made of beryllium, silicon, epoxy anddiamond using different methods. Results from measurements ofsurface roughness and figure error show that the imperfectionsof the silicon and epoxy lenses should have a small impact,while the beryllium lenses should suffer from strongscattering. Experiments were performed at the EuropeanSynchrotron Radiation Facility and sub-µm focal linewidths, close to theoretical expectations, were measured forsilicon and epoxy lenses at 30 keV and 14 keV, respectively.Insertion gains up to 40 were reached. Two crossed lenses wereused to obtain focusing in two dimensions and a point focus.The smallest measured focal spot size was 1.0 µm by 5 .4µm, and an insertion gain exceeding 100 was achieved usingepoxy lenses. The diamond lenses suffered from voids in the materialformed in the chemical vapor deposition process, butnevertheless provided focal lines less than 2 µm in width,albeit at at relatively low insertion gain of 13. Due to theirexcellent thermal properties, these lenses are put forward ascandidates for optics at the next generationultra-high-intensity synchrotron beams and x-ray free electronlasers. Keywords:x-ray, optics, refractive, lens, mammography,synchrotron.
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| 2. |
- Cederström, Björn, et al.
(författare)
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Focusing hard X-rays with old LPs
- 2000
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 404:6781, s. 951-951
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Cederström, Björn, 1973-, et al.
(författare)
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Multi-prism x-ray lens
- 2002
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 81:8, s. 1399-1401
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Tidskriftsartikel (refereegranskat)abstract
- Refractive x-ray lenses with a triangular surface profile have been used to focus a synchrotron beam to sub-mum line width. These lenses are free from spherical aberration and work in analogy with one-dimensional focusing parabolic compound refractive lenses. However, the focal length can be easily varied by changing the gap between the two jaws. Silicon lenses were fabricated by wet anisotropic etching, and epoxy replicas were molded from the silicon masters. The lenses provided intensity gains up to a factor of 32 and the smallest focal line width was 0.87 mum. The simplified geometry and associated fabrication technique open possibilities for low-Z materials such as beryllium, which should greatly enhance the performance of refractive x-ray optics. (C) 2002 American Institute of Physics.
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| 4. |
- Cederström, Björn
(författare)
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Refractive lens for x-rays, contains sawtooth shaped grooves for x-rays to pass through as they enter one end of lens and exit opposite end
- 2001
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Patent (populärvet., debatt m.m.)abstract
- The lens contains sawtooth-shaped grooves (103, 104) located between the two ends of the lens in at least two surfaces. A refractive device for x-rays comprises a low Z-material part (101) with one end (105) for receiving x-rays from an x-ray source, and an opposite end (106) for these x-rays to exit from. The device also includes a number of essentially sawtooth-shaped grooves located between the two ends in at least two surfaces. The grooves are arranged so that x-rays entering the device will have to pass through them as they travel between the two ends of the device, after which they are focused to a refraction point. Independent claims are also included for (a) a lens containing this refractive device, (b) an x-ray system for two-dimensional focusing of x-rays and including at least two of these lenses, each x-ray beam intersecting the two lenses one after the other, and at least one lens being rotated about an optical axis relative to the other lens, (c) a method for two-dimensional focusing using these lenses, (d) a method for obtaining a bimodal energy distribution from an x-ray source using this lens, (e) a method for making a refractive x-ray lens with a sawtooth profile by engraving the profiles in a substrate, processing an original piece and using the original to press grooves into a suitable material.
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| 5. |
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| 6. |
- Cederström, Björn
(författare)
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Refractive X-ray arrangement
- 2003
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Patent (populärvet., debatt m.m.)abstract
- The present invention refers to a refractive arrangement for X-rays, and specially to a lens comprising: a member of low-Z material, said member of low-Z material having a first end adapted to receive x-rays emitted from an x-ray source and a second end from which emerge said x-rays received at said first end. It further comprises a plurality of substantially saw-tooth formed grooves disposed between said first and second ends, said plurality of grooves oriented such that said x-rays which are received at said first end, pass through said member of low-Z material and said plurality of grooves, and emerge from said second end, are refracted to a focal point.
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| 7. |
- Lundqvist, M., et al.
(författare)
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Computer simulations and performance measurements on a silicon strip detector for edge-on imaging
- 2000
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 47:4, s. 1487-1492
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Tidskriftsartikel (refereegranskat)abstract
- Silicon strip detectors to be used edge-on for imaging in a scanned slit geometry have been simulated. A software program was developed which can simulate the motion of free charges in the bulk detector and calculate the signals they induce on the electrodes. The purpose was to quantify the impact of charge sharing on system detective quantum efficiency(DQE). The energy spectrum that was used in this study is typical for mammography. The detectors are working in single photon counting mode and the optimal threshold level to discriminate noise from useful signals has been calculated. The loss in detective quantum efficiency due to charge sharing was found to be around 5% for a 100 mu m pitched detector. Coincidence circuits can be included in the electronics to eliminate this problem. Furthermore, it is described how the relationship between charge collection efficiency and photon interaction position in the detector can be measured.
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| 8. |
- Lundqvist, M., et al.
(författare)
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Evaluation of a photon-counting X-ray imaging system
- 2001
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 48:4, s. 1530-1536
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Tidskriftsartikel (refereegranskat)abstract
- A digital imaging system has been developed for mammography using silicon strip detectors operated in a pulse-counting mode and configured in a scanned slit geometry. More than 90% of the photons are absorbed in the sensor. The scatter rejection is very efficient and the image formation is nearly optimal since each X ray is processed individually. The result is a very dose-efficient system. In this paper, we present measurements that verify that the performance of the readout electronics is sufficient to count photons at high rates with high quantum efficiency and a charge collection efficiency that does not limit the dose efficiency. The spatial resolution of the system was measured to provide a modulation transfer function of approximately 0.5 at a spatial frequency of 10 lp/mm. Images of a mammography phantom were recorded experimentally to test overall system performance.
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| 9. |
- Ribbing, C., et al.
(författare)
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Microfabrication of saw-tooth refractive x-ray lenses in low-Z materials
- 2003
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 13:5, s. 714-720
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Tidskriftsartikel (refereegranskat)abstract
- Saw-tooth x-ray refractive lenses have been fabricated in silicon, epoxy and diamond. Silicon lenses were made by anisotropic wet etching of single crystalline silicon. Epoxy lenses were moulded from silicon masters. Diamond lenses were replicated by. chemical vapour deposition on silicon masters and subsequent sacrificial etching of silicon. Beryllium saw-tooth test structures were embossed using a diamond master. Silicon and epoxy lenses gave sub-micron focal lines and provided gains of up to 40 when tested in a synchrotron set-up. Focal lengths ranged from 0.33 to 0.61 m for x-ray energies between 14 and 30 keV.
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| 10. |
- Ribbing, C., et al.
(författare)
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Microstructured diamond X-ray source and refractive lens
- 2003
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Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 12:11-okt, s. 1793-1799
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Tidskriftsartikel (refereegranskat)abstract
- This paper treats microstructured CVD diamond in two X-ray applications, a miniature X-ray source and a refractive X-ray lens. The X-ray source consists of boron doped diamond membrane electrodes and an intermediate insulator. The cathode has a pyramidal shape, which is field-emitting and the anode is a metal film on a diamond membrane. Anode radiation emerges through both membrane electrodes. The source has not been vacuum sealed, therefore, all measurements so far have been made in a vacuum chamber. The refractive X-ray lens has saw-tooth geometry and a tunable focal length. It was made by microwave plasma assisted CVD of diamond onto anisotropically etched silicon masters. The lens has been used for one-dimensional focusing of a synchrotron beam to 1.9 mum line width.
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