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Sample records for bragg diffraction

  1. Bragg diffraction of fermions at optical potentials

    International Nuclear Information System (INIS)

    This thesis describes the Bragg diffraction of ultracold fermions at an optical potential. A moving optical lattice was created, by overlaying two slightly detuned lasers. Atoms can be diffracted at this lattice if the detuning fulfills the Bragg condition for resting atoms. This Bragg diffraction is analyzed systematically in this thesis. To this end Rabi oscillations between the diffraction states were driven, as well in the weakly interacting Bragg regime, as in the strongly interacting Kapitza-Dirac regime. Simulations, based on a driven two-, respectively multilevel-system describe the observed effects rather well. Furthermore, the temporal evolution of the diffracted states in the magnetic trapping potential was studied. The anharmonicity of the trap in use and the scattering cross section for p-wave collisions in a 6Li system was determined from the movement of these states. Moreover the momentum distribution of the fermions was measured with Bragg spectroscopy and first signs of Fermi degeneracy were found. Finally an interferometer with fermions was build, exhibiting a coherence time of more than 100 μs. With this, the possibility for measurement and manipulation of ultracold fermions with Bragg diffraction could bee shown. (orig.)

  2. X-ray diffraction at Bragg angles around π/2

    International Nuclear Information System (INIS)

    X-ray diffraction at Bragg angles around π/2 is studied from the theoretical and experimental points of view. The proposed corrections to the dynamical theory in the θβ ≅ π/2 cases, has been reviewed showing the equivalence between two formalisms leading to a corrected expression for the dependence of the angular parameter y with the angle of incidence. An expression for y valid in the conventional and θ β ≅ π/2 cases has been obtained. A general expression for Bragg law and for energy resolution after a Bragg diffraction was also deduced. (author)

  3. Observation of sub-Bragg diffraction of waves in crystals

    CERN Document Server

    Huisman, Simon R; Hartsuiker, Alex; Woldering, Léon A; Mosk, Allard P; Vos, Willem L

    2011-01-01

    We investigate the diffraction conditions and associated formation of stopgaps for waves in crystals with different Bravais lattices. We identify a prominent stopgap in high-symmetry directions that occurs at a frequency below the ubiquitous first-order Bragg condition. This sub-Bragg diffraction condition is demonstrated by reflectance spectroscopy on two-dimensional photonic crystals with a centred rectangular lattice, revealing prominent diffraction peaks for both the sub-Bragg and first-order Bragg condition. These results have implications for wave propagation in 2 of the 5 two-dimensional Bravais lattices and 7 out of 14 three-dimensional Bravais lattices, such as centred rectangular, triangular, hexagonal and body-centred cubic.

  4. Holographic Bragg gratings: measurements and examination diffraction parameters

    CERN Document Server

    Tikhonov, E A

    2015-01-01

    Measurement and analysis of diffraction parameters of thick transmission holographic phase gratings recorded on PHC-488 photopolymer are presented. Precision determination of the spatial grating period is executed by Bragg angle measurement for two precisely known wavelengths in the first diffraction order and also by Bragg angle measurement on one wavelength in the first and second diffraction orders. Determination of actual grating thickness and depths of spatial modulation of a holographic recording, which are responsible for their main optical characteristics, is carried out with the application of H. Kogelnik 2-wave coupled model. Calculated and experimental Bragg angles in two orthogonal orientated planes of linear polarized laser light were used to confirm theoretical model with experimental results. Extreme values of the diffraction parameters, efficiency and spectral resolution, important for holographic phase grating applications are analyzed.

  5. Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

    Institute of Scientific and Technical Information of China (English)

    LI Lin; LI Yong-da; LIU Wen-li; LU Bin; JU Guo-xian; ZHANG Yong-ming; HAO Yong-qin; SU Wei; ZHONG Jing-chang

    2004-01-01

    Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double- crystal X- ray diffraction measurement. The expected high quality epitaxial DBR structure was verified. In the X- ray double- crystal rocking curves of DBR the zeroth- order peak, the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed. The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.

  6. Bragg diffraction and the Iron crust of Neutron Stars

    CERN Document Server

    Llanes-Estrada, Felipe J

    2009-01-01

    If neutron stars have a thin atomic crystalline-iron crust, they must diffract X-rays of appropriate wavelength. So that the diffracted beam is visible from Earth, the illuminating source must be very intense and near the reflecting star. An example is a binary system with two neutron stars, one of them inert, the other an X-ray pulsar, in close orbit. The observable to be searched for is a secondary peak added (quasi-) periodically to the main X-ray pulse. The distinguishing feature of this secondary is that it appears at wavelengths related by simple integer numbers, lambda, lambda/2, lambda/3... lambda/n because of Bragg's diffraction law.

  7. X-ray wavefront modeling of Bragg diffraction from crystals

    Science.gov (United States)

    Sutter, John P.

    2011-09-01

    The diffraction of an X-ray wavefront from a slightly distorted crystal can be modeled by the Takagi-Taupin theory, an extension of the well-known dynamical diffraction theory for perfect crystals. Maxwell's equations applied to a perturbed periodic medium yield two coupled differential equations in the incident and diffracted amplitude. These equations are discretized for numerical calculation into the determination of the two amplitudes on the points of an integration mesh, beginning with the incident amplitudes at the crystal's top surface. The result is a set of diffracted amplitudes on the top surface (in the Bragg geometry) or the bottom surface (in the Laue geometry), forming a wavefront that in turn can be propagated through free space using the Fresnel- Huygens equations. The performance of the Diamond Light Source I20 dispersive spectrometer has here been simulated using this method. Methods are shown for transforming displacements calculated by finite element analysis into local lattice distortions, and for efficiently performing 3-D linear interpolations from these onto the Takagi-Taupin integration mesh, allowing this method to be extended to crystals under thermal load or novel mechanical bender designs.

  8. Nuclear Bragg diffraction of synchrotron x-rays

    International Nuclear Information System (INIS)

    In the last few years several groups have successfully carried out experiments involving the excitation of nuclear resonances using synchrotron radiation. All the experiments so far have used 57Fe as the resonant nucleus. The extremely narrow width of the 14.4 keV resonance in 57Fe makes these experiments very difficult at even the highest-brightness synchrotron beam lines currently available, so much effort is being devoted toward improvements in equipment and techniques. The general aim of this work is to use resonant scattering to produce high-flux beams of extremely monochromatic radiation, which can then be used as source beams for a variety of experiments. This talk, however, will stress the kinds of physics questions that can be answered using broad-band synchrotron radiation to induce resonant nuclear diffraction in perfect crystal samples. Experiments of this type are being carried out today, albeit with difficulty, using present synchrotron sources. They will become technically easy when advanced sources such as the APS become available, and it is expected that nuclear Bragg diffraction will become a standard technique

  9. Bragg diffraction of fermions at optical potentials; Braggbeugung von Fermionen an optischen Potentialen

    Energy Technology Data Exchange (ETDEWEB)

    Deh, Benjamin

    2008-10-27

    This thesis describes the Bragg diffraction of ultracold fermions at an optical potential. A moving optical lattice was created, by overlaying two slightly detuned lasers. Atoms can be diffracted at this lattice if the detuning fulfills the Bragg condition for resting atoms. This Bragg diffraction is analyzed systematically in this thesis. To this end Rabi oscillations between the diffraction states were driven, as well in the weakly interacting Bragg regime, as in the strongly interacting Kapitza-Dirac regime. Simulations, based on a driven two-, respectively multilevel-system describe the observed effects rather well. Furthermore, the temporal evolution of the diffracted states in the magnetic trapping potential was studied. The anharmonicity of the trap in use and the scattering cross section for p-wave collisions in a {sup 6}Li system was determined from the movement of these states. Moreover the momentum distribution of the fermions was measured with Bragg spectroscopy and first signs of Fermi degeneracy were found. Finally an interferometer with fermions was build, exhibiting a coherence time of more than 100 {mu}s. With this, the possibility for measurement and manipulation of ultracold fermions with Bragg diffraction could bee shown. (orig.)

  10. High-Resolution Neutron Diffraction Employing Bragg Diffraction Optics - A Tool for Advanced Nondestructive Testing of Materials

    Czech Academy of Sciences Publication Activity Database

    Mikula, Pavol; Vrána, Miroslav; Mráz, L.; Karlsson, L.

    Haifa : Technion - Israel Institute of Technology, 2008, ESDA2008 59174/1-4. ISBN 0-7918-3827-7. [Biennial ASME Conference on Engineering Systems Design and Analysis (ESDA 2008). Haifa (IL), 07.07.2008-09.07.2008] R&D Projects: GA ČR(CZ) GA202/06/0601 Institutional research plan: CEZ:AV0Z10480505 Keywords : Neutron Diffraction * Bragg Diffraction Optics Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. Time-dependent Bragg diffraction and short-pulse reflection by one-dimensional photonic crystals

    CERN Document Server

    André, Jean-michel

    2015-01-01

    The time-dependence of the Bragg diffraction by one-dimensional photonic crystals and its influence on the short pulse reflection are studied in the framework of the coupled- wave theory. The indicial response of the photonic crystal is calculated and it appears that it presents a time-delay effect with a transient time conditioned by the extinction length. A numerical simulation is presented for a Bragg mirror in the x-ray domain and a pulse envelope modelled by a sine-squared shape. The potential consequences of the time-delay effect in time-dependent optics of short-pulses are emphasized.

  12. Diffraction contrast of a Bragg-Fresnel lens in white and monochromatic radiation

    International Nuclear Information System (INIS)

    Recent advances in the studies of x-ray diffraction phenomena and the technology of structures with elements up to hundreds of angstroms in size open up possibilities for fabrication of effective x-ray focusing elements with three-dimensional Fresnel zone structures, namely, Bragg-Fresnel lenses (BFL). BFL differs favorably from the Fresnel zone plate by the absence of chromatic aberrations which is due to the high spectral selectivity of Bragg reflection, triangle λ/λ∼10-4 divided by 10-5. This enables observation of focusing and image transmission in the white spectrum of synchrotron radiation (SR). 7 refs., 7 figs

  13. Bragg diffraction and the Iron crust of cold Neutron Stars

    OpenAIRE

    Llanes-Estrada, Felipe J.; Navarro, Gaspar Moreno

    2009-01-01

    If cooled-down neutron stars have a thin atomic crystalline-iron crust, they must diffract X-rays of appropriate wavelength. If the diffracted beam is to be visible from Earth, the illuminating source must be very intense and near the reflecting star. An example is a binary system composed of two neutron stars in close orbit, one of them inert, the other an X-ray pulsar (perhaps an "anomalous" X-ray pulsar or magnetar, not powered by gas absorption from the companion or surrounding space, wou...

  14. Extraction of polychromatic thermal neutrons by Bragg diffraction to use for prompt gamma neutron activation analysis

    International Nuclear Information System (INIS)

    Extraction method of thermal neutron beam by Bragg diffraction is investigated. A thermal neutron beam is used for the Prompt Gamma Neutron Activation Analysis system at HANARO, a 30 MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic beam including all orders of diffraction is obtained by setting a pair of pyrolytic graphite crystals with a Bragg angle of 45 deg. on a horizontal white beam line. Diffracted neutron flux at the sample position is calculated by considering the integrated reflectivity and mosaic spread of crystals. Due to the divergence effect, the mosaic spread of crystals is optimized to give the maximum and flat flux at the sample position. An experiment has been performed to verify the reflectivities for high order diffractions from pyrolytic graphite. When the focusing technique of bending the crystals is adopted, a design value of 1.0x108 n/cm2s is expected at the sample position. Hence Bragg diffraction is a promising method of extracting thermal neutrons for PGNAA

  15. Extraction of polychromatic thermal neutrons by Bragg diffraction to use for prompt gamma neutron activation analysis

    Science.gov (United States)

    Byun, S. H.; Choi, H. D.; Jun, B. J.; Kim, M. S.

    2000-07-01

    Extraction method of thermal neutron beam by Bragg diffraction is investigated. A thermal neutron beam is used for the Prompt Gamma Neutron Activation Analysis system at HANARO, a 30 MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic beam including all orders of diffraction is obtained by setting a pair of pyrolytic graphite crystals with a Bragg angle of 45° on a horizontal white beam line. Diffracted neutron flux at the sample position is calculated by considering the integrated reflectivity and mosaic spread of crystals. Due to the divergence effect, the mosaic spread of crystals is optimized to give the maximum and flat flux at the sample position. An experiment has been performed to verify the reflectivities for high order diffractions from pyrolytic graphite. When the focusing technique of bending the crystals is adopted, a design value of 1.0×108n/cm2s is expected at the sample position. Hence Bragg diffraction is a promising method of extracting thermal neutrons for PGNAA.

  16. Multifrequency Magneto-optic Bragg Diffraction and Radio Frequency Signal Parallel Processing

    Institute of Scientific and Technical Information of China (English)

    SHANG Dan; WU Bao-jian; QIU Kun

    2008-01-01

    Magneto-optic(MO) coupling of guided optical waves with microwave magnetostatic waves(MSWs) simultaneously excited by multiple radio frequency(RF) signals can lead to multifrequency diffraction effects and then parallel processing of RF signals can be realized by using of the characteristics that diffraction efficiencies(Des) are approximately in direct proportion to RF signals intensities and diffraction angles are related to frequencies of the corresponding RF signals within linear MO interaction region. In this paper, studied is the multifrequency MO Bragg diffraction in first-order MO interaction approximation, and obtained was the approximate analytical expression for principle diffraction efficiency(PDE). Also, put forward was a parallel imaging method of relative intensity of RF signals based on single-frequency diffraction. By calculation and analysis, it is shown that the relative error is not more than 0.3 dB for the case of three RF signals within the frequency space of 60 MHz.

  17. Measuring h /mCs and the Fine Structure Constant with Bragg Diffraction and Bloch Oscillations

    Science.gov (United States)

    Parker, Richard

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We suppress many systematic effects, e.g., Zeeman shifts and effects from Earth's gravity and vibrations, use Bloch oscillations to increase the signal and reduce the diffraction phase, simulate multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implement spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  18. A simple method of shielding area detectors from unwanted Bragg diffraction

    Czech Academy of Sciences Publication Activity Database

    Fábry, Jan; Kopecký, Miloš; Kub, Jiří

    2006-01-01

    Roč. 39, - (2006), s. 127-127. ISSN 0021-8898 R&D Projects: GA AV ČR(CZ) IAA100100529 Grant ostatní: IA-SFS(XE) RII3-CT-2004-506008 Institutional research plan: CEZ:AV0Z10100520 Keywords : shilelding unwanted Bragg diffraction * synchrotron X-ray sources * permanent magnets Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.495, year: 2006

  19. Ultrafast Self-Gating Bragg Diffraction of Exploding Nanocrystals in an X-ray Laser

    OpenAIRE

    Caleman, Carl; Tîmneanu, Nicuşor; Martin, Andrew V.; Jönsson, H. Olof; Aquila, Andrew; Barty, Anton; Scott, Howard A.; White, Thomas; Chapman, Henry N.

    2015-01-01

    In structural determination of crystalline proteins using intense femtosecond X-ray lasers, damage processes lead to loss of structural coherence during the exposure. We use a nonthermal description for the damage dynamics to calculate the ultrafast ionization and the subsequent atomic displacement. These effects degrade the Bragg diffraction on femtosecond time scales and gate the ultrafast imaging. This process is intensity and resolution dependent. At high intensities the signal is gated b...

  20. Some Novel Bragg Diffraction Optics Elements for Neutron Scattering at Steady State Neutrons Sources

    Czech Academy of Sciences Publication Activity Database

    Mikula, Pavol; Lukáš, Petr; Šaroun, Jan; Vrána, Miroslav; Wagner, V.

    2001-01-01

    Roč. 70, - (2001), s. 477-479. ISSN 0031-9015. [Proceedings of the 1st International Symposium on Advanced Science Research (ASR-2000). Tokai, 31.10.2000-02.11.2000] R&D Projects: GA ČR GV202/97/K038; GA AV ČR IAA1048003 Keywords : bragg diffraction * neutron optics * bent crystals Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.628, year: 2001

  1. Measuring the fine structure constant with Bragg diffraction and Bloch oscillations

    Science.gov (United States)

    Yu, Chenghui; Estey, Brian; Parker, Richard; Dudley, Jordan; Müller, Holger

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We have suppressed many systematic effects known in most atom interferometers with Raman beam splitters such as light shift, Zeeman effect shift as well as vibration. We have also simulated multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implemented spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  2. Magnetic symmetries in neutron and resonant x-ray Bragg diffraction patterns of four iridium oxides

    Science.gov (United States)

    Lovesey, S. W.; Khalyavin, D. D.; Manuel, P.; Chapon, L. C.; Cao, G.; Qi, T. F.

    2012-12-01

    The magnetic properties of Sr2IrO4, Na2IrO3, Sr3Ir2O7 and CaIrO3 are discussed, principally in the light of experimental data in recent literature for Bragg intensities measured in x-ray diffraction with enhancement at iridium L-absorption edges. The electronic structure factors we report, which incorporate parity-even and acentric entities, serve the immediate purpose of making full use of crystal and magnetic symmetry to refine our knowledge of the magnetic properties of the four iridates from resonant x-ray diffraction data. They also offer a platform on which to interpret future investigations, using dichroic signals, resonant x-ray diffraction and neutron diffraction, for example, as well as ab initio calculations of electronic structure. Unit-cell structure factors, suitable for x-ray Bragg diffraction enhanced by an electric dipole-electric dipole (E1-E1) event, reveal exactly which iridium multipoles are visible, e.g., a magnetic dipole parallel to the crystal c-axis (z-axis) and an electric quadrupole with yz-like symmetry in the specific case of CaIrO3. Magnetic space-groups are assigned to Sr2IrO4, Sr3Ir2O7 and CaIrO3, namely, PIcca, PAban and Cm‧cm‧, respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr2IrO4 is possible because of our new high-resolution neutron diffraction data, gathered on a powder sample. In addition, the new data are used to show that the ordered magnetic moment of an Ir4+ ion in Sr2IrO4 does not exceed 0.29(4) μB. Na2IrO3 has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  3. Metal layer Bragg-Fresnel lenses for diffraction focusing of hard x-rays

    International Nuclear Information System (INIS)

    A thin-film Bragg-Fresnel lens (BFL) was developed for diffractive focusing of hard x-rays into submicron to nanometer spots for scanning x-ray spectromicroscopy. The lens is made of metal-layer Fresnel zones deposited on an x-ray reflective substrate. The use of a high-density lens structure reduces the thickness of the lens and simplifies the fabrication process. Linear and elliptical lenses made of a 200-nm-thick Au film were fabricated using e-beam lithography and a metal deposition process. The focusing capabilities of the Au layer BFLs were demonstrated at the Advanced Photon Source

  4. Dependence of image quality on energy spread for a Bragg diffraction based radiography system

    International Nuclear Information System (INIS)

    The aim of this work is to investigate the relationship between contrast and energy resolution of a quasi-monochromatic X-ray system based on Bragg diffraction on a mosaic crystal. Three different energies have been considered: 18, 22 and 26 keV. A commercial phantom containing large and small area details and a digital detector have been used. Results show that for large area details and for a certain value of energy, the energy spread of the incident X-ray beams produces a small reduction of the contrast, while for small area details the high reduction of the contrast is principally due to the spatial resolution properties of the system

  5. Materials science in the time domain using Bragg coherent diffraction imaging

    International Nuclear Information System (INIS)

    Materials are generally classified by a phase diagram which displays their properties as a function of external state variables, typically temperature and pressure. A new dimension that is relatively unexplored is time: a rich variety of new materials can become accessible in the transient period following laser excitation from the ground state. The timescale of nanoseconds to femtoseconds, is ripe for investigation using x-ray free-electron laser (XFEL) methods. There is no shortage of materials suitable for time-resolved materials-science exploration. Oxides alone represent most of the minerals making up the Earth’s crust, catalysts, ferroelectrics, corrosion products and electronically ordered materials such as superconductors, to name a few. Some of the elements have metastable phase diagrams with predicted new phases. There are some examples known already: an oxide ‘hidden phase’ living only nanoseconds and an electronically ordered excited phase of fullerene C60, lasting only femtoseconds. In a completely general way, optically excited states of materials can be probed with Bragg coherent diffraction imaging, both below the damage threshold and in the destructive regime. Prospective methods for carrying out such XFEL experiments are discussed. (paper)

  6. Materials science in the time domain using Bragg coherent diffraction imaging

    Science.gov (United States)

    Robinson, Ian; Clark, Jesse; Harder, Ross

    2016-05-01

    Materials are generally classified by a phase diagram which displays their properties as a function of external state variables, typically temperature and pressure. A new dimension that is relatively unexplored is time: a rich variety of new materials can become accessible in the transient period following laser excitation from the ground state. The timescale of nanoseconds to femtoseconds, is ripe for investigation using x-ray free-electron laser (XFEL) methods. There is no shortage of materials suitable for time-resolved materials-science exploration. Oxides alone represent most of the minerals making up the Earth’s crust, catalysts, ferroelectrics, corrosion products and electronically ordered materials such as superconductors, to name a few. Some of the elements have metastable phase diagrams with predicted new phases. There are some examples known already: an oxide ‘hidden phase’ living only nanoseconds and an electronically ordered excited phase of fullerene C60, lasting only femtoseconds. In a completely general way, optically excited states of materials can be probed with Bragg coherent diffraction imaging, both below the damage threshold and in the destructive regime. Prospective methods for carrying out such XFEL experiments are discussed.

  7. Neutron Back- and Front-Face Bragg Diffraction on a Thin Si Single Crystal Excited by Ultrasound

    OpenAIRE

    Raitman, E.; Gavrilov, V.; D. Mjasischev; Ju. Ekmanis; Hoser, A.; Hoffmann, T.

    2015-01-01

    In this research project, we measured and analyzed the spatial distribution of neutron beam Bragg diffracted from the front- and back-faces of thin Si single crystal undergoing on ultrasound excitation. For the perfect crystal, it is shown that when the acoustic wave amplitude is increased, the front-face peak position remains unchanged and its value grows linearly. The values of ultrasound wave amplitude were determined. The back-face peak becomes asymmetric and tends to ...

  8. Fabrication of Au- and Ag-SiO2 inverse opals having both localized surface plasmon resonance and Bragg diffraction

    Science.gov (United States)

    Erola, Markus O. A.; Philip, Anish; Ahmed, Tanzir; Suvanto, Sari; Pakkanen, Tuula T.

    2015-10-01

    The inverse opal films of SiO2 containing metal nanoparticles can have both the localized surface plasmon resonance (LSPR) of metal nanoparticles and the Bragg diffraction of inverse opal crystals of SiO2, which are very useful properties for applications, such as tunable photonic structures, catalysts and sensors. However, effective processes for fabrication of these films from colloidal particles have rarely been reported. In our study, two methods for preparation of inverse opal films of SiO2 with three different crystal sizes and containing gold or silver nanoparticles (NPs) via self-assembly using electrostatic interactions and capillary forces are reported. The Bragg diffraction of inverse opal films of SiO2 in the presence and absence of the template was measured and predicted on the basis of with UV-vis spectroscopy and scanning electron microscopy. The preparation methods used provided good-quality inverse opal SiO2 films containing highly dispersed, plasmonic AuNPs or AgNPs and having both Bragg diffractions and LSPRs.

  9. Optical Effects Accompanying the Dynamical Bragg Diffraction in Linear 1D Photonic Crystals Based on Porous Silicon

    Directory of Open Access Journals (Sweden)

    Anton Maydykovskiy

    2014-10-01

    Full Text Available We survey our recent results on the observation and studies of the effects accompanying the dynamical Bragg diffraction in one-dimensional photonic crystals (PhC. Contrary to the kinematic Bragg diffraction, the dynamical one considers a continuous interaction between the waves travelling within a spatially-periodic structure and is the most pronounced in the so called Laue geometry, leading to a number of exciting phenomena. In the described experiments, we study the PhC based on porous silicon or porous quartz, made by the electrochemical etching of crystalline silicon with the consequent thermal annealing. Importantly, these PhC are approximately hundreds of microns thick and contain a few hundreds of periods, so that the experiments in the Laue diffraction scheme are available. We discuss the effect of the temporal splitting of femtosecond laser pulses and show that the effect is quite sensitive to the polarization and the phase of a femtosecond laser pulse. We also show the experimental realization of the Pendular effect in porous quartz PhC and demonstrate the experimental conditions for the total spatial switching of the output radiation between the transmitted and diffracted directions. All described effects are of high interest for the control over the light propagation based on PhC structures.

  10. Characterizing the hard x-ray diffraction properties of a GaAs linear Bragg-Fresnel lens

    International Nuclear Information System (INIS)

    We investigated the diffractive focusing properties of (111) GaAs linear Bragg-Fresnel lenses (BFLs) developed for hard x-ray microscopy and microdiffraction of complex materials in confined geometries. We demonstrated that the use of GaAs yields significant processing advantages due to the reduced zone depth. Focal plane diffraction patterns of linear BFLs measured at the advanced photon source using 8-40 keV x rays were compared to a simple model based on Kirchhoff-Fresnel diffraction theory. Good agreement was obtained between experimental data and model calculations using only zones within an effective aperture defined by the transverse coherence of the source. (c) 2000 American Institute of Physics

  11. Bulk strains in Si induced by thickness mode ultrasonic waves and analysed with x-ray Bragg diffraction

    International Nuclear Information System (INIS)

    In-depth thickness mode ultrasonic deformations were monitored by hard (22 keV) x-ray diffraction in Bragg geometry on a Si (1 1 1) crystal. The ultrasonic thickness mode standing wave was applied with a PZT transducer coupled to the Si crystal. Measurements were taken on the time-integrated mode and also at different phases of the ultrasonic excitation in stroboscopic mode. In-depth (2 mm) x-ray stroboscopic measurements on Si showed dynamical strains that were enough to set the crystal out of the diffraction condition. This opens new possibilities for applications such as a stroboscopic gradient x-ray monochromator made out of Si at back-diffraction geometry and stress-strain curve determination of crystals

  12. Three-dimensional reconstruction of the size and shape of protein microcrystals using Bragg coherent diffractive imaging

    Science.gov (United States)

    Coughlan, H. D.; Darmanin, C.; Kirkwood, H. J.; Phillips, N. W.; Hoxley, D.; Clark, J. N.; Harder, R. J.; Maxey, E.; Abbey, B.

    2016-05-01

    Three-dimensional imaging of protein crystals during x-ray diffraction experiments opens up a range of possibilities for optimizing crystal quality and gaining new insights into the fundamental processes that drive radiation damage. Obtaining this information at the appropriate length-scales however is extremely challenging. One approach that has been recently demonstrated as a promising avenue for characterizing the size and shape of protein crystals at nanometre length-scales is Bragg coherent diffractive imaging (BCDI). BCDI is a recently developed technique that is able to recover the phase of the continuous diffraction intensity signal around individual Bragg peaks. When data is collected at multiple points on a rocking curve, a reciprocal space map (RSM) can be assembled and then inverted using BCDI to obtain a three-dimensional image of the crystal. The first demonstration of two-dimensional biological BCDI was reported by Boutet et al on holoferritin, recently this work was extended to the study of radiation damage in micron-sized protein crystals. Here we present the first three-dimensional reconstructions of a Lysozyme protein crystal using BDI. The results are validated against RSM and transmission electron microscopy data and have implications for both radiation damage studies and for developing new approaches for structure retrieval from micron-sized protein crystals.

  13. Melting of chiral order in terbium manganate (TbMnO3) observed with resonant x-ray Bragg diffraction

    OpenAIRE

    Lovesey, S W; Scagnoli, V.; Garganourakis, M; Koohpayeh, S. M.; Detlefs, C.; Staub, U

    2013-01-01

    Resonant Bragg diffraction of soft, circularly polarized x-rays has been used to observe directly the temperature dependence of chiral-order melting in a motif of Mn ions in terbium manganate. The underlying mechanism uses the b-axis component of a cycloid, which vanishes outside the polar phase. Melting is witnessed by the first and second harmonics of a cycloid, and we explain why the observed temperature dependence is different in the two harmonics. Our direct observation of melting is sup...

  14. X-ray Raman scattering with Bragg diffraction in a La-based superlattice

    OpenAIRE

    André, Jean-Michel; Jonnard, Philippe; Bonnelle, Christiane; O. Filatova, E.; Michaelsen, C.; Wiesmann, J

    2005-01-01

    11 pages The non-dispersed soft x-ray emission from a La/B4C periodic multilayer irradiated by monochromatic x-rays has been measured as a function of the incident photon energy in the 125-200 eV range for different scattering angles. We have observed a scattered intensity peak at incident energies which shift towards the low-energy side as the value of the scattering angle increases. These observations are interpreted as Raman scattering by the 5p level of lanthanum assisted by Bragg diff...

  15. Fabrication of Au- and Ag–SiO{sub 2} inverse opals having both localized surface plasmon resonance and Bragg diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Erola, Markus O.A.; Philip, Anish; Ahmed, Tanzir; Suvanto, Sari; Pakkanen, Tuula T., E-mail: Tuula.Pakkanen@uef.fi

    2015-10-15

    The inverse opal films of SiO{sub 2} containing metal nanoparticles can have both the localized surface plasmon resonance (LSPR) of metal nanoparticles and the Bragg diffraction of inverse opal crystals of SiO{sub 2}, which are very useful properties for applications, such as tunable photonic structures, catalysts and sensors. However, effective processes for fabrication of these films from colloidal particles have rarely been reported. In our study, two methods for preparation of inverse opal films of SiO{sub 2} with three different crystal sizes and containing gold or silver nanoparticles (NPs) via self-assembly using electrostatic interactions and capillary forces are reported. The Bragg diffraction of inverse opal films of SiO{sub 2} in the presence and absence of the template was measured and predicted on the basis of with UV–vis spectroscopy and scanning electron microscopy. The preparation methods used provided good-quality inverse opal SiO{sub 2} films containing highly dispersed, plasmonic AuNPs or AgNPs and having both Bragg diffractions and LSPRs. - Graphical abstract: For syntheses of SiO{sub 2} inverse opals containing Au/Ag nanoparticles two approaches and three template sizes were employed. Self-assembly of template molecules and metal nanoparticles occurred using electrostatic interactions and capillary forces. Both the Bragg diffraction of the photonic crystal and the localized surface plasmon resonance of Au/Ag nanoparticles were detected. - Highlights: • Fabrication methods of silica inverse opals containing metal nanoparticles studied. • Three template sizes used to produce SiO{sub 2} inverse opals with Au/Ag nanoparticles. • PS templates with Au nanoparticles adsorbed used in formation of inverse opals. • Ag particles infiltrated in inverse opals with capillary and electrostatic forces. • Bragg diffractions of IOs and surface plasmon resonances of nanoparticles observed.

  16. Integrated intensities in Laue-Bragg cases for non-absorbing crystals in X-ray dynamical diffraction

    International Nuclear Information System (INIS)

    Integrated power ratios in Laue-Bragg cases are obtained for non-absorbing crystals. The reciprocity theorem is used to show that wave fields on exit surfaces in Laue-Bragg cases are identical to crystal wave fields of the Bragg case. The formulae are expressed analytically by a combination of modified Bessel and Struve functions of the first order. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  17. Operation manual for EDXRDDA - a software package for Bragg peak analysis of energy dispersive powder X-ray diffraction data

    International Nuclear Information System (INIS)

    EDXRDDA is a software package for analysis of raw data for energy dispersive x-ray diffraction from powder samples. It resolves the spectra into individual peaks by a constrained non-linear least squares method (Hughes and Sexton, 1988). The profile function adopted is the Gaussian/Lorentzian product with the mixing ratio refinable in the program. The program is implemented on an IBM PC and is highly interactive with extensive plotting facilities. This report is a user's guide for running the program. In the first step after inputting the spectra, the full spectra is plotted on the screen. The user then chooses a portion of this for peak resolution. The initial guess for the peak intensity, peak position are input with the help of a cursor or a mouse. Upto twenty peaks can be fitted at a time in an interval of 500 channels. For overlapping peaks, various constraints can be applied. Bragg peaks and fluorescence peaks with different half widths can be handled simultaneously. The program on execution produces a look up table which contains the refined values of the peak position, half width, peak intensity, integrated intensity, and their error estimates of each peak. The program is very general and can also be used for curve fitting of data from many other experiments. (author). 2 refs., 7 figs., 2 appendices

  18. Performance enhancement of thin film silicon solar cells based on distributed Bragg reflector and diffraction grating

    International Nuclear Information System (INIS)

    The influence of various designing parameters were investigated and explored for high performance solar cells. Single layer grating based solar cell of 50 μm thickness gives maximum efficiency up to 24 % whereas same efficiency is achieved with the use of three bilayers grating based solar cell of 30 μm thickness. Remarkably, bilayer grating based solar cell design not only gives broadband absorption but also enhancement in efficiency with reduced cell thickness requirement. This absorption enhancement is attributed to the high reflection and diffraction from DBR and grating respectively. The obtained short-circuit current were 29.6, 32.9, 34.6 and 36.05 mA/cm2 of 5, 10, 20 and 30 μm cell thicknesses respectively. These presented designing efforts would be helpful to design and realize new generation of solar cells

  19. Effective increase in beam emittance by phase-space expansion using asymmetric Bragg diffraction.

    Science.gov (United States)

    Chu, Chia-Hung; Tang, Mau-Tsu; Chang, Shih-Lin

    2015-08-24

    We propose an innovative method to extend the utilization of the phase space downstream of a synchrotron light source for X-ray transmission microscopy. Based on the dynamical theory of X-ray diffraction, asymmetrically cut perfect crystals are applied to reshape the position-angle-wavelength space of the light source, by which the usable phase space of the source can be magnified by over one hundred times, thereby "phase-space-matching" the source with the objective lens of the microscope. The method's validity is confirmed using SHADOW code simulations, and aberration through an optical lens such as a Fresnel zone plate is examined via matrix optics for nano-resolution X-ray images. PMID:26368150

  20. Time-resolved x-ray diffraction study of laser-ultrasonic generation. Development of bragg coherent x-ray diffraction using a free electron laser and the perspectives

    International Nuclear Information System (INIS)

    Time-resolved (TR) x-ray diffraction (XRD) is a powerful method to reveal dynamical property of lattice motions in crystalline materials. Highly brilliant pulsed x-ray sources are indispensable for probe beams of TR-XRD. The pulsed time structures of x-ray beams are briefly described for the synchrotron radiation facility (SPring-8) and the x-ray free electron laser (SACLA). The synchronization technique between ultrashort laser pulse and x-ray pulse enables us to make pump and probe measurements with 40 ps time resolution. When the surface of a semiconductor plate was irradiated by a femtosecond pulsed laser with higher energies than the band gap, transient lattice deformation was generated around the surface and induces acoustic pulse propagating toward the rear surface. The pulse was then reflected at the rear surface and the deformation was again observed at the front surface at certain delayed time. Initial strains after laser irradiation were expansion and shrinkage for GaAs and Si crystals, respectively. Ultrafast time-resolved Bragg coherent x-ray diffraction was performed to investigate lattice dynamics in a thin layer with nanoscal thickness by using free electron laser facility. Single-shot Bragg coherent diffraction patterns of a 100 nm-thick silicon crystal were measured in the asymmetric configuration with a grazing exit using two dimensional detectors. The broadening of single-shot Bragg profile was observed at a delay time of 20 ps, indicating the transient lattice fluctuation induced by an optical laser. (author)

  1. Depth profiles of the interfacial strains of Si0.7Ge0.3/Si using three-beam Bragg-surface diffraction.

    Science.gov (United States)

    Zheng, Yan-Zong; Soo, Yun-Liang; Chang, Shih-Lin

    2016-01-01

    Interfacial strains are important factors affecting the structural and physical properties of crystalline multilayers and heterojunctions, and the performance of the devices made of multilayers used, for example, in nanowires, optoelectronic components, and many other applications. Currently existing strain measurement methods, such as grazing incidence X-ray diffraction (GIXD), cross-section transmission electron microscope, TEM, and coherent diffractive imaging, CDI, are limited by either the nanometer spatial resolution, penetration depth, or a destructive nature. Here we report a new non-destructive method of direct mapping the interfacial strain of [001] Si0.7Ge0.3/Si along the depth up to ~287 nm below the interface using three-beam Bragg-surface X-ray diffraction (BSD), where one wide-angle symmetric Bragg reflection and a surface reflection are simultaneously involved. Our method combining with the dynamical diffraction theory simulation can uniquely provide unit cell dimensions layer by layer, and is applicable to thicker samples. PMID:27156699

  2. Calculated x-ray dichroic signals and resonant Bragg diffraction structure factors for dysprosium borocarbide (DyB2C2)

    International Nuclear Information System (INIS)

    Low temperature properties of dysprosium borocarbide display evidence of two continuous phase transitions; it has been proposed that the first involves ordering of Dy quadrupole moments and, at a lower temperature, the second involves ordering of Dy magnetic moments. The latter has been established by magnetic neutron diffraction. Insight to the first phase transition, at TQ, has been sought by resonant x-ray Bragg diffraction, which reveals charge-forbidden (Templeton-Templeton) intensities (00l + 1/2) that increase continuously with decreasing temperature. We show that this scattering is absent if the space group is P4/mbm which has been proposed for the high temperature crystal structure. Tanaka et al. (1999) report evidence that at TQ the lattice distorts and the new space group is P42/mnm. The lower point-group symmetry of Dy ions in this space group is shown by us to allow diffraction at (00l + 1/2) and, indeed, in part it is due to Dy quadrupole moments. In the magnetically ordered phase two neighbouring Dy moments along the c-axis are mutually perpendicular and two neighbouring moments in the plane normal to the c-axis are almost oppositely aligned. This magnetic configuration and point-group symmetry 2/m for Dy sites lead us to predict magnetic and charge scattering at reflections (00l + 1/2) in the magnetically ordered phase. At reflections (h0l) and h odd calculated structure factors are purely magnetic. Our finding is consistent with data collected by Hirota et al. (2000) at the reflection (102). We report expressions for circular and linear dichroic signals and structure factors for Bragg scattering for the interpretation of future experiments. The structure factors are appropriate for azimuthal-angle scans in which the crystal is rotated about the (00l + 1/2) or the (h0l) Bragg wavevectors. (author)

  3. Double Bragg Interferometry.

    Science.gov (United States)

    Ahlers, H; Müntinga, H; Wenzlawski, A; Krutzik, M; Tackmann, G; Abend, S; Gaaloul, N; Giese, E; Roura, A; Kuhl, R; Lämmerzahl, C; Peters, A; Windpassinger, P; Sengstock, K; Schleich, W P; Ertmer, W; Rasel, E M

    2016-04-29

    We employ light-induced double Bragg diffraction of delta-kick collimated Bose-Einstein condensates to create three symmetric Mach-Zehnder interferometers. They rely on (i) first-order, (ii) two successive first-order, and (iii) second-order processes which demonstrate the scalability of the corresponding momentum transfer. With respect to devices based on conventional Bragg scattering, these symmetric interferometers double the scale factor and feature a better suppression of noise and systematic uncertainties intrinsic to the diffraction process. Moreover, we utilize these interferometers as tiltmeters for monitoring their inclination with respect to gravity. PMID:27176520

  4. Bragg diffraction from magnetic materials

    DEFF Research Database (Denmark)

    Lebech, B.

    2002-01-01

    Neutrons form a penetrating neutral probe, which makes it possible to use neutrons scattering techniques to study bulk materials, localise both light and heavy atoms and to distinguish between isotopes (e.g. hydrogen and deuterium). These properties make neutron scattering complementary to X...... materials. This will be illustrated by reviewing the ordered magnetic structures found in some simple elements and in some chemically more complex systems containing several magnetic elements. The different scattering techniques (two- and three-axis neutron scattering, small angle neutron scattering...

  5. Bragg diffraction from magnetic materials

    DEFF Research Database (Denmark)

    Lebech, B.

    2002-01-01

    Neutrons form a penetrating neutral probe, which makes it possible to use neutrons scattering techniques to study bulk materials, localise both light and heavy atoms and to distinguish between isotopes (e.g. hydrogen and deuterium). These properties make neutron scattering complementary to X......-ray scattering when studying crystalline properties of matter. In addition, neutrons possess magnetic moments of the same order of magnitude as the atomic magnetic moments in elements and this makes neutrons highly suited for studies of the order and interactions between the magnetic moments in magnetic...... materials. This will be illustrated by reviewing the ordered magnetic structures found in some simple elements and in some chemically more complex systems containing several magnetic elements. The different scattering techniques (two- and three-axis neutron scattering, small angle neutron scattering...

  6. Principles of Bragg-Fresnel multilayer optics

    OpenAIRE

    Aristov, V. V.; Erko, A.I.; Martynov, V.V.

    1988-01-01

    The paper describes the principles and theoretical models of new X-ray optical elements based on the behaviour of Bragg-Fresnel diffraction. The use of volume diffraction permits one to achieve better spatial resolution compared with conventional plane optics and bending mirrors. The construction of Bragg-Fresnel elements combines the advantages of high-resolution Fresnel optics with stability of multilayer mirrors.

  7. Study of the magnetic order in a Co/Cr multilayer by magnetic Bragg diffraction at the Co 2p resonance

    Energy Technology Data Exchange (ETDEWEB)

    Mirone, Alessandro E-mail: mirone@lure.u-psud.fr; Sacchi, Maurizio; Dudzik, Esther; Duerr, Hermann; Laan, Gerrit van der; Vaures, Annie; Petroff, Frederic

    2000-08-01

    We have measured the resonant scattering from an antiferromagnetic Co/Cr multilayer at photon energies close to the cobalt 2p{yields}3d transitions. The cobalt dielectric tensor has an anisotropic component, enhanced by resonance, which depends on the magnetic order and follows its modulation inside the sample. We have studied the vertical distribution of this component through the dependence of the reflectivity on the scattering angle. Using s-polarized light, we have observed the signature of the cobalt-cobalt antiferromagnetic coupling as an half-integer-order Bragg peak. Experimental results have been analyzed by numerical simulation.

  8. Analysis of azimuthal-angle scans in resonant X-ray Bragg diffraction and parity even and odd atomic multipoles in the multiferroic modification of the terbium manganate, TbMnO3

    International Nuclear Information System (INIS)

    We present a theoretical analysis of resonant x-ray Bragg diffraction data from multiferroic TbMnO3 presented by Mannix et al PRB76, 184420 and Voigt et al. PRB 76, 104431. We have chosen an approach that does not rely on knowledge of the low-temperature phase space group of the sample, which is not precisely known. Results show that the low-temperature satellite reflections originate from dipole-dipole (E1-E1) and dipole-quadrupole (E1-E2) events. Presence on quadrupole-quadrupole (E2-E2) events can be excluded. The physical origin of the data is discussed in terms of atomic multipoles that represent magnetization, lattice distortions, and magneto-electric properties of the Tb and Mn ions. A handed cycloid of atomic multipoles, traced out in the b-c plane, is shown to be a plausible model of the Tb electron structure within a multiferroic modification that exists in the temperature interval 7 K < T < 28 K. (author)

  9. Are Bragg Peaks Gaussian?

    OpenAIRE

    Hammouda, Boualem

    2014-01-01

    It is common practice to assume that Bragg scattering peaks have Gaussian shape. The Gaussian shape function is used to perform most instrumental smearing corrections. Using Monte Carlo ray tracing simulation, the resolution of a realistic small-angle neutron scattering (SANS) instrument is generated reliably. Including a single-crystal sample with large d-spacing, Bragg peaks are produced. Bragg peaks contain contributions from the resolution function and from spread in the sample structure....

  10. Sangac interferometer on the holographic bragg grating

    CERN Document Server

    Tikhonov, E A

    2015-01-01

    The ring interferometer with zero optical path difference known as Sagnac one is offered with a diffraction splitting of the entering light beam. As the beamsplitter, a transmission holographic Bragg grating is used. Conditions of normal operation of this interferometer achieve under the equal intensity of beam copies and the adjustable phase shift between them in its two interferometer shoulders. These conditions are met with the holographic grating, which provides the phase shift 180^0 on the central Bragg wavelength. Experimental approbation of the modified interferometer validates the expected results.

  11. Ground effects on magnetooptic Bragg cells

    Institute of Scientific and Technical Information of China (English)

    WEN Feng; WU BaoJian; QIU Kun

    2008-01-01

    Propagation equation of magnetostatic waves in an arbitrarily magnetized yttrium-iron-garnet/gadolinium-gallium-garnet waveguide coated with perfect metal planes is obtained using the method of the surface magnetic permeability. And ground effects on magnetooptic Bragg cells are investigated with the magnetooptic coupled-mode theory. Theoretical analysis indicates that, diffraction efficiency of guided optical waves can be improved by adjusting the spacing of the metal plane from the ferrite film, and ground effects on the diffraction efficiency will be enhanced using an appropriately tilted bias magnetic field. In the metal clad waveguide system, the magnetostatic wave frequency at which the diffraction efficiency peak is obtained corresponds to the "zero-dispersion" point. Performance of RF spectrum analyzers in this system can also be improved by comparing with the case of the sandwich waveguide. Therefore, magnetooptic Bragg cells with the metal clad waveguide are potential applications to the microwave communication and optical signal processing.

  12. Bragg grating rogue wave

    CERN Document Server

    Degasperis, Antonio; Aceves, Alejandro B

    2015-01-01

    We derive the rogue wave solution of the classical massive Thirring model, that describes nonlinear optical pulse propagation in Bragg gratings. Combining electromagnetically induced transparency with Bragg scattering four-wave mixing, may lead to extreme waves at extremely low powers.

  13. Bragg grating rogue wave

    Energy Technology Data Exchange (ETDEWEB)

    Degasperis, Antonio [Dipartimento di Fisica, “Sapienza” Università di Roma, P.le A. Moro 2, 00185 Roma (Italy); Wabnitz, Stefan, E-mail: stefan.wabnitz@unibs.it [Dipartimento di Ingegneria dell' Informazione, Università degli Studi di Brescia and INO-CNR, via Branze 38, 25123 Brescia (Italy); Aceves, Alejandro B. [Southern Methodist University, Dallas (United States)

    2015-06-12

    We derive the rogue wave solution of the classical massive Thirring model, that describes nonlinear optical pulse propagation in Bragg gratings. Combining electromagnetically induced transparency with Bragg scattering four-wave mixing may lead to extreme waves at extremely low powers.

  14. Bragg Curve Spectroscopy

    International Nuclear Information System (INIS)

    An alternative utilization is presented for the gaseous ionization chamber in the detection of energetic heavy ions, which is called Bragg Curve Spectroscopy (BCS). Conceptually, BCS involves using the maximum data available from the Bragg curve of the stopping heavy ion (HI) for purposes of identifying the particle and measuring its energy. A detector has been designed that measures the Bragg curve with high precision. From the Bragg curve the range from the length of the track, the total energy from the integral of the specific ionization over the track, the dE/dx from the specific ionization at the beginning of the track, and the Bragg peak from the maximum of the specific ionization of the HI are determined. This last signal measures the atomic number, Z, of the HI unambiguously

  15. High-resolution atom interferometers with suppressed diffraction phases

    OpenAIRE

    Estey, B; C. Yu; Müller, H; Kuan, PC; Lan, SY

    2015-01-01

    © 2015 American Physical Society. We experimentally and theoretically study the diffraction phase of large-momentum transfer beam splitters in atom interferometers based on Bragg diffraction. We null the diffraction phase and increase the sensitivity of the interferometer by combining Bragg diffraction with Bloch oscillations. We demonstrate agreement between experiment and theory, and a 1500-fold reduction of the diffraction phase, limited by measurement noise. In addition to reduced systema...

  16. Grazing incidence diffraction : A review

    International Nuclear Information System (INIS)

    Different Grazing Incidence Diffraction (GID) methods for the analysis of thin films and multilayer structures are reviewed in three sections: the reflectivity is developed in the first one, which includes the non-specular diffuse scattering. The second one is devoted to the extremely asymmetric Bragg diffraction and the third one to the in-plane Bragg diffraction. Analytical formulations of the scattered intensities are developed for each geometry, in the framework of the kinetical analysis as well as the dynamical theory. Experimental examples are given to illustrate the quantitative possibility of the GID techniques

  17. Grazing incidence diffraction : A review

    Energy Technology Data Exchange (ETDEWEB)

    Gilles, B. [LTPCM, ENSEEG. St. Martin d`Heres. (France)

    1996-09-01

    Different Grazing Incidence Diffraction (GID) methods for the analysis of thin films and multilayer structures are reviewed in three sections: the reflectivity is developed in the first one, which includes the non-specular diffuse scattering. The second one is devoted to the extremely asymmetric Bragg diffraction and the third one to the in-plane Bragg diffraction. Analytical formulations of the scattered intensities are developed for each geometry, in the framework of the kinetical analysis as well as the dynamical theory. Experimental examples are given to illustrate the quantitative possibility of the GID techniques.

  18. Recent advances and prospects of Bragg-Fresnel optics

    International Nuclear Information System (INIS)

    Diffraction optics, i.e. Fresnel zone plates, holograms and diffraction gratings, has a limited application in the optical wavelength range. A decrease in wavelength to 100 nm and less changes conventional relationships between different types of optical elements owing to the change in the radiation-substance interaction since absorption starts to play a more important role as compared to refraction. Therefore at 1 nm approx lt λ approx lt 100 nm focusing elements may be fabricated only from thin membranes distinguished by an abrupt change of either absorption (amplitude zone plates) or transmitted wave phase (phase zone plates). In this wavelength range it is necessary that three-dimensional Bragg and Bragg-Fresnel elements should be used. Three-dimensional elements appear to be efficient for the whole short wavelength range 10-2 nm approx lt λ approx lt 100 nm. In doing so, the use of Bragg diffraction enables fabrication of high resolution gratings, radiation modulators and prisms. Thus, two- and three-dimensional diffraction elements form the basis for production of multifunctional x-ray optics in a wide wavelength range. It is essential that these elements can be reproduced in production quantities. Below is a summary of the results obtained at the Institute of Problems of Microelectronics Technology and High Purity Materials (IPMT) of the USSR Academy of Sciences in 1984-88. Emphasis is placed on Bragg- and Bragg-Fresnel elements that are fundamental for future x-ray optics. 15 refs., 2 figs., 1 tab

  19. Supersymmetric Bragg gratings

    International Nuclear Information System (INIS)

    The supersymmetric (SUSY) structure of coupled-mode equations that describe scattering of optical waves in one-dimensional Bragg gratings is highlighted. This property can find applications to the synthesis of special Bragg filters and distributed-feedback (DFB) optical cavities. In particular, multiple SUSY (Darboux–Crum) transformations can be used to synthesize DFB filters with any desired number of resonances at target frequencies. As an example, we describe the design of a DFB structure with a set of equally-spaced resonances, i.e. a frequency comb transmission filter. (paper)

  20. Diffraction of collinear correlated photon pairs by an ultrasonic wave

    OpenAIRE

    Kwiek, Piotr

    2013-01-01

    The phenomenon of collinear correlated photon pairs diffraction by an ultrasonic wave is investigated for Bragg incidence. A BBO crystal was used for producing collinear correlated photon pairs via type-I spontaneous parametric down-conversion (SPDC I-type). It is shown experimentally that the Bragg angle for photon pairs diffraction is identical to the one corresponding to single photons diffraction. The numbers of single photons and photon pairs counts in discrete diffraction orders were me...

  1. Bragg-Fresnel optics: New field of applications

    International Nuclear Information System (INIS)

    Bragg-Fresnel Optics shows excellent compatibility with the third generation synchrotron radiation sources such as ESRF and is capable of obtaining monochromatic submicron focal spots with 108-109 photons/sec in an energy bandwidth of 10-4-10-6 and in a photon energy range between 2-100 keV. New types of Bragg-Fresnel lenses like modified, ion implanted, bent and acoustically modulated were tested. Microprobe techniques like microdiffraction and microfluorescence based on Bragg-Fresnel optics were realised at the ESRF beamlines. Excellent parameters of the X-ray beam at the ESRF in terms of low emittance and quite small angular source size allow for Bragg-Fresnel optics to occupy new fields of applications such as high resolution diffraction, holography, interferometry and phase contrast imaging

  2. Bragg-Fresnel optics: New field of applications

    Energy Technology Data Exchange (ETDEWEB)

    Snigirev, A. [ESRF, Grenoble (France)

    1997-02-01

    Bragg-Fresnel Optics shows excellent compatibility with the third generation synchrotron radiation sources such as ESRF and is capable of obtaining monochromatic submicron focal spots with 10{sup 8}-10{sup 9} photons/sec in an energy bandwidth of 10{sup -4}-10{sup -6} and in a photon energy range between 2-100 keV. New types of Bragg-Fresnel lenses like modified, ion implanted, bent and acoustically modulated were tested. Microprobe techniques like microdiffraction and microfluorescence based on Bragg-Fresnel optics were realised at the ESRF beamlines. Excellent parameters of the X-ray beam at the ESRF in terms of low emittance and quite small angular source size allow for Bragg-Fresnel optics to occupy new fields of applications such as high resolution diffraction, holography, interferometry and phase contrast imaging.

  3. Silicon graphene Bragg gratings

    OpenAIRE

    Capmany, Jose; Domenech, David; Munoz, Pascual

    2013-01-01

    We propose the use of interleaved graphene sections on top of a silicon waveguide to implement tunable Bragg gratings. The filter central wavelength and bandwidth can be controlled changing the chemical potential of the graphene sections. Apodization techniques are also presented.

  4. Bragg reflection program

    International Nuclear Information System (INIS)

    This user's guide to the Bragg Reflection Program (BRP) is in the nature of an informal report. The general purpose of BRP is to scan a series of Bragg reflections automatically in order to obtain profiles and integrated intensities. The program is used in conjunction with the SUPERVISOR and READ packages, and the procedures for using it are similar to those for the Triple-Axis Control program. All the general features of the system, SUPERVISOR and READ packages as described in the Spectrometer Control Systems User's Guide are preserved. The presentation assumes that the reader is familiar with these. Sections are given on the READ package, execution and use, error messages, and output. A few sample problems are shown. (1 figure) (U.S.)

  5. A new generation of multilayer Bragg-Fresnel lenses

    International Nuclear Information System (INIS)

    A new type of Bragg-Fresnel multilayer lens (BFML) have been fabricated at IMT RAS and tested at LURE. The idea to combine different diffraction orders of a zone plate in one focal spot introduced by Simpson and Michette has been realized in a BFML with extended aperture. Matching of the two diffraction orders, the first and third, into one focal plane increases the output flux by a factor of two and the spatial resolution in the same order of magnitude

  6. Texture investigation by neutron diffraction

    International Nuclear Information System (INIS)

    In the conventional angle dispersive neutron diffraction a monochromatic neutron beam is used. The pole figures under investigation have to be scanned one after another. The commonly applied angle dispersive method is limited to the consideration of Bragg reflection being isolated in the diffraction pattern. The application of multidetectors or position sensitive detectors is discussed. In the neutron time-of-flight (TOF) diffraction a white pulsed neutron beam allows one to satisfy the Bragg law for all lattice spacing at a fixed scattering angle. The main charateristics of the TOF diffraction experiment are shortly outlined. In this method all non-forbidden Bragg reflections are recorded in one pattern simultaneously. The TOF technique is well-suited to study low symmetric or multiphased specimens, especially geological materials, requiring a large number of pole figures for mathematical texture analysis. Multidetector systems can be used to shorten the necessary time for experiments. The registration of all Bragg reflections of fixed scattering geometry is equivalent to the information of the inverse pole figure for the corresponding sample position. Having short exposition times this approach can be applied for in-situ investigations. The magnetic moments of neutrons can be used to study magnetic anisotropies in materials. Two different techniques are discussed

  7. Neutron forward diffraction by single crystal prisms

    Indian Academy of Sciences (India)

    Sohrab Abbas; Apoorva G Wagh; Markus Strobl; Wolfgang Treimer

    2008-11-01

    We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to the incidence angle. We have measured the variation of neutron deflection and transmission across a Bragg reflection, for several single crystal prisms. The results agree well with theory.

  8. Superradiance in volume diffraction grating

    OpenAIRE

    Baryshevsky, V. G.; Batrakov, K. G.

    2001-01-01

    Volume Free Electron Laser (VFEL) was proposed in [1-4]. It can operate in the wide spectral range from microwaves to X-rays. To simulate the processes which take place in VFEL the superradiance from a short electron pulse moving in a volume diffraction grating is studied in wavelength range ~4 mm. It is supposed that Bragg condition for emitted photons is fulfilled and dynamical diffraction takes place. The spectral-angular distributions for transmitted and diffracted waves are derived. It i...

  9. Diffraction leveraged modulation of X-ray pulses using MEMS-based X-ray optics

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

    2016-08-09

    A method and apparatus are provided for implementing Bragg-diffraction leveraged modulation of X-ray pulses using MicroElectroMechanical systems (MEMS) based diffractive optics. An oscillating crystalline MEMS device generates a controllable time-window for diffraction of the incident X-ray radiation. The Bragg-diffraction leveraged modulation of X-ray pulses includes isolating a particular pulse, spatially separating individual pulses, and spreading a single pulse from an X-ray pulse-train.

  10. Bragg transmission phase plates for the production of circularly polarized x-rays

    International Nuclear Information System (INIS)

    A thin-crystal Si (400) Bragg transmission x-ray phase plate has been constructed for the production of 5 to 12 keV circularly polarized x-rays. Using multiple beam diffraction from a GaAs crystal, a direct measurement of the degree of circular polarization as a function of off-Bragg position was made. These measurements indicated nearly complete circular polarization (|Pc| ≥ 0.95) and full helicity reversal on opposite sides of the rocking curve

  11. Diffraction Profile Pole Figures Measured with a Position Sensitive Detector

    OpenAIRE

    Wcislak, L.; Bunge, H.J.

    1996-01-01

    Pole figures in the classical sense are defined by the integral intensities of Bragg reflections. The conventional technique of pole figure measurement uses a single detector (usually a scintillation counter) with a wide receiving slit where the integral intensity of a given Bragg reflection is obtained directly. The usage of a position sensitive detector instead of a single detector allows to measure whole diffraction profiles simultaneously. Integral intensities of the diffraction peaks can...

  12. MEMS Bragg grating force sensor

    DEFF Research Database (Denmark)

    Reck, Kasper; Thomsen, Erik Vilain; Hansen, Ole

    2011-01-01

    We present modeling, design, fabrication and characterization of a new type of all-optical frequency modulated MEMS force sensor based on a mechanically amplified double clamped waveguide beam structure with integrated Bragg grating. The sensor is ideally suited for force measurements in harsh...... environments and for remote and distributed sensing and has a measured sensitivity of -14 nm/N, which is several times higher than what is obtained in conventional fiber Bragg grating force sensors. © 2011 Optical Society of America....

  13. Large-momentum-transfer Bragg interferometer with strontium atoms

    CERN Document Server

    Mazzoni, T; Del Aguila, R; Salvi, L; Poli, N; Tino, G M

    2015-01-01

    We report on the first atom interferometer based on Bragg diffraction in a fountain of alkaline-earth atoms, namely $^{88}$Sr. We demonstrate large momentum transfer to the atoms up to eight photon recoils and the use of the interferometer as a gravimeter with a sensitivity $\\delta g/g=4\\times 10^{-8}$. Thanks to the special characteristics of strontium atoms for precision measurements, this result opens a new way for experiments in fundamental and applied physics.

  14. Soft x-ray resonant magnetic diffraction.

    OpenAIRE

    Wilkins, S. B.; Hatton, P. D.; Roper, M.D.; Prabhakaran, D.; Boothroyd, A. T.

    2003-01-01

    We have conducted the first soft x-ray diffraction experiments from a bulk single crystal, studying the bilayer manganite La22xSr12xMn2O7 with x 0:475 in which we were able to access the (002) Bragg reflection using soft x rays. The Bragg reflection displays a strong resonant enhancement at the LIII and LII manganese absorption edges. We demonstrate that the resonant enhancement of the magnetic diffraction of the (001) is extremely large, indeed so large that it exceeds that of t...

  15. Takagi-Taupin Description of X-ray Dynamical Diffraction from Diffractive Optics with Large Numerical Aperture

    OpenAIRE

    Yan, Hanfei; Maser, Jorg; Macrander, Albert; Shen, Qun; Vogt, Stefan; Stephenson, Brian; Kang, Hyon Chol

    2007-01-01

    We present a formalism of x-ray dynamical diffraction from volume diffractive optics with large numerical aperture and high aspect ratio, in an analogy to the Takagi-Taupin equations for strained single crystals. We derive a set of basic equations for dynamical diffraction from volume diffractive optics, which enable us to study the focusing property of these optics with various grating profiles. We study volume diffractive optics that satisfy the Bragg condition to various degrees, namely fl...

  16. Advances in structure research by diffraction methods

    CERN Document Server

    Brill, R

    1970-01-01

    Advances in Structure Research by Diffraction Methods reviews advances in the use of diffraction methods in structure research. Topics covered include the dynamical theory of X-ray diffraction, with emphasis on Ewald waves in theory and experiment; dynamical theory of electron diffraction; small angle scattering; and molecular packing. This book is comprised of four chapters and begins with an overview of the dynamical theory of X-ray diffraction, especially in terms of how it explains all the absorption and propagation properties of X-rays at the Bragg setting in a perfect crystal. The next

  17. Can Kinematic Diffraction Distinguish Order from Disorder?

    CERN Document Server

    Baake, Michael

    2008-01-01

    Diffraction methods are at the heart of structure determination of solids. While Bragg-like scattering (pure point diffraction) is a characteristic feature of crystals and quasicrystals, it is not straightforward to interpret continuous diffraction intensities, which are generally linked to the presence of disorder. However, based on simple model systems, we demonstrate that it may be impossible to draw conclusions on the degree of order in the system from its diffraction image. In particular, we construct a family of one-dimensional binary systems which cover the entire entropy range but still share the same purely diffuse diffraction spectrum.

  18. Polymer optical fiber bragg grating sensors

    DEFF Research Database (Denmark)

    Stefani, Alessio; Yuan, Scott Wu; Andresen, Søren;

    2010-01-01

    Fiber-optical accelerometers based on polymer optical fiber Bragg gratings are reported. We have written fiber Bragg gratings for 1550 nm and 850 nm operations, characterized their temperature and strain response, and tested their performance in a prototype accelerometer....

  19. Detecting antiferromagnetism of atoms in an optical lattice via optical Bragg scattering

    OpenAIRE

    Corcovilos, T. A.; Baur, S. K.; Hitchcock, J. M.; Mueller, E. J.; Hulet, R. G.

    2009-01-01

    Antiferromagnetism of ultracold fermions in an optical lattice can be detected by Bragg diffraction of light, in analogy to the diffraction of neutrons from solid state materials. A finite sublattice magnetization will lead to a Bragg peak from the (1/2 1/2 1/2) crystal plane with an intensity depending on details of the atomic states, the frequency and polarization of the probe beam, the direction and magnitude of the sublattice magnetization, and the finite optical density of the sample. Ac...

  20. Synchrotron radiation focusing by a Bragg--Fresnel lens

    International Nuclear Information System (INIS)

    Since the discovery of x rays and until the present time the possibilities of their controlling and focusing have been widely discussed. In the hard spectrum region (λ∼1 A) the main focusing schemes are the following: geometrical focusing based on incoherent interaction of wave packets reflected by different regions of bending crystals and coherent (dynamic) focusing performed at the cost of the effect of refraction index angular dispersion near the exact Bragg angle value -θB. A main disadvantage of geometrical focusing is low spatial resolution (∼0.1 mm) and temperature stability. In the case of coherent focusing a main disadvantage is a narrow angular aperture (∼10 sec. of arc) at spatial resolution (∼1--10 μm). Recently, advances in the development of diffraction physics and microstructuring technology open up possibilities for fabricating effective focusing x-ray optical elements---Bragg--Fresnel lenses (BFL)---with high spatial resolution (∼0.1 μm) at a wide angular aperture and high temperature stability. The present paper describes the main principles of Bragg--Fresnel optics (BFO). It presents the results on the synchrotron experiment and on observation of focusing. In this work the peculiarities of BFL diffraction contrast formation are investigated and image transmission using a BFL is performed. Possibilities of developing x-ray optical schemes of ultrahigh resolution on the basis of BFL elements are also discussed

  1. Improved Phase-Mask Fabrication of Fiber Bragg Gratings

    Science.gov (United States)

    Grant, Joseph; Wang, Ying; Sharma, Anup

    2004-01-01

    An improved method of fabrication of Bragg gratings in optical fibers combines the best features of two prior methods: one that involves the use of a phase mask and one that involves interference between the two coherent laser beams. The improved method affords flexibility for tailoring Bragg wavelengths and bandwidths over wide ranges. A Bragg grating in an optical fiber is a periodic longitudinal variation in the index of refraction of the fiber core. The spatial period (Bragg wavelength) is chosen to obtain enhanced reflection of light of a given wavelength that would otherwise propagate relatively unimpeded along the core. Optionally, the spatial period of the index modulation can be made to vary gradually along the grating (such a grating is said to be chirped ) in order to obtain enhanced reflection across a wavelength band, the width of which is determined by the difference between the maximum and minimum Bragg wavelengths. In the present method as in both prior methods, a Bragg grating is formed by exposing an optical fiber to an ultraviolet-light interference field. The Bragg grating coincides with the pattern of exposure of the fiber core to ultraviolet light; in other words, the Bragg grating coincides with the interference fringes. Hence, the problem of tailoring the Bragg wavelength and bandwidth is largely one of tailoring the interference pattern and the placement of the fiber in the interference pattern. In the prior two-beam interferometric method, a single laser beam is split into two beams, which are subsequently recombined to produce an interference pattern at the location of an optical fiber. In the prior phase-mask method, a phase mask is used to diffract a laser beam mainly into two first orders, the interference between which creates the pattern to which an optical fiber is exposed. The prior two-beam interferometric method offers the advantage that the period of the interference pattern can be adjusted to produce gratings over a wide range

  2. High-resolution neutrons diffraction techniques for strain scanning

    Czech Academy of Sciences Publication Activity Database

    Mikula, Pavol; Vrána, Miroslav; Lukáš, Petr; Wagner, V.

    Dordrecht : Kluwer Academic Publishers, 2002 - (Gdoutos, E.), s. 457-466 ISBN 1-4020-0683-7 R&D Projects: GA ČR GV202/97/K038; GA AV ČR IAA1048003 Keywords : high-resolution * neutron diffraction techniques * Bragg diffraction optics Subject RIV: BM - Solid Matter Physics ; Magnetism

  3. Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis

    NARCIS (Netherlands)

    Sulyanova, Elena A.; Shabalin, Anatoly; Zozulya, Alexey V.; Meijer, Janne-Mieke; Dzhigaev, Dmitry; Gorobtsov, Oleg; Kurta, Ruslan P.; Lazarev, Sergey; Lorenz, Ulf; Singer, Andrej; Yefanov, Oleksandr; Zaluzhnyy, Ivan; Besedin, Ilya; Sprung, Michael; Petukhov, A. V.; Vartanyants, Ivan A.

    2015-01-01

    In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of

  4. Fiber Bragg Grating Based Thermometry

    OpenAIRE

    Ahmed, Zeeshan; Filla, James; Guthrie, William; Quintavalle, John

    2016-01-01

    In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in a hermetically sealed dry Argon environment, that FBG devices show a quadratic dependence on temperature with expanded uncertainties (k = 2) of ~500 mK. Our measurements indicate that the combined m...

  5. Multilayer Bragg Fresnel zone plate for coherent HHG radiation

    International Nuclear Information System (INIS)

    Coherent diffractive imaging in the (soft) X-ray regime is an emerging new lens-less X-ray microscopy technique with the future potential of molecular or even atomic resolution, because it is ultimately limited by the wavelength of the illuminating radiation and not by the imaging quality of the X-ray lens. However, this technique depends on the availability of coherent x-ray sources as well as optics for spectral filtering and focusing. We describe the development fabrication and testing of a reflective multilayer Bragg Fresnel phase zone plate for focusing coherent XUV radiation at 13 nm wavelength from a High Harmonic Generation source. This X-ray optical device serves for spectral filtering as well as sub-micron focusing of the HH spectrum in a single element for largely reduced losses. Large zone plate structures (conventional, spiral) matching the HH beam size are recorded by e-beam lithography in ultrathin HSQ e-beam resist and over-coated with a reflective Mo/Si multilayer by ion beam deposition. By accurately matching the groove depth of the diffractive structure to odd multiples of the quarter Bragg wavelength, the total diffraction efficiency can be improved by a factor of 4 theoretically compared to amplitude structures.

  6. Bragg-Berry mirrors: reflective broadband q-plates

    CERN Document Server

    Rafayelyan, Mushegh

    2016-01-01

    We report on the experimental realization of flat mirrors enabling the broadband generation of optical vortices upon reflection. The effect is based on the geometric Berry phase associated with the circular Bragg reflection phenomenon from chiral uniaxial media. We show the reflective optical vortex generation from both diffractive and nondiffractive paraxial light beams using spatially patterned chiral liquid crystal films. The intrinsic spectrally broadband character of spin-orbit generation of optical phase singularities is demonstrated over the full visible domain. Our results do not rely on any birefringent retardation requirement and consequently foster the development of a novel generation of robust optical elements for spin-orbit photonic technologies.

  7. BESSY Bragg-Fresnel multilayer beam monitors

    International Nuclear Information System (INIS)

    X-ray optical systems based on Bragg-Fresnel multilayer components imaging an electron beam in a storage ring with microm resolution are presented. Design concepts are compared to alternative methods, and the aberrations and limits of Bragg-Fresnel multilayer optics are discussed. Experimental results of imaging the BESSY 1 source with sub 10 microm resolution are presented and the development of a compact Bragg-Fresnel multilayer telescope as a BESSY 2 standard beam monitor is described

  8. Numerical analysis of the harmonic components of the Bragg wavelength content in spectral responses of apodized fiber Bragg gratings written by means of a phase mask with a variable phase step height.

    Science.gov (United States)

    Osuch, Tomasz

    2016-02-01

    The influence of the complex interference patterns created by a phase mask with variable diffraction efficiency in apodized fiber Bragg grating (FBGs) formation on their reflectance spectra is studied. The effect of the significant contributions of the zeroth and higher (m>±1) diffraction orders on the Bragg wavelength peak and its harmonic components is analyzed numerically. The results obtained for Gaussian and tanh apodization profiles are compared with similar data calculated for a uniform grating. It is demonstrated that when an apodized FBG is written using a phase mask with variable diffraction efficiency, significant enhancement of the harmonic components and a reduction of the Bragg wavelength peak in the grating spectral response are observed. This is particularly noticeable for the Gaussian apodization profile due to the substantial contributions of phase mask sections with relatively small phase steps in the FBG formation. PMID:26831768

  9. High Resolving Power Volume Diffractive Gratings for 400-2700 nm Spectral Range Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of this NASA SBIR Phase I proposal is to develop a novel type of high resolving power diffraction gratings based on volume Bragg gratings technology....

  10. High Resolving Power Volume Diffractive Gratings for 400-2700 nm Spectral Range Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The main purpose of this NASA SBIR Phase II proposal is development of a novel type of high resolving power diffraction gratings based on volume Bragg gratings...

  11. Bragg concentrators for hard (> 10keV) x-ray astronomy: Status report

    DEFF Research Database (Denmark)

    Pareschi, G.; Frontera, F.; Pasqualini, G.

    1997-01-01

    The use of focusing telescopes in hard X-ray (E > 10 keV) astronomy will provide better flux sensitivity and imaging performances with respect to the direct-viewing detectors, utilized until now. We present recent results obtained from our group regarding the possible use of Bragg-diffraction tec......The use of focusing telescopes in hard X-ray (E > 10 keV) astronomy will provide better flux sensitivity and imaging performances with respect to the direct-viewing detectors, utilized until now. We present recent results obtained from our group regarding the possible use of Bragg...

  12. A new theory for X-ray diffraction

    International Nuclear Information System (INIS)

    By considering the scattering distributed throughout space, there is an intensity enhancement at the Bragg angle even when the Bragg condition is not satisfied. This leads to an alternative explanation for the diffraction from powders and small crystals. This article proposes a new theory of X-ray scattering that has particular relevance to powder diffraction. The underlying concept of this theory is that the scattering from a crystal or crystallite is distributed throughout space: this leads to the effect that enhanced scatter can be observed at the ‘Bragg position’ even if the ‘Bragg condition’ is not satisfied. The scatter from a single crystal or crystallite, in any fixed orientation, has the fascinating property of contributing simultaneously to many ‘Bragg positions’. It also explains why diffraction peaks are obtained from samples with very few crystallites, which cannot be explained with the conventional theory. The intensity ratios for an Si powder sample are predicted with greater accuracy and the temperature factors are more realistic. Another consequence is that this new theory predicts a reliability in the intensity measurements which agrees much more closely with experimental observations compared to conventional theory that is based on ‘Bragg-type’ scatter. The role of dynamical effects (extinction etc.) is discussed and how they are suppressed with diffuse scattering. An alternative explanation for the Lorentz factor is presented that is more general and based on the capture volume in diffraction space. This theory, when applied to the scattering from powders, will evaluate the full scattering profile, including peak widths and the ‘background’. The theory should provide an increased understanding of the reliability of powder diffraction measurements, and may also have wider implications for the analysis of powder diffraction data, by increasing the accuracy of intensities predicted from structural models

  13. Fiber Bragg Grating Based Thermometry

    CERN Document Server

    Ahmed, Zeeshan; Guthrie, William; Quintavalle, John

    2016-01-01

    In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in a hermetically sealed dry Argon environment, that FBG devices show a quadratic dependence on temperature with expanded uncertainties (k = 2) of ~500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining the peak center fitting and by thermal aging of polyimide coated fibers.

  14. A Laue–Bragg monolithic beam splitter for efficient X-ray 2-beam imaging

    Energy Technology Data Exchange (ETDEWEB)

    Oberta, P., E-mail: peter.oberta@rigaku.com [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Na Slovance 2, CZ-18221 Praha 8 (Czech Republic); Mokso, R. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen (Switzerland)

    2013-03-01

    Newly emerging techniques for probing matter simultaneously by two spatially and angularly separated X-ray beams require efficient and versatile beam splitting. We present a Laue–Bragg monolithic crystal beam splitter in the form of an L-shaped monolithic Si crystal. By simultaneous Laue and Bragg diffractions the X-ray beam is split into a transmitted polychromatic and a diffracted monochromatic branch with a spatial separation of tens of millimeters. The energy spectrum of the transmitted branch can be tuned via diffraction on a second crystal re-creating a beam intersection on the sample. We propose three multi-modal imaging setups exploiting the large angular separation of the two intersecting beams provided by the proposed optics. Photon efficiency and dual-energy operation are the main assets of our scheme as compared to other existing setups. The theoretical description for an energy range between 10 keV and 30 keV was developed.

  15. High order Bragg grating microfluidic dye laser

    DEFF Research Database (Denmark)

    Balslev, Søren; Kristensen, Anders

    2004-01-01

    We demonstrate a single mode distributed feedback liquid dye laser, based on a short 133 'rd order Bragg grating defined in a single polymer layer between two glass substrates.......We demonstrate a single mode distributed feedback liquid dye laser, based on a short 133 'rd order Bragg grating defined in a single polymer layer between two glass substrates....

  16. Photosensitivity of Germanium-Doped Silica Fibers, Mask Fabrication of Fiber Bragg Gratings, and Their Application as a Strain Sensor.

    Science.gov (United States)

    Prohaska, John Dennis

    This thesis addresses issues related to the formation and application of fiber Bragg gratings. A description of existing methods of grating formation is reviewed. Also, mechanisms for photo-induced refractive index changes in germanium doped silica fibers are examined. A new method of fiber Bragg grating formation is proposed and experimentally verified using diffraction masks. The near field diffraction theory of Fresnel images is described in relation to this new method. Bragg reflectors have been experimentally produced in germanium doped silica optical fibers through the use of a surface relief phase mask. By the addition of an optical system the period of the produced grating may be changed. The wavelength of a fiber Bragg grating has been experimentally tuned using wave front shaping optics. The application of fiber Bragg grating as a strain sensor is examined in the context of a civil engineering environment. The issues and advantages of fiber Bragg gratings as devices for distributed strain measurements in large scale concrete structures are experimentally evaluated.

  17. High-Resolution Atom Interferometers with Suppressed Diffraction Phases.

    Science.gov (United States)

    Estey, Brian; Yu, Chenghui; Müller, Holger; Kuan, Pei-Chen; Lan, Shau-Yu

    2015-08-21

    We experimentally and theoretically study the diffraction phase of large-momentum transfer beam splitters in atom interferometers based on Bragg diffraction. We null the diffraction phase and increase the sensitivity of the interferometer by combining Bragg diffraction with Bloch oscillations. We demonstrate agreement between experiment and theory, and a 1500-fold reduction of the diffraction phase, limited by measurement noise. In addition to reduced systematic effects, our interferometer has high contrast with up to 4.4×10(6) radians of phase difference, and a resolution in the fine structure constant of δα/α=0.25  ppb in 25 h of integration time. PMID:26340186

  18. Autoindexing the diffraction patterns from crystals with a pseudotranslation

    International Nuclear Information System (INIS)

    Lattice patterns containing alternating strong and weak reflections can be identified by a targeted search for the weak signals, permitting a wider range of diffraction patterns to be indexed automatically. Rotation photographs can be readily indexed if enough candidate Bragg spots are identified to properly sample the reciprocal lattice. However, while automatic indexing algorithms are widely used for macromolecular data processing, they can produce incorrect results in special situations where a subset of Bragg spots is systematically overlooked. This is a potential outcome in cases where a noncrystallographic translational symmetry operator closely mimics an exact crystallographic translation. In these cases, a visual inspection of the diffraction image will reveal alternating strong and weak reflections. However, reliable detection of the weak-intensity reflections by software requires a systematic search for a diffraction signal targeted at specific reciprocal-space locations calculated a priori by considering all possible pseudotranslations. Care must be exercised to distinguish between true lattice diffraction and spurious signals contributed by neighboring overlapping Bragg spots, non-Bragg diffraction and noise. Such procedures have been implemented within the autoindexing program LABELIT and applied to known cases from publicly available data sets. Routine use of this type of signal search adds only a few seconds to the typical run time for autoindexing. The program can be downloaded from http://cci.lbl.gov/labelit

  19. Coherence and sampling requirements for diffractive imaging

    International Nuclear Information System (INIS)

    Coherent Diffractive Imaging (CDI) allows images to be reconstructed from diffraction patterns by solving the non-crystallographic phase problem for isolated nanostructures. We show that the Shannon sampling of diffraction intensities needed in CDI requires a coherence width about twice the lateral dimensions of the object, and that the linear number of detector pixels fixes the energy spread needed in the beam. The Shannon sampling, defined by the transform of the periodically repeated autocorrelation of the object, is related to Bragg scattering from an equivalent crystal, and shown to be consistent with the sampling of Young's fringes established by scattering from extreme points in the object. The results are relevant to the design of diffraction cameras for CDI and plans for femotosecond X-ray diffraction from individual proteins

  20. Stationary processes with pure point diffraction

    CERN Document Server

    Lenz, Daniel

    2011-01-01

    We consider the construction and classification of some new mathematical objects, called ergodic spatial stationary processes, on locally compact Abelian groups, which provide a natural and very general setting for studying diffraction and the famous inverse problems associated with it. In particular we can construct complete families of solutions to the inverse problem from any given pure point measure that is chosen to be the diffraction. In this case these processes can be classified by the dual of the group of relators based on the set of Bragg peaks, and this gives a solution to the homometry problem for pure point diffraction. An ergodic spatial stationary process consists of a measure theoretical dynamical system and a mapping linking it with the ambient space in which diffracting density is supposed to exist. After introducing these processes we study their general properties and link pure point diffraction to almost periodicity. Given a pure point measure we show how to construct from it and a given ...

  1. Reflectivity and Braggs Wavelength in FBG

    Directory of Open Access Journals (Sweden)

    Dinesh Arora

    2011-12-01

    Full Text Available We have presented an analytical model of splitters based on Fiber Bragg grating used to detect a Bragg wavelength from the number of wavelengths which are traveling in an optical fiber. The number of grids and grating length can be used as a wavelength shifter.This paper presents experimental results that are used to show the effect of number of grids and the length of the grating on the Bragg wavelength and reflectivity of Fiber Bragg Grating (FBG. The pitch of grating is directly proportional to the grating length and inversely proportional to number of grids. When the grating length is fixed and the number of grids is increased, the Bragg wavelength decreases and reflectivity increases. This increase in reflectivity is very small. Further when the number of grids was kept constant and the grating length was increased the Bragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. In our model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.

  2. BESSY Bragg-Fresnel multilayer beam monitors

    International Nuclear Information System (INIS)

    X-ray optical systems based on Bragg-Fresnel multilayer components imaging an electron beam in a storage ring with μm resolution are presented. Design concepts are compared to alternative methods, and the aberrations and limits of Bragg-Fresnel multilayer optics are discussed. Experimental results of imaging the BESSY I source with sub-10-μm resolution are presented, and the development of a compact Bragg-Fresnel multilayer telescope as a BESSY II standard beam monitor is described. copyright 1996 American Institute of Physics

  3. Macromolecular diffractive imaging using imperfect crystals

    Science.gov (United States)

    Ayyer, Kartik; Yefanov, Oleksandr M.; Oberthür, Dominik; Roy-Chowdhury, Shatabdi; Galli, Lorenzo; Mariani, Valerio; Basu, Shibom; Coe, Jesse; Conrad, Chelsie E.; Fromme, Raimund; Schaffer, Alexander; Dörner, Katerina; James, Daniel; Kupitz, Christopher; Metz, Markus; Nelson, Garrett; Xavier, Paulraj Lourdu; Beyerlein, Kenneth R.; Schmidt, Marius; Sarrou, Iosifina; Spence, John C. H.; Weierstall, Uwe; White, Thomas A.; Yang, Jay-How; Zhao, Yun; Liang, Mengning; Aquila, Andrew; Hunter, Mark S.; Robinson, Joseph S.; Koglin, Jason E.; Boutet, Sébastien; Fromme, Petra; Barty, Anton; Chapman, Henry N.

    2016-02-01

    The three-dimensional structures of macromolecules and their complexes are mainly elucidated by X-ray protein crystallography. A major limitation of this method is access to high-quality crystals, which is necessary to ensure X-ray diffraction extends to sufficiently large scattering angles and hence yields information of sufficiently high resolution with which to solve the crystal structure. The observation that crystals with reduced unit-cell volumes and tighter macromolecular packing often produce higher-resolution Bragg peaks suggests that crystallographic resolution for some macromolecules may be limited not by their heterogeneity, but by a deviation of strict positional ordering of the crystalline lattice. Such displacements of molecules from the ideal lattice give rise to a continuous diffraction pattern that is equal to the incoherent sum of diffraction from rigid individual molecular complexes aligned along several discrete crystallographic orientations and that, consequently, contains more information than Bragg peaks alone. Although such continuous diffraction patterns have long been observed—and are of interest as a source of information about the dynamics of proteins—they have not been used for structure determination. Here we show for crystals of the integral membrane protein complex photosystem II that lattice disorder increases the information content and the resolution of the diffraction pattern well beyond the 4.5-ångström limit of measurable Bragg peaks, which allows us to phase the pattern directly. Using the molecular envelope conventionally determined at 4.5 ångströms as a constraint, we obtain a static image of the photosystem II dimer at a resolution of 3.5 ångströms. This result shows that continuous diffraction can be used to overcome what have long been supposed to be the resolution limits of macromolecular crystallography, using a method that exploits commonly encountered imperfect crystals and enables model-free phasing.

  4. Strain imaging by Bragg edge neutron transmission

    CERN Document Server

    Santisteban, J R; Fitzpatrick, M E; Steuwer, A; Withers, P J; Daymond, M R; Johnson, M W; Rhodes, N; Schooneveld, E M

    2002-01-01

    The Bragg edges appearing in the transmitted time-of-flight spectra of polycrystalline materials have been recorded using a two-dimensional array of detectors. Subsequent analysis has enabled maps of the elastic strain to be produced.

  5. Mode characteristics of hollow core Bragg fiber

    Institute of Scientific and Technical Information of China (English)

    Minning Ji; Zhidong Shi; Qiang Guo

    2005-01-01

    Analytical expression to calculate propagation constant and mode field of the hollow core Bragg fiber is derived. Numerical results are presented. It is shown that the fundamental mode of the hollow core Bragg fiber is circularly symmetric TE01 mode with no polarization degeneracy, while the higher order mode may be HE11, TM01, or TE02 etc.. This property is different from conventional optical fiber that its fundamental mode is the linearly polarized HE11 mode and is polarization degeneracy.

  6. Reflectivity and Braggs Wavelength in FBG

    Directory of Open Access Journals (Sweden)

    Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason

    2011-12-01

    Full Text Available We have presented an analytical model of splitters based on Fiber Bragg Grating used to detect a Braggwavelength from the number of wavelengths which are traveling in an optical fiber. The number of gridsand grating length can be used as a wavelength shifter. This paper presents experimental results that areused to show the effect of number of grids, the length of the grating on the Bragg wavelength andreflectivity of Fiber Bragg Grating (FBG. The pitch of grating is directly proportional to the grating lengthand inversely proportional to number of grids. When the grating length is fixed and the number of grids isincreased, the Bragg wavelength decreases resulting in increased reflectivity. This increased reflectivity isvery small. Further when the number of grids is kept constant and the grating length is increased theBragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. Inour model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.

  7. Silicon waveguide polarization rotation Bragg grating with phase shift section and sampled grating scheme

    Science.gov (United States)

    Okayama, Hideaki; Onawa, Yosuke; Shimura, Daisuke; Yaegashi, Hiroki; Sasaki, Hironori

    2016-08-01

    We describe a Bragg grating with a phase shift section and a sampled grating scheme that converts input polarization to orthogonal polarization. A very narrow polarization-independent wavelength peak can be generated by phase shift structures and polarization-independent multiple diffraction peaks by sampled gratings. The characteristics of the device were examined by transfer matrix and finite-difference time-domain methods.

  8. Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis

    OpenAIRE

    Sulyanova, Elena; Shabalin, Anatoly; Yefanov, Oleksandr; Zaluzhnyy, Ivan; Besedin, Ilya; Sprung, Michael; Petukhov, Andrei; Vartaniants, Ivan; Zozulya, Alexey; Meijer, Janne-Mieke; Dzhigaev, Dmitry; Gorobtsov, Oleg; Kurta, Ruslan; Lazarev, Sergey; Lorenz, Ulf

    2015-01-01

    In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of temperature. A quantitative study of colloidal crystal lattice distortions and mosaic spread as a function of temperature was carried out using Williamson–Hall plots based on mosaic block model. T...

  9. Study on focusing of hard x-radiation by combined Bragg-Fresnel lenses

    International Nuclear Information System (INIS)

    The program ZON is used to calculate the topology of zone plates focusing the source point into the image point. It allows to create combined lenses of different orders. Diffraction properties of x-ray optical elements are analyzed. Experimental results of x-radiation focusing by means of combined Bragg-Fresnel lenses calculated on 6, 10 and 14 keV, are presented. The spatial resolution for all lenses is 6 μm

  10. Channel Spectral Separation Narrowing for Spectral Beam Combining by Apodisation of the Reflecting Volume Bragg Grating

    OpenAIRE

    Shen Benjian; Tan Jichun; Guangwei Zheng; Yanlan He

    2011-01-01

    The sidelobe in diffraction efficiency of reflecting volume Bragg grating (RVBG) limits the wavelength channel spectral separation, which determines the combining power output in spectral beam combining (SBC) systems. A novel SBC system based on the apodised RVBG has been proposed to suppress the sidelobe. Several apodised RVBGs have been compared and the optimal apodised RVBG is obtained by using the chain-matrix approach. Numerical results show that the sidelobe could be suppressed excellen...

  11. A Laue-Bragg monolithic beam splitter for efficient X-ray 2-beam imaging

    Czech Academy of Sciences Publication Activity Database

    Oberta, Peter; Mokso, R.

    2013-01-01

    Roč. 703, MAR (2013), s. 59-63. ISSN 0168-9002 R&D Projects: GA MPO FR-TI1/412 Institutional research plan: CEZ:AV0Z10100522 Keywords : X-ray imaging * Laue-Bragg diffraction * monolithic crystal * dueal energy option Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.316, year: 2013 http://www.sciencedirect.com/science/article/pii/S0168900212013794

  12. Self-consistent electrodynamic scattering in the symmetric Bragg case

    International Nuclear Information System (INIS)

    We have analyzed the symmetric Bragg case, introducing a model of self consistent scattering for two elliptically polarized beams. The crystal is taken as a set of mathematical planes, each of them defined by a surface density of dipoles. We have considered the mesofield and the epifield differently from that of the Ewald's theory and, we assumed a plane of dipoles and the associated fields as a self consistent scattering unit. The exact analytical treatment when applied to any two neighbouring planes, results in a general and self consistent Bragg's equation, in terms of the amplitude and phase variations. The generalized solution for the set of N planes was obtained after introducing an absorption factor in the incident radiation, in two ways: (i) the analytical one, through a rule of field similarity, which says that the incidence occurs in both faces of the all crystal planes and also, through a matricial development with the Chebyshev polynomials; (ii) using the numerical solution we calculated, iteratively, the reflectivity, the reflection phase, the transmissivity, the transmission phase and the energy. The results are showed through reflection and transmission curves, which are characteristics as from kinematical as dynamical theories. The conservation of the energy results from the Ewald's self consistency principle is used. In the absorption case, the results show that it is not the only cause for the asymmetric form in the reflection curves. The model contains basic elements for a unified, microscope, self consistent, vectorial and exact formulation for interpretating the X ray diffraction in perfect crystals. (author)

  13. Neutron Larmor diffraction measurements for materials science

    International Nuclear Information System (INIS)

    Neutron Larmor diffraction (LD) is a high-resolution diffraction technique based on the Larmor precession of polarized neutrons. In contrast to conventional diffraction, LD does not depend on the accurate measurement of Bragg angles, and thus the resolution is independent of the beam collimation and monochromaticity. At present, a relative resolution for the determination of the crystal lattice spacing d of Δd/d∼10-6 is achieved, i.e. at least one order of magnitude superior to conventional neutron or X-ray techniques. This work is a first step to explore the application of LD to high-resolution problems in the analysis of residual stresses, where both the accurate measurement of absolute d values and the possibility of measuring type II and III stresses may provide additional information beyond those accessible by conventional diffraction techniques. Data obtained from Inconel 718 samples are presented.

  14. Optical diffraction by inhomogeneous volume objects

    Science.gov (United States)

    Forte, Gustavo; Lencina, Alberto; Tebaldi, Myrian; Bolognini, Nestor

    2008-08-01

    Electromagnetic waves propagation research in volume media increases considerably in the last years. The study evolved from thick hologram gratings, Bragg and Raman-Nath diffraction regimes up to current research in photonics materials. Usually differential methods are employed to account for the light transmitted for volume media. In our proposal, we develop a simple and versatile integral method to calculate the diffracted field provided the media refractive index has low variations in a wavelength scale. In fact, starting from first principles, we obtain a modified version of the Fresnel propagator of the scalar diffraction theory. Our method is valid for some kind of magnetic, dielectric and absorbent inhomogeneous media. In particular, for TE (TM) fields, we can study media where the permittivity (permeability) gradient is perpendicular to the electric (magnetic) field and its permeability (permittivity) is constant. To validate the approach, we applied it to (in) homogeneous media having well known diffraction properties.

  15. Stretching of Picosecond Laser Pulses with Uniform Reflecting Volume Bragg Gratings

    Science.gov (United States)

    Mokhov, Sergiy

    It is shown that a uniform reflecting volume Bragg grating (VBG) can be used as a compact monolithic stretcher of high-power picosecond laser pulses in cases when chirped Bragg gratings with an appropriate chirp rate are difficult to fabricate. A chirp-free reflected stretched pulse is generated of almost rectangular shape when incident short pulse propagates along a grating and experiences local Bragg diffraction. The increase in duration of the reflected pulse is approximately equal to twice the propagation times along the grating. We derived the analytic expression for diffraction efficiency, which incorporates incident pulse duration, grating thickness, and amplitude of refractive index modulation, enabling an optimum selection of the grating for pulse stretching. The typical expected theoretical value of diffraction efficiency is about 10% after taking into account the spectral narrowing of the reflected emission. We believe that the relatively low energy efficiency of the proposed method is more than offset by a number of advantages, which are chirp-free spectrum of a stretched pulse, compactness, robustness, preservation of setup alignment and beam quality, and tolerance to high power. Obtained pulses of several tens of picoseconds can be amplified by standard methods which are not requiring special measures to avoid undesirable non-linear effects. We propose a simple and reliable method to control the temporal parameters of the high-power picosecond pulses using the same laser source and the VGB of variable thickness that can significantly simplify the experiments requiring different pulse durations.

  16. Diffraction dissociation

    International Nuclear Information System (INIS)

    An attempt is made to analyse the present theoretical situation in the field of diffraction scattering. Two not yet fully answered questions related with a typical diffraction process AB→CD, namely: what is the structure of the transition matrix elements, and what is the structure of the exchange mechanism responsible for the scattering, are formulated and various proposals for answers are reviewed. Interesting general statement that the products (-1)sup(J)P, where J and P are respectively spin and parity, is conserved at each vertex has been discussed. The exchange mechanism in diffractive scattering has been considered using the language of the complex J-plane as the most appropriate. The known facts about the exchange mechanism are recalled and several routs to way out are proposed. The idea to consider the moving pole and associated branch points as like a particle and the associated two and many particle unitarity cuts is described in more details. (S.B.)

  17. Neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Heger, G. [Rheinisch-Westfaelische Technische Hochschule Aachen, Inst. fuer Kristallographie, Aachen (Germany)

    1996-12-31

    X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (author) 15 figs., 1 tab., 10 refs.

  18. The discovery of X-ray diffraction by crystals and its great impact on science

    International Nuclear Information System (INIS)

    In April 1912, Friedrich, Knipping and Laue discovered X-ray diffraction in a CuSO4 crystal. Later, Laue derived the famous Laue equations which explain the diffraction phenomenon. For this, Laue was awarded a Nobel Prize for Physics in 1914. In 1912 W. H. Bragg and W. L. Bragg received news of Laue 's discovery, and from X-ray diffraction experiments in a ZnS crystal they derived the famous Bragg equation. For this work, father and son were together awarded the Nobel Prize for Physics in 1915, To commemorate the 100th anniversary of the discovery of X-ray diffraction, this article reviews the important contributions of the early pioneers and their historic impact on science and technology worldwide. (author)

  19. Microwave Bragg-scattering zone-axis-pattern analysis

    CERN Document Server

    Fraundorf, P; Garver, W; Freeman, M; Proctor, D

    2013-01-01

    Louis deBroglie's connection between momentum and spatial-frequency vectors is perhaps most viscerally-experienced via the real-time access that electron-diffraction provides to transverse slices of a crystal's reciprocal lattice. The classic introductory (and/or advanced) physics lab-experiment on microwave Bragg-scattering can with a bit of re-arrangement also give students access to "zone-axis-pattern" slices through the 3D spatial-frequency (i.e. reciprocal) lattice of a ball-bearing crystal. In this paper we show how data from the standard experimental set up can be used to generate zone-axis-patterns oriented down the crystal rotation-axis. This may be used to give students direct experience with crystal shape-transforms (which help to explain anomalous peaks), as well as to the complementary relation between non-Cartesian basis-vectors in direct and reciprocal (co-vector) space.

  20. Fiber Bragg Grating Filter High Temperature Sensors

    Science.gov (United States)

    Lyons, Donald R.; Brass, Eric D.; Pencil, Eric (Technical Monitor)

    2001-01-01

    We present a scaled-down method for determining high temperatures using fiber-based Bragg gratings. Bragg gratings are distributed along the length of the optical fiber, and have high reflectivities whenever the optical wavelength is twice the grating spacing. These spatially distinct Bragg regions (located in the core of a fiber) are sensitive to local temperature changes. Since these fibers are silica-based they are easily affected by localized changes in temperature, which results in changes to both the grating spacing and the wavelength reflectivity. We exploit the shift in wavelength reflectivity to measure the change in the local temperature. Note that the Bragg region (sensing area) is some distance away from where the temperature is being measured. This is done so that we can measure temperatures that are much higher than the damage threshold of the fiber. We do this by affixing the fiber with the Bragg sensor to a material with a well-known coefficient of thermal expansion, and model the heat gradient from the region of interest to the actual sensor. The research described in this paper will culminate in a working device as well as be the second portion of a publication pending submission to Optics Letters.

  1. Results from a Bragg Curve Spectrometer

    International Nuclear Information System (INIS)

    The Bragg Curve Spectrometer (BCS) is an ionization chamber long enough to stop particles of interest. Particles enter through the cathode window and leave an ionization track parallel to the electric field. The ionization electrons drift through a Frisch grid and are collected on an anode. The anode current, as a function of time, is split and used as input for two amplifiers, one with a long integration time constant for energy measurement, and one with a short time constant to pick off the maximum ionization or Bragg peak. The Bragg peak, which is proportional to the nuclear charge, is used for particle identification. We have constructed and tested several versions of the BCS. The results are described

  2. Results from a Bragg curve spectrometer

    Science.gov (United States)

    Leach, D. D.; Davis, K. J.

    The Bragg Curve Spectrometer (BCS) is an ionization chamber long enough to stop particles of interest. Particles enter through the cathode window and leave an ionization track parallel to the electric field. The ionization electrons drift through a Frisch grid and are collected on an anode. The anode current, as a function of time, is split and used as input for two amplifiers, one with a long integration time constant for energy measurement, and one with a short time constant to pick off the maximum ionization or Bragg peak. The Bragg peak, which is proportional to the nuclear charge, is used for particle identification. Several versions of the BCS have been constructed and tested. The results are described.

  3. POLICRYPS-based electrically switchable Bragg reflector.

    Science.gov (United States)

    De Sio, Luciano; Tabiryan, Nelson; Bunning, Timothy J

    2015-12-14

    The formation and characterization of a switchable volume reflective element fabricated from a polymer liquid crystal (LC) polymer slice (POLICRYPS) structure by holographic photopolymerization at high temperature (65 °C) using a photosensitive/nematic liquid crystal prepolymer mixture is reported. The submicron Bragg structure formed consists of periodic continuous polymeric walls separated by periodic LC channels. The phase separated NLC self-aligns in a homeotropic alignment between the polymer walls as indicated by polarizing optical microscopy analysis (Maltese cross). The resulting periodic grating structure results in a Bragg reflection notch upon illumination with white light due to the periodic variation in refractive index. Electro-optical experiments realized through in-plane electrodes and temperature experiments confirm that the multilayer structure acts as a Bragg mirror whose reflection efficiency can be controlled by either a small (~3V/µm) electric field or temperature. PMID:26699059

  4. BRAGG-FRESNEL OPTICS AND SUPERMIRRORS

    OpenAIRE

    A. Erko; Vidal, B.

    1996-01-01

    The main principles and some applications of Bragg-Fresnel multilayer optics and X-ray supermirrors are described. An elliptical Bragg-Fresnel multilayer lens (BFML), designed and fabricated in the IMT RAS has been used for 2-dimensional focusing of the white X-ray synchrotron beam. For the beam energy of about 12 KeV the spot size checked with the knife edge method was about 1 mm. Applications of BFML and supermirrors in x-ray imaging are discussed.

  5. A neural network for the Bragg synthetic curves recognition

    International Nuclear Information System (INIS)

    A ionization chamber was employed named Bragg curve spectroscopy. The Bragg peak amplitude is a monotone growing function of Z, which permits to identify elements through their measurement. A better technique for this measurement is to improve the use of neural networks with the purpose of the identification of the Bragg curve. (Author)

  6. X-ray diffraction imaging and analysis

    International Nuclear Information System (INIS)

    The first papers dealing with the very important application of x-ray diffraction to crystal structure analysis were also published in 1912 by W.L. Bragg, while a student at Cambridge. Bragg performed an analysis of the Laue diffraction pattern of zinc blend and determined the correct structure of the crystal lattice. There have been many practical applications for x-ray diffraction techniques. Historically conventional x-ray machines were used as generators and film used as the recording medium. Prior to 1966, all attempts to directly image x-ray diffraction patterns used a large format x-ray image intensifier tube of the same type as conventionally used for medical and industrial fluoroscopy. Since the 1960's numerous electro-optical systems have been developed which are far better suited for real-time viewing and recording of x-ray diffraction patterns. Modern x-ray diffraction imaging systems incorporating rotating anode and pulsed x-ray generators, synchrotron x-ray sources, and optimized electro-optical systems have been used to orient single crystals, to study crystal lattice rotation accompanying plastic deformation, to measure the rate of grain boundary migration during recrystallization annealing of cold-worked metals, to determine the physical state of exploding metals, to rapidly measure residual stress (strain), to study the dynamics of structural phase transitions in ferroelectric crystals, to monitor the amorphous to crystalline phase transformation of rapidly solidified metals, and to record topographic images of lattice defects in quartz, gallium arsenide and nickel alloy turbine blade crystals

  7. Femtosecond laser pulse written Volume Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Richter Daniel

    2013-11-01

    Full Text Available Femtosecond laser pulses can be applied for structuring a wide range of ransparent materials. Here we want to show how to use this ability to realize Volume-Bragg-Gratings in various- mainly non-photosensitive - glasses. We will further present the characteristics of the realized gratings and a few elected applications that have been realized.

  8. Modal analysis of Bragg onion resonators

    OpenAIRE

    Xu, Yong; Liang, Wei; Yariv, Amnon; Fleming, James G.; Lin, Shawn-Yu

    2004-01-01

    From analysis of the high Q modes in a Bragg onion resonator with an omnidirectional reflector cladding, we establish a close analogy between such a resonator and a spherical hollow cavity in perfect metal. We demonstrate that onion resonators are ideal for applications that require a large spontaneous-emission factor ß, such as thresholdless lasers and single-photon devices.

  9. Efficient iterative technique for designing bragg gratings

    DEFF Research Database (Denmark)

    Plougmann, Nikolai; Kristensen, Martin

    2004-01-01

    We present a new iterative method for designing Bragg gratings based on the Levenberg-Marquardt method of minimizing a chi-squared merit function. It is effective for designing both weak and strong gratings and is particularly well suited for unchirped gratings....

  10. Detecting stripe phase in spin-orbit coupled condensates via optical Bragg scattering

    Science.gov (United States)

    Putra, Andika; Carcoba, Francisco Salces; Yue, Yuchen; Sugawa, Seiji; Spielman, Ian

    2016-05-01

    The stripe phase in spin-orbit coupled condensates has been predicted theoretically but not yet been observed. This peculiar feature, analogue to supersolidity, originates from the interaction effects and spin-momentum locking between different spin states. Motivated by recent observation of antiferromagnetic correlations in cold atoms, we explore the feasibility of Bragg diffraction to observe the stripe phase. Here, we create spin-orbit coupled condensates in f = 1 ground state manifold of Rb87 using a pair of cross-polarized 790.02 nm counter-propagating laser beams. Using similar setup, we make a spin-dependent one dimensional lattice and demonstrate Bragg scattering of light to calibrate the atomic density distribution. This enables us to do a direct measure of the stripe phase.

  11. Measurements of Ion Stopping Around the Bragg Peak in High-Energy-Density Plasmas.

    Science.gov (United States)

    Frenje, J A; Grabowski, P E; Li, C K; Séguin, F H; Zylstra, A B; Gatu Johnson, M; Petrasso, R D; Glebov, V Yu; Sangster, T C

    2015-11-13

    For the first time, quantitative measurements of ion stopping at energies around the Bragg peak (or peak ion stopping, which occurs at an ion velocity comparable to the average thermal electron velocity), and its dependence on electron temperature (T(e)) and electron number density (n(e)) in the range of 0.5-4.0 keV and 3×10(22) to 3×10(23) cm(-3) have been conducted, respectively. It is experimentally demonstrated that the position and amplitude of the Bragg peak varies strongly with T(e) with n(e). The importance of including quantum diffraction is also demonstrated in the stopping-power modeling of high-energy-density plasmas. PMID:26613448

  12. Quantum theory of X-ray radiation at Bragg angles at channeling

    International Nuclear Information System (INIS)

    In the framework of quantum electrodynamics the theory of the new type of X-ray radiation from the channeled electrons in vicinity of the Bragg angle—Diffracted Channeling Radiation (DCR) is developed beyond the dipole approximation. The DCR occurs due to transitions of the channeled electrons from one transverse energy level to another with the diffraction of the emitted photon. It is demonstrated that dipole approximation is valid for the first order of diffraction DCR and not valid for higher orders of diffraction. On the basis of obtained equations for the first time it is theoretically shown that the angular distribution of the DCR is a system of very narrow ring-shaped peaks around of the Bragg direction. The calculations were performed taking into account the band structure of the transverse motion energy. - Highlights: • For the first time we developed theory of the DCR beyond the dipole approximation. • The applicability of the dipole approximation is considered. • Analytically shown that DCR angular distribution represents system of double rings. • In planar case angular distribution is not symmetrical with respect to X- and Y-axis

  13. Diffraction of entangled photon pairs by ultrasonic waves

    Science.gov (United States)

    Deng, Lü-bi

    2012-04-01

    In this paper, we have presented and established a new theoretical formulation of photon optics based on photon path and Feynman path integral idea. We have used Feynman path integral approach to discuss Fraunhofer, Fresnel diffraction of single photon and entangled photon pairs by ultrasonic wave and obtained the following results: i) quantum state and probability distribution of single photon and entangled photon pairs by Fraunhofer and Fresnel ultrasonic diffraction, ii) oblique incidence Raman-Nath and Bragg diffraction conditions, iii) total correlation state and its probability distribution. Our calculation results are in agreement with the experiment results. Comparing one-photon and two-photon diffraction effects by ultrasonic waves, we have found that two-photon diffraction by ultrasonic waves is also a sub-wavelength diffraction.

  14. Ion implanted Bragg endash Fresnel lens

    International Nuclear Information System (INIS)

    We have investigated the feasibility of widening the bandpath of the Bragg endash Fresnel optical element through the use of ion implantation. The focusing properties of Bragg endash Fresnel lenses (BFLs) were studied as a function of the implantation dose and energy. An enhancement of the focus intensity of up to 15% was found, which is less than expected. Due to the complicated scattering of the low energy ions inside the micrometer- and submicrometer-sized crystal features that make up the BFL relief, the implantation technology destroys the peripheral zones of the BFL more than it increases the intensity in the focus. Nevertheless we believe that high energy implantation can be successfully used to modify the BFL reflectivity, especially in the case of nearly backscattering reflection. copyright 1996 American Institute of Physics

  15. Bragg Curve Counter for primary beam monitor

    International Nuclear Information System (INIS)

    The prototype Bragg Curve Counter (BCC) has been tested by α-source (241Am) with a continuous gas flow system (P-10: 90% Ar+10% CH4, at 300Torr). Two types of the Frisch grid were prepared for the BCC. One was made of expanded metal meshes, which consist of 175 meshes/inch2 with a 100μmt nickel sheet. The other was made of a 1mm pitch wire with φ 50 μm of the tungsten. The shape of Bragg peak signal was compared each other. It was found that the energy spectrum obtained by the wire grid is a little sharper than that obtained by the meshes grid. However the meshes grid is superior than the wire grid so far as handling and durability are concerned. (author)

  16. Sampled phase-shift fiber Bragg gratings

    Institute of Scientific and Technical Information of China (English)

    Xu Wang(王旭); Chongxiu Yu(余重秀); Zhihui Yu(于志辉); Qiang Wu(吴强)

    2004-01-01

    A phase-shift fiber Bragg grating (FBG) with sampling is proposed to generate a multi-channel bandpass filter in the background of multi-channel stopbands. The sampled noire fiber gratings are analyzed by Fourier transform theory first, and then simulation and experiment are performed, the results show that transmission peaks are opened in every reflective channel, the spectrum shape of every channel is identical.It can be used to fabricate multi-wavelength distributed feedback (DFB) fiber laser.

  17. Study on position sensitive Bragg detector

    International Nuclear Information System (INIS)

    A position sensitive Bragg Curve Spectroscopy (PS-BCS) for heavy ion identification is introduced. The position signal is extracted via an auxiliary grid (P grid) between the anode and the Frisch grid. The position is determined by the wires. The charge division method have been used for position read-out. The test results of the detector with 252Cf α source have shown a position resolution ΔX<9 mm

  18. Improvement of soybean variety 'Bragg' through mutagenesis

    International Nuclear Information System (INIS)

    Full text: Variety 'Bragg' (Jackson x D49-2491) of soybean (Glycine max. (L.) Merrill) was found to be high yielding and widely adaptable throughout India. Its yield stability, however, is unsatisfactory, probably due to low germinability necessitating use of higher seed rate. With the main objective to rectify this defect, mutagenesis involving chemical as well as physical mutagens was used. Dry seeds were treated with EMS or MMS (0.2, 0.4 and 0.6%), or gamma rays (15, 20 and 25 kR) with and without additional exposure to UV (2 hrs at 260 nm) in 1982. In M2, a mutation frequency ranging from 2.24 to 22.85% was observed. Screening of M2 and of subsequent generations yielded a broad spectrum of mutations. Some of the mutants are agronomically useful. Among them, mutant 'T214' resulting from 25 kR gamma rays + UV, was found to possess better germinability (+15%), earliness (5 days) and high yield during both rainy and post-rainy seasons in 1986 and 1987, when compared with the parent variety 'Bragg'. The mutant has smaller seed-size (TGW 125 g) than the parent (145 g). In soybean, large-seeded varieties were reported to have poorer seed germinability. Thus, the better germinability of the mutant might be related to its reduced seed size. Seeds of the mutant show a light brown colour of the hilum in contrast to the black hilum of 'Bragg'. In other characters the mutant is similar to 'Bragg'. The mutant should have potential for commercial cultivation in India. For confirmation of its agronomically superior performance, it is undergoing national evaluation in multilocational trials under 'All India Co-ordinated Research Project on Soybean (ICAR)'. The strain has been named 'NRC-2'. (author)

  19. Fort Bragg Embraces Groundbreaking Heat Pump Technology

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2013-03-01

    The U.S. Army’s Fort Bragg partnered with the Department of Energy (DOE) to develop and implement solutions to build new, low-energy buildings that are at least 50% below Standard 90.1-2007 of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), the American National Standards Institute (ANSI), and the Illuminating Engineering Society of North America (IESNA) as part of DOE’s Commercial Building Partnerships (CBP) Program.

  20. Room temperature continuous wave operation of single-mode, edge-emitting photonic crystal Bragg lasers

    OpenAIRE

    Zhu, Lin; Sun, Xiankai; DeRose, Guy A.; Scherer, Axel; Yariv, Amnon

    2008-01-01

    We report the first room temperature CW operation of two dimensional single-mode edge-emitting photonic crystal Bragg lasers. Single-mode lasing with single-lobed, diffraction limited far-fields is obtained for 100μm wide and 550μm long on-chip devices. We also demonstrate the tuning of the lasing wavelength by changing the transverse lattice constant of the photonic crystal. This enables a fine wavelength tuning sensitivity (change of the lasing wavelength/change of the lattice constant) of ...

  1. Distributed Bragg reflectors in comparison to RUGATE and nested super lattices - growth, reflectivity, and conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Figge, Stephan; Dartsch, Heiko; Aschenbrenner, Timo; Kruse, Carsten; Hommel, Detlef [University of Bremen (Germany)

    2008-07-01

    This paper investigates the feasibility of conductive Al-GaN reflectors with corRUGATEd (RUGATE) index profiles in comparison to standard distributed Bragg reflectors (DBR) and nested super lattice (NSL) DBRs. The samples are analyzed by reflectometry, X-ray diffraction, and electrical measurements. The RUGATE implementation of the reflectors exhibited two times higher vertical conductivity in comparison to the DBRs and showed slightly lower reflectivity. The nested super lattice approach for DBRs turned out to be an alternative which is easy to manufacture and which shows high reflectivity values. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. X-ray Mirage Diffraction and Its Interference Fringes

    Science.gov (United States)

    Fukamachi, Tomoe; Kawamura, Takaaki

    When the dispersion angle of X-rays in a perfect crystal is large, interference fringes are observed between the beams in the Bragg-Laue mode and Bragg-Bragg-Laue mode in the emitted beams from the lateral surface. If the crystal is weakly bent, X-rays propagate along a path of hyperbolic form and are diffracted from the incident surface, which is called mirage diffraction. Under the condition, mirage interference fringes between two mirage diffraction beams are observed not only from the incident surface but also from the lateral surface. Two approaches are proposed to determine strain parameters in the bent crystal by using the mirage interference fringes from the incident surface or the lateral surface. In one approach, the third peak of the mirage interference fringes is used. In the other, the region is used where no direct beam reaches to the lateral surface. The resultant strain parameters determined by the two approaches show excellent agreement. Some characteristics and advantages of using mirage interference fringes are discussed.

  3. A Linear Single-Crystal Bragg-Fresnel Lens With SiO2 Surface Structure

    International Nuclear Information System (INIS)

    Bragg-Fresnel lens (BFL) as thin silicon dioxide strips grown on the surface of perfect silicon crystal was designed, manufactured and experimentally tested. In this case the BFL structure consists of a set of silicon dioxide rectangular shape etched zones arranged by the Fresnel zone law. The stress within coated and uncoated crystal regions is opposite in sign, whether tensile or compressive. The strain in the substrate crystal lattice directly underneath discontinuities in the deposited film give rise to phase difference between waves diffracted from coated and uncoated crystal regions. This phase difference is known to be dependent on the thickness and composition of film and substrate. The focusing properties of Si/SiO2 BFLs with 107 zones and 0.3 micrometer outermost zone width were experimentally studied as a function of the silicon oxide thickness in the range of 100 - 400 nanometers. It was shown that deformation Bragg-Fresnel lenses could effectively focus hard X-rays to a linear focal spot of about 2 microns. The efficiency of focusing was found to be about 16% at energy 10 keV. The developed lens design is a promising approach to extend the angular range of focusing by Bragg-Fresnel optical elements and to avoid some drawbacks of BFL properties related to aspect-ratio dependent etching

  4. Fiber Bragg Grating Sensors for Harsh Environments

    Directory of Open Access Journals (Sweden)

    Stephen J. Mihailov

    2012-02-01

    Full Text Available Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments.

  5. Spatially Resolved Analysis of Bragg Selectivity

    Directory of Open Access Journals (Sweden)

    Tina Sabel

    2015-11-01

    Full Text Available This paper targets an inherent control of optical shrinkage in photosensitive polymers, contributing by means of spatially resolved analysis of volume holographic phase gratings. Point by point scanning of the local material response to the Gaussian intensity distribution of the recording beams is accomplished. Derived information on the local grating period and grating slant is evaluated by mapping of optical shrinkage in the lateral plane as well as through the depth of the layer. The influence of recording intensity, exposure duration and the material viscosity on the Bragg selectivity is investigated.

  6. Status of the OCS Bragg-Spectrometer for SODART

    DEFF Research Database (Denmark)

    Wiebicke, H.J.; Halm, I.; Christensen, Finn Erland; Rasmussen, Inga; Rasmussen, H.E.

    OCS, the Bragg spectrometer for the SODART X-ray telescope onboard the SPECTRUM-RONTGEN-GAMMA (SRG) satellite has been completed. Preliminary results of his performance are presented.......OCS, the Bragg spectrometer for the SODART X-ray telescope onboard the SPECTRUM-RONTGEN-GAMMA (SRG) satellite has been completed. Preliminary results of his performance are presented....

  7. Status of the OCS Bragg-Spectrometer for SODART

    DEFF Research Database (Denmark)

    Wiebicke, H.J.; Halm, I.; Christensen, Finn Erland;

    1998-01-01

    OCS, the Bragg spectrometer for the SODART X-ray telescope onboard the SPECTRUM-RONTGEN-GAMMA (SRG) satellite has been completed. Preliminary results of his performance are presented.......OCS, the Bragg spectrometer for the SODART X-ray telescope onboard the SPECTRUM-RONTGEN-GAMMA (SRG) satellite has been completed. Preliminary results of his performance are presented....

  8. Optical fibre Bragg grating recorded in TOPAS cyclic olefin copolymer

    DEFF Research Database (Denmark)

    Johnson, I.P.; Yuan, Scott Wu; Stefani, Alessio; Nielsen, Kristian; Rasmussen, Henrik K.; Khan, L.; Webb, D.J.; Kalli, K.; Bang, Ole

    2011-01-01

    A report is presented on the inscription of a fibre Bragg grating into a microstructured polymer optical fibre fabricated from TOPAS cyclic olefin copolymer. This material offers two important advantages over poly (methyl methacrylate), which up to now has formed the basis for polymer fibre Bragg...

  9. Diffraction Anomalous Fine Structure spectroscopy at the beamline BM2 at the European Synchrotron Radiation Facility

    OpenAIRE

    Renevier, H.; Grenier, S.; ARNAUD, S; Berar, J.F.; Caillot, B.; Hodeau, J. L.; Letoublon, A.; Proietti, M. G.; Ravel, B.

    2003-01-01

    Diffraction Anomalous Fine Structure (DAFS) spectroscopy uses resonant elastic x-rays scattering as an atomic, shell and site selective probe that gives information on the electronic structure and the local atomic environment as well as on the long range ordered crystallographic structure. A DAFS experiment consists of measuring the Bragg peak intensities as a function of the energy of the incoming x-ray beam. The French CRG (Collaborative Research Group) beamline BM2-D2AM (Diffraction Diffus...

  10. Structural characterization of thin-film cadmium stearate by X-ray diffraction technique

    International Nuclear Information System (INIS)

    X-ray diffraction measurement were carried out on thin films of cadmium stearate using an X-ray diffractometer at Unit Tenaga Nuklear. Structure characteristic obtained from the measured diffraction pattern are compared with that of thin films of manganese stearate reported earlier by Pomerantz et. al. Some of the structural similarities (such as inter-planar spacing) and differences (such as the absence of subsidiary peak between Bragg peaks) are found and discussed

  11. Video-STM, LEED and X-ray diffraction investigations of PTCDA on graphite

    OpenAIRE

    Ludwig, Christoph; Gompf, Bruno; Glatz, Wolfgang; Petersen, Jörg; Eisenmenger, Wolfgang; Möbus, Manfred; ZIMMERMANN, UWE; Karl, Norbert

    1992-01-01

    Thin films of the organic molecule perylene-3,4,9,10-tetracarboxylic-dianhydride ("PTCDA") on graphite (0001) have been investigated from the mono- to the multilayer regime with low energy electron diffraction (LEED), X-ray-diffraction in Bragg-Brentano geometry, and high resolution scanning tunneling microscopy (STM). These different methods proved epitaxial growth in a coincident superstructure and yielded congruent results concerning details of the crystallographic structure of the epilaye...

  12. X-ray diffraction microtomography using synchrotron radiation

    CERN Document Server

    Barroso, R C; Jesus, E F O; Oliveira, L F

    2001-01-01

    The X-ray diffraction computed tomography technique is based on the interference phenomena of the coherent scatter. For low-momentum transfer, it is most probable that the scattering interaction will be coherent. A selective discrimination of a given element in a scanned specimen can be realized by fixing the Bragg angle which produces an interference peak and then, to carry out the computed tomography in the standard mode. The image reconstructed exalts the presence of this element with respect to other ones in a sample. This work reports the feasibility of a non-destructive synchrotron radiation X-ray diffraction imaging technique. This research was performed at the X-ray Diffraction beam line of the National Synchrotron Light Laboratory (LNLS) in Brazil. The coherent scattering properties of different tissue and bone substitute materials were evaluated. Furthermore, diffraction patterns of some polycrystalline solids were studied due to industrial and environmental human exposure to these metals. The obtai...

  13. Colloquium: Optical simulations of electron diffraction by carbon nanotubes

    International Nuclear Information System (INIS)

    This colloquium discusses the atomic structure of carbon nanotubes as deduced from high-resolution electron microscopy and electron diffraction in transmission through a single nanotube. The principal features of the observed micrographs are interpreted in terms of the cylindrical, chiral geometry of the atomic distribution of single-wall or multiwall nanotubes. In order to better understand the mechanism of image formation in electron diffraction, the authors propose optical simulation experiments using a laser pointer and a little 'diffraction laboratory on a slide'. The simulations visibly reproduce all the features of the observed electron micrographs, namely, the quasihexagonal patterns of Bragg spots, the streaked nature of the spots, the doubling of the spot number induced by chirality, etc. The present colloquium should allow a general readership to appreciate the continuing efficiency and power of diffraction methods for the determination of the structure of macromolecules

  14. Fused-silica sandwiched three-port grating under second Bragg angle incidence

    Science.gov (United States)

    Li, Hongtao; Wang, Bo; Pei, Hao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2016-05-01

    The fused-silica sandwiched three-port grating under second Bragg angle incidence is presented with operation in transmission. To obtain a highly-efficient three-port grating for a working wavelength of 800 nm, the grating depth and period should be optimized by using rigorous coupled-wave analysis. With the optimized different three-port grating depths and periods, both TE-polarized and TM-polarized waves can be diffracted into three orders with nearly 33% efficiency for the given duty cycle of 0.6. Based on the grating parameters of numerical optimization, modal method may be employed to explain the physical mechanism of the beam propagation in the grating and analyze the splitting behavior. For the sandwiched three-port grating, it is feasible that the diffraction efficiencies can be enhanced for both TE and TM polarizations.

  15. Layered synthetic microstructures as Bragg diffractors for x rays and extreme ultraviolet: theory and predicted performance

    International Nuclear Information System (INIS)

    Recent developments in thin film technology have made possible the construction of multilayered thin film structures that act as efficient Bragg diffractors for x rays and extreme ultraviolet (EUV) radiation. These structures (which we term layered synthetic microstructures or LSMs) are analogous to multilayers interference filters for the visible spectral region and have important potential applications in many areas of x-ray/EUV instrumentation. In this paper the theory of x-ray diffraction by periodic structures is applied to LSMs, and approximate formulas for estimating their performance are presented. A more complete computation scheme based on optical multilayer theory is described, and it is shown that, by adjusting the refractive indices and thicknesses of the component layers, the diffracting properties may be tailored to specific applications. Finally, it is shown how the theory may be modified to take account of imperfections in the LSM structure and to compute the properties of nonperiodic structures

  16. Fano resonances in integrated silicon Bragg reflectors for sensing applications.

    Science.gov (United States)

    Chang, Chia-Ming; Solgaard, Olav

    2013-11-01

    We investigate theoretically and experimentally Fano resonances in integrated silicon Bragg reflectors. These asymmetric resonances are obtained by interference between light reflected from the Bragg waveguide and from the end facet. The Bragg reflectors were designed and modeled using the 1D transfer matrix method, and they were fabricated in standard silicon wafers using a CMOS-compatible process. The results show that the shape and asymmetry of the Fano resonances depend on the relative phase of the reflected light from the Bragg reflectors and end facet. This phase relationship can be controlled to optimize the lineshapes for sensing applications. Temperature sensing in these integrated Bragg reflectors are experimentally demonstrated with a temperature sensitivity of 77 pm/°C based on the thermo-optic effect of silicon. PMID:24216944

  17. Process and device for diffracting rays of photons or neutrons

    International Nuclear Information System (INIS)

    The diffraction crystal or the diffraction rating instrument has an improved crystal structure or an improved grid spacing. The structure has a surface, on which a ray of photons or neutrons impinges and planar diffraction spaces or grid spaces along this surface with progressively larger spaces along this surface, so that a reducing Bragg diffraction angle is created for monochromatic radiation, and the useful range and acceptance angle are increased. The progressively increased planar grid spacing for the diffraction crystal is created by producing a temperature difference or a temperature gradient over the crystal structure, by combining several crystal structures with different compositions, by using a single crystal structure of different composition and by thus altering the planar grid spacing along the crystal surface and/or using combinations of these processes. The progressively larger grid spacings in diffraction gratings of this type are produced in the manufacture of diffraction gratings by controlling the cutting tool cutting grooves or the laser, electron or ion beam for irradiating the photon top layer etc. It is also possible to create these different grid spacings by the diffraction gratings having a temperature gradient applied to them in the same way as the diffraction crystal. (orig.)

  18. Structural and optical properties of ZrO2 and Al2O3 thin films and Bragg reflectors grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Our objective is to build a threshold-less laser based on the emission from a Bose-Einstein condensate of exciton-polaritons in a semiconductor microcavity-resonator. For this purpose, high reflective mirrors with smooth boundaries are necessary. The aspired resonator structure consists of a half-wavelength ZnO cavity embedded between two ZrO2/Al2O3 Bragg reflectors. We present high-reflective ZrO2/Al2O3 Bragg reflectors grown by pulsed laser deposition on c-plane sapphire and silicon substrates. For ZrO2/Al2O3 Bragg reflectors with a layer pair number of 12.5, reflectivity values of 99.8% at 3.3 eV and smooth surfaces have been reached. As preceding investigations, the optical and structural properties as the refractive indices, the crystal structure, and the surface properties of the used materials have been determined and optimised. It was found that these properties depend on the substrate and the position in the Bragg reflector layer stack. The optical and structural properties of the single layers and Bragg reflectors have been gained from spectroscopic ellipsometry in the energy range (1.0-4.5) eV, X-ray diffraction measurements, atomic force microscopy, and transmission scanning electron microscopy

  19. Research of fiber Bragg grating geophone based on cantilever beam

    Science.gov (United States)

    Wang, Liang; Chen, Shao-hua; Tao, Guo; Lu, Gui-wu; Zhao, Kun

    2009-07-01

    Along with the development of seismic exploration, the demand of frequency, dynamic range, precision and resolution ration is increased. However, the traditional geophone has disadvantages of narrower bandwidth, lower dynamic range and resolution, and cannot meet the new needs of seismic exploration. Geophone technology is a choke point, which constrains the development of petroleum prospecting in recent years. Fiber Bragg Grating seism demodulation technology is the newest kind of seism demodulation technology. The sensing probe of the Fiber Bragg Grating geophone is made up of Fiber Bragg Gating. The information which it collects is embodied by wavelength. The modulation-demodulation is accomplished by Fiber Bragg Gating geophone directly. In this paper, we design different size Fiber Bragg Grating geophones based on the transmission properties of Fiber Bragg Grating and cantilever beam method. Beryllium bronze and stainless steel are chosen as the elastic beam and shell materials, respectively. The parameters such as response function and sensitivity are given theoretically. In addition, we have simulated the transmission characteristics of Fiber Bragg Grating geophone by virtue of finite element analysis. The influences of wavelength, mass block, fiber length on the characteristics of geophones are discussed in detail, and finally the appropriate structural parameters are presented.

  20. Laser diffraction microscopy

    OpenAIRE

    Schall, P.

    2009-01-01

    Crystals composed of micrometer size colloidal particles diffract light and are both of fundamental interest as well as having important applications as filters, sensors and photonic devices. Laser light is used to diffract from these crystals in close analogy to x-ray or electron diffraction used for atomic crystals. Laser diffraction microscopy explores optical diffraction contrast to image crystals and crystal defects in analogy to the transmission electron microscopy technique used to ima...

  1. Frequency shift of the Bragg and Non-Bragg backscattering from periodic water wave.

    Science.gov (United States)

    Wen, Biyang; Li, Ke

    2016-01-01

    Doppler effect is used to measure the relative speed of a moving target with respect to the radar, and is also used to interpret the frequency shift of the backscattering from the ocean wave according to the water-wave phase velocity. The widely known relationship between the Doppler shift and the water-wave phase velocity was deduced from the scattering measurements data collected from actual sea surface, and has not been verified under man-made conditions. Here we show that this ob- served frequency shift of the scattering data from the Bragg and Non-Bragg water wave is not the Doppler shift corresponding to the water-wave phase velocity as commonly believed, but is the water-wave frequency and its integral multiple frequency. The power spectrum of the backscatter from the periodic water wave consists of serials discrete peaks, which is equally spaced by water wave frequency. Only when the water-wave length is the integer multiples of the Bragg wave, and the radar range resolution is infinite, does the frequency shift of the backscattering mathematically equal the Doppler shift according to the water-wave phase velocity. PMID:27531469

  2. ''Experimental and theoretical study of bragg-Fresnel optics etched on multilayer structures. Application: lenses for X-Ray imaging''

    International Nuclear Information System (INIS)

    This work concerns the study of a new type of X-ray focusing optics known as Bragg-Fresnel lenses developed for imaging in the X and X-UV range. These optics, etched on multilayer structure, combine the focusing properties of zone plate with the Bragg reflection of multilayer used like support. Using synchrotron sources and a plasma source produced by a laser, we tested the efficiency and the spatial resolution of these lenses. With a monochromatic beam, we first obtained the image of a object by using the first order diffraction of an elliptical off-axis Bragg-Fresnel lens. By using only one part of a lens, the superposition of different diffraction orders in focal plane can be avoided, thus improving the image contrast. In order to evaluate the chromatic aberrations of these lenses, we have summed on the same image, three exposures at different energies in the band pass of the multilayer. To reduce these kind of aberrations, we used a system composed of two off-axis lenses. To simplify the alignment, we tested an elliptical off-axis lens associated with a lamellar grating. Thus we are able to validate the theoretical approximation of an off-axis Bragg-Fresnel lens to a variable spaced grating. Finally, to show the perturbation brought by the zeroth order, we successively imaged a laser plasma source with a centred and an off-axis elliptical lenses. As with the synchrotron source, a set of images of a test object enabled us to improve the spatial resolution. (author)

  3. A ballistic motion disrupted by Bragg reflections

    CERN Document Server

    Clark, Jeremy Thane

    2012-01-01

    I study a Lindblad dynamics modeling a quantum test particle in a Dirac comb that collides with particles from a background gas. The main result is a homogenization theorem in a semi-classical limiting regime involving large mass for the test particle and a rescaling for the strength and period of the Dirac comb. Over the time interval considered, the particle would exhibit essentially ballistic motion if either the singular periodic potential or the kicks from the gas were removed. However, the particle behaves diffusively when both sources of forcing are present. The conversion of the motion from ballistic to diffusive is generated by occasional Bragg reflections that result when the test particle's momentum is driven through a collision near an element of the half-spaced reciprocal lattice of the Dirac comb.

  4. Fiber Bragg gratings for microwave photonics subsystems.

    Science.gov (United States)

    Wang, Chao; Yao, Jianping

    2013-09-23

    Microwave photonics (MWP) is an emerging filed in which photonic technologies are employed to enable and enhance functionalities in microwave systems which are usually very challenging to fulfill directly in the microwave domain. Various photonic devices have been used to achieve the functions. A fiber Bragg grating (FBG) is one of the key components in microwave photonics systems due to its unique features such as flexible spectral characteristics, low loss, light weight, compact footprint, and inherent compatibility with other fiber-optic devices. In this paper, we discuss the recent development in employing FBGs for various microwave photonics subsystems, with an emphasis on subsystems for microwave photonic signal processing and microwave arbitrary waveform generation. The limitations and potential solutions are also discussed. PMID:24104174

  5. Digital electron diffraction – seeing the whole picture

    International Nuclear Information System (INIS)

    Computer control of beam tilt and image capture allows the collection of electron diffraction patterns over a large angular range, without any overlap in diffraction data and from a region limited only by the size of the electron beam. This results in a significant improvement in data volumes and ease of interpretation. The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters

  6. Solgel grating waveguides for distributed Bragg reflector lasers.

    Science.gov (United States)

    Fardad, M A; Luo, H; Beregovski, Y; Fallahi, M

    1999-04-01

    Solgel grating waveguides and their application to the fabrication of external-cavity distributed Bragg reflector (DBR) lasers are demonstrated. A new composition of aluminosilicate material is developed for the fabrication of single-mode waveguides and Bragg reflectors. An average loss of <0.2 dB/cm is measured in the single-mode waveguides at 1550 nm. The reflectors show filtering greater than 97% near 1530 nm, with a bandwidth of ~0.6 nm . The Bragg reflectors are used as feedback resonators for DBR lasers. Single-mode lasing with a sidemode suppression of better than 25 dB is demonstrated. PMID:18071539

  7. Modeling Component-based Bragg gratings Application: tunable lasers

    Directory of Open Access Journals (Sweden)

    Hedara Rachida

    2011-09-01

    Full Text Available The principal function of a grating Bragg is filtering, which can be used in optical fibers based component and active or passive semi conductors based component, as well as telecommunication systems. Their ideal use is with lasers with fiber, amplifiers with fiber or Laser diodes. In this work, we are going to show the principal results obtained during the analysis of various types of grating Bragg by the method of the coupled modes. We then present the operation of DBR are tunable. The use of Bragg gratings in a laser provides single-mode sources, agile wavelength. The use of sampled grating increases the tuning range.

  8. Thermally tunable integrated planar Bragg-grating stabilized diode laser

    Science.gov (United States)

    Lynch, S. G.; Gates, J. C.; Berry, S. A.; Holmes, C.; Smith, P. G. R.

    2015-03-01

    A pair of external cavity diode lasers are fabricated using an integrated planar Bragg grating. The planar waveguide and Bragg reflector is UV-written within a glass-on-silicon chip. Intensity isolated, continuous wavelength tuning at > 1kHz modulation rate is acheived using micro-heating elements fabricated directly over the Bragg grating. Low RIN (<140dB) and low linewidth (δν ~ 200 kHz) operation is found using a heterodyne measurement. We demonstrate the lasers operating in phase-locked loop configuration where one laser is frequency-offset locked to the other.

  9. Dispersion blue-shift in an aperiodic Bragg reflection waveguide

    Science.gov (United States)

    Fesenko, Volodymyr I.; Tuz, Vladimir R.

    2016-04-01

    A particular feature of an aperiodic design of cladding of Bragg reflection waveguides to demonstrate a dispersion blue-shift is elucidated. It is made on the basis of a comparative study of dispersion characteristics of both periodic and aperiodic configurations of Bragg mirrors in the waveguide system, wherein for the aperiodic configuration three procedures for layers alternating, namely Fibonacci, Thue-Morse and Kolakoski substitutional rules are considered. It was found out that, in a Bragg reflection waveguide with any considered aperiodic cladding, dispersion curves of guided modes appear to be shifted to shorter wavelengths compared to the periodic configuration regardless of the modes polarization.

  10. Dispersion blue-shift in an aperiodic Bragg reflection waveguide

    CERN Document Server

    Fesenko, Volodymyr I

    2016-01-01

    A particular feature of an aperiodic design of cladding of Bragg reflection waveguides to demonstrate a dispersion blue-shift is elucidated. It is made on the basis of a comparative study of dispersion characteristics of both periodic and aperiodic configurations of Bragg mirrors in the waveguide system, wherein for the aperiodic configuration three procedures for layers alternating, namely Fibonacci, Thue-Morse and Kolakoski substitutional rules are considered. It was found out that, in a Bragg reflection waveguide with any considered aperiodic cladding, dispersion curves of guided modes appear to be shifted to shorter wavelengths compared to the periodic configuration regardless of the modes polarization.

  11. Resonantly enhanced Bragg-scattering spectroscopy of an atomic transition

    Science.gov (United States)

    Yang, Xudong; Qiao, Cuifang; Li, Chuanliang; Chen, Fenghua

    2016-07-01

    A novel resonantly enhanced Bragg-scattering (REBS) spectroscopy from a population difference grating (PDG) is reported. The PDG is formed by a standing-wave (SW) pump field, which periodically modulates the space population distributions of two levels in the 87Rb D1 line. Then, a probe beam, having identical frequency and orthogonal polarization with the SW pump field, is Bragg-scattered by the PDG. The research achievement shows that the Bragg-scattered light is strongest at an atomic transition, and forms an REBS spectrum with a high signal-to-noise ratio and sub-natural linewidth. The observed REBS can be applied in precise frequency measurements.

  12. The Bragg Crystal Spectrometer for AXAF

    International Nuclear Information System (INIS)

    MIT's High Resolution X-ray Spectroscopy investigation on AXAF involves two complementary dispersive instruments, a Bragg Crystal Spectrometer (BCS) and a High Energy Transmission Grating Spectrometer (HETGS). The overall goal of the investigation is to study the physical conditions in celestial sources by means of detailed measurements of their X-ray spectra. High spectral resolution measurements can be used to perform diagnostics of emitting and absorbing matter, leading to knowledge of temperature, ionization state, elemental abundance, density and optical depth. The Bragg Crystal Spectrometer gives resolving powers of 200-2000 over the energy band 0.5-8 keV and resolving powers of 50-70 over 0.14-0.5 keV. The effective collecting areas in a typical scanning observation are 4-60 cm/sup 2/, and the minimum detectable line flux is 4-30 X 10/sup -6/ photons cm/sup -2/ s/sup -1/. The BCS will be located at the AXAF focal plane. The instrument consists of 10 curved diffractors each of which has a quasi-toroidal geometry, two types of imaging proportional counters optimized for low background (one sealed and one flow), an internal monitor counter that can be inserted into the beam to measure total source flux, a mechanical system that maintains Rowland circle geometry and an appropriate command and data system. The BCS is an upgraded and improved version of the Focal Plane Crystal Spectrometer flown on the Einstein Observatory. It will be used to measure the strengths of individual lines from both point and extended objects in order to apply plasma diagnostic techniques to the study of cosmic X-ray sources

  13. Influence of Stacking Faults on Diffraction Properties of Diamond by Synchrotron Topographic Imaging

    Science.gov (United States)

    Huang, Xian Rong; Macrander, Albert T.

    2010-06-01

    Diamond crystals are becoming more important or indispensable as critical 3rd- and 4th-generation synchrotron optical components. However, diamond generally contains various defects, among which stacking faults (SFs) are most detrimental since they are planar defects that can exist in all kinds of diamonds with dimensions up to square millimeters. Here we introduce our topographic studies of common defects and particularly SFs in diamonds. In monochromatic topography, SFs show strong black contrast on the rocking curve tails, thus broadening the rocking curve width and reducing the cleanness of the diffraction spectrum. On the Bragg peak, SFs appear as white-line contrast (absence of diffraction), indicating that they can significantly reduce the Bragg reflectivity. SFs always show black contrast in white-beam topography caused by the simultaneous diffraction of a range of wavelengths from the SFs. These results may provide clear guidelines for understanding the performance of diamonds in synchrotron optics and also for diamond crystal growth.

  14. Diffraction coherence in optics

    CERN Document Server

    Françon, M; Green, L L

    2013-01-01

    Diffraction: Coherence in Optics presents a detailed account of the course on Fraunhofer diffraction phenomena, studied at the Faculty of Science in Paris. The publication first elaborates on Huygens' principle and diffraction phenomena for a monochromatic point source and diffraction by an aperture of simple form. Discussions focus on diffraction at infinity and at a finite distance, simplified expressions for the field, calculation of the path difference, diffraction by a rectangular aperture, narrow slit, and circular aperture, and distribution of luminous flux in the airy spot. The book th

  15. Single crystal surface structure by bragg scattering

    DEFF Research Database (Denmark)

    Nielsen, Mogens

    1985-01-01

    X-ray diffraction is becoming an important tool in the measurements of surface structures. Single crystalline samples are used as in Low Energy Electron Diffraction (LEED)-studies. The X-ray technique is somewhat more involved due to the need of bright, collimated photon sources, in general...... synchrotron X-rays, and of very accurate angular settings in the ultrahigh-vacuum environment of the sample. We present the technique and discuss examples of experimental results....

  16. UV writing of advanced Bragg gratings in optical waveguides

    DEFF Research Database (Denmark)

    Jensen, Jesper Bo Damm

    2002-01-01

    The subject of this ph.d. thesis is the fabrication of Bragg gratings in optical waveguides. During the study Bragg gratings were written in both planar waveguides and optical fibers using pulsed or continuous-wave lasers operating in the ultraviolet (UV) range. The main result is the development...... half the periodicity of the index modulation profile in the Bragg grating. A phase shift in the grating is realized by shifting the UV irradiance from one polarization to the other during the grating inscription. The amplitude of the modulation can also be varied continuously by changing the ration...... phase shifts were then translated into a polarizer angle profile and the Bragg grating were written using a pulsed excimer laser. Only optical fibers were used in this part of the thesis. The high quality planar waveguides used during the study were produced in the cleanroom facility at the...

  17. Bragg Reflection of Waves by Different Shapes of Artificial Bars

    Institute of Scientific and Technical Information of China (English)

    许泰文; 张宪国; 蔡立宏

    2002-01-01

    Experiments are performed in a wave flume to demonstrate the Bragg reflection of linear gravity waves by artificialbars. Three different artificial bars with rectangular, triangular and rectified cosinoidal shapes are placed discretely on theseabed for measurement of the Bragg reflection. A series of experimental conditions including the number of bars, the pe-riodic bar spacing, the water depth and various wave conditions are tested. Key parameters influencing the Bragg reso-nances are investigated. The experimental data are compared with the values from both theoretical and numerical models.Some key parameters have proved to be effective in describing the primary resonances. Predictive equations of the charac-teristics for the Bragg reflection are proposed in this paper.

  18. Structural Health Monitoring Using Fiber Bragg Grating Sensor Matrix Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Fiber Bragg Grating had been identified as very important elements, especially for strain measurements in smart structures. In many applications, arrays of FBG...

  19. The localized surface plasmon resonances based on a Bragg reflector

    Science.gov (United States)

    Wang, Jie; Liu, Yumin; Yu, Zhongyuan; Ye, Chunwei; Lv, Hongbo; Shu, Changgan

    2014-09-01

    In this paper, we present the theoretical analysis on how the wavelength of the localized surface plasmon resonances of gold nanoparticle can lead shift for the resonance wavelength. In our results, we calculate the scattering cross-section, the absorption cross-section and the field enhancement due to the nanoparticle. Numerical simulation were done using the finite element method (FEM). The work that we do here is different from the previous work because we use the Bragg reflector as a substrate. The Bragg reflector has a property of high reflectivity in some certain frequency bandwidth because of its periodic structure. The coherence interference of the Bragg reflector contributes to the plasmon resonances and results in some special character for a wide variety application, from sensing to photovoltaic. The periodic number of the Bragg reflector substrate and shapes of the nanoparticles are also discussed that result in a shift of the resonance wavelength.

  20. Time/Wavelength Fiber Bragg Grating Multiplexing Sensor Array

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A novel time/wavelength-multiplexed fiber Bragg grating sensor array is presented. This type of sensor array has the advantages of more points for multi-point measurement, simple structure and low cost.

  1. Coherent X-ray diffraction studies of mesoscopic materials

    Energy Technology Data Exchange (ETDEWEB)

    Shabalin, Anatoly

    2015-12-15

    This thesis is devoted to three separate projects, which can be considered as independent. First, the dynamical scattering effects in the Coherent X-ray Diffractive Imaging (CXDI) method are discussed. Based on the simulation results, a straightforward method for correction for the refraction and absorption artifacts in the Bragg CXDI reconstruction is suggested. The second part summarizes the results of an Coherent X-ray Diffractive Imaging experiment with a single colloidal crystal grain. A remarkable result is that positions of individual particles in the crystal lattice have been resolved in three dimensions. The third project is devoted to X-ray diffraction experimental studies of structural evolution of colloidal crystalline films upon incremental heating. Based on the results of the analysis a model of structural evolution of a colloidal crystal upon heating on nanoscopic and mesoscopic length scales is suggested.

  2. Quantitative multiphase analysis of archaeological bronzes by neutron diffraction

    CERN Document Server

    Siano, S; Celli, M; Pini, R; Salimbeni, R; Zoppi, M; Kockelmann, W A; Iozzo, M; Miccio, M; Moze, O

    2002-01-01

    In this paper, we report the first investigation on the potentials of neutron diffraction to characterize archaeological bronze artifacts. The preliminary feasibility of phase and structural analysis was demonstrated on standardised specimens with a typical bronze alloy composition. These were realised through different hardening and annealing cycles, simulating possible ancient working techniques. The Bragg peak widths that resulted were strictly dependent on the working treatment, thus providing an important analytical element to investigate ancient making techniques. The diagnostic criteria developed on the standardised specimens were then applied to study two Etruscan museum pieces. Quantitative multiphase analysis by Rietveld refinement of the diffraction patterns was successfully demonstrated. Furthermore, the analysis of patterns associated with different artifact elements also yielded evidence for some peculiar perspective of the neutron diffraction diagnostics in archeometric applications. (orig.)

  3. Femtosecond Time-resolved MeV Electron Diffraction

    CERN Document Server

    Zhu, Pengfei; Cao, J; Geck, J; Hidaka, Y; Kraus, R; Pjerov, S; Shen, Y; Tobey, R I; Zhu, Y; Hill, J P; Wang, X J

    2013-01-01

    We report the experimental demonstration of electron diffraction with 130 femtosecond time resolution using bench-top MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminium and single-crystal 1T-TaS_{2} are obtained utilizing a 5 femto-Coulomb (~3x10^{4} electrons) pulse of electrons at 2.8 MeV. The timing jitter between the pump laser and probe electron beam was found to be ~ 100 fs. The time resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS_{2} following an optical pump. Our experiemntal results demonstrate the feasibility of ultimately realizing 40 fs time-resolved electron diffraction.

  4. Diffraction of collinear correlated photon pairs by an ultrasonic wave

    CERN Document Server

    Kwiek, Piotr

    2013-01-01

    The phenomenon of collinear photon pairs diffraction by an ultrasonic wave is investigated for Bragg incidence. A BBO crystal was used for producing collinear correlated photon pairs via type-I spontaneous parametric down-conversion. The experimental setup for diffraction of collinear correlated photon pairs was tested based on Malus' law for pairs of photons. The obtained results do not support the L. B. Deng's theory of 2012, presented in his work entitled "Diffraction of entangled photon pairs by ultrasonic waves" [Front. Phys. 7, 239 (2012)] . An alternative simple theoretical description of interaction of collinear photon pairs with ultrasonic waves is shown in the present paper which reveals very good agreement with corresponding experimental data.

  5. Coherent X-ray diffraction studies of mesoscopic materials

    International Nuclear Information System (INIS)

    This thesis is devoted to three separate projects, which can be considered as independent. First, the dynamical scattering effects in the Coherent X-ray Diffractive Imaging (CXDI) method are discussed. Based on the simulation results, a straightforward method for correction for the refraction and absorption artifacts in the Bragg CXDI reconstruction is suggested. The second part summarizes the results of an Coherent X-ray Diffractive Imaging experiment with a single colloidal crystal grain. A remarkable result is that positions of individual particles in the crystal lattice have been resolved in three dimensions. The third project is devoted to X-ray diffraction experimental studies of structural evolution of colloidal crystalline films upon incremental heating. Based on the results of the analysis a model of structural evolution of a colloidal crystal upon heating on nanoscopic and mesoscopic length scales is suggested.

  6. Fibre Bragg Grating Components for Filtering, Switching and Lasing

    OpenAIRE

    Yu, Zhangwei

    2008-01-01

    Fibre Bragg gratings (FBGs) are key components for a vast number of applications in optical communication systems, microwave photonics systems, and optical sensors, etc. The main topic of this thesis is fibre Bragg grating fabrication and applications in direct microwave optical filtering, high speed switching and switchable dual-wavelength fibre lasers. First, a brief overview is given about the photosensitivity in optical fibre, basic FBG fabrication techniques, the popular coupled-mode the...

  7. Photonic scanning receiver using an electrically tuned fiber Bragg grating.

    Science.gov (United States)

    Rugeland, P; Yu, Z; Sterner, C; Tarasenko, O; Tengstrand, G; Margulis, W

    2009-12-15

    A 5-cm-long electrically tuned fiber Bragg grating is used to filter a microwave signal on an optical carrier at 1.55 mum. A chirped distributed-feedback structure is employed, with a transmission bandwidth of 54 MHz and relative optical carrier rejection of >30 dB for rf frequencies >2 GHz. The rapid monotonic sweep of the Bragg wavelength is translated into a fast-frequency sweep for rf analysis. PMID:20016616

  8. X-Ray Diffraction.

    Science.gov (United States)

    Smith, D. K.; Smith, K. L.

    1980-01-01

    Reviews applications in research and analytical characterization of compounds and materials in the field of X-ray diffraction, emphasizing new developments in applications and instrumentation in both single crystal and powder diffraction. Cites 414 references. (CS)

  9. Bragg-von Laue diffraction generalized to twisted X-rays.

    Science.gov (United States)

    Jüstel, Dominik; Friesecke, Gero; James, Richard D

    2016-03-01

    A pervasive limitation of nearly all practical X-ray methods for the determination of the atomic scale structure of matter is the need to crystallize the molecule, compound or alloy in a sufficiently large (∼10 × 10 × 10 µm) periodic array. In this paper an X-ray method applicable to structure determination of some important noncrystalline structures is proposed. It is designed according to a strict mathematical analog of von Laue's method, but replacing the translation group by another symmetry group, and simultaneously replacing plane waves by different exact closed-form solutions of Maxwell's equations. Details are presented for helical structures like carbon nanotubes or filamentous viruses. In computer simulations the accuracy of the determination of structure is shown to be comparable to the periodic case. PMID:26919370

  10. Robustness via Diffractal Architectures

    CERN Document Server

    Moocarme, Matthew

    2015-01-01

    When plane waves diffract through fractal-patterned apertures, the resulting far-field profiles or diffractals also exhibit iterated, self-similar features. Here we show that this specific architecture enables robust signal processing and spatial multiplexing: arbitrary parts of a diffractal contain sufficient information to recreate the entire original sparse signal.

  11. Neutron polarisers for diffraction experiments

    International Nuclear Information System (INIS)

    Full text: Every neutron in a neutron beam has a spin which is either up or down. In an unpolarised beam, half the neutrons are up and half are down. A neutron polariser is a device which creates an imbalance in the number of up and down spin neutrons in the beam, thus giving a net beam polarisation. The three most common techniques for polarising neutron beams are supermirrors, Heusler alloy polarising monochromators and neutron spin filters. Supermirrors use the difference in refractive index for up and down spin neutrons at a magnetic/non-magnetic interface to selectively remove neutrons of one spin state from the beam. Heusler alloy polarisers give polarised beams through spin dependent Bragg reflection, and transmission filters work by preferentially absorbing the neutrons in one spin state. The most promising filter material is polarised gaseous 3He, in which the lone neutron is polarised and then the atom will preferentially absorb a neutron of the opposite spin. All three techniques have different advantages. Here, we compare the three techniques by generating quality factors which relate closely to an instruments performance in an experiment and determining which polariser will give the best quality factor for a given type of experiment. We find that supermirrors give the best results when narrow angular divergence of the neutron beam is desired, while filters are best when short wavelengths and wide angular divergence is required. For a powder diffractometer, this implies that a supermirror would be used to polarise the incident beam, while a large array of supermirrors or a single curved transmission filter could be used to analyse the polarisation of the diffracted intensity. We note that while Heusler alloys have advantages in that they combine polarisation with monochromation, on purely performance based criteria, they are not competitive with supermirrors or well-developed transmission filter technology

  12. Forward Diffracted Parametric X Radiation From a Thick Tungsten Single Crystal at 855 MeV Electron Energy

    CERN Document Server

    Backe, H; Scharafutdinov, A F; Kunz, P; Gogolev, A S; Potylitsin, A P

    2006-01-01

    Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward diffracted PXR may be employed to diagnose bending radii of lattice planes in large area single crystals.

  13. Application of Bragg-Fresnel lenses for microfluorescent analysis and microdiffraction

    International Nuclear Information System (INIS)

    In creating an X-ray superprobe, the main characteristics are the focus size and the number of photons collected in it (efficiency). In Bragg-Fresnel focusing elements, both characteristics are related to the minimum zone size. However, an increase in the efficiency can be achieved by creating compound elliptical zone plates. To analyze the operation of zone plates of different constructions, an effective program for calculating the image of a point source was developed. The main advantage of the program is a new method for the fast calculation of Kirchhoff integral, detailed description of which is presented in appendix A. The program allows to obtain a diffraction pattern from real lenses as well as to analyze their changes at different deviations of the lens position from the ideal position with respect to an incident X-ray beam. Different constructions of compound elliptical zone-plates designed on the base of the program and then fabricated are described in the work. The results of using a high-aperture Bragg-Fresnel lens for microfluorescent analysis and microdiffraction are presented. (orig.)

  14. Experimental and theoretical study of Bragg-Fresnel focalizing optical systems engraved on multi layers interferential mirrors adapted to X and X-UV fields

    International Nuclear Information System (INIS)

    This work concerns the study of a particular type of X-ray focusing optics known as Bragg-Fresnel lenses, formed through ion-etching of multilayered structures. Using the Super-ACO (LURE/Orsay) synchrotron storage ring, we tested several Bragg-Fresnel lenses having either linear or elliptical geometries (producing a line or a point focus, respectively). Diffraction profiles were first obtained for the linear lenses ion-etched on W/Si multilayers of nano-metric period. The experimental results were compared with our theoretical predictions. We next proposed and tested a solution to the problem superposing the different diffraction orders in the focal plane, that of fabricating Bragg-Fresnel lenses with an off-axis configuration, first for the linear and then the elliptical geometry. An experimental application, for an off-axis elliptical lens produced a focused X-ray spot of 5 x 10 microns2 for the Super-ACO synchrotron source. The same lens also produced a 1/3-size X-ray image of a grid-like object at 1750 eV using the first and third diffraction orders. (author)

  15. A double focusing SAXS camera with µm focal spot based on a circular bragg-fresnel lens

    OpenAIRE

    Snigirev, A.; Snigireva, I.; Riekel, C.; Miller, A.; Wess, L.; Wess, T.

    1993-01-01

    A 2D focusing SAXS camera has been build based on a circular Bragg-Fresnel lens. The camera has been tested at the Microfocus beamline at the European Synchrotron Radiation Facility. An undulator was used as radiation source. The focused beam size at the sample position of about 1,5*2µm2 and intensity of about 109 photons/s was obtained at a wavelength of 1.24A (10keV). A Molecular Dynamics image plate was used to detect the low-angle diffraction pattern. For native turkey leg tendon collagen...

  16. Comparison of DTR spectral-angular characteristics of divergent beam of relativistic electrons in scattering geometry of Laue and Bragg

    Science.gov (United States)

    Blazhevich, S. V.; Koskova, T. V.; Ligidov, A. Z.; Noskov, A. V.

    2016-07-01

    Diffracted transition radiation (DTR) generated by a divergent beam of relativistic electrons crossing a single-crystal plate in different (Laue, Bragg) scattering geometry has been considered for the general case of asymmetric reflection of the electron coulomb field relative to the entrance target surface. The expressions for spectral-angular density of DTR and parametric X-ray Radiation (PXR) has been derived. Then DTR and PXR has been considered in case of a thin target, when multiple scattering of electron is negligibly small, which is important for divergence measurement in real time regime. Numerical calculation of spectral-angular density of DTR by a beam of relativistic electrons has been made using averaging over the bivariate Gauss distribution as angular distribution of relativistic electrons in the beam. It has been shown that in Bragg scattering geometry the angular density of DTR is bigger, than in Laue geometry, which can be explained by the existence of the frequency range, in which the incident wave propagation vector takes complex value even under absence of absorption. In this range, all of photons are reflected in Bragg direction. It means that the range of total reflection defines the width of DTR spectrum.

  17. Writing Bragg Gratings in Multicore Fibers.

    Science.gov (United States)

    Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

    2016-01-01

    Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers. PMID:27167576

  18. Dynamic fiber Bragg grating sensing method

    Science.gov (United States)

    Ho, Siu Chun Michael; Ren, Liang; Li, Hongnan; Song, Gangbing

    2016-02-01

    The measurement of high frequency vibrations is important in many scientific and engineering problems. This paper presents a novel, cost effective method using fiber optic fiber Bragg gratings (FBGs) for the measurement of high frequency vibrations. The method uses wavelength matched FBG sensors, with the first sensor acting as a transmission filter and the second sensor acting as the sensing portion. Energy fluctuations in the reflection spectrum of the second FBG due to wavelength mismatch between the sensors are captured by a photodiode. An in-depth analysis of the optical circuit is provided to predict the behavior of the method as well as identify ways to optimize the method. Simple demonstrations of the method were performed with the FBG sensing system installed on a piezoelectric transducer and on a wind turbine blade. Vibrations were measured with sampling frequencies up to 1 MHz for demonstrative purposes. The sensing method can be multiplexed for use with multiple sensors, and with care, can be retrofitted to work with FBG sensors already installed on a structure.

  19. Direct Phasing of Nanocrystal Diffraction

    OpenAIRE

    Elser, Veit

    2013-01-01

    Recent experiments at free-electron laser x-ray sources have been able to resolve the intensity distributions about Bragg peaks in nanocrystals of large biomolecules. Information derived from small shifts in the peak positions augment the Bragg samples of the particle intensity with samples of its gradients. Working on the assumption that the nanocrystal is entirely generated by lattice translations of a particle, we develop an algorithm that reconstructs the particle from intensities and int...

  20. First order Bragg grating filters in silicon on insulator waveguides

    Science.gov (United States)

    Waugh, Peter Michael

    2008-08-01

    The subject of this project is the design; analysis, fabrication and characterisation of first order Bragg Grating optical filters in Silicon-on-Insulator (SOI) planar waveguides. It is envisaged that this work will result in the possibility of Bragg Grating filters for use in Silicon Photonics. It is the purpose of the work to create as far as is possible flat surface waveguides so as to facilitate Thermo-Optic tuning and also the incorporation into rib-waveguide Silicon Photonics. The spectral response of the shallow Bragg Gratings was modelled using Coupled Mode Theory (CMT) by way of RSoft Gratingmod TM. Also the effect of having a Bragg Grating with alternate layers of refractive index of 1.5 and 3.5 was simulated in order to verify that Silica and Silicon layered Bragg Gratings could be viable. A series of Bragg Gratings were patterned on 1.5 micron SOI at Philips in Eindhoven, Holland to investigate the variation of grating parameters with a) the period of the gratings b) the mark to space ratio of the gratings and c) the length of the region converted to Bragg Gratings (i.e. the number of grating period repetitions). One set of gratings were thermally oxidised at Philips in Eindhoven and another set were ion implanted with Oxygen ions at the Ion Beam Facility, University of Surrey, England. The gratings were tested and found to give transmission minima at approximately 1540 nanometres and both methods of creating flat surfaces were found to give similar minima. Atomic Force Microscopy was applied to the grating area of the as-implanted samples in the Advanced Technology Institute, University of Surrey, which were found to have surface undulations in the order of 60 nanometres.

  1. High-Reflectivity AlGaN/AlN Distributed Bragg Reflector in Ultraviolet Region

    Institute of Scientific and Technical Information of China (English)

    JI Xiao-Li; GONG Hai-Mei; JIANG Ruo-Lian; XIE Zi-Li; LIU Bin; ZHOU Jian-Jun; LI Liang; HAN Ping; ZHANG Rong; ZHENG You-Dou

    2007-01-01

    Thirty-pair Al0.3Ga0.7N/AlN distributed Bragg reflectors centred at 320nm are designed and grown on sapphire substrates by metalorganic chemical vapour deposition. No cracks are observed in the main area of the 2-inch wafer except for about 4 mm margin under an optical microscope. Regular stack of alternating layers is shown by scanning electron microscopy. Clear two-dimensional growth steps and very low surface roughness are shown by atomic force microscopy (AFM). Well-defined periodicity is shown by high resolution x-ray diffraction. High reflectivity of 93% at 313 nm with a bandwidth of 13 nm is obtained.

  2. Nonlinear light propagation in cholesteric liquid crystals with a helical Bragg microstructure

    CERN Document Server

    Liu, Yikun; Zhu, Xing; Xie, Xiangsheng; Feng, Mingneng; Zhou, Jianying; Li, Yongyao; Xiang, Ying; Malomed, Boris A; Kurizki, Gershon

    2015-01-01

    Nonlinear optical propagation in cholesteric liquid crystals (CLC) with a spatially periodic helical molecular structure is studied experimentally and modeled numerically. This periodic structure can be seen as a Bragg grating with a propagation stopband for circularly polarized light. The CLC nonlinearity can be strengthened by adding absorption dye, thus reducing the nonlinear intensity threshold and the necessary propagation length. As the input power increases, a blue shift of the stopband is induced by the self-defocusing nonlinearity, leading to a substantial enhancement of the transmission and spreading of the beam. With further increase of the input power, the self-defocusing nonlinearity saturates, and the beam propagates as in the linear-diffraction regime. A system of nonlinear couple-mode equations is used to describe the propagation of the beam. Numerical results agree well with the experiment findings, suggesting that modulation of intensity and spatial profile of the beam can be achieved simult...

  3. Deep ultraviolet distributed Bragg reflectors based on graded composition AlGaN alloys

    Energy Technology Data Exchange (ETDEWEB)

    Brummer, Gordie, E-mail: gbrummer@bu.edu [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Photonics Center, Boston University, Boston, Massachusetts 02215 (United States); Nothern, Denis [Photonics Center, Boston University, Boston, Massachusetts 02215 (United States); Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215 (United States); Nikiforov, A. Yu. [Photonics Center, Boston University, Boston, Massachusetts 02215 (United States); Moustakas, T. D., E-mail: tdm@bu.edu [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Photonics Center, Boston University, Boston, Massachusetts 02215 (United States); Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215 (United States)

    2015-06-01

    Distributed Bragg reflectors (DBRs) with peak reflectivity at approximately 280 nm, based on compositionally graded Al{sub x}Ga{sub 1−x}N alloys, were grown on 6H-SiC substrates by plasma-assisted molecular beam epitaxy. DBRs with square, sinusoidal, triangular, and sawtooth composition profiles were designed with the transfer matrix method. The crystal structure of these DBRs was studied with high-resolution x-ray diffraction of the (1{sup ¯}015) reciprocal lattice point. The periodicity of the DBR profiles was confirmed with cross-sectional Z-contrast scanning transmission electron microscopy. The peak reflectance of these DBRs with 15.5 periods varies from 77% to 56% with corresponding full width at half maximum of 17–14 nm. Coupled mode analysis was used to explain the dependence of the reflectivity characteristics on the profile of the graded composition.

  4. Performance of multi-crystal Bragg X-ray spectrometers under the influence of angular misalignments

    International Nuclear Information System (INIS)

    X-ray beams have long been analyzed by series of Bragg reflections from crystals arranged in various configurations. The dependence of reflectivity and selected wavelength on the beam's incidence angle makes proper crystal alignment crucial, particularly as the number of crystals increases. A list of possible misalignments and a method for calculating their effects on the selected wavelengths, output beam positions, and throughputs are presented here. The following goes beyond the DuMond diagram to include rolls and rotation axis misalignments. These are described for a single crystal, and a ray-tracing method is derived for multiple crystals assuming that the misalignment angles are small. The angles are classified by their lowest-order term. Reflectivities for each ray are calculated by the equations of plane-wave dynamical diffraction theory. Then, as a practical application, sample calculations are discussed for the (+--+) four-crystal monochromator being designed for beamline I20 at the Diamond Light Source

  5. A Bragg-Fresnel multilayer electron beam monitor for third generation storage rings

    International Nuclear Information System (INIS)

    In anticipation of the small emittance of the third generation light source, BESSY II, we have developed a new approach to beam diagnostics based on the use of Bragg-Fresnel multilayer (BFM) optical components which will be able to withstand the high heat load expected. We report here on the successful performance of such a system as tested on a BESSY I dipole source. Because BESSY II will provide significantly smaller electron beam dimensions than BESSY I, the system was designed for operation at 6.53 nm (190 eV), well below the diffraction limit of BESSY II. The optical system, designed with a reflecting lens and plane mirror, provides 1 : 0.8 image transfer with a spatial resolution of similar 7 μm. The source shape for different ring currents and operation modes of the storage ring has been measured and is represented here. (orig.)

  6. Double focusing of hard x rays using combined multilayer and Bragg-Fresnel optics

    International Nuclear Information System (INIS)

    A multilayer Bragg-Fresnel x-ray lens (MBFL) structure that combines diffraction and geometric focusing on a single device is presented. With the MBFL, the linear BFL focuses the x-ray beam vertically while the bent multilayer focuses x rays horizontally. This combination eliminates the need for a second mirror in the conventional Kirkpatrick-Baez-based microprobe, which will be advantageous in x-ray fluorescence microscopy as well as microdiffraction applications. The characterization of the MBFL was carried out at the European Synchrotron Radiation Facility and a 1.6 μm (vertical)x12 μm (horizontal) focus was obtained from a 250 μm (V)x200 μm (H) incident beam. With a binary Fresnel lens efficiency of about 35% this yields a gain of almost three orders of magnitude compared to obtaining the same spot size by a raw aperture

  7. Detuned Plasmonic Bragg Grating Sensor Based on a Defect Metal-Insulator-Metal Waveguide

    Science.gov (United States)

    Qu, Shinian; Song, Ci; Xia, Xiushan; Liang, Xiuye; Tang, Baojie; Hu, Zheng-Da; Wang, Jicheng

    2016-01-01

    A nanoscale Bragg grating reflector based on the defect metal-insulator-metal (MIM) waveguide is developed and numerically simulated by using the finite element method (FEM). The MIM-based structure promises a highly tunable broad stop-band in transmission spectra. The narrow transmission window is shown to appear in the previous stop-band by changing the certain geometrical parameters. The central wavelengths can be controlled easily by altering the geographical parameters. The development of surface plasmon polarition (SPP) technology in metallic waveguide structures leads to more possibilities of controlling light at deep sub-wavelengths. Its attractive ability of breaking the diffraction limit contributes to the design of optical sensors. PMID:27240381

  8. Fabrication and optical characterization of Bragg resonance luminescence porous silicon

    Science.gov (United States)

    Park, Mi-Ae; Sohn, Honglae

    2016-01-01

    The synthesis and characterization of Bragg resonance luminescence porous silicon (BRL PS) exhibiting both optical reflectivity and strong narrow visible photoluminescence (PL) prepared from highly doped n-type silicon wafers through the electrochemical etching are reported. BRL PS showing the luminescence at 702 nm with an excitation wavelength of 400 nm was prepared by applying the current of 360 mA cm-2 for 1.6 s and 75 mA cm-2 for 3.6 s with 50 repeats in etching solution of 1:1 volume mixture of absolute ethanol and aqueous 48% HF. BRL PS exhibited sharp PL peak which reached full width at half maximum of 14 nm, originated from the result of Bragg resonance in PS multilayer. The sharp PL peak at 702 nm of BRL PS is the second-order transmitted luminescence peak by Bragg resonance phenomenon. The simultaneous measurement of reflectivity and luminescence in the BRL PS under an exposure to a vapor flux of acetone showed that a narrow transmitted luminescence based on Bragg resonance in BRL PS quenched as well as the red-shifted by 37 nm of reflection wavelength was observed. A dramatic quenching PL of BRL PS compare to that of the monolayer PS, is probably due to the Bragg resonance effect on luminescence.

  9. Diffraction of Electromagnetic Waves

    CERN Document Server

    Brosa, Ulrich

    2009-01-01

    The general method to obtain solutions of the Maxwellian equations from scalar representatives is developed and applied to the diffraction of electromagnetic waves. Kirchhoff's integral is modified to provide explicit expressions for these representatives. The respective integrals are then evaluated using the method of stationary phase in two dimensions. Hitherto unknown formulae for the polarization appear as well as for imaging by diffraction. Ready-to-use formulae describing Fresnel diffraction behind a round stop are presented.

  10. Neutron powder diffraction

    International Nuclear Information System (INIS)

    Neutron powder diffraction is a powerful technique that provides a detailed description of moderately complex crystal structures. This is nowhere more apparent than in the area of high temperature superconductors where neutron powder diffraction has provided precise structural and magnetic information, not only under ambient conditions but also at high and low temperatures and high pressures. Outside superconductor research, the variety of materials studied by neutron powder diffraction is equally impressive including zeolites, fast ionic conductors, permanent magnets and materials undergoing phase transitions. Recent advances that include high resolution studies and real-time crystallography are presented. Future possibilities of neutron powder diffraction are discussed

  11. Dynamical Diffraction of Light from 1D Photonic Crystals with Sinusoidal Profile of Permittivity

    International Nuclear Information System (INIS)

    Bragg reflection and transmission spectra of the 1D photonic crystals characterized by a spatially sinusoidal profile of permittivity are studied as a function of the crystal-plate thickness. Applicability of the dynamical theory of diffraction in describing such spectra is considered. In the framework of the dynamical theory, we (i) calculated and analysed the reflection and transmission spectra for oblique incidence of polarized light, (ii) computed the spectra making use of the transfer matrix technique, and (iii) compared quantitatively the results of the two approaches. As a result, the analytical dynamical theory of diffraction is found to be correct in calculating the Bragg spectra in the vicinity of single photonic band-gap when the plate thickness is equal to the integer number of the spatial periods, or the permittivity is symmetric about the middle plane of the structure

  12. Temperature Compensation for Double Fiber Bragg Grating Sensors

    Institute of Scientific and Technical Information of China (English)

    WANG Chun-cheng; LIU Jia; ZHENG Jian-bang

    2006-01-01

    A novel double fiber Bragg grating(FBG) strain sensor configuration is presented. Temperature compensation method is based on double FBG moored on a rhombus frame. Through the theoretical analysis,the relation between relative shift of Bragg wavelength and the strain applied on the sensor is obtained,and the analytical expression of strain sensitivity coefficient is also given. The experiment results show that:in the strain range of 0~0.8 mm,the relation between the relative shift of Bragg wavelength and applied strain is linear,and the dispersion of double FBG wavelength at the range of -25 ℃~60 ℃ is 0~0.002 nm. The strain sensitivity of the displacement sensor configuration is 0.171 nm/με,and is nearly twice than that of single FC sensor.

  13. Performance of a Bragg curve detector for heavy ion identification

    International Nuclear Information System (INIS)

    By using Bragg curve spectroscopy, one can measure atomic number and energy of high energy heavy ions stopping in a gas-filled ionization chamber with longitudinal electric field. In this paper, we report on the results obtained with an isobutane filled detector. An energy resolution of 0.8% fwhm and a Z resolution of 2.7% fwhm were achieved for elastically scattered 300 MeV 40Ar ions. We study the Bragg peak amplitude dependence on the energy of the incoming ions, a dependence presumably due to the Frisch grid screening inefficiency. The corrected Bragg peak spectrum of inelastically scattered 300 MeV 40Ar ions exhibits a satisfactory Z separation around Z = 18. (orig.)

  14. Performance of a Bragg curve detector for heavy ion identification

    Science.gov (United States)

    Asselineau, J. M.; Duchon, J.; L'Haridon, M.; Mosrin, P.; Regimbart, R.; Tamain, B.

    1982-12-01

    By using Bragg curve spectroscopy, one can measure atomic number and energy of high energy heavy ions stopping in a gas-filled ionization chamber with longitudinal electric field. In this paper, we report on the results obtained with an isobutane filled detector. An energy resolution of 0.8% fwhm and a Z resolution of 2.7% fwhm were achieved for elastically scattered 300 MeV 40Ar ions. We study the Bragg peak amplitude dependence on the energy of the incoming ions, a dependence presumably due to the Frisch grid screening inefficiency. The corrected Bragg peak spectrum of inelastically scattered 300 MeV 40Ar ions exhibits a satisfactory Z separation around Z=18.

  15. Flexible nanofiber-coupled hybrid plasmonic Bragg grating.

    Science.gov (United States)

    Liu, Sheng; Zhou, Linjie; Xu, Jian; Wang, Xinyi; Chen, Jianping

    2016-05-01

    We report a hybrid plasmonic Bragg grating composed of a nanofiber coupled with orthogonally oriented metal strips. Numerical simulations are performed to study the transmission and reflection spectra of the grating. It shows that the TM polarization has much stronger Bragg reflection due to the excitation of hybrid plasmonic modes. The dependence of reflection peaks on several key device parameters is analyzed. Light propagation simulation further reveals that both fundamental and first-order TM modes are excited upon Bragg reflection, leading to two separate peaks in the spectrum. We implement the prototype device by attaching a nanofiber onto the surface of an array of sub-micrometer-wide metal strips. The main reflection peak is measured to have a 3-dB bandwidth of 15 nm and out-of-band rejection of more than 30 dB. The effects of nanofiber radius, alignment angle and coupling length on the device performance are also experimentally investigated. PMID:27137547

  16. Tunable plasmonic Bragg reflector with different graphene nanoribbon widths

    Science.gov (United States)

    Zhuang, Huawei; Kong, Fanmin; Li, Kang; Sheng, Shiwei

    2015-09-01

    We propose and numerically analyze a Bragg reflector composed of periodically arranged graphene nanoribbon waveguides with different widths. Because of the unique property of the graphene edge mode, the effective index contrast used for the reflector can be obtained by designing graphene nanoribbons with different widths without changing the dielectric substrate structure. Good band stop filtering characteristics are shown at the band gap of the transmission spectrum by numerical simulation. The performance of the proposed Bragg reflector is analyzed in terms of different parameters, such as the chemical potential, the number of periods, and the size of the unit cell. The proposed Bragg reflector will be expected to have important potential applications in the highly integrated SPP-based photonic devices.

  17. A plating method for metal coating of fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    Yulong Li; Hua Zhang; Yan Feng; Gang Peng

    2009-01-01

    We present a method for metal coating optical fiber and in-fiber Bragg grating. The technology process which is based on electroless plating and electroplating method is described in detail. The fiber is firstly coated with a thin copper or nickel plate with electroless plating method. Then, a thicker nickel plate is coated on the surface of the conductive layer. Under the optimum conditions, the surfaces of chemical plating and electroplating coatings are all smooth and compact. There is no visible defect found in the cross-section. Using this two-step metallization method, the in-fiber Bragg grating can be well protected and its thermal sensitivity can be enhanced. After the metallization process, the fiber sensor is successfully embedded in the 42CrMo steel by brazing method. Thus a smart metal structure is achieved. The embedding results show that the plating method for metallization protection of in-fiber Bragg grating is effective.

  18. Phasing of coherent femtosecond x-ray diffraction from size- varying nanocrystals

    OpenAIRE

    Spence, J. C. H.; Kirian, R. A.; X. Wang; Weierstall, U.; Schmidt, K. E.; White, T.; Barty, A.; Chapman, H. N.; Marchesini, S.; Holton, J

    2011-01-01

    The scattering between Bragg reflections from nanocrystals is used to aid solution of the phase problem. We describe a method for reconstructing the charge density of a typical molecule within a single unit cell, if sufficiently finely-sampled "snap-shot" diffraction data (as provided a free-electron X-ray laser) are available from many nanocrystals of different sizes lying in random orientations. By using information on the particle-size distribution within the patterns, this digital method ...

  19. The early development of neutron diffraction: science in the wings of the Manhattan Project

    OpenAIRE

    Mason, T. E.; Gawne, T. J.; Nagler, S. E.; Nestor, M. B.; Carpenter, J. M.

    2012-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key...

  20. Experimental and theoretical study of Bragg-Fresnel focalizing optical systems engraved on multi layers interferential mirrors adapted to X and X-UV fields; Etude experimentale et theorique d`optiques focalisantes de type Bragg-Fresnel gravees sur des miroirs interferentiels multicouches adaptes aux domaines X et X-UV

    Energy Technology Data Exchange (ETDEWEB)

    Idir, M.

    1995-02-01

    This work concerns the study of a particular type of X-ray focusing optics known as Bragg-Fresnel lenses, formed through ion-etching of multilayered structures. Using the Super-ACO (LURE/Orsay) synchrotron storage ring, we tested several Bragg-Fresnel lenses having either linear or elliptical geometries (producing a line or a point focus, respectively). Diffraction profiles were first obtained for the linear lenses ion-etched on W/Si multilayers of nano-metric period. The experimental results were compared with our theoretical predictions. We next proposed and tested a solution to the problem superposing the different diffraction orders in the focal plane, that of fabricating Bragg-Fresnel lenses with an off-axis configuration, first for the linear and then the elliptical geometry. An experimental application, for an off-axis elliptical lens produced a focused X-ray spot of 5 x 10 microns{sup 2} for the Super-ACO synchrotron source. The same lens also produced a 1/3-size X-ray image of a grid-like object at 1750 eV using the first and third diffraction orders. (author).

  1. Fractal Diffraction Grating

    OpenAIRE

    Bak, Dongsu; Kim, Sang Pyo; Kim, Sung Ku; Soh, Kwang-Sup; Yee, Jae Hyung

    1998-01-01

    We consider an optical diffraction grating in which the spatial distribution of open slits forms a fractal set. The Fraunhofer diffraction patterns through the fractal grating are obtained analytically for the simplest triad Cantor type and its generalized version. The resulting interference patterns exhibit characteristics of the original fractals and their scaling properties.

  2. Surprises in aperiodic diffraction

    CERN Document Server

    Baake, Michael

    2009-01-01

    Mathematical diffraction theory is concerned with the diffraction image of a given structure and the corresponding inverse problem of structure determination. In recent years, the understanding of systems with continuous and mixed spectra has improved considerably. Moreover, the phenomenon of homometry shows various unexpected new facets. Here, we report on some of the recent results in an exemplary and informal fashion.

  3. Modifications to 8x8 dynamical theory: Polarizations redefined according to x-ray diffraction convention

    International Nuclear Information System (INIS)

    Dynamical x-ray diffraction theory can be cast in matrix form. In recent years, an 8x8 matrix theory was developed that treated asymmetric reflections from strained crystals. The polarization of the incident, specularly reflected, reflected diffracted, transmitted diffracted, and transmitted electromagnetic wave fields were all defined as s or p. That is, polarizations were defined with respect to the plane containing the incident beam direction and the surface normal. The authors present modifications of the theory to treat σ and π polarizations for Bragg diffraction from asymmetric planes, that is, for polarizations defined with respect to the plane containing the incident beam direction and the reciprocal lattice vector for Bragg diffraction. They present results of this theory for unstrained crystals in the inclined geometry. In this geometry the incident beam wavevector, the reciprocal lattice vector, and the surface normal are not coplanar. The inclined crystal geometry appears promising for use in a high-heat-load monochromator for undulator radiation at the Advanced Photon Source. As expected, they find a weak π-polarization component in the diffracted beam when the polarization of the incident beam is pure σ

  4. Femtosecond X-ray Diffraction From Two-Dimensional Protein Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Frank, Matthias [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Carlson, David B. [Univ. of California, Davis, CA (United States); Hunter, Mark [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Williams, Garth J. [SLAC National Accelerator Lab., Menlo Park, CA (United States). Linac Coherent Light Source (LCLS); Messerschmidt, Marc [Univ. of California, Davis, CA (United States); Zatsepin, Nadia A. [Arizona State Univ., Tempe, AZ (United States); Barty, Anton [Univ. of Hamburg (Germany); Benner, Henry [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chu, Kaiqin [Center for Biophotonics, Sacramento, CA (United States); Graf, Alexander [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hau-Riege, Stefan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kirian, Rick [Univ. of Hamburg (Germany); Padeste, Celestino [Paul Scherrer Inst., Villigen (Switzerland); Pardini, Tommaso [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pedrini, Bill [Paul Scherrer Inst., Villigen (Switzerland); Segelke, Brent [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Seibert, M. M. [Univ. of California, Davis, CA (United States); Spence, John C. [Arizona State Univ., Tempe, AZ (United States); Tsai, Ching-Ju [Paul Scherrer Inst., Villigen (Switzerland); Lane, Steve M. [Center for Biophotonics, Sacramento, CA (United States); Li, Xiao-Dan [Paul Scherrer Inst., Villigen (Switzerland); Schertler, Gebhard [Paul Scherrer Inst., Villigen (Switzerland); Boutet, Sebastien [Univ. of California, Davis, CA (United States); Coleman, Matthew A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Evans, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of California, Davis, CA (United States)

    2014-02-28

    Here we present femtosecond x-ray diffraction patterns from two-dimensional (2-D) protein crystals using an x-ray free electron laser (XFEL). To date it has not been possible to acquire x-ray diffraction from individual 2-D protein crystals due to radiation damage. However, the intense and ultrafast pulses generated by an XFEL permits a new method of collecting diffraction data before the sample is destroyed. Utilizing a diffract-before-destroy methodology at the Linac Coherent Light Source, we observed Bragg diffraction to better than 8.5 Å resolution for two different 2-D protein crystal samples that were maintained at room temperature. These proof-of-principle results show promise for structural analysis of both soluble and membrane proteins arranged as 2-D crystals without requiring cryogenic conditions or the formation of three-dimensional crystals.

  5. Precipitation in silicon wafers after high temperature preanneal studied by X-ray diffraction methods

    International Nuclear Information System (INIS)

    We have investigated oxygen precipitation in Czochralski silicon wafers focusing on influence of nucleation temperature and high temperature pre-anneal during common three step treatment. Thick Si wafers were studied mainly by x-ray diffraction in Laue transmission geometry using Mo x-ray tube, but were also compared to reciprocal space maps obtained in Bragg reflection geometry. The analysis of measured diffraction scans in Laue geometry was performed by means of Takagi equations and statistical dynamical theory of diffraction. From the simulated Laue diffraction curves we find the size of the individual defect area and the fraction of strain area volume in the wafer. The results obtained from x-ray diffraction were compared to loss of interstitial oxygen according to infrared absorption spectroscopy and the size of SiO2 precipitate core was estimated. These techniques are in agreement with transmission electron microscopy images.

  6. Characterization of wax as a potential diffraction intensity standard for macromolecular crystallography beamlines.

    Science.gov (United States)

    Brandao-Neto, J; Thompson, S P; Lennie, A R; Ferreira, F F; Tang, C C

    2010-01-01

    A number of commercially available waxes in the form of thin disc samples have been investigated as possible diffraction intensity standards for macromolecular crystallography synchrotron beamlines. Synchrotron X-ray powder diffraction measurements show that beeswax offers the best performance of these waxes owing to its polycrystallinity. Crystallographic lattice parameters and diffraction intensities were examined between 281 and 309 K, and show stable and predictable thermal behaviour. Using an X-ray beam of known incident flux at lambda = 1 A, the diffraction power of two strong Bragg reflections for beeswax were quantified as a function of sample thickness and normalized to 10(10) photons s(-1). To demonstrate its feasibility as a diffraction intensity standard, test measurements were then performed on a new third-generation macromolecular crystallography synchrotron beamline. PMID:20029111

  7. BRAGG-PEAK LOCATION EMPLOYING A MAXIMUM-ENTROPY FORMALISM

    OpenAIRE

    Lehmann, M.; Robinson, T.; Wilkins, S.

    1986-01-01

    The maximum entropy method has been tried on simulated data from a small 2-dimensional position-sensitive detector. Constraints were introduced to account for smoothness and the fact that only one peak was found within the frame of the recording. Analysis of a large number of weak Bragg peaks with I/σ(I) < 9 and of different size and background showed the method to give virtually bias-free results. The computing time is sufficiently low to allow real time use on measurements of a single Bragg...

  8. Temperature sensor based on dual fiber Bragg gratings

    OpenAIRE

    Ekestam, Henrik; Larsson, Jim

    2015-01-01

    The objective of the project was to examine if it was possible to develop a low-cost temperature sensor using dual fiber Bragg gratings (FBGs). The intention was to use one FBG as a reference and let the other FBG function as the sensor. The study shows that it is possible to characterize the temperature sensitivity of each FBG and use the reference to sweep over the applicable spectrum to find the Bragg-wavelength of the sensor. This could be done measuring only the total intensity instead o...

  9. A novel optical filter of fiber Bragg grating

    Institute of Scientific and Technical Information of China (English)

    LI; Xiaolu; JIANG; Yuesong

    2006-01-01

    A theory of a novel optical filter of drawing the fiber Bragg grating by the heated elastic sheet is advanced. Based on the heat conduction equation, a set of functions of temperature and thermal expansion on the heated elastic sheet are calculated. And the most displacement of the heated elastic sheet is also described. Finally the expression of the reflected Bragg wavelength deviation in terms of the thermal power density of heat-source is deduced. The physics feasibility of these conclusions mentioned above is proved. It is a potential value for the novel optical filter to research.

  10. Bridge pier scour measurement by means of Bragg grating arrays

    Directory of Open Access Journals (Sweden)

    Manzoni S.

    2010-06-01

    Full Text Available This paper deals with a new method to measure scour level at bridge piers. The proposed technique is based on an array of Bragg grating temperature sensors, heated by an electrical circuit. The Bragg gratings in water sense a lower temperature than those buried in the river bed, because of the different heat scattering principles in the two situations. Furthermore the response of each sensor is slower if it is buried in the bed, with respect to the case it is in water. The paper presents laboratory tests, showing the method effectiveness and reliability, and it explains the advantages with respect to other more traditional methodologies to measure scour level.

  11. Bragg grating chemical sensor with hydrogel as sensitive element

    Institute of Scientific and Technical Information of China (English)

    Xiaomei Liu(刘小梅); Shilie Zheng(郑史烈); Xianmin Zhang(章献民); Jun Cong(丛军); Kangsheng Chen(陈抗生); Jian Xu(徐坚)

    2004-01-01

    A novel fiber Bragg grating (FBG) based chemical sensor using hydrogel, a swellable polymer, as sensitive element is demonstrated. The sensing mechanism relies on the shift of Bragg wavelength due to the stress resulted from volume change of sensitive swellable hydrogel responding to the change of external environment. A polyacrylamide hydrogel fiber grating chemical sensor is made, and the experiments on its sensitivity to the salinity are performed. The sensitivity is low due to the less stress from the shrinking or swelling of hydrogels. Reducing the cross diameter of the grating through etching with hydrofluoric acid can greatly improve the sensitivity of the sensor.

  12. X-Ray Diffraction Project Final Report, Fiscal Year 2006

    International Nuclear Information System (INIS)

    An x-ray diffraction diagnostic system was developed for determining real-time shock-driven lattice parameter shifts in single crystals at the gas gun at TA-IV at Sandia National Laboratories (SNL). The signal-to-noise ratio and resolution of the system were measured using imaging plates as the detector and by varying the slit width. This report includes tests of the x-ray diffraction system using a phosphor coupled to a charge-coupled device (CCD) camera by a coherent fiber-optic bundle. The system timing delay was measured with a newly installed transistor-transistor logic (TTL) bypass designed to reduce the x-ray delay time. The axial misalignment of the Bragg planes was determined with respect to the optical axis for a set of eight LiF [lithium fluoride] crystals provided by SNL to determine their suitability for gas gun experiments

  13. Measurement of distributed strain and temperature based on higher order and higher mode Bragg conditions

    Science.gov (United States)

    Sirkis, James S. (Inventor); Sivanesan, Ponniah (Inventor); Venkat, Venki S. (Inventor)

    2001-01-01

    A Bragg grating sensor for measuring distributed strain and temperature at the same time comprises an optical fiber having a single mode operating wavelength region and below a cutoff wavelength of the fiber having a multimode operating wavelength region. A saturated, higher order Bragg grating having first and second order Bragg conditions is fabricated in the optical fiber. The first order of Bragg resonance wavelength of the Bragg grating is within the single mode operating wavelength region of the optical fiber and the second order of Bragg resonance wavelength is below the cutoff wavelength of the fiber within the multimode operating wavelength region. The reflectivities of the saturated Bragg grating at the first and second order Bragg conditions are less than two orders of magnitude of one another. In use, the first and second order Bragg conditions are simultaneously created in the sensor at the respective wavelengths and a signal from the sensor is demodulated with respect to each of the wavelengths corresponding to the first and second order Bragg conditions. Two Bragg conditions have different responsivities to strain and temperature, thus allowing two equations for axial strain and temperature to be found in terms of the measure shifts in the primary and second order Bragg wavelengths. This system of equations can be solved for strain and temperature.

  14. Observation of optical second-harmonic generation in porous-silicon-based photonic crystals in the Laue diffraction scheme

    Science.gov (United States)

    Kopylov, D. A.; Svyakhovskiy, S. E.; Dergacheva, L. V.; Bushuev, V. A.; Mantsyzov, B. I.; Murzina, T. V.

    2016-05-01

    Second-harmonic generation (SHG) in the Laue scheme of the dynamical Bragg diffraction in one-dimensional photonic crystal (PhC) is studied. The experiments are performed for partially annealed porous-silicon PhC containing 250 periods of the structure. Our measurements confirm that the phase-matched optical SHG is observed under the Bragg conditions, which is evidenced by a narrow angular and spectral distribution of the diffracted SHG outgoing the PhC. This is confirmed by both the analytical description of the SHG process performed in the two-wave approximation, and by direct calculations of the PhC dispersion curves for the fundamental and SHG wavelengths by the revised plane wave method. Possible types of phase- and quasi-phase-matching realized in the studied PhC under the Laue diffraction scheme are discussed.

  15. Novel diffraction gratings fabricated by means of plasma nanotechnologies

    Science.gov (United States)

    Ebizuka, N.; Sekine, Makoto; Ishikawa, K.; Kondo, H.; Hori, M.; Sasaki, M.; Bianco, A.; Maria Zerbi, F.; Hirahara, Y.; Aoki, W.

    2012-09-01

    A volume phase holographic grating (VPHG) achieves very high diffraction efficiency up to 100% for S or P polarized light at the first diffraction order. However, diffraction efficiency of the VPHG for non-polarized light becomes low according as Bragg angle becomes large, and bandwidth of diffraction efficiency becomes narrow according as refractive index modulation of grating lattice becomes small. A volume binary grating with rectangular lattice, consists of high and low refractive index media with large or small duty ratio, is able to achieve very high efficiency nearly 100% and a wide band width for both S and P polarization light. We have successfully fabricated germanium immersion gratings of step groove shape with resolving power of 45,000 at 10 micron by using a nano-precision 3D grinding machine and ELID (ELectrolytic In-process Dressing) method. However, the method requires a large amount of machine times and efforts. We had proposed a novel immersion grating with slot shape lattice of total reflection mirrors, which achieves high performance and lower fabrication cost. We describe the photolithography and the latest plasma nano-technologies for fabrications of the novel diffraction gratings in our presentation. We also introduce birefringence volume gratings in this article.

  16. Nucleon nucleon diffraction

    International Nuclear Information System (INIS)

    The physical importance of nucleon-nucleon diffraction and the main differences with well understood nucleon nucleus diffraction is discused. In the theoretical description of nucleon-nucleon diffraction in terms of the eikonal model, the hypothesis of factorization is shown to be in contradiction with the energy dependence of the impact parameter profile in proton-proton scattering at CERN - ISR. This dependence is highly non-uniform in impact parameter, giving rise to a pronounced peripheral increase with energy of the inelastic overlap function. Two experimental findings in inelastic diffraction indicate the existence of a deep relation of this process with the peripheral increase of the profile function. The first refers to the clear-cut proof that inelastic diffraction is peripheral in impact parameter space, in coherent production on deuteron. The second is the analysis of the integrated cross sections for inelastic diffraction, which leads to the conclusion that most of the total cross section increase in the ISR energy range comes from this process. It is then clear that the eikonal model should be modified in order to include inelastic diffraction. A recent trial in this direction by Miettinen and Thomas shows the existence of a substantial difference between the matter and the charge distribution inside the proton. Their results favours a description of the proton in terms of the string model. (Author)

  17. Diffraction. Powder, amorphous, liquid

    International Nuclear Information System (INIS)

    Neutron powder diffraction is a unique tool to observe all possible diffraction effects appearing in crystal. High-resolution neutron diffractometers have to be used in this study. Analysis of the magnetic structure of polycrystalline materials requires the use of high-resolution neutron diffraction in the range of large interplanar distances. As distinguished from the double axis diffractometers (DAS), which show high resolution only at small interplanar distances, TOF (time-of-flight) diffractometry offers the best resolution at large interplanar distances. (K.A.)

  18. Non-diffractive waves

    CERN Document Server

    Hernandez-Figueroa, Hugo E; Recami, Erasmo

    2013-01-01

    This continuation and extension of the successful book ""Localized Waves"" by the same editors brings together leading researchers in non-diffractive waves to cover the most important results in their field and as such is the first to present the current state.The well-balanced presentation of theory and experiments guides readers through the background of different types of non-diffractive waves, their generation, propagation, and possible applications. The authors include a historical account of the development of the field, and cover different types of non-diffractive waves, including Airy

  19. Coherent diffractive ρ production

    International Nuclear Information System (INIS)

    Coherent diffractive ρ production by neutrinos occurs at low four-momentum transfer and high energy transfer. These interactions are generally understood to occur via the coupling of the weak charged current to the vector meson, which scatters diffractively from the target nucleus. Since coherent events are those in which the nucleus interacts as a whole, ie without breakup, and with small recoil energy, these events have a very sharp |t|-distribution. This presentation deals mostly with the Monte Carlo simulation of the coherent diffractive production of the ρ production and in particular with the reconstruction algorithm (description and efficiency) and the |t| distribution

  20. Multilayer dielectric diffraction gratings

    Science.gov (United States)

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  1. Rational solitons in deep nonlinear optical Bragg grating

    NARCIS (Netherlands)

    Alatas, H.; Iskandar, A.A.; Tjia, M.O.; Valkering, T.P.

    2006-01-01

    We have examined the rational solitons in the Generalized Coupled Mode model for a deep nonlinear Bragg grating. These solitons are the degenerate forms of the ordinary solitons and appear at the transition lines in the parameter plane. A simple formulation is presented for the investigation of the

  2. The Wavelength Shifting and Temperature Athermalization of Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    Yu; e; Kong

    2003-01-01

    The wavelength shifting properties and the temperature athermalization technology of fiber Bragg grating (FBG) were studied in this paper, and then two different athermalization methods were introduced. The research shows that FBG with athermalization by applying the substrate with negative coefficient of thermal expansion is effective and can be used in many fields.

  3. A Bragg curve ionization chamber for acceleration mass spectrometry

    International Nuclear Information System (INIS)

    An ionization chamber based on the Bragg curve spectrometry method to be used as the final detector in a accelerator mass spectrometry system is described. The first tests with a Cl beam give energy resolution of 1% and Z resolving power of 72 at Z=17

  4. A highly sensitive fiber Bragg grating diaphragm pressure transducer

    Science.gov (United States)

    Allwood, Gary; Wild, Graham; Lubansky, Alex; Hinckley, Steven

    2015-10-01

    In this work, a novel diaphragm based pressure transducer with high sensitivity is described, including the physical design structure, in-depth analysis of optical response to changes in pressure, and a discussion of practical implementation and limitations. A flat circular rubber membrane bonded to a cylinder forms the body of the transducer. A fiber Bragg grating bonded to the center of the diaphragm structure enables the fractional change in pressure to be determined by analyzing the change in Bragg wavelength of the reflected spectra. Extensive evaluation of the physical properties and optical characteristics of the transducer has been performed through experimentation, and modeling using small deformation theory. The results show the transducer has a sensitivity of 0.116 nm/kPa, across a range of 15 kPa. Ultra-low cost interrogation of the optical signal was achieved through the use of an optically mismatched Bragg grating acting as an edge filter to convert the spectral change into an intensity change. A numerical model of the intensity based interrogation was implemented in order to validate the experimental results. Utilizing this interrogation technique and housing both the sensing and reference Bragg gratings within the main body of the transducer means it is effectively temperature insensitive and easily connected to electronic systems.

  5. Ultrafast Laser Fabrication of Bragg Waveguides in GLS Chalcogenide Glass

    Directory of Open Access Journals (Sweden)

    McMillen Ben

    2013-11-01

    Full Text Available We present work on the fabrication of Bragg waveguides in gallium-lanthanum-sulfide chalcogenide glass using an ultrafast laser. Waveguides were written with a single pass while modulating the writing beam. The spatial and temporal profile of the writing beam was ontrolled during waveguide fabrication in order to control the shape and size of the waveguide cross-section.

  6. Crystal clear the autobiographies of Sir Lawrence and Lady Bragg

    CERN Document Server

    Thomson, Patience

    2015-01-01

    The main body of this book contains the hitherto unpublished autobiographies of both William Lawrence Bragg, an innovative scientist who won the Nobel Prize for Physics in 1915, and his wife, Alice, a Mayor of Cambridge and National Chairman of Marriage Guidance. Their autobiographies give unusual insights into the lives and times of two distinguished people and the real personalities behind their public appearance.

  7. Linearized Bragg grating assisted electro-optic modulator.

    Science.gov (United States)

    Khurgin, Jacob B; Morton, Paul A

    2014-12-15

    We propose a new linearized electro-optic modulator in which linearization is achieved by modulating the index of a Bragg grating reflector placed in the arm(s) of a Michelson Interferometer. This grating-assisted Michelson (GAMI) modulator can operate as either an intensity or amplitude modulator, and is shown to significantly improve the linearity of microwave photonics links. PMID:25503037

  8. Growth and characterization of nitride-based distributed Bragg reflectors

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, Carsten; Dartsch, Heiko; Aschenbrenner, Timo; Figge, Stephan; Hommel, Detlef [Section Semiconductor Epitaxy, Institute of Solid State Physics, University of Bremen (Germany)

    2011-08-15

    We report on a systematic study concerning the realization of nitride-based distributed Bragg reflectors (DBRs) for opto-electronic applications in the near-UV to visible spectral range. Different material combinations are used in order to find an optimized trade-off concerning peak reflectivity, stop band width, and strain state of the Bragg mirrors. For the high refractive index material GaN is used in all cases, while for the low index material a layer of either AlGaN or AlInN, respectively, or a AlN/(In)GaN short-period superlattice (SL) is employed. The best peak reflectivity of 97% at a wavelength of 495 nm is achieved for a lattice matched Bragg reflector based on the GaN/AlInN material combination. Transmission electron microscopy image of a 30-fold distributed Bragg reflector consisting of AlInN (dark) and GaN (bright) layers. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Dynamic gate algorithm for multimode fiber Bragg grating sensor systems

    DEFF Research Database (Denmark)

    Ganziy, Denis; Jespersen, O.; Woyessa, Getinet;

    2015-01-01

    -to-noise ratio and different peak shapes. Our simulations and experiments demonstrate that the DGA method is fast and robust with better stability and accuracy than conventional algorithms. This makes it very attractive for future implementation in sensing systems, especially based on multimode fiber Bragg...

  10. Laser sensor with Bragg gratings of fiber optics to physics parameter measuring

    International Nuclear Information System (INIS)

    We present the operation of a fiber laser sensor made by an Erbium Doped Fiber pumped at 980nm, an 4.23 km passive fiber and two fiber Bragg gratings placed at the ends of the laser cavity. Under normal conditions, the Bragg gratings have different reflection wavelengths and laser emission is not generated. The two Bragg gratings can be placed at the same reflection wavelength when the Bragg grating with the lowest reflective wavelength increases their temperature which can be used as a sensor element. The laser generation thus shows that the Bragg grating is increasing their temperature. We used a Peltier cell for to change gradually the temperature. (Author)

  11. Single-Crystal Diffraction from Two-Dimensional Block Copolymer Arrays

    International Nuclear Information System (INIS)

    The structure of oriented 2D block copolymer single crystals is characterized by grazing-incidence small-angle x-ray diffraction, demonstrating long-range sixfold orientational order. From line shape analysis of the higher-order Bragg diffraction peaks, we determine that translational order decays algebraically with a decay exponent η=0.2, consistent with the Kosterlitz-Thouless-Halperin-Nelson-Young theory for a 2D crystal with a shear modulus μ=2x10-4 N/m

  12. Duality in diffraction dissociations

    International Nuclear Information System (INIS)

    Diffractive dissociations (aN→a*πN) are naturally explained and a model that accounts for the three-variable correlation (mass-transfer-Jackson angle correlation) is presented. This model takes into account the three possible exchanges: t (pion), u(a*) and s(a) channel exchanger. The physical consequences of the model are: a strong mass-slope correlation due to the zeros of the amplitude, a factorization of diffractive dissociations (factorization of the Pomeron), the possibility of extending this model to double diffractive dissociation and diffraction by nuclei. This model was applied to the NN→NπN reaction. Using the usual parameters of the Deck model, a comparison is made with experiments for all available distributions. the strong slope of the peak at 1400 MeV is naturally explained

  13. Diffraction of Electromagnetic Waves

    OpenAIRE

    Brosa, Ulrich

    2009-01-01

    The general method to obtain solutions of the Maxwellian equations from scalar representatives is developed and applied to the diffraction of electromagnetic waves. Kirchhoff's integral is modified to provide explicit expressions for these representatives. The respective integrals are then evaluated using the method of stationary phase in two dimensions. Hitherto unknown formulae for the polarization appear as well as for imaging by diffraction. Ready-to-use formulae describing Fresnel diffra...

  14. Diffraction tomography of strain

    OpenAIRE

    Lionheart, W R B; Withers, P. J.

    2015-01-01

    We consider whether it is possible to recover the three dimensional strain field tomographically from neutron and x-ray diffraction data for polycrystalline materials. We show that the distribution of strain transverse to a ray cannot be deduced from one diffraction pattern accumulated along that path, but that a certain moment of that data corresponds to the transverse ray transform of the strain tensor and so may be recovered by inverting that transform given sufficient data. We show that t...

  15. Spectrometer with CMOS demodulation of fiber optic Bragg grating sensors

    Science.gov (United States)

    Christiansen, Martin Brokner

    A CMOS imager based spectrometer is developed to interrogate a network containing a large number of Bragg grating sensors. The spectrometer uses a Prism-Grating- Prism (PGP) to spectrally separate serially multiplexed Bragg reflections on a single fiber. As a result, each Bragg grating produces a discrete spot on the CMOS imager that shifts horizontally as the Bragg grating experiences changes in strain or temperature. The reflected wavelength of the spot can be determined by finding the center of the spot produced. The use of a randomly addressable CMOS imager enables a flexible sampling rate. Some fibers can be interrogated at a high sampling rate while others can be interrogated at a low sampling rate. However, the use of a CMOS imager leads to several unique problems in terms of signal processing. These include a logarithmic pixel response, a low signal-to-noise ratio, a long pixel time constant, and software issues. The expected capabilities of the CMOS imager based spectrometer are determined with a theoretical model. The theoretical model tests three algorithms for determining the center of the spot: single row centroid, single row parabolic fit, and entire spot centroid. The theoretical results are compared to laboratory test data and field test data. The CMOS based spectrometer is capable of interrogating many optical fibers, and in the configuration tested, the fiber bundle consisted of 23 fibers. Using this system, a single fiber can be interrogated from 778 nm to 852 nm at 2100 Hz or multiple fibers can be interrogated over the same wavelength so that the total number of fiber interrogations is up to 2100 per second. The reflected Bragg wavelength can be determined within +/-3pm, corresponding to a +/-3μɛ uncertainty.

  16. Powder Diffraction: By Decades

    Science.gov (United States)

    David, William I. F.

    This introductory chapter reviews the first 100 years of powder diffraction, decade by decade, from the earliest X-ray powder diffraction measurements of the crystal structure of graphite through to the diversity and complexity of twenty-first century powder diffraction. Carbon features as an illustrative example throughout the discussion of these ten decades from graphite and the disorder of carbon black through to lonsdaleite, the elusive hexagonal polymorph of diamond, and C60, the most symmetrical of molecules. Electronics and computing have played a leading role in the development of powder diffraction, particularly over the past 60 years, and the Moore's Law decade-by-decade rise in computing power is clear in the increasing complexity of powder diffraction experiments and material systems that can be studied. The chapter concludes with a final discussion of decades - the four decades of length-scale from the ångstrom to the micron that not only represent the domain of powder diffraction but are also the distances that will dominate twenty-first century science and technology.

  17. ON THE CHARACTERIZATION OF METALLIC SUPERLATTICE STRUCTURES BY X—RAY DIFFRACTION

    Institute of Scientific and Technical Information of China (English)

    MINGXU; WenxueYU; 等

    1999-01-01

    To solve the problem on the microstructural characterization of metallic superlattices,taking the NiFe/Cu superlattices as example,we show that the sturctures of metallic superlattices can be characterized exactly by combining low-angle X-ray diffraction with high-angle X-ray diffraction.First,we determine exactly the total film thickness by a straightforward and precise method based on a modified Bragg law from the subsidiary maxima around the low-angle X-ray diffraction peak.Then.by combining with the simulation of high-angle X-ray diffraction.we obtain the sturctural parameters such as the superlattice period,the sublayer and buffer thickness,This characterization procedure is also applicable to other types of metallic superlattices.

  18. The early development of neutron diffraction: science in the wings of the Manhattan Project.

    Science.gov (United States)

    Mason, T E; Gawne, T J; Nagler, S E; Nestor, M B; Carpenter, J M

    2013-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan's group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool. PMID:23250059

  19. Diffraction contrast tomography for the study of polycrystalline stainless steel microstructures and stress corrosion cracking

    International Nuclear Information System (INIS)

    X-ray diffraction contrast tomography is a non-destructive technique for the 3D characterisation of polycrystalline microstructures containing up to a few 1000 grains. The sample is illuminated with a monochromatic beam of high energy synchrotron radiation. As the sample is rotated, and as grains pass through alignments for Bragg diffraction, diffraction spots are recorded on a 2D detector placed close behind the sample. The diffraction geometry is used to assign spots to the grains from which they arise, and to determine the crystallographic orientations of grains. The spots are used as projections of the grains to reconstruct the grain shapes. The technique has been applied to several materials science investigations in stainless steels, including the 3D characterisation of grain boundary networks, and in-situ studies of intergranular stress corrosion cracking. (authors)

  20. Ionoacoustic characterization of the proton Bragg peak with submillimeter accuracy

    Energy Technology Data Exchange (ETDEWEB)

    Assmann, W., E-mail: walter.assmann@lmu.de; Reinhardt, S.; Lehrack, S.; Edlich, A.; Thirolf, P. G.; Parodi, K. [Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, Garching 85748 (Germany); Kellnberger, S.; Omar, M.; Ntziachristos, V. [Institute for Biological and Medical Imaging, Technische Universität München and Helmholtz Zentrum München, Ingolstädter Landstrasse 1, Neuherberg 85764 (Germany); Moser, M.; Dollinger, G. [Institute for Applied Physics and Measurement Technology, Universität der Bundeswehr, Werner-Heisenberg-Weg 39, Neubiberg 85577 (Germany)

    2015-02-15

    Purpose: Range verification in ion beam therapy relies to date on nuclear imaging techniques which require complex and costly detector systems. A different approach is the detection of thermoacoustic signals that are generated due to localized energy loss of ion beams in tissue (ionoacoustics). Aim of this work was to study experimentally the achievable position resolution of ionoacoustics under idealized conditions using high frequency ultrasonic transducers and a specifically selected probing beam. Methods: A water phantom was irradiated by a pulsed 20 MeV proton beam with varying pulse intensity and length. The acoustic signal of single proton pulses was measured by different PZT-based ultrasound detectors (3.5 and 10 MHz central frequencies). The proton dose distribution in water was calculated by Geant4 and used as input for simulation of the generated acoustic wave by the matlab toolbox k-WAVE. Results: In measurements from this study, a clear signal of the Bragg peak was observed for an energy deposition as low as 10{sup 12} eV. The signal amplitude showed a linear increase with particle number per pulse and thus, dose. Bragg peak position measurements were reproducible within ±30 μm and agreed with Geant4 simulations to better than 100 μm. The ionoacoustic signal pattern allowed for a detailed analysis of the Bragg peak and could be well reproduced by k-WAVE simulations. Conclusions: The authors have studied the ionoacoustic signal of the Bragg peak in experiments using a 20 MeV proton beam with its correspondingly localized energy deposition, demonstrating submillimeter position resolution and providing a deep insight in the correlation between the acoustic signal and Bragg peak shape. These results, together with earlier experiments and new simulations (including the results in this study) at higher energies, suggest ionoacoustics as a technique for range verification in particle therapy at locations, where the tumor can be localized by ultrasound

  1. Engineering related neutron diffraction measurements probing strains, texture and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Bjorn [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Balogh, Levente [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory

    2010-01-01

    Neutron diffraction has been used for engineering applications for nearly three decades. The basis of the technique is powder diffraction following Bragg's Law. From the measured diffraction patterns information about internal, or residual, strain can be deduced from the peak positions, texture information can be extracted from the peak intensities, and finally the peak widths can provide information about the microstructure, e.g. dislocation densities and grain sizes. The strains are measured directly from changes in lattice parameters, however, in many cases it is non-trivial to determine macroscopic values of stress or strain from the measured data. The effects of intergranular strains must be considered, and combining the neutron diffraction measurements with polycrystal deformation modeling has proven invaluable in determining the overall stress and strain values of interest in designing and dimensioning engineering components. Furthelmore, the combined use of measurements and modeling has provided a tool for elucidating basic material properties, such as critical resolved shear stresses for the active deformation modes and their evolution as a function of applied deformation.

  2. Diffraction. Single crystal, magnetic

    International Nuclear Information System (INIS)

    The analysis of crystal structure and magnetic ordering is usually based on diffraction phenomena caused by the interaction of matter with X-rays, neutrons, or electrons. Complementary information is achieved due to the different character of X-rays, neutrons and electrons, and hence their different interactions with matter and further practical aspects. X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (K.A.)

  3. Nuclear dynamical diffraction using synchrotron radiation

    International Nuclear Information System (INIS)

    The scattering of synchrotron radiation by nuclei is extensively explored in this thesis. From the multipole electric field expansion resulting from time-dependent nonrelativistic perturbation theory, a dynamical scattering theory is constructed. This theory is shown, in the many particle limit, to be equivalent to the semi-classical approach where a quantum mechanical scattering amplitude is used in the Maxwell inhomogeneous wave equation. The Moessbauer specimen whose low-lying energy levels were probed is a ferromagnetic lattice of 57Fe embedded in a yttrium iron garnet (YIG) crystal matrix. The hyperfine fields in YIG thin films were studied at low and room temperature using time-resolved quantum beat spectroscopy. Nuclear hyperfine structure quantum beats were measured using a fast plastic scintillator coincidence photodetector and associated electronics having a time resolution of 2.5 nsec. The variation of the quantum beat patterns near the Bragg [0 0 2] diffraction peak gave a Lamb-Moessbauer factor of 8.2±0.4. Exploring characteristic dynamical features in the higher order YIG [0 0 10] reflection revealed that one of the YIG crystals had bifurcated into two different layers. The dynamics of nuclear superradiance was explored. This phenomenon includes the radiative speedup exhibited by a collective state of particles, and, in striking concurrence, resonance frequency shifts. A speedup of a factor of 4 in the total decay rate and a beat frequency shift of 1 1/2 natural resonance linewidths were observed. Nuclear resonance scattering was also found to be a useful way of performing angular interferometry experiments, and it was used to observe the phase shift of a rotated quantum state. On the whole, nuclear dynamical diffraction theory has superbly explained many of the fascinating features of resonant magnetic dipole radiation scattered by a lattice of nuclei

  4. First observation of new effects at the set-up for searching for a neutron electric dipole moment by a crystal-diffraction method

    CERN Document Server

    Fedorov, V V; Semenikhin, S Y; Voronin, V V

    2002-01-01

    First observation of new effects was carried out using the set-up created for searching for a neutron electric dipole moment (EDM) by a crystal-diffraction method. For the first time the neutron dynamical Laue diffraction for the Bragg angles close to a right angle (up to 87 ) was studied, using the direct diffraction beam and a thick (propor to 3.5-cm) crystal. The effect of an essential time delay of diffracting neutrons inside the crystal for Bragg angles close to 90 was experimentally observed, using a time-of-flight method. The phenomenon of neutron-beam depolarization was first experimentally observed for the case of Laue diffraction in a noncentrosymmetric alpha-quartz crystal. It is experimentally proved that the interplanar electric field, affecting a neutron in a crystal, maintains its value up to Bragg angles equal to 87 . These results confirm the opportunity to increase by more than an order of magnitude the sensitivity of the method to the neutron EDM, using the diffraction angles close to 90 , ...

  5. Distribution of Micronuclei in Human Fibroblasts across the Bragg Curve of Light and Heavy Ions

    Science.gov (United States)

    Hada, M.; Lacy, S.; Gridley, D. S.; Rusek, A.; Cucinotta, F. A.; Wu, H.

    2007-01-01

    The space environment consists of energetic particles of varying mass and energy, and understanding the :biological Bragg curve" is essential in optimizing shielding effectiveness against space radiation induced biological impacts. The "biological Bragg curve" is dependent on the energy and the type of the primary particle, and may vary for different biological endpoints. Previously, we studied the induction of micronuclei (MN) across the Bragg curve of energetic Fe and Si ions, and observed no increased yield of MN at the location of the Bragg peak. However, the ratio of mono- to bi-nucleated cells, which indicates inhibition of cell progression, was found higher at the Bragg peak location in comparison to the plateau region of the Bragg curve. Here, we report the induction of MN in normal human fibroblast cells across the Bragg curve of incident protons generated at Loma Linda University. Similar to Si and Fe ions, the ratio of mono- to bi-nucleated cells showed a clear spike as the protons reached the Bragg peak. Unlike the two heavy ions, however, the MN yield also increased at the Bragg peak location. These results confirm the hypothesis that severely damaged cells at the Bragg peak of heavy, but not light ions are more likely to go through reproductive death and not be evaluated for micronuclei.

  6. Nonparaxial anamorphic diffractive lenses

    International Nuclear Information System (INIS)

    Applications of anamorphic diffractive lenses, or in other words elliptical zone plates, are growing in number and diversity. Following this progress, the manufacturing methods of anamorphic diffractive lenses are also a subject of continuous improvement. On the other hand, their design is still based mainly on the paraxial approximation. In the present paper nonparaxial elliptical zone plates are presented and their difference from the paraxial version, termed as the elliptical aberration is shown. A comparison of their focusing quality was performed based on results of numerical modelling as well as experiments. (paper)

  7. Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Klaus Mann

    2009-11-01

    Full Text Available Home-based soft X-ray time-resolved scattering experiments with nanosecond time resolution (10 ns and nanometer spatial resolution were carried out at a table top soft X-ray plasma source (2.2–5.2 nm. The investigated system was the lyotropic liquid crystal C16E7/paraffin/glycerol/formamide/IR 5. Usually, major changes in physical, chemical, and/or optical properties of the sample occur as a result of structural changes and shrinking morphology. Here, these effects occur as a consequence of the energy absorption in the sample upon optical laser excitation in the IR regime. The liquid crystal shows changes in the structural response within few hundred nanoseconds showing a time decay of 182 ns. A decrease of the Bragg peak diffracted intensity of 30% and a coherent macroscopic movement of the Bragg reflection are found as a response to the optical pump. The Bragg reflection movement is established to be isotropic and diffusion controlled (1 μs. Structural processes are analyzed in the Patterson analysis framework of the time-varying diffraction peaks revealing that the inter-lamellar distance increases by 2.7 Å resulting in an elongation of the coherently expanding lamella crystallite. The present studies emphasize the possibility of applying TR-SXRD techniques for studying the mechanical dynamics of nanosystems.

  8. Andreev-Bragg Reflection from an Amperian Superconductor

    Science.gov (United States)

    Baireuther, P.; Hyart, T.; Tarasinski, B.; Beenakker, C. W. J.

    2015-08-01

    We show how an electrical measurement can detect the pairing of electrons on the same side of the Fermi surface (Amperian pairing), recently proposed by Patrick Lee for the pseudogap phase of high-Tc cuprate superconductors. Bragg scattering from the pair-density wave introduces odd multiples of 2 kF momentum shifts when an electron incident from a normal metal is Andreev reflected as a hole. These Andreev-Bragg reflections can be detected in a three-terminal device, containing a ballistic Y junction between normal leads (1, 2) and the superconductor. The cross-conductance d I1/d V2 has the opposite sign for Amperian pairing than it has either in the normal state or for the usual BCS pairing.

  9. Bragg-peak spectroscopy of low-energy heavy ions

    International Nuclear Information System (INIS)

    A small axial ionization chamber with the electric field lines parallel to the particle trajectory (Bragg ionization chamber) allowing the determination of the nuclear charge and the energy of low energetic low mass heavy ions (E/A approximately 0.8 - 2.0 MeV/amu) is presented together with an adapted shaping amplifier. Using the usual technique of pulse shaping with a long and a short time constant the energy and the Bragg peak resolutions for projectiles between 24He and 1632S were determined. With commercially available low purity n-pentane purified from water and oxygene by a threefold destillation an energy resolution of ΔE/E = 1% and a charge resolving power of Z/ΔZ = 47 are attainable for 41.4 MeV 28Si ions elastically scattered from 197Au. No significant pulse height defect is observable for the energy determination of particles with Z <= 17. (author)

  10. Magneto-Optic Field Coupling in Optical Fiber Bragg Gratings

    Science.gov (United States)

    Carman, Gregory P. (Inventor); Emmons, Michael C. (Inventor); Richards, William Lance (Inventor); Mohanchandra, Panduranga K. (Inventor)

    2016-01-01

    The invention is a magneto-optic coupled magnetic sensor that comprises a standard optical fiber Bragg grating system. The system includes an optical fiber with at least one Bragg grating therein. The optical fiber has at least an inner core and a cladding that surrounds the inner core. The optical fiber is part of an optical system that includes an interrogation device that provides a light wave through the optical fiber and a system to determine the change in the index of refraction of the optical fiber. The cladding of the optical fiber comprises at least a portion of which is made up of ferromagnetic particles so that the ferromagnetic particles are subject to the light wave provided by the interrogation system. When a magnetic field is present, the ferromagnetic particles change the optical properties of the sensor directly.

  11. Self-aligned Coupled Waveguide Distributed Bragg Reflector Lasers

    Institute of Scientific and Technical Information of China (English)

    LIU Guoli; WANG Wei; ZHU Hongliang; ZHANG Jingyuan; HU Xiaohua; LU Yu; ZHANG Jing

    2002-01-01

    A novel self-aligned coupled waveguide (SACW) multi-quantum-well (MQW) distributed Bragg reflector (DBR) laser is proposed and demonstrated for the first time. By selectively removing the MQW layer and leaving the low SCH/SACW layer the Bragg grating is partially formed on this layer. By optimizing the thickness of the low SCH/SACW layer, a~80% coupling efficiency between the MQW gain region and the passive region are obtained. The typical threshold current of the SACW DBR laser is 39 mA, the slope efficiency can reach to 0.2 mW/mA and the output power is more than 20 mW with a more than 30dB side mode suppression ratio.

  12. Processing of Signals from Fiber Bragg Gratings Using Unbalanced Interferometers

    Science.gov (United States)

    Adamovsky, Grigory; Juergens, Jeff; Floyd, Bertram

    2005-01-01

    Fiber Bragg gratings (FBG) have become preferred sensory structures in fiber optic sensing system. High sensitivity, embedability, and multiplexing capabilities make FBGs superior to other sensor configurations. The main feature of FBGs is that they respond in the wavelength domain with the wavelength of the returned signal as the indicator of the measured parameter. The wavelength is then converted to optical intensity by a photodetector to detect corresponding changes in intensity. This wavelength-to-intensity conversion is a crucial part in any FBG-based sensing system. Among the various types of wavelength-to-intensity converters, unbalanced interferometers are especially attractive because of their small weight and volume, lack of moving parts, easy integration, and good stability. In this paper we investigate the applicability of unbalanced interferometers to analyze signals reflected from Bragg gratings. Analytical and experimental data are presented.

  13. Investigations on birefringence effects in polymer optical fiber Bragg gratings

    DEFF Research Database (Denmark)

    Hu, Xiaolian; Saez-Rodriguez, D.; Bang, Ole;

    2014-01-01

    Step-index polymer optical fiber Bragg gratings (POFBGs) and microstructured polymer optical fiber Bragg gratings (mPOFBGs) present several attractive features, especially for sensing purposes. In comparison to FBGs written in silica fibers, they are more sensitive to temperature and pressure...... because of the larger thermo-optic coefficient and smaller Young's modulus of polymer materials. (M)POFBGs are most often photowritten in poly(methylmethacrylate) (PMMA) materials using a continuous-wave 325 nm HeCd laser. For the first time to the best of our knowledge, we study photoinduced...... birefringence effects in (m)POFBGs. To achieve this, highly reflective gratings were inscribed with the phase mask technique. They were then monitored in transmission with polarized light. For this, (m)POF sections a few cm in length containing the gratings were glued to angled silica fibers. Polarization...

  14. Andreev-Bragg Reflection from an Amperian Superconductor.

    Science.gov (United States)

    Baireuther, P; Hyart, T; Tarasinski, B; Beenakker, C W J

    2015-08-28

    We show how an electrical measurement can detect the pairing of electrons on the same side of the Fermi surface (Amperian pairing), recently proposed by Patrick Lee for the pseudogap phase of high-Tc cuprate superconductors. Bragg scattering from the pair-density wave introduces odd multiples of 2k(F) momentum shifts when an electron incident from a normal metal is Andreev reflected as a hole. These Andreev-Bragg reflections can be detected in a three-terminal device, containing a ballistic Y junction between normal leads (1, 2) and the superconductor. The cross-conductance dI1/dV2 has the opposite sign for Amperian pairing than it has either in the normal state or for the usual BCS pairing. PMID:26371674

  15. Planar Bragg Grating Sensors—Fabrication and Applications: A Review

    Directory of Open Access Journals (Sweden)

    I. J. G. Sparrow

    2009-01-01

    Full Text Available We discuss the background and technology of planar Bragg grating sensors, reviewing their development and describing the latest developments. The physical operating principles are discussed, relating device operation to user requirements. Recent performance of such devices includes a planar Bragg grating sensor design which allows refractive index resolution of 1.9×10−6 RIU and temperature resolution of 0.03∘C. This sensor design is incorporated into industrialised applications allowing the sensor to be used for real time sensing in intrinsically safe, high-pressure pipelines, or for insertion probe applications such as fermentation. Initial data demonstrating the ability to identify solvents and monitor long term industrial processes is presented. A brief review of the technology used to fabricate the sensors is given along with examples of the flexibility afforded by the technique.

  16. Fiber Bragg grating strain sensors for marine engineering

    Science.gov (United States)

    Wang, Tingting; Yuan, Zilin; Gong, Yuan; Wu, Yu; Rao, Yunjiang; Wei, Lili; Guo, Peng; Wang, Junpu; Wan, Fu

    2013-09-01

    For the health monitoring of the offshore drilling platform in the salt-fog environment, three nonmetallic materials, i.e., silica, FR-4 epoxy board and sheet molding compound (SMC), with the good anti-corrosion ability were chosen as the packaging materials for the fiber Bragg grating (FBG) strain sensors. By selecting a highly sensitive structure of the fiber Bragg grating strain sensor, the performances of the sensors with three materials were investigated both numerically and experimentally. The strain sensitivities were 3.76 pm/μɛ, 3.02 pm/μɛ and 3.03 pm/μɛ, respectively. The linearity was better than 0.998. It provides useful information for developing sensors for the marine engineering.

  17. Photonic crystal distributed feedback fiber lasers with Bragg gratings

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2000-01-01

    Two new types of optical fibers, where air-holes are running down their length, are considered for making fiber lasers with Bragg gratings. The mode areas for pump and signal in these fiber lasers may be either larger or smaller compared to the corresponding mode areas for fiber lasers based on...... standard step index fibers. This makes possible realization of fiber lasers with a low pump threshold (small mode area), and fiber lasers suitable for high-power applications (large mode area)...

  18. DESIGN AND SIMULATION OF FIBER BRAGG GRATING BASED SENSORS

    OpenAIRE

    MOHAMED M. SALEH; RIADH K. A. Al-ANI; ILHAM K. ONEES

    2014-01-01

    In this paper the temperature and strain sensing principle of FBG based sensors are design & simulated by using Optigrating software. Simulation tools provide valuable help in optimizing the design parameters.From the graphical simulations, it can be concluded that there is a linear relationship between the Bragg wavelength shift and the temperature as well as the strain change. Also different values of grating period due to increasing the value of shifted wavelength.

  19. Simulation of Novel Tunable Nonlinear Chirped Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    LIU Yu-min; YU Zhong-yuan; ZHANG Xiao-guang; YU Li; YANG Bo-jun

    2003-01-01

    A novel tunable chirped fiber Bragg grating technology is proposed and simulated numerically by Matlab. If we adhere a uniform fiber grating with super magnetostrictive film and expose them in a non-uniform magnetic field, the period of the grating can be changed with the strain imposed on it by the magnetostrictive effect .The chirped characteristics can be tuned by changing the magnetic filed which is very flexible in designing.

  20. Trial analysis of swine's periodontal ligament with Bragg grating sensors

    Science.gov (United States)

    Menegotto, G. F.; Grabarski, L.; Kalinowski, H. J.; Simões, J. A.

    2009-10-01

    In this work it is reported the measurement of the differential strain between the dental and bone tissues under effect of an applied load. Slices of swine mandible, containing the premolar tooth, are cut and measured in fresh condition. The strain is measured using fibre Bragg grating sensors glued to both tissues. In the measured range the results show a linear behaviour and confirm the importance of the periodontal ligament in the load transfer mechanism.

  1. Bragg optics computer codes for neutron scattering instrument design

    Energy Technology Data Exchange (ETDEWEB)

    Popovici, M.; Yelon, W.B.; Berliner, R.R. [Missouri Univ. Research Reactor, Columbia, MO (United States); Stoica, A.D. [Institute of Physics and Technology of Materials, Bucharest (Romania)

    1997-09-01

    Computer codes for neutron crystal spectrometer design, optimization and experiment planning are described. Phase space distributions, linewidths and absolute intensities are calculated by matrix methods in an extension of the Cooper-Nathans resolution function formalism. For modeling the Bragg reflection on bent crystals the lamellar approximation is used. Optimization is done by satisfying conditions of focusing in scattering and in real space, and by numerically maximizing figures of merit. Examples for three-axis and two-axis spectrometers are given.

  2. Boron-doped superlattices and Bragg mirrors in diamond

    OpenAIRE

    Fiori, Alexandre; Bousquet, Jessica; Eon, David; Omnès, Franck; Bellet-Amalric, E.; Bustarret, Etienne

    2014-01-01

    International audience A periodic modulation of the boron doping level of single crystal diamond multilayers over more than three orders of magnitude during epitaxial growth by microwave plasma-enhanced chemical vapor deposition is shown to yield Bragg mirrors in the visible. The thicknesses and doping level of the individual layers were controlled by in situ spectroscopic ellipsometry, enabling to tune the reflec-tance peak to the wavelength range of diamond color centers, such as NV 0 or...

  3. Fiber Bragg Gratings Embedded in 3D-Printed Scaffolds

    CERN Document Server

    Liacouras, Peter; Choudhry, Khazar; Strouse, G F; Ahmed, Zeeshan

    2015-01-01

    In recent years there has been considerable interest in utilizing embedded fiber optic based sensors for fabricating smart materials. One of the primary motivations is to provide real-time information on the structural integrity of the material so as to enable proactive actions that prevent catastrophic failure. In this preliminary study we have examined the impact of embedding on the temperature-dependent response of fiber Bragg gratings.

  4. Degradation of the Bragg peak due to inhomogeneities.

    Science.gov (United States)

    Urie, M; Goitein, M; Holley, W R; Chen, G T

    1986-01-01

    The rapid fall-off of dose at the end of range of heavy charged particle beams has the potential in therapeutic applications of sparing critical structures just distal to the target volume. Here we explored the effects of highly inhomogeneous regions on this desirable depth-dose characteristic. The proton depth-dose distribution behind a lucite-air interface parallel to the beam was bimodal, indicating the presence of two groups of protons with different residual ranges, creating a step-like depth-dose distribution at the end of range. The residual ranges became more spread out as the interface was angled at 3 degrees, and still more at 6 degrees, to the direction of the beam. A second experiment showed little significant effect on the distal depth-dose of protons having passed through a mosaic of teflon and lucite. Anatomic studies demonstrated significant effects of complex fine inhomogeneities on the end of range characteristics. Monoenergetic protons passing through the petrous ridges and mastoid air cells in the base of skull showed a dramatic degradation of the distal Bragg peak. In beams with spread out Bragg peaks passing through regions of the base of skull, the distal fall-off from 90 to 20% dose was increased from its nominal 6 to well over 32 mm. Heavy ions showed a corresponding degradation in their ends of range. In the worst case in the base of skull region, a monoenergetic neon beam showed a broadening of the full width at half maximum of the Bragg peak to over 15 mm (compared with 4 mm in a homogeneous unit density medium). A similar effect was found with carbon ions in the abdomen, where the full width at half maximum of the Bragg peak (nominally 5.5 mm) was found to be greater than 25 mm behind gas-soft-tissue interfaces. We address the implications of these data for dose computation with heavy charged particles. PMID:3952143

  5. A high sensitive fiber Bragg grating cryogenic temperature sensor

    Institute of Scientific and Technical Information of China (English)

    Kuo Li; Zhen'an Zhou; Aichun Liu

    2009-01-01

    At cryogenic temperature, a fiber Bragg grating (FBG) temperature sensor with controllable sensitivity and variable measurement range is demonstrated by using bimetal configuration. In experiments, sensitivities of -51.2, -86.4, and -520 pm/K are achieved by varying the lengths of the metals. Measurement ranges of 293 - 290.5, 283 - 280.5, and 259 - 256.5 K are achieved by shortening the distance of the gap among the metals.

  6. Underwater Acoustic Sensors Based on Fiber Bragg Gratings

    OpenAIRE

    Giuseppe Parente; Giuseppe Lanza; Armando Laudati; Michele Giordano; Andrea Cusano; Stefania Campopiano; Antonello Cutolo

    2009-01-01

    We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, sho...

  7. Measurement of sensors with fiber Bragg gratings by laser interferometer

    Czech Academy of Sciences Publication Activity Database

    Mikel, Břetislav; Čížek, Martin; Řeřucha, Šimon; Číp, Ondřej

    Budva : University of Montenegro, 2013. s. 47. [ALT´13. Annual International Conference on Advanced Laser Technologies /21./. 16.09.2013-20.09.2013, Budva] R&D Projects: GA MŠk ED0017/01/01; GA TA ČR TA01010995; GA TA ČR(CZ) TA03010835 Institutional support: RVO:68081731 Keywords : fiber Bragg sensors * laser interferometry * optical spectrum analysis * fiber sensors Subject RIV: BH - Optics, Masers, Laser s

  8. Calibration of elongation of fiber Bragg gratings by laser interferometer

    Czech Academy of Sciences Publication Activity Database

    Mikel, Břetislav; Čížek, Martin; Holík, M.; Číp, Ondřej

    Bellingham : SPIE, 2013, 89161I:1-6. ISSN 0277-786X. [International Symposium on Precision Mechanical Measurements /6./. Guiyang (CN), 10.10.2013] R&D Projects: GA MŠk ED0017/01/01; GA TA ČR TA01010995; GA TA ČR(CZ) TA03010835; GA MV VG20132015124 Institutional support: RVO:68081731 Keywords : Fiber Bragg gratings * Interferometers * Laser s * Optical fibers * Buildings Subject RIV: BH - Optics, Masers, Laser s

  9. High frequency strain measurements with fiber Bragg grating sensors

    Science.gov (United States)

    Koch, J.; Angelmahr, M.; Schade, W.

    2015-05-01

    In recent years fiber Bragg grating sensors gained interest in structural health monitoring and concepts for smart structures. They are small, lightweight, and immune to electromagnetic interference. Using multiplexing techniques, several sensors can be addressed by a single fiber. Therefore, well-established structures and materials in industrial applications can be easily equipped with fiber optical sensors with marginal influence on their mechanical properties. In return, critical components can be monitored in real-time, leading to reduced maintenance intervals and a great reduction of costs. Beside of generally condition monitoring, the localization of failures in a structure is a desired feature of the condition monitoring system. Detecting the acoustic emission of a sudden event, its place of origin can be determined by analyzing the delay time of distributed sensor signals. To achieve high localization accuracies for the detection of cracks, breaks, and impacts high sampling rates combined with the simultaneous interrogation of several fiber Bragg grating sensors are required. In this article a fiber Bragg grating interrogator for high frequency measurements up to the megahertz range is presented. The interrogator is based on a passive wavelength to intensity conversion applying arrayed waveguide gratings. Light power fluctuations are suppressed by a differential data evaluation, leading to a reduced signal-to-noise ratio and a low strain detection limit. The measurement system is used to detect, inter alia, wire breaks in steel wire ropes for dockside cranes.

  10. Identification of inversion domains in KTiOPO{sub 4}via resonant X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fabrizi, Federica, E-mail: federica.fabrizi@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Thomas, Pamela A. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Nisbet, Gareth; Collins, Stephen P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom)

    2015-05-14

    The identification and high-resolution mapping of the absolute crystallographic structure in multi-domain ferroelectric KTiOPO{sub 4} is achieved through a novel synchrotron X-ray diffraction method. On a single Bragg reflection, the intensity ratio in resonant diffraction below and above the Ti absorption K edge demonstrates a domain contrast up to a factor of ∼270, thus implementing a non-contact, non-destructive imaging technique with micrometre spatial resolution, applicable to samples of arbitrarily large dimensions. A novel method is presented for the identification of the absolute crystallographic structure in multi-domain polar materials such as ferroelectric KTiOPO{sub 4}. Resonant (or ‘anomalous’) X-ray diffraction spectra collected across the absorption K edge of Ti (4.966 keV) on a single Bragg reflection demonstrate a huge intensity ratio above and below the edge, providing a polar domain contrast of ∼270. This allows one to map the spatial domain distribution in a periodically inverted sample, with a resolution of ∼1 µm achieved with a microfocused beam. This non-contact, non-destructive technique is well suited for samples of large dimensions (in contrast with traditional resonant X-ray methods based on diffraction from Friedel pairs), and its potential is particularly relevant in the context of physical phenomena connected with an absence of inversion symmetry, which require characterization of the underlying absolute atomic structure (such as in the case of magnetoelectric coupling and multiferroics)

  11. A Method to Discriminate Strain and Temperature in Fiber Bragg Grating Sensors

    OpenAIRE

    Chalapati, Madhan T; Pattnaik, PK; Selvarajan, A; T. Srinivas

    2005-01-01

    A significant limitation to the applications of fiber Bragg gratings (FBG) sensors is the sensitivity of the Bragg wavelength to both temperature and strain, complicating the independent measurement of these paremeters. In this letter, we explore a new method to discriminate strain and temperature in FBG sensors, which utilises the additioanl wavelength dependent phase introduced by Fiber Bragg grating written on sensing arm of Mach Zehnder Interferometer (MZI). The intensity variations of th...

  12. Influence of Non-uniform Temperature Field on Spectra of Fibre Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yan; HE Xing-Fang; YUAN Jie; YIN Li-Qun; FANG Xiao-Yong; CAO Mao-Sheng

    2009-01-01

    We simulate the spectrum characteristics of fibre Bragg grating (FBG) with non-uniform temperature using the transmission matrix method, and the results are analysed. It is found that firstly the modulated coefficient of average refractive index is a very important parameter that influences the spectrum characteristic of the fibre Bragg grating, and secondly the spectrum curves are different in different temperature fields at the same parameter. Hence, we can determine the metrical temperature by analysing the spectrum of fibre Bragg grating.

  13. Spectral characteristics of draw-tower step-chirped fiber Bragg gratings

    Science.gov (United States)

    Idrisov, Ravil F.; Varzhel, Sergey V.; Kulikov, Andrey V.; Meshkovskiy, Igor K.; Rothhardt, Manfred; Becker, Martin; Schuster, Kay; Bartelt, Hartmut

    2016-06-01

    This paper presents research results on the spectral properties of step-chirped fiber Bragg grating arrays written during the fiber drawing process into a birefringent optical fiber with an elliptical stress cladding. The dependences of resonance shift of the step-chirped fiber Bragg grating on bending, on applied tensile stress and on temperature have been investigated. A usage of such step-chirped fiber Bragg gratings in fiber-optic sensing elements creation has been considered.

  14. SPECTRAL CHARACTERISTIC OF UNIFORM FIBER BRAGG GRATING USING COUPLE MODE THEORY

    Directory of Open Access Journals (Sweden)

    JYOTSNA RANI MAHAPATRA, MANISHA CHATTOPADHYAY

    2013-08-01

    Full Text Available This paper presents spectral characteristic of Fiber Bragg Grating. Here the modeling and simulation of an optical fiber Bragg grating for reflectivity based on coupled mode theory is discussed in details. Grating length represent as one of the important parameters in contributing to a high performance Fiber Bragg Grating. The reflection spectrum is analyzed with different parameters like wavelength, grating lengths and induced index change

  15. Distinguishing crystallite size effects from those of structural disorder on the powder X-ray diffraction patterns of layered materials

    Indian Academy of Sciences (India)

    Sylvia Britto; Sumy Joseph; P Vishnu Kamath

    2010-09-01

    Both crystallite size effects and structural disorder contribute to the broadening of lines in the powder X-ray diffraction (PXRD) patterns of layered materials. Stacking faults, in particular, are ubiquitous in layered materials and aside from broadening also induce peaks due to select reflections to shift away from the Bragg positions. The effect of structural disorder has to be suitably discounted before the application of the Scherrer formula for the estimation of crystallite size.

  16. Contribution to diffraction theory

    International Nuclear Information System (INIS)

    In a first part, we have given a general and detailed treatment of the modern theory of diffraction. The rigorous theory is formulated as a boundary value problem of the wave equation or Maxwell equations. However, up to the present time, such a program of treating diffraction by optical systems, even for simple optical instruments, has not been realized due to the complicated character of the boundary conditions. The recent developments show clearly the nature of the approximation of the classical theories originally due to Fresnel and Young, later formulated in a rigorous manner by Kirchhoff and Rubinowicz, respectively and, at the same time the insufficiency of these theories in explaining a number of diffraction phenomena. Furthermore, we have made a study of the limitations of the approximate theories and the recent attempts to improve these. The second part is devoted to a general mathematical treatment of the theory of diffraction of optical systems including aberrations. After a general and specific analysis of geometrical and wave aberrations along classical and modern (Nijboer) lines, we have been able to evaluate the diffraction integrals representing the image field at any point in image space explicitly, when the aberrations are small. Our formulas are the generalisations of all anterior results obtained by previous investigators. Moreover, we have discussed the Zernike-Nijboer theory of aberration and generalised it not only for rotational systems, but also for non-symmetric systems as well, including the case of non circular apertures. The extension to non-circular apertures is done by introducing orthogonal functions or polynomials over such aperture shapes. So far the results are valid for small aberrations, that is to say, where the deformation of the real wave front emerging from the optical system is less than a wave length of light or of the electromagnetic wave from the ideal wave front. If the aberrations are large, then one must employ the

  17. Measurements of transient electron density distributions by femtosecond X-ray diffraction

    International Nuclear Information System (INIS)

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  18. Central Diffraction at ALICE

    CERN Document Server

    Lämsä, Jerry W

    2011-01-01

    The ALICE experiment is shown to be well suited for studies of exclusive final states from central diffractive reactions. The gluon-rich environment of the central system allows detailed QCD studies and searches for exotic meson states, such as glueballs, hybrids and new charmonium-like states. It would also provide a good testing ground for detailed studies of heavy quarkonia. Due to its central barrel performance, ALICE can accurately measure the low-mass central systems with good purity. The efficiency of the Forward Multiplicity Detector (FMD) and the Forward Shower Counter (FSC) system for detecting rapidity gaps is shown to be adequate for the proposed studies. With this detector arrangement, valuable new data can be obtained by tagging central diffractive processes.

  19. Central diffraction at ALICE

    Energy Technology Data Exchange (ETDEWEB)

    Laemsae, J W; Orava, R, E-mail: risto.orava@helsinki.fi [Helsinki Insitute of Physics, and Division of Elementary Particle Physics, Department of Physics, PL 64 (Gustaf Haellstroeminkatu 2a), FI-00014 University of Helsinki (Finland)

    2011-02-01

    The ALICE experiment is shown to be well suited for studies of exclusive final states from central diffractive reactions. The gluon-rich environment of the central system allows detailed QCD studies and searches for exotic meson states, such as glueballs, hybrids and new charmonium-like states. It would also provide a good testing ground for detailed studies of heavy quarkonia. Due to its central barrel performance, ALICE can accurately measure the low-mass central systems with good purity. The efficiency of the Forward Multiplicity Detector (FMD) and the Forward Shower Counter (FSC) system for detecting rapidity gaps is shown to be adequate for the proposed studies. With this detector arrangement, valuable new data can be obtained by tagging central diffractive processes.

  20. Magnetic hysteresis of an artificial square ice studied by in-plane Bragg x-ray resonant magnetic scattering

    Directory of Open Access Journals (Sweden)

    J. P. Morgan

    2012-06-01

    Full Text Available We report X-ray resonant magnetic scattering studies of a Permalloy artificial square ice nanomagnet array, focussing on the field-driven evolution of the sum Σ and difference Δ signals of left and right handed circularly polarized synchrotron X-rays at different lateral positions in reciprocal space Qx. We used X-rays tuned to the Fe L3 resonance energy, with the scattering plane aligned along a principal symmetry axis of the array. Details of the specular Δ hysteresis curve are discussed, following the system magnetization from an initial demagnetized state. The periodic structure gives rise to distinct peaks at in-plane reciprocal Bragg positions, as shown by fitting Σ(Qx to a model based on a simple unit cell structure. Diffraction order-dependent hysteresis in Δ is observed, indicative of the reordering of magnetization on the system's two interpenetrating sublattices, which markedly deviates from an ideal Ising picture under strong applied fields.

  1. Special properties of X-ray diffraction on carbon onions

    International Nuclear Information System (INIS)

    The kinematic theory of X-ray diffraction was applied to the study of the most intense Bragg's reflection observed for carbon onions. It was shown that the agreement with experimental data was attained using a convolution of a Lorentzian contour with regard to the distribution of onion sizes and of an asymmetric contour taking into account the fluctuations of intershell distances inside the particle. It can be assumed that the observed scatter in intershell distances indicates a nonequilibrium state of the internal configuration of onion shells. It appeared to be possible to estimate not only the average onion size, which exceeds the average size of pristine nanodiamonds that are used for onion preparation by annealing, but their size distribution function as well

  2. Mini-computer control of a crystal diffraction spectrometer

    International Nuclear Information System (INIS)

    For experiments to analyze the ion charge spectrum in electron-ion rings of the electron-ring accelerator of the Division of New Acceleration Methods of the JINR, based on the measurement of the characteristic X-radiation of ions, a crystal diffraction spectrometer has been developed. The control electronics of the spectrometer is described, that guarantess the Bragg angle set-up in the region of 9 deg <= theta <= 83 deg with 0.1'' accuracy. This is possible due to the use of a laser interferometer in connection with a system for ground and fine adjustment of the analyzer crystal and for the adjustment of the radiation entrance slit and the detector. A system for control and stabilization of the temperature to 0.05 K, necessary for accurate measurements is described. For automatization of the control the electronics is connected via CAMAC with a Mera 60-30 computer

  3. Serial femtosecond X-ray diffraction of enveloped virus microcrystals

    Directory of Open Access Journals (Sweden)

    Robert M. Lawrence

    2015-07-01

    Full Text Available Serial femtosecond crystallography (SFX using X-ray free-electron lasers has produced high-resolution, room temperature, time-resolved protein structures. We report preliminary SFX of Sindbis virus, an enveloped icosahedral RNA virus with ∼700 Å diameter. Microcrystals delivered in viscous agarose medium diffracted to ∼40 Å resolution. Small-angle diffuse X-ray scattering overlaid Bragg peaks and analysis suggests this results from molecular transforms of individual particles. Viral proteins undergo structural changes during entry and infection, which could, in principle, be studied with SFX. This is an important step toward determining room temperature structures from virus microcrystals that may enable time-resolved studies of enveloped viruses.

  4. Anomalous shift of magnetic diffuse scattering studied by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Prokes, K [Helmholtz Centre Berlin for Materials and Energy, SF-2, Glienicker Strasse 100, 14109 Berlin (Germany); Lander, G H [European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe (Germany); Bernhoeft, N [CEA Grenoble, DRFMC/SPSMS, F-38054 Grenoble (France)], E-mail: prokes@helmholtz-berlin.de

    2009-07-15

    Neutron diffraction results, in the vicinity of the magnetic phase transition of USb and MnF{sub 2}, are reported. The thermal evolution of the magnetic diffuse signal and nuclear Bragg reflections demonstrate that the centre of gravity of the magnetic signals does not lie at the predicted position as calculated from nuclear reflections. This phenomenon, called the q-shift, was first found using resonance x-ray scattering (RXS). The present results show that, (i) the effect is not an artefact of RXS and is also found with neutrons (ii) that the effect arises from the bulk of the sample and is not restricted to the near surface layer ({approx}2000 A) associated with the RXS probe in actinide systems, (iii) the effect is not restricted to actinide compounds.

  5. X-ray diffraction

    International Nuclear Information System (INIS)

    We have been interested in structural elucidation by x-ray diffraction of compounds of biological interest. Understanding exactly how atoms are arranged in three-dimensional arrays as molecules can help explain the relationship between structure and functions. The species investigated may vary in size and shape; our recent studies included such diverse substances as antischistosomal drugs, a complex of cadmium with nucleic acid base, nitrate salts of adenine, and proteins

  6. Direct Phasing of Nanocrystal Diffraction

    CERN Document Server

    Elser, Veit

    2013-01-01

    Recent experiments at free-electron laser x-ray sources have been able to resolve the intensity distributions about Bragg peaks in nanocrystals of large biomolecules. Information derived from small shifts in the peak positions augment the Bragg samples of the particle intensity with samples of its gradients. Working on the assumption that the nanocrystal is entirely generated by lattice translations of a particle, we develop an algorithm that reconstructs the particle from intensities and intensity gradients. Unlike traditional direct phasing methods that require very high resolution data in order to exploit sparsity of the electron density, our method imposes no constraints on the contrast other than positivity and works well at low resolution. We demonstrate successful reconstructions with simulated P1 lysozyme nanocrystal data down to a signal-to-noise ratio of 2 in the intensity gradients.

  7. Polychromatic diffraction contrast tomography

    Energy Technology Data Exchange (ETDEWEB)

    King, A., E-mail: king@synchrotron-soleil.fr [Synchrotron SOLEIL, Gif-sur-Yvette 91192 (France); Reischig, P. [Xnovo Technology ApS, 4600 Køge (Denmark); Department of Materials Science and Engineering, Delft University of Technology, Delft 2628 CD (Netherlands); Adrien, J. [MATEIS, INSA de Lyon, Villeurbanne 69621 (France); Peetermans, S. [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Ludwig, W. [MATEIS, INSA de Lyon, Villeurbanne 69621 (France); European Synchrotron Radiation Facility, Grenoble 38043 (France)

    2014-11-15

    This tutorial review introduces the use of polychromatic radiation for 3D grain mapping using X-ray diffraction contrast tomography. The objective is to produce a 3D map of the grain shapes and orientations within a bulk, millimeter-sized polycrystalline sample. The use of polychromatic radiation enables the standard synchrotron X-ray technique to be applied in a wider range of contexts: 1) Using laboratory X-ray sources allows a much wider application of the diffraction contrast tomography technique. 2) Neutron sources allow large samples, or samples containing high Z elements to be studied. 3) Applied to synchrotron sources, smaller samples may be treated, or faster measurements may be possible. Challenges and particularities in the data acquisition and processing, and the limitations of the different variants, are discussed. - Highlights: • We present a tutorial review of polychromatic diffraction contrast tomography techniques. • The use of polychromatic radiation allows the standard synchrotron DCT technique to be extended to a range of other sources. • The characteristics and limitations of all variants of the techniques are derived, discussed and compared. • Examples using laboratory X-ray and cold neutron radiation are presented. • Suggestions for the future development of these techniques are presented.

  8. Polychromatic diffraction contrast tomography

    International Nuclear Information System (INIS)

    This tutorial review introduces the use of polychromatic radiation for 3D grain mapping using X-ray diffraction contrast tomography. The objective is to produce a 3D map of the grain shapes and orientations within a bulk, millimeter-sized polycrystalline sample. The use of polychromatic radiation enables the standard synchrotron X-ray technique to be applied in a wider range of contexts: 1) Using laboratory X-ray sources allows a much wider application of the diffraction contrast tomography technique. 2) Neutron sources allow large samples, or samples containing high Z elements to be studied. 3) Applied to synchrotron sources, smaller samples may be treated, or faster measurements may be possible. Challenges and particularities in the data acquisition and processing, and the limitations of the different variants, are discussed. - Highlights: • We present a tutorial review of polychromatic diffraction contrast tomography techniques. • The use of polychromatic radiation allows the standard synchrotron DCT technique to be extended to a range of other sources. • The characteristics and limitations of all variants of the techniques are derived, discussed and compared. • Examples using laboratory X-ray and cold neutron radiation are presented. • Suggestions for the future development of these techniques are presented

  9. Nonlinear light propagation in cholesteric liquid crystals with a helical Bragg microstructure

    International Nuclear Information System (INIS)

    Nonlinear optical propagation in cholesteric liquid crystals (CLC) with a spatially periodic helical molecular structure is studied experimentally and modeled numerically. This periodic structure can be seen as a Bragg grating with a propagation stopband for circularly polarized light. The CLC nonlinearity can be strengthened by adding absorption dye, thus reducing the nonlinear intensity threshold and the necessary propagation length. As the input power increases, a blue shift of the stopband is induced by the self-defocusing nonlinearity, leading to a substantial enhancement of the transmission and spreading of the beam. With further increase of the input power, the self-defocusing nonlinearity saturates, and the beam propagates as in the linear-diffraction regime. A system of nonlinear couple-mode equations is used to describe the propagation of the beam. Numerical results agree well with the experiment findings, suggesting that modulation of intensity and spatial profile of the beam can be achieved simultaneously under low input intensities in a compact CLC-based micro-device. (paper)

  10. High brightness sub-nanosecond Q-switched laser using volume Bragg gratings

    Science.gov (United States)

    Anderson, Brian M.; Hale, Evan; Venus, George; Ott, Daniel; Divliansky, Ivan; Glebov, Leonid

    2016-03-01

    The design of Q-switched lasers capable of producing pulse widths of 100's of picoseconds necessitates the cavity length be shorter than a few centimeters. Increasing the amount of energy extracted per pulse requires increasing the mode area of the resonator that for the same cavity length causes exciting higher order transverse modes and decreasing the brightness of the output radiation. To suppress the higher order modes of these multimode resonators while maintaining the compact cavity requires the use of intra-cavity angular filters. A novel Q-switched laser design is presented using transmitting Bragg gratings (TBGs) as angular filters to suppress the higher order transverse modes. The laser consists of a 5 mm thick slab of Nd:YAG, a 3 mm thick slab of Cr:YAG with a 20% transmission, one TBG aligned to suppress the higher order modes along the x-axis, and a 40% output coupler. The gratings are recorded in photo-thermo-refractive (PTR) glass, which has a high damage threshold that can withstand both the high peak powers and high average powers present within the resonator. Using a 4.1 mrad TBG in a 10.8 mm long resonator with an 800μm x 400 μm pump beam, a nearly diffraction limited beam quality of M2 = 1.3 is obtained in a 0.76 mJ pulse with a pulse width of 614 ps.

  11. Transmission comb of a distributed Bragg reflector induced by two surface dielectric gratings

    CERN Document Server

    Zhao, Xiaobo; Zhang, Yongyou

    2015-01-01

    With transfer matrix theory, we study the transmission of a distributed Bragg reflector (DBR) with two dielectric gratings on top and on the bottom. Owing to the diffraction of the two gratings, the transmission shows a comb-like spectrum which red shifts with increasing the grating period during the forbidden band of the DBR. The number density of the comb peaks increases with increasing the number of the DBR cells, while the ratio of the average full width at half maximum (FWHM) of the transmission peaks in the transmission comb to the corresponding average free spectral range, being about 0.04 and 0.02 for the TE and TM incident waves, is almost invariant. The average FWHM of the TM waves is about half of the TE waves, and both they could be narrower than 0.1 nm. In addition, the transmission comb peaks of the TE and TM waves can be fully separated during certain waveband. We further prove that the transmission comb is robust against the randomness of the heights of the DBR layers, even when a 15\\% randomn...

  12. Properties of an AlGaN/AlN distributed-Bragg-reflector structure

    International Nuclear Information System (INIS)

    An AlGaN/AlN distributed-Bragg-reflector (DBR) structure with a high Al content was grown by using plasma-assisted molecular beam epitaxy (PA-MBE). The properties of the sample were characterized by using the transmission electron microscopy, high-resolution X-ray diffraction, atomic force microscopy, and reflectivity spectrum measurements. The reciprocal space mapping analysis indicated that the strain in the AlGaN layers was partially relaxed. The morphology of the DBR exhibited a surface covered by grains (average size of about 130 nm), and the surface roughness was about 2 nm. The spectral measurements showed that the DBR structure presented a peak reflectivity of 68.8% at the center wavelength of 247 nm, which indicated that this DBR structure could work in the deep solar-blind UV region with acceptable reflectivity. However, the optical properties of the DBR structure were deteriorated by the fluctuation of the Al composition, non-uniformity of the layer thickness, the blurry, rough interface in the DBR structure, and so on.

  13. Surface modification of optical materials with hydrogen plasma for fabrication of Bragg gratings.

    Science.gov (United States)

    Salgaeva, Uliana O; Volyncev, Anatoliy B; Mendes, Sergio B

    2016-01-20

    We investigate the hydrogen plasma process as a route for creating Bragg gratings (BGs) on optoelectronic materials such as undoped lithium niobate (LiNbO(3)), proton-exchanged LiNbO(3), and soda-lime glass. Photopatterns (periodic modulations, Λ=323-2000  nm) were created on those substrates and the hydrogen plasma process was investigated for its ability to transfer the microstructures and the underlying mechanisms involved in this process. The diffraction efficiency and surface topology of the BG were characterized, as well as the optical properties of corresponding bulk materials undergoing the same plasma treatment. It is shown that the hydrogen plasma treatment changes the complex refractive index and modifies the surface topology with a volume expansion in the near-surface region, and both features are connected to the appearance of structural defects in the materials. The hydrogen plasma offers unique flexibility and advantages that can be explored for the fabrication of integrated photonic components. PMID:26835921

  14. In-Situ Characterization of Three-Dimensional Optical Matters by Light Diffraction

    Institute of Scientific and Technical Information of China (English)

    JIANG Lai-Dong; DAI Qiao-Feng; FENG Tian-Hua; LIU Jin; WU Li-Jun; LAN Sheng; A.V.Gopal; V.A.Trofimov

    2009-01-01

    Three-dimensional optical matters are created by combining the single beam optical trapping with the conven-tional Z-scan technique. Dynamic light diffraction is employed to evaluate the structure and quality of the optical matter formed at the optimum trapping power. The lattice constant of the optical matter is extracted based on the Bragg and Snell laws, showing that polystyrene spheres are nearly close-packed in the optical matter,confirmed by comparing the diffraction pattern of the optical matter with that of a colloidal photonic crystal fabricated by the self-assembled technique. The relatively broad diffraction peaks observed in the optical matter indicate that the density of disorders in it is higher than that in the photonic crystal. It is suggested that the optical matter possesses a random close-packed structure rather than a face centered cubic one.

  15. Imaging nanoscale lattice variations by machine learning of x-ray diffraction microscopy data

    Science.gov (United States)

    Laanait, Nouamane; Zhang, Zhan; Schlepütz, Christian M.

    2016-09-01

    We present a novel methodology based on machine learning to extract lattice variations in crystalline materials, at the nanoscale, from an x-ray Bragg diffraction-based imaging technique. By employing a full-field microscopy setup, we capture real space images of materials, with imaging contrast determined solely by the x-ray diffracted signal. The data sets that emanate from this imaging technique are a hybrid of real space information (image spatial support) and reciprocal lattice space information (image contrast), and are intrinsically multidimensional (5D). By a judicious application of established unsupervised machine learning techniques and multivariate analysis to this multidimensional data cube, we show how to extract features that can be ascribed physical interpretations in terms of common structural distortions, such as lattice tilts and dislocation arrays. We demonstrate this ‘big data’ approach to x-ray diffraction microscopy by identifying structural defects present in an epitaxial ferroelectric thin-film of lead zirconate titanate.

  16. Optical pendulum effect in one-dimensional diffraction-thick porous silicon based photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, V. B., E-mail: vb.novikov@physics.msu.ru; Svyakhovskiy, S. E.; Maydykovskiy, A. I.; Murzina, T. V.; Mantsyzov, B. I. [Department of Physics, M. V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

    2015-11-21

    We present the realization of the multiperiodic optical pendulum effect in 1D porous silicon photonic crystals (PhCs) under dynamical Bragg diffraction in the Laue scheme. The diffraction-thick PhC contained 360 spatial periods with a large variation of the refractive index of adjacent layers of 0.4. The experiments reveal switching of the light leaving the PhC between the two spatial directions, which correspond to Laue diffraction maxima, as the fundamental wavelength or polarization of the incident light is varied. A similar effect can be achieved when the temperature of the sample or the intensity of the additional laser beam illuminating the crystal are changed. We show that in our PhC structures, the spectral period of the pendulum effect is down to 5 nm, while the thermal period is about 10 °C.

  17. Optical pendulum effect in one-dimensional diffraction-thick porous silicon based photonic crystals

    International Nuclear Information System (INIS)

    We present the realization of the multiperiodic optical pendulum effect in 1D porous silicon photonic crystals (PhCs) under dynamical Bragg diffraction in the Laue scheme. The diffraction-thick PhC contained 360 spatial periods with a large variation of the refractive index of adjacent layers of 0.4. The experiments reveal switching of the light leaving the PhC between the two spatial directions, which correspond to Laue diffraction maxima, as the fundamental wavelength or polarization of the incident light is varied. A similar effect can be achieved when the temperature of the sample or the intensity of the additional laser beam illuminating the crystal are changed. We show that in our PhC structures, the spectral period of the pendulum effect is down to 5 nm, while the thermal period is about 10 °C

  18. The Physical Meanings of 5 Basic Parameters for an X-Ray Diffraction Peak and Their Application

    Institute of Scientific and Technical Information of China (English)

    周健; 王河锦

    2003-01-01

    This paper derives the physical meanings of peak position, peak width and height ofan X-ray diffraction peak from the analyses of the Bragg's equation, the Scherrer' s formula andthe principle of peak intensity calculation. The geometric characteristics of an asymmetric peakare clarified by means of experiment. The relationships between neak shape and domain size/lattice strain have been verified by geological events. Therefore this paper integrates the physicalmeanings of all 5 basic parameters for an X-ray diffraction peak. Applications of these 5 parame-ters are exemplified.

  19. X-ray diffraction

    International Nuclear Information System (INIS)

    The seventh edition of Philips' Review of literature on X-ray diffraction begins with a list of conference proceedings on the subject, organised by the Philips' organisation at regular intervals in various European countries. This is followed by a list of bulletins. The bibliography is divided according to the equipment (cameras, diffractometers, monochromators) and its applications. The applications are subdivided into sections for high/low temperature and pressure, effects due to the equipment, small angle scattering and a part for stress, texture and phase analyses of metals and quantitative analysis of minerals

  20. Diffractive Alvarez lens

    International Nuclear Information System (INIS)

    A diffractive Alvarez lens is demonstrated that consists of two separate phase plates, each having complementary 16-level surface-relief profiles that contain cubic phase delays. Translation of these two components in the plane of the phase plates is shown to produce a variable astigmatic focus. Both spherical and cylindrical phase profiles are demonstrated with good accuracy, and the discrete surface-relief features are shown to cause less than λ/10 wave-front aberration in the transmitted wave front over a 40 mmx80 mm region. (c) 2000 Optical Society of America

  1. Elastic slopes and diffraction

    International Nuclear Information System (INIS)

    It is well known that elastic hadronic slopes grow with energy and appear sizeably larger when measured very close to t=0 than at intermediate t-values. This has been confirmed by the recent anti-p p measurements at the CERN SPS-Collider. By comparing the data with a formula derived recently which gives the slope as a function of the four momentum transfer squared t and of the average multiplicity we argue that all the basic properties of hadronic slopes may be attributed to the role of multiparticle unitarity, i.e. to diffraction

  2. Extended Diffraction Tomography

    CERN Document Server

    Schlottmann, R B

    2009-01-01

    We present the development of extended diffraction tomography, a new approach to the solution of the linear seismic waveform inversion problem. This method has several appealing features, such as the use of arbitrary depth-dependent reference models and the decomposition of the full 2D or 3D inverse problem into a large number of independent 1D problems. This decomposition makes the method naturally highly parallelizable. Careful implementation yields significant robustness with respect to noise. Several synthetic examples are shown which characterize the benefits of our method and demonstrate the usefulness of choosing realistic 1D reference media.

  3. Underwater Acoustic Sensors Based on Fiber Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Giuseppe Parente

    2009-06-01

    Full Text Available We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating.

  4. Weldable fibre Bragg grating sensors for steel bridge monitoring

    International Nuclear Information System (INIS)

    For applications related to the structural health monitoring of steel bridges, novel weldable strain and temperature sensors based on fibre Bragg gratings were developed. These sensors, which can be directly welded to metallic structures, reveal linear responses over typical required measurement ranges and stability over thousands of load and temperature cycles. Proper installation procedures and in-field mechanical protection were also developed and implemented. The significance of the developed sensors was demonstrated through the installation of a complete sensing network on a new circular pedestrian bridge in Aveiro, Portugal, where it was used for loading tests, and also for in-service monitoring of its structural health

  5. Application of the Transmission Bragg Gratings for Vibration Monitoring

    CERN Document Server

    Tikhonov, E A

    2010-01-01

    It is shown that the optical-electronic system consisted of the transmission Bragg grating, a laser and the intermediate sensitive to the vibrations mirror can detect the vibrations, when touched by them laser beam scan will exceed the angular divergence of the beam. The mathematical model of the sensor of the vibrations presented in the form of Taylor series describes the system response taking into account the operating point, in particular, describes the effect of the doubling of the modulation frequency response relative to the frequency of acting vibrations.

  6. On-Chip Silicon Waveguide Bragg Grating Photonic Temperature Sensor

    CERN Document Server

    Klimov, Nikolai N; Berger, Michaela; Ahmed, Zeeshan

    2015-01-01

    Resistance thermometry is a time-tested method for taking temperature measurements. In recent years fundamental limits to resistance-based approaches spurred considerable interest in developing photonic temperature sensors as a viable alternative. In this study we demonstrate that our photonic thermometer, which consists of a silicon waveguide integrated with a Bragg grating, can be used to measure temperature changes over the range from 5 C to 160 C with a combined expanded uncertainty [k = 2 ; 95% confidence level] of 1.25 degree C. The computational modeling of the sensor predicts the resonance wavelength and effective refractive index within 4% of the measured value.

  7. Reannealed Fiber Bragg Gratings Demonstrated High Repeatability in Temperature Measurements

    Science.gov (United States)

    Adamovsky, Grigory; Juergens, Jeffrey R.

    2004-01-01

    Fiber Bragg gratings (FBGs) are formed by periodic variations of the refractive index of an optical fiber. These periodic variations allow an FBG to act as an embedded optical filter, passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change the wavelengths that are transmitted and reflected by it. Both thermal and mechanical forces acting on the grating will alter its physical characteristics, allowing the FBG sensor to detect both the temperature variations and the physical stresses and strains placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. To assess the feasibility of using Bragg gratings as temperature sensors for propulsion applications, researchers at the NASA Glenn Research Center evaluated the performance of Bragg gratings at elevated temperatures for up to 300 C. For these purposes, commercially available polyimide-coated high-temperature gratings were used that were annealed by the manufacturer to 300 C. To assure the most thermally stable gratings at the operating temperatures, we reannealed the gratings to 400 C at a very slow rate for 12 to 24 hr until their reflected optical powers were stabilized. The reannealed gratings were then subjected to periodic thermal cycling from room temperature to 300 C, and their peak reflected wavelengths were monitored. The setup shown is used for reannealing and thermal cycling the FBGs. Signals from the photodetectors and the spectrum analyzer were fed into a computer equipped with LabVIEW software. The software synchronously monitored the oven/furnace temperature and the optical spectrum analyzer

  8. OPTIMIZATION OF INTRAGRATING SENSING USING FIBER BRAGG GRATING

    OpenAIRE

    B.B.PADHY; HAFTAY ABADI GEBRU; SANDIPAN M.NALAWADE

    2011-01-01

    Linearly Chirped Fiber Bragg Gratings (FBGs) have been optimized and investigated for intragrating sensing. The side lobes have been suppressed using Gaussian apodization while maintaining the peak reflectivity and the bandwidth of the reflected signal. We have achieved a chirp rate of 0.5 to 2 nm/mm for intragrating sensing.Average thermal sensitivity of 11.55 pm/ oC is obtained which is higher than uniform FBGs. We have achieved novel characteristics of linearly chirped FBGs under the effec...

  9. OPTIMIZATION OF INTRAGRATING SENSING USING FIBER BRAGG GRATING

    Directory of Open Access Journals (Sweden)

    B.B.PADHY

    2011-01-01

    Full Text Available Linearly Chirped Fiber Bragg Gratings (FBGs have been optimized and investigated for intragrating sensing. The side lobes have been suppressed using Gaussian apodization while maintaining the peak reflectivity and the bandwidth of the reflected signal. We have achieved a chirp rate of 0.5 to 2 nm/mm for intragrating sensing.Average thermal sensitivity of 11.55 pm/ oC is obtained which is higher than uniform FBGs. We have achieved novel characteristics of linearly chirped FBGs under the effect of non-monotonic physical parameter distribution fields for excellent spectral response profile for intragrating sensing.

  10. Microfiber-Based Bragg Gratings for Sensing Applications: A Review

    Directory of Open Access Journals (Sweden)

    Jun-Long Kou

    2012-06-01

    Full Text Available Microfiber-based Bragg gratings (MFBGs are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of MFBGs are introduced first. Then, the sensing properties and applications of MFBGs are discussed, including measurement of refractive index (RI, temperature, and strain/force. Finally a summary of selected MFBG sensing elements from previous literature are tabulated.

  11. Passive Temperature-Compensating Technique for Microstructured Fiber Bragg Gratings

    CERN Document Server

    Huy, Minh Châu Phan; Dewynter, Véronique; Ferdinand, Pierre; Pagnoux, Dominique; Dussardier, Bernard; Blanc, Wilfried; 10.1109/JSEN.2008.926169

    2010-01-01

    The thermal drift of the characteristic wavelength of fiber Bragg gratings (FBGs) photowritten in the core of microstructured fibers (MOFs) is significantly reduced by inserting a liquid of suitable refractive index into their holes. For instance, the spectral range of variations is divided by a factor of 4 over a temperature range larger than 20\\degree C in a six-hole MOF, and the maximum sensitivity is reduced. Such passive FBG temperature compensation technique is of great interest for applications involving accurate sensing free of thermal effects.

  12. Dynamic gate algorithm for multimode fiber Bragg grating sensor systems.

    Science.gov (United States)

    Ganziy, D; Jespersen, O; Woyessa, G; Rose, B; Bang, O

    2015-06-20

    We propose a novel dynamic gate algorithm (DGA) for precise and accurate peak detection. The algorithm uses a threshold-determined detection window and center of gravity algorithm with bias compensation. We analyze the wavelength fit resolution of the DGA for different values of the signal-to-noise ratio and different peak shapes. Our simulations and experiments demonstrate that the DGA method is fast and robust with better stability and accuracy than conventional algorithms. This makes it very attractive for future implementation in sensing systems, especially based on multimode fiber Bragg gratings. PMID:26193010

  13. Underwater acoustic sensors based on fiber bragg gratings.

    Science.gov (United States)

    Campopiano, Stefania; Cutolo, Antonello; Cusano, Andrea; Giordano, Michele; Parente, Giuseppe; Lanza, Giuseppe; Laudati, Armando

    2009-01-01

    We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension and the material characteristics of the coating. PMID:22408534

  14. A porous silicon Bragg grating waveguide by direct laser writing

    Energy Technology Data Exchange (ETDEWEB)

    Rea, Ilaria; Iodice, Mario; Coppola, Giuseppe; Rendina, Ivo; De Stefano, Luca [National Council of Research, Institute for Microelectronic and Microsystems, Department of Naples, Via P Castellino 111, I-80131 Naples (Italy); Marino, Antigone [Department of Physics, ' Federico II' University of Naples, Via Cinthia, I-80126 Naples (Italy)], E-mail: ilaria.rea@na.imm.cnr.it

    2008-09-10

    We have designed, fabricated and characterized a porous silicon-based Bragg grating integrated in an optical waveguide, by using a low cost and fast technique, direct laser writing. A periodic optical structure with a pitch of 10 {mu}m, resonant in the near-infrared wavelength region, has been obtained. The simulated transmission spectra, calculated by the transfer matrix method and waveguide modal computation, are in good qualitative agreement with the experimental ones. The waveguide transmission losses have been quantified as 22 dB cm{sup -1}.

  15. A porous silicon Bragg grating waveguide by direct laser writing

    International Nuclear Information System (INIS)

    We have designed, fabricated and characterized a porous silicon-based Bragg grating integrated in an optical waveguide, by using a low cost and fast technique, direct laser writing. A periodic optical structure with a pitch of 10 μm, resonant in the near-infrared wavelength region, has been obtained. The simulated transmission spectra, calculated by the transfer matrix method and waveguide modal computation, are in good qualitative agreement with the experimental ones. The waveguide transmission losses have been quantified as 22 dB cm-1

  16. Ultrafast laser inscribed fiber Bragg gratings for sensing applications

    Science.gov (United States)

    Mihailov, Stephen J.

    2016-05-01

    Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on femtosecond infrared laser-material processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This tutorial paper will present a review of some of the more recent developments.

  17. Fiber-bragg grating-loop ringdown method and apparatus

    Science.gov (United States)

    Wang, Chuji

    2008-01-29

    A device comprising a fiber grating loop ringdown (FGLRD) system of analysis is disclosed. A fiber Bragg grating (FBG) or Long-Period grating (LPG) written in a section of single mode fused silica fiber is incorporated into a fiber loop. By utilizing the wing areas of the gratings' bandwidth as a wavelength dependent attenuator of the light transmission, a fiber grating loop ringdown concept is formed. One aspect of the present invention is temperature sensing, which has been demonstrated using the disclosed device. Temperature measurements in the areas of accuracy, stability, high temperature, and dynamic range are also described.

  18. Field Guide to Diffractive Optics

    CERN Document Server

    Soskind, Yakov

    2011-01-01

    This SPIE Field Guide provides the operational principles and established terminology of diffractive optics as well as a comprehensive overview of the main types of diffractive optics components. An emphasis is placed on the qualitative explanation of the diffraction phenomenon by the use of field distributions and graphs, providing the basis for understanding the fundamental relations and important trends.

  19. Optical Properties of High Sensitivity Fiber Bragg Grating on Temperature Sensor

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this paper, the spectrum shift properties of the center reflection wavelength detected to be based on the FBG sensor with ambient temperature change. The basic theoretical methods and numerical simulation for the spectral properties of uniform Bragg grating is analyzed by using coupling mode theory which is optical properties of high sensitivity fiber Bragg grating on temperature sensor in accordance with experiment.

  20. Numerical Simulation of Bragg Reflection Based on Linear Waves Propagation over A Series of Rectangular Seabed

    Institute of Scientific and Technical Information of China (English)

    Chih-Chung WEN; Li-Hung TSAI

    2008-01-01

    A numerical model, Evolution Equation of Mild-Slope Equation (EEMSE) developed by Hsu et al. (2003), was applied to study the Bragg reflection of water waves over a series of rectangular seabed. Three key parameters of the Bragg reflection including the peak coefficient of primary Bragg reflection, its corresponding relative wavelength, and the bandwidth, have shown to be effective in describing the characteristics of the primary Bragg reflection. The characteristics of the Bragg reflection were investigated under the various conditions comprising number, height, and spacing interval of a series of rectangular seabed. The results reveal that the peak of Bragg reflection increases with the increase of rectangular seabed height and number, the bandwidth and the shift value of the Bragg reflection depend on the increase of the rectangular seabed height as well as the decrease of rectangular seabed number, and the relative rectangular seabed spacing in the rang of 3 and 4 could produce higher Bragg reflection. Finally, a correlative and regressive analysis is performed by use of the calculated data. Based on the results of the analysis, empirical equations were established. Our study results can provide an appropriate choice of a series of rectangular seabed field for a practical design.

  1. Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature

    OpenAIRE

    Zheng WenJun; Fei GuangTao; Wang Biao; Zhang Li

    2009-01-01

    Abstract We have successfully prepared anodized alumina membrane distributed Bragg reflector (DBR) using electrochemical anodization method. The transmission peak of this distributed Bragg reflector could be easily and effectively modulated to cover almost any wavelength range of the whole visible spectrum by adjusting anodization temperature.

  2. Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature

    Directory of Open Access Journals (Sweden)

    Zheng WenJun

    2009-01-01

    Full Text Available Abstract We have successfully prepared anodized alumina membrane distributed Bragg reflector (DBR using electrochemical anodization method. The transmission peak of this distributed Bragg reflector could be easily and effectively modulated to cover almost any wavelength range of the whole visible spectrum by adjusting anodization temperature.

  3. Imaging of an undulator source by phase circular Bragg-Fresnel lenses

    OpenAIRE

    Hartman, Ya.; Tarazona, E; Elleaume, P.; Snigireva, I.; Snigirev, A.

    1994-01-01

    Focusing properties and heatload resistance of a Bragg-Fresnel lens placed in an undulator beam have been demonstrated. The electron beam at an undulator source has been imaged by two setups using Bragg-Fresnel lenses. The first setup is a two-lenses telescope and the second one consists of one circular BFL and an asymmetrically cut crystal.

  4. Imaging of an undulator source by phase circular Bragg-Fresnel lenses

    International Nuclear Information System (INIS)

    Focusing properties and heatload resistance of a Bragg-Fresnel lens placed in an undulator beam have been demonstrated. The electron beam at an undulator source has been imaged by two setups using Bragg-Fresnel lenses. The first setup is a two-lenses telescope and the second one consists of one circular BFL and an asymmetrically cut crystal. (orig.)

  5. Fabrication of the Long Bragg Grating by Excimer Laser Micro Machining with High-Precision Positioning XXY Platform

    OpenAIRE

    Jian-Zhong Wu; Jian-Cin Chao; Jui-Yi Hu; Chia-Chin Chiang

    2014-01-01

    With the advancement of technology, the application of fiber Bragg grating is widely used as a Bragg grating sensor. Fiber Bragg grating is fabrication using excimer laser machining with the phase masker. The grating length is decided by the width of laser beam. In this paper, we proposed fabrication of the long Bragg grating by excimer Laser micro machining with a high-precision positioning XXY platform. The high-precision positioning XXY platform plays an important role for long FBG. It nee...

  6. POINT-BY-POINT INSCRIPTION OF FIBER BRAGG GRATINGS INTO BIREFRINGENT OPTICAL FIBER THROUGH PROTECTIVE ACRYLATE COATING BY TI:SA FEMTOSECOND LASER

    Directory of Open Access Journals (Sweden)

    S. V. Arkhipov,

    2016-05-01

    Full Text Available The paper deals withpoint-by-point inscriptionof fiber Bragg gratings by the 800 nm Ti:Sa femtosecond laser pulses into a unique birefringent fiber with elliptical stress cladding of home manufacture. The proposed inscriptionmethod has advantages over the conventional phase mask method. The possibility to create complex grating structures and relatively high transparency of acrylate coating to the Ti:Sa femtosecond laser radiation of 800 nm gives the possibility for inscriptionof phase shifting gratings, chirped grating and superstructures without stripping the fiber. Also, this method makes it possible to inscribethese diffractive structures with and without co-doping of GeO2 in the fiber core. Achieved reflectance was 10%. The microscopic image of the diffractive structure in the fiber core is presented. The grating of 1.07 µm is realized by pulling the fiber with constant speed while the laser pulses are applied with a repetition frequency of 1 kHz. The results are usable in the sphere of creation of different fiber optic sensitive elements based on Bragg gratings.

  7. Hard diffraction in Pythia 8

    Science.gov (United States)

    Overgaard Rasmussen, Christine

    2016-07-01

    We present an overview of the options for diffraction implemented in the general-purpose event generator Pythia 8 [1]. We review the existing model for soft diffraction and present a new model for hard diffraction. Both models use the Pomeron approach pioneered by Ingelman and Schlein, factorising the diffractive cross section into a Pomeron flux and a Pomeron PDF, with several choices for both implemented in Pythia 8. The model of hard diffraction is implemented as a part of the multiparton interactions (MPI) framework, thus introducing a dynamical gap survival probability that explicitly breaks factorisation.

  8. Hard Diffraction in Pythia 8

    CERN Document Server

    Rasmussen, Christine O

    2015-01-01

    We present an overview of the options for diffraction implemented in the general-purpose event generator Pythia 8. We review the existing model for soft diffraction and present a new model for hard diffraction. Both models use the Pomeron approach pioneered by Ingelman and Schlein, factorising the diffractive cross section into a Pomeron flux and a Pomeron PDF, with several choices for both implemented in Pythia 8. The model of hard diffraction is implemented as a part of the multiparton interactions (MPI) framework, thus introducing a dynamical gap survival probability that explicitly breaks factorisation.

  9. Muscular condition monitoring system using fiber bragg grating sensors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Heon Young; Lee, Jin Hyuk; Kim, Dae Hyun [Seoul National University of Technology, Seoul (Korea, Republic of)

    2014-10-15

    Fiber optic sensors (FOS) have advantages such as electromagnetic interference (EMI) immunity, corrosion resistance and multiplexing capability. For these reasons, they are widely used in various condition monitoring systems (CMS). This study investigated a muscular condition monitoring system using fiber optic sensors (FOS). Generally, sensors for monitoring the condition of the human body are based on electro-magnetic devices. However, such an electrical system has several weaknesses, including the potential for electro-magnetic interference and distortion. Fiber Bragg grating (FBG) sensors overcome these weaknesses, along with simplifying the devices and increasing user convenience. To measure the level of muscle contraction and relaxation, which indicates the muscle condition, a belt-shaped FBG sensor module that makes it possible to monitor the movement of muscles in the radial and circumferential directions was fabricated in this study. In addition, a uniaxial tensile test was carried out in order to evaluate the applicability of this FBG sensor module. Based on the experimental results, a relationship was observed between the tensile stress and Bragg wavelength of the FBG sensors, which revealed the possibility of fabricating a muscular condition monitoring system based on FBG sensors.

  10. A simple Bragg detector design for AMS and IBA applications

    Science.gov (United States)

    Müller, Arnold Milenko; Döbeli, Max; Seiler, Martin; Synal, Hans-Arno

    2015-08-01

    A new compact Bragg type gas ionization chamber (GIC) has been built for use as particle counter in AMS and IBA applications. The detector stands out due to its simple concept, which does not include a Frisch grid. Test experiments have been performed with ions in the mass range from He to Th and energies ranging from 30 keV to 2.5 MeV, in order to find optimal measurement conditions and to characterize the detector performance. For projectiles heavier than Al at energies below 2.5 MeV the obtained energy resolution is comparable with that of a state-of-the-art GIC with Frisch grid and clearly outperforms solid state detectors. Additionally the operation of this simplified Bragg GIC in the electron multiplication mode was investigated for the first time, which allows the detection of radiocarbon ions at energies below 50 keV with an energy resolution of the order of 10 keV.

  11. Muscular condition monitoring system using fiber bragg grating sensors

    International Nuclear Information System (INIS)

    Fiber optic sensors (FOS) have advantages such as electromagnetic interference (EMI) immunity, corrosion resistance and multiplexing capability. For these reasons, they are widely used in various condition monitoring systems (CMS). This study investigated a muscular condition monitoring system using fiber optic sensors (FOS). Generally, sensors for monitoring the condition of the human body are based on electro-magnetic devices. However, such an electrical system has several weaknesses, including the potential for electro-magnetic interference and distortion. Fiber Bragg grating (FBG) sensors overcome these weaknesses, along with simplifying the devices and increasing user convenience. To measure the level of muscle contraction and relaxation, which indicates the muscle condition, a belt-shaped FBG sensor module that makes it possible to monitor the movement of muscles in the radial and circumferential directions was fabricated in this study. In addition, a uniaxial tensile test was carried out in order to evaluate the applicability of this FBG sensor module. Based on the experimental results, a relationship was observed between the tensile stress and Bragg wavelength of the FBG sensors, which revealed the possibility of fabricating a muscular condition monitoring system based on FBG sensors.

  12. Self-heated fiber Bragg grating sensors for cryogenic environments

    Science.gov (United States)

    Chen, Tong; Swinehart, Philip R.; Maklad, Mokhtar S.; Buric, Michael P.; Chen, Kevin P.

    2010-04-01

    Cryogenic fuels are often considered as major energy alternatives to coal and petroleum based fuels. Safe and reliable sensor networks are required for on-demand, real-time fuel management in cryogenic environments. In this paper, a new sensor design is described that enhances the low-temperature performance of fiber sensors. FBGs inscribed in high attenuation fiber (HAF) are used to absorb in-fiber power light to raise the local sensor temperature in the cryogenic environment. When in-fiber power light is turned off, FBG sensors can serve as passive sensors to gauge temperature and stress in the cryogenic system. When the in-fiber power light is turned on, the heated sensors can be used to rapidly gauge fuel level and fuel leaks. In one example, a hydrogen gas sensor is demonstrated with a palladium-coated fiber Bragg grating (FBG). The low-temperature performance of the sensor was improved by heating the gratings as much as 200 K above the ambient temperature, and hydrogen concentration well below the 4% explosion limit was measured at 123K. In a second example, an array of four aluminum coated fiber Bragg gratings was used to measure liquid level in a cryogenic environment.

  13. A simple Bragg detector design for AMS and IBA applications

    International Nuclear Information System (INIS)

    A new compact Bragg type gas ionization chamber (GIC) has been built for use as particle counter in AMS and IBA applications. The detector stands out due to its simple concept, which does not include a Frisch grid. Test experiments have been performed with ions in the mass range from He to Th and energies ranging from 30 keV to 2.5 MeV, in order to find optimal measurement conditions and to characterize the detector performance. For projectiles heavier than Al at energies below 2.5 MeV the obtained energy resolution is comparable with that of a state-of-the-art GIC with Frisch grid and clearly outperforms solid state detectors. Additionally the operation of this simplified Bragg GIC in the electron multiplication mode was investigated for the first time, which allows the detection of radiocarbon ions at energies below 50 keV with an energy resolution of the order of 10 keV

  14. Polarization-independent light-dispersing device based on diffractive optics

    Science.gov (United States)

    Amako, J.; Fujii, E.

    2015-03-01

    We report a light-dispersing device comprised of two transmission gratings and a wave plate. The gratings split the light incident at the Bragg angle into two orthogonally polarized components. The wave plate, which is placed between the gratings, functions as a polarization converter for oblique illumination. Appropriate assembly of these optical parts results in efficient diffraction of the unpolarized light with high spectral resolution. Using coupled-wave theories and Mueller matrix analysis, we constructed a device with a grating period of 400 nm for the spectral range of 680 ± 50 nm. We verified the proposed polarization-independent light-dispersing concept from the evaluation of this device.

  15. Enhancing the Area of a Raman Atom Interferometer Using a Versatile Double-Diffraction Technique

    International Nuclear Information System (INIS)

    In this Letter, we demonstrate a new scheme for Raman transitions which realize a symmetric momentum-space splitting of 4(ℎ/2π)k, deflecting the atomic wave packets into the same internal state. Combining the advantages of Raman and Bragg diffraction, we achieve a three pulse state labeled an interferometer, intrinsically insensitive to the main systematics and applicable to all kinds of atomic sources. This splitting scheme can be extended to 4N(ℎ/2π)k momentum transfer by a multipulse sequence and is implemented on a 8(ℎ/2π)k interferometer. We demonstrate the area enhancement by measuring inertial forces.

  16. Study of crystal structure of kidney stones in Homs by x-ray diffraction

    International Nuclear Information System (INIS)

    The crystal structure, grain size, and the crystal potential for calculi have been studied using x-ray diffraction instrument P W 1840 which depends on Bragg reflection. This study required creation of data bank (Dat-Stone) specified for kidney stones for the automatic detection of the crystallographic components using P W 1480 instrument and the PC connected to it. The results help in identifying the conditions of calculi formation and helps physicians in determining the treatment in order to prevent the formation of the stone again

  17. Model-independent structure factors from powder X-ray diffraction: a novel approach.

    Science.gov (United States)

    Straasø, Tine; Dippel, Ann-Christin; Becker, Jacob; Als-Nielsen, Jens

    2014-01-01

    Under the experimental condition that all Bragg peaks in a powder X-ray diffraction (PXRD) pattern have the same shape, one can readily obtain the Bragg intensities without fitting any parameters. This condition is fulfilled at the P02.1 beamline at PETRA III using the seventh harmonic from a 23 mm-period undulator (60 keV) at a distance of 65 m. For grain sizes of the order of 1 µm, the Bragg peak shape in the PXRD is entirely determined by the diameter of the capillary containing the powder sample and the pixel size of the image plate detector, and consequently it is independent of the scattering angle. As an example, a diamond powder has been chosen and structure factors derived which are in accordance with those calculated from density functional theory methods of the WIEN2k package to within an accuracy that allows a detailed electron density analysis. PMID:24365925

  18. Multilayer diffraction grating

    Science.gov (United States)

    Barbee, Jr., Troy W.

    1990-01-01

    This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages.

  19. Resolution in diffraction

    International Nuclear Information System (INIS)

    The in-plane resolution of a diffraction apparatus is discussed in the Gaussian approximation. This approximation is generally adequate to find half-widths of the resolution function, but the detailed resolution line-shape may differ from a Gaussian line-shape for instance in using perfect crystals as monochromator or analyzer. In combining the contributions from different elements in the apparatus to the resolution function the method of conjugate diameters is useful. The resulting resolution widths are not given in explicit formulae but by means of a few simple subroutines in a computer program, e.g. transforming a set of conjugate diameters to another set with a prescribed direction of one diameter, the method seems to be readily applicable to a variety of instruments. (Auth.)

  20. Quantification of rutile in anatase by X-ray diffraction

    International Nuclear Information System (INIS)

    Nowadays the discovering of new and better materials required in all areas of the industry has been lead to the human being to introduce him to this small and great world. The crystalline materials, have properties markedly directional. When it is necessary to realize a quantitative analysis to these materials the task is not easy. The main objective of this work is the research of a real problem, its solution and perfecting of a technique involving the theoretical and experimental principles which allow the quantification of crystalline phases. The chapter 1 treats about the study of crystalline state during the last century, by means of the X-ray diffraction technique. The chapter 2 studies the nature and production of X-rays, the chapter 3 expounds the principles of the diffraction technique which to carry out when it is satisfied the Bragg law studying the powder diffraction method and its applications. In the chapter 4 it is explained how the intensities of the beams diffracted are determined by the atoms positions inside of the elemental cell of the crystal. The properties of the crystalline samples of anatase and rutile are described in the chapter 5. The results of this last analysis are the information which will be processed by means of the auxiliary software: Diffrac AT, Axum and Peakfit as well as the TAFOR and CUANTI software describing this part with more detail in the chapters 6 and 7 where it is mentioned step by step the function of each software until to reach the quantification of crystalline phases, objective of this work. Finally, in the chapter 8 there are a results analysis and conclusions. The contribution of this work is for those learned institutions of limited resources which can tackle in this way the characterization of materials. (Author)

  1. High resolution neutron diffraction using bragg diffraction optics - a novel technique for nondestructive scanning of macro- and/or microstrains in polycrystalline materials

    Czech Academy of Sciences Publication Activity Database

    Mikula, Pavol; Lukáš, Petr; Vrána, Miroslav; Ono, M.; Wagner, V.

    Crete : nakl., 1999. s. 7. [ International Conference on Application of Nuclear Technics "Nuclear Technology for Safety, Security and Industrial Development" /6./. 20.06.1999-26.06.1999, Crete] R&D Projects: GA ČR GV202/97/K038; GA AV ČR KSK1010601 Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  2. Diffraction radiation from relativistic particles

    CERN Document Server

    Potylitsyn, Alexander Petrovich; Strikhanov, Mikhail Nikolaevich; Tishchenko, Alexey Alexandrovich

    2010-01-01

    This book deals with diffraction radiation, which implies the boundary problems of electromagnetic radiation theory. Diffraction radiation is generated when a charged particle moves in a vacuum near a target edge. Diffraction radiation of non-relativistic particles is widely used to design intense emitters in the cm wavelength range. Diffraction radiation from relativistic charged particles is important for noninvasive beam diagnostics and design of free electron lasers based on Smith-Purcell radiation which is diffraction radiation from periodic structures. Different analytical models of diffraction radiation and results of recent experimental studies are presented in this book. The book may also serve as guide to classical electrodynamics applications in beam physics and electrodynamics. It can be of great use for young researchers to develop skills and for experienced scientists to obtain new results.

  3. Diffraction radiation from relativistic particles

    International Nuclear Information System (INIS)

    This book deals with diffraction radiation, which implies the boundary problems of electromagnetic radiation theory. Diffraction radiation is generated when a charged particle moves in a vacuum near a target edge. Diffraction radiation of non-relativistic particles is widely used to design intense emitters in the cm wavelength range. Diffraction radiation from relativistic charged particles is important for noninvasive beam diagnostics and design of free electron lasers based on Smith-Purcell radiation which is diffraction radiation from periodic structures. Different analytical models of diffraction radiation and results of recent experimental studies are presented in this book. The book may also serve as guide to classical electrodynamics applications in beam physics and electrodynamics. It can be of great use for young researchers to develop skills and for experienced scientists to obtain new results. (orig.)

  4. Detecting deformations in uncompacted strata by fiber Bragg grating sensors incorporated into GFRP

    Energy Technology Data Exchange (ETDEWEB)

    Chai, J.; Liu, J.X.; Qiu, B.A.; Li, Y.; Zhu, L.; Wei, S.M.; Wang, Z.P.; Zhang, G.W.; Yang, J.H. [Xian University of Science & Technology, Xian (China). School of Energy Engineering

    2011-01-15

    Coalfields based in east China, such as Huaibei, Datun, Xuzhou, Yanzhou, Yongxia and Huainan, have suffered paroxysmal shaft lining fracture and repeated deformation after repair in the last three decades. This phenomenon has required the development of fractured shaft lining repairing technology and a method for detecting rock strata settlement. It is proposed in this paper that, with the method of fiber Bragg grating sensor incorporated into GFRP, a sensing network of fiber Bragg grating wavelength division multiplexing (WDM)/spatial division multiplexing (SDM) mixing array composed of 18 fiber gratings is formed, and it is used for monitoring the settlement of uncompacted hydrous strata. It is the first time that the fiber Bragg grating sensing system is embedded into the 180-m deep uncompacted strata, and the field experiments are conducted at No. 3 Jingning Coal Mine. The layout of optical sensors, the fiber Bragg grating detecting system, the drilling of the borehole and the embedding method of fiber Bragg grating sensors are introduced. The monitoring results of fiber Bragg grating sensors are compared with groundwater level monitoring results. Engineering practice shows that the fiber Bragg grating sensors are working normally and they can be used to detect strain safely and stably.

  5. Integrated high-order surface diffraction gratings for diode lasers

    Science.gov (United States)

    Zolotarev, V. V.; Leshko, A. Yu; Pikhtin, N. A.; Slipchenko, S. O.; Sokolova, Z. N.; Lubyanskiy, Ya V.; Voronkova, N. V.; Tarasov, I. S.

    2015-12-01

    High-order surface diffraction gratings acting as a distributed Bragg reflector (DBR) in mesa stripe semiconductor lasers (λ = 1030 nm) have been studied theoretically and experimentally. Higher order interfering radiation modes (IRMs), which propagate off the plane of the waveguide, have been shown to have a crucial effect on the reflection and transmission spectra of the DBR. The decrease in the reflectivity of the DBR in response to the increase in the diffraction efficiency of these modes may reach 80% and more. According to theoretical analysis results, the intensity of the higher order IRMs is determined by the geometry of the DBR groove profile. Experimental data demonstrate that the noncavity modes are responsible for parasitic light leakage losses in the laser cavity. It has been shown that, in the case of nonoptimal geometry of the grating groove profile, the overall external differential quantum efficiency of the parasitic laser emission may exceed 45%, which is more than half of the laser output power. The optimal geometry of the DBR groove profile is trapezoidal, with the smallest possible lower base. Experimental evidence has been presented that this geometry considerably reduces the power of the higher order IRMs and minimises the parasitic light leakage loss.

  6. Arbitrary shape surface Fresnel diffraction

    OpenAIRE

    Shimobaba, Tomoyoshi; Masuda, Nobuyuki; Ito, Tomoyoshi

    2012-01-01

    Fresnel diffraction calculation on an arbitrary shape surface is proposed. This method is capable of calculating Fresnel diffraction from a source surface with an arbitrary shape to a planar destination surface. Although such calculation can be readily calculated by the direct integral of a diffraction calculation, the calculation cost is proportional to $O(N^2)$ in one dimensional or $O(N^4)$ in two dimensional cases, where $N$ is the number of sampling points. However, the calculation cost ...

  7. Diffraction at HFIR

    International Nuclear Information System (INIS)

    Of the planned suite of powder and single-crystal diffractometers for the HFIR, only two are currently operating, the Neutron Residual Stress Mapping Facility (NRSF2) diffractometer, and the Wide Angle Neutron Diffractometer (WAND). The NSRF2 was recently upgraded and is available to external users via the High Temperature Materials Laboratory (HTML) User Program for studies of stress, texture and phase mapping. The WAND is a flat-cone geometry diffractometer equipped with a curve 1-D PSD, suitable for high intensity powder diffraction (e.g., kinetics, high pressure) and diffuse scattering studies of single-crystals. A rebuild of the old HFIR powder diffractometer, originally located at HB-4 station is now underway, and is expected to begin commissioning by summer 2008. This instrument has a Debye-Scherrer geometry, with a detector bank consisting of 44 3He tubes each with 6' Soller collimators. A four-circle single-crystal diffractometer is located at the HB-3A station, and is slowly being brought back to life after the long hiatus connected to the reactor upgrade. A Letter of Intent to build a quasi-Laue diffractometer, called IMAGINE, in the HFIR Cold Guide Hall has been presented to and endorsed by the Neutron Scattering Science Advisory Committee.

  8. A fast response temperature sensor based on fiber Bragg grating

    International Nuclear Information System (INIS)

    Aimed at the requirement for a fast-response expendable ocean temperature sensor, this paper presents a new design scheme for an optic fiber sensor. Ocean temperature sensors require high sensitivity and high response speed, which must be up to milliseconds. The fiber Bragg grating (FBG) temperature sensor with high sensitivity has been declared in the last decade, but its response speed has been rarely reported. In this paper, a method is proposed which is to package an FBG with a metal tube. The response time of this sensor is 48.6 ms, which is an order of magnitude greater than that of an ordinary optical fiber temperature sensor. Temperature sensitivity is 27.6 pm/°C and the linearity is up to 0.9999. In addition, the sensor can be less than 15 mm. It offers a new way to detect ocean temperature. (paper)

  9. Humidity insensitive TOPAS polymer fiber Bragg grating sensor

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Khan, Lutul; Webb, David J.;

    2011-01-01

    We report the first experimental demonstration of a humidity insensitive polymer optical fiber Bragg grating (FBG), as well as the first FBG recorded in a TOPAS polymer optical fiber in the important low loss 850nm spectral region. For the demonstration we have fabricated FBGs with resonance...... wavelength around 850 nm and 1550 nm in single-mode microstructured polymer optical fibers made of TOPAS and the conventional poly (methyl methacrylate) (PMMA). Characterization of the FBGs shows that the TOPAS FBG is more than 50 times less sensitive to humidity than the conventional PMMA FBG in both...... wavelength regimes. This makes the TOPAS FBG very appealing for sensing applications as it appears to solve the humidity sensitivity problem suffered by the PMMA FBG....

  10. Prospects for solar axion searches with crystals via Bragg scattering

    International Nuclear Information System (INIS)

    A calculation of the expected signal due to Primakov coherent conversion of solar axions into photons via Bragg scattering in several solid-state detectors is presented and compared with present and future experimental sensitivities. The axion window ma > or approx. 0.03 eV (not accessible at present by other techniques) could be explored in the foreseeable future with crystal detectors to constrain the axion-photon coupling constant gaγγ below the latest bounds coming from helioseismology. On the contrary a positive signal in the sensitivity region of such devices would imply revisiting other more stringent astrophysical limits derived for the same range of the axion mass. The application of this technique to the COSME germanium detector which is taking data at the Canfranc Underground Laboratory leads to a 95% C.L. limit gaγγ ≤ 2.8 x 10-9 GeV-1

  11. Fiber Bragg grating strain sensor for hard rocks

    Science.gov (United States)

    Castro-Caicedo, Alvaro; Nieto-Callejas, María. J.; Torres, Pedro

    2015-09-01

    Strain is an important property to be measured in rock structures such as tunnels, slopes, dams, and mining. However, commercial surface mountable fiber Bragg grating (FBG) strain sensors are packaged in planar configuration, which is not appropriate for the irregular surface of the rocks since an unacceptable bonding layer fails to transfer the strain from the rock to the FBG. As a first approach to this problem, in this work we analyze packaged FBG sensors for cylindrical samples of hard rocks. A calibration process was carried out to evaluate the performance of the packaging and bonding layer as compared to electrical resistance strain gage methods. We show the importance of both packaging and bonding layer in FBG sensor technology for measuring strain in hard rocks.

  12. Wavefront distortion optimized with volume Bragg gratings in photothermorefractive glass.

    Science.gov (United States)

    Gao, Fan; Zhang, Xiang; Sun, Xiaojie; Yuan, Xiao

    2016-03-15

    The wavefront characteristics in 2D angular filtering on the basis of two orthogonal transmitting volume Bragg gratings (VBGs) is presented. The experimental results show that middle-high frequency wavefront distortions are efficiently suppressed with VBGs. The peak-valley value of the beam at a wavelength of 1053 nm reduces from 2.075λ to 0.209λ, and the root mean square value reduces from 0.207λ to 0.041λ. The wavefront power spectrum density shows that the wavefront distribution of the beam in medium and high frequencies is corrected by the VBGs. Additionally, the far-field distribution and focusing properties of the beam are improved. The beam Strehl ratio increases from 0.43 to 0.96, and the encircled energy improves from 95% energy at 4.01 mrad to 95% energy at 1.26 mrad. PMID:26977639

  13. Fiber Bragg grating demodulation through innovative numerical procedures

    Science.gov (United States)

    Dinardo, Giuseppe; Vacca, Gaetano

    2016-01-01

    The aim of this article is to introduce an innovative algorithm for the calculation of the shift of the maximum reflectivity wavelength of a Fiber Bragg Grating experiencing an applied strain. An accurate and precise evaluation of the FBG spectrum displacement is crucial for determining the amount of the physical quantity inducing such perturbations. The proposed method is based on the Fast Fourier Transform based Cross Correlation function. Such method is compared to Least Squares Fitting (LSF) and the centroid algorithms, pointing out remarkable improvements in accuracy, precision, and time consumption performance. In addition, a further improvement of the proposed algorithm is introduced. It consists in an iteratively performed Cross Correlation algorithm. It has been proved that such improvement leads to estimations characterized by better accuracy and precision, thanks also to a considerable reduction of the peak-locking effect due to the FBG spectral resolution.

  14. Dynamic and static strain gauge using superimposed fiber Bragg gratings

    International Nuclear Information System (INIS)

    This paper demonstrates a simple and fast interrogation method for the dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to decrease nonequidistant space of generated a sensing pulse train in a time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A four times increase in the interrogation speed of dynamic strain, by generating a 2 kHz optical sensing pulse train from a 500 Hz scanning frequency, is demonstrated experimentally. The interrogation uncertainty and total harmonic distortion characterization of superimposed FBGs are tested and less than 4 pm standard deviation is obtained. (paper)

  15. Fiber Bragg grating (FBG) sensors used in coal mines

    Science.gov (United States)

    Wang, Jinyu; Liu, Tongyu; Song, Guangdong; Xie, Hongjing; Li, Lianqing; Deng, Xiaolin; Gong, Zhijie

    2014-06-01

    The fiber Bragg grating (FBG) strain sensors were used for on-line monitoring of the stress variation of the lined wall in the gateway retained along the goaf of No. 3203 coal mining face in Dongtan Mine. The results showed that the FBG strain sensor with the wide measuring range could measure the stress variation accurately during the support process of the gateway retained along the goaf and could provide the basis to further optimize the support structure and to determine the support plan of the gateway retained along the goaf. The FBG micro-seismic sensors were used in Xinglong Mine to detect the micro-seismic signal. The signals were well received and analyzed to determine the location and energy level of the source of the micro-seismic event warning. The FBG sensors and detecting system show a significant potential for micro-seismic detection and geological disasters detection.

  16. Contact microphone using optical fibre Bragg grating technology

    International Nuclear Information System (INIS)

    A contact microphone using optical fibre Bragg grating has been developed. It enables one to listen and record a human voice and/or breathing by monitoring the vibration generated by the outer wall of the throat during speech. This system can have many applications such as detecting defects in vocal folds, measuring and monitoring the vibration and defection generated by intubations of a patient throat and other voice related problem, low level speaking recording and transmitting is also possible, the microphone can be also used to monitor breathing and the system can be used as a microphone in very harsh environments for example it would allow one to hear the patient during a cat scan

  17. Contact microphone using optical fibre Bragg grating technology

    Energy Technology Data Exchange (ETDEWEB)

    Bezombes, F A; Lalor, M J; Burton, D R [General Engineering Research Institute (GERI), Liverpool John Moores University, James Parsons Building, Byrom Street, Liverpool (United Kingdom)

    2007-07-15

    A contact microphone using optical fibre Bragg grating has been developed. It enables one to listen and record a human voice and/or breathing by monitoring the vibration generated by the outer wall of the throat during speech. This system can have many applications such as detecting defects in vocal folds, measuring and monitoring the vibration and defection generated by intubations of a patient throat and other voice related problem, low level speaking recording and transmitting is also possible, the microphone can be also used to monitor breathing and the system can be used as a microphone in very harsh environments for example it would allow one to hear the patient during a cat scan.

  18. Research of embedded fiber Bragg grating temperature sensor system

    Science.gov (United States)

    Hu, Ji; Wan, Shengpeng; Xie, Changlin; Zhang, Zhimin; Luo, Ningning; He, Shuai

    2010-10-01

    In this article, an embedded fiber Bragg grating temperature sensor system is proposed and researched. The demodulating system controls a Piezoelectric Ceramic (PZT) with sawteeth wave to scan the matching grating, then do photoelectric conversion using a detector, and use Digital Signal Processor (DSP) to find the max intensity. Meanwhile, use PZT drive voltage to control the central wavelength of sensor grating to demodulate. Then use the USB interface chip to realize the communication between DSP and the host computer, and send the collected data to the host computer. Finally, the real time temperature can be inquired and stored through the inquiring interface programmed by computer. The result demonstrates that this experimental system has the wave addressing range from 1540 to 1565 nm and the temperature resolution of 0.1°C.

  19. Focusing properties of ellipsoidal Bragg-Fresnel multilayer lenses

    International Nuclear Information System (INIS)

    Principles of calculation of the Bragg-Fresnel multilayer lenses (BFL) structure topology and the first results of test of ellipsoidal BFL using the Sibir'-1 synchrotron radiation source are presented. The picture of cross section of the rotation ellipsoids of the equal phase surfaces by the multilayer structure under the angle to the optical axis was used as the initial model of calculation of the BFL structure. As a result of this experiment, the pictures, reduced by a factor of 350, in the region of X-ray generation with 4.5 nm wavelength are obtained; focusing properties of ellipsoidal BFL with a circular form of a focal pit are demonstrated for the first time

  20. Fibre Bragg grating based accelerometer with extended bandwidth

    Science.gov (United States)

    Basumallick, Nandini; Biswas, Palas; Chakraborty, Rajib; Chakraborty, Sushanta; Dasgupta, Kamal; Bandyopadhyay, Somnath

    2016-03-01

    We have shown experimentally that the operable bandwidth of a fibre Bragg grating (FBG) based accelerometer can be extended significantly, without compromising its sensitivity, using a post-signal processing technique which involves frequency domain weighting. It has been demonstrated that using the above technique acceleration can be correctly interpreted even when the operating frequency encroaches on the region where the frequency response of the sensor is non-uniform. Two different excitation signals, which we often encounter in structural health monitoring applications, e.g. (i) a signal composed of multi-frequency components and (ii) a sinusoidal excitation with a frequency sweep, have been considered in our experiment. The results obtained have been compared with a piezo accelerometer.

  1. Remote (250 km Fiber Bragg Grating Multiplexing System

    Directory of Open Access Journals (Sweden)

    Manuel Lopez-Amo

    2011-09-01

    Full Text Available We propose and demonstrate two ultra-long range fiber Bragg grating (FBG sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6–8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system.

  2. Notes on Evanescent Wave Bragg-Reflection Waveguides

    CERN Document Server

    Pressl, Benedikt

    2013-01-01

    We investigate an extended version of the Bragg reflection waveguide (BRW) with air gaps as one of the layers. This design has the potential of drastically simplifying the epitaxial structure for integrated nonlinear optical elements at the expense of more complicated structuring. This approach would afford much more flexibility for designing and varying BRW structures. Here, we discuss an extension of the established theory for BRW slabs and report our results of applying Marcatili's method for rectangular waveguides to the BRW case. With this analytic approach we can estimate the effective index of the modes orders of magnitudes faster than with full numerical techniques such as finite-difference time-domain (FDTD) or finite elements. Initial results are mixed; while phase-matched designs have been found, they currently have no significant advantage over other schemes.

  3. Pure Bending Characteristic of Tilted Fiber Bragg Grating

    Institute of Scientific and Technical Information of China (English)

    Bo Liu; Yin-Ping Miao; Hai-Bin Zhou; Qi-Da Zhao

    2008-01-01

    a novel structure of the pure macro-bending sensor based on the tilted fiber Bragg grating (TFBG) is proposed. The TFBG located in the half circle with the different diameters is bent at a constant angle with respect to the tilted grating planes. With the variations of the curvature, the core-mode resonance is unchanged and the transmission power of cladding modes detected by the photodiodes varies linearly with curvature, while the ghost mode changes by the form of two-order polynomial. So we can use the transmission power of ghost mode or other cladding modes to detect bending curvature as shape sensor. From a practical point of view, the sensor proposed here is simple, low cost and easy to implement. Moreover, it is possible to make a temperature-insensitive shape sensor due to the same temperature characteristic between the core mode and the cladding modes.

  4. Modulational instability in a fibre and a fibre Bragg grating

    International Nuclear Information System (INIS)

    In this review article, we study the influence of cross-phase modulation, higher order nonlinear effects such as self-steepening, self-induced Raman scattering and higher order dispersion effects such as third and fourth order dispersion on cross-phase modulational instability for a highly elliptical birefringent optical fibre, and obtain the conditions for the occurrence of cross-phase modulational instability in the normal dispersion regime. In addition, we also consider the pulse propagation through a fibre Bragg grating structure where we investigate the occurrence of modulational instability at the two edges of the photonic bandgap as well as on the upper and lower branches of the dispersion curves. (review article)

  5. Femtosecond soliton diode on heterojunction Bragg-grating structure

    CERN Document Server

    Deng, Zhigui; Li, Hongji; Fu, Shenhe; Liu, Yikun; Xiang, Ying; Li, Yongyao

    2016-01-01

    We numerically propose a scheme for realizing an all-optical femtosecond soliton diode based on a tailored heterojunction Bragg grating, which is designed by two spatially asymmetric chirped cholesteric liquid crystals. Our simulations demonstrate that with the consideration of optical nonlinearity, not only the femtosecond diode effect with nonreciprocal transmission ratio up to 120 can be achieved, but also the optical pulse evolving into soliton which maintains its shape during propagation through the sample is observed. Further, the influence of pulse width and the carrier wavelength to the femtosecond diode effect is also discussed in detail. Our demonstrations might suggest a new direction for experimentally realizing the femtosecond soliton diode based on the cholesteric liquid crystals.

  6. Direct UV-written planar Bragg grating sensors

    International Nuclear Information System (INIS)

    Integrated photonics is a proven platform for physical and chemical sensing. It offers miniaturised solutions that are suited for use in extreme environments, including strong EM-fields, EM-pulses and contact with flammable materials, often far exceeding electronic sensors in this regard. This review looks into direct UV-written planar Bragg grating technology and its application to integrated photonic sensors. The platform has been demonstrated widely for measurement of physical properties such as temperature, pressure and strain. In addition, by using an evanescent interaction, refractive index can be measured allowing for chemical and biochemical detection. Further to this, the platform has recently been utilised in quantum information processing, where quantum gate operations and single photon detection has been shown. (topical review)

  7. Vibration measurement of electrical machines using integrated fibre Bragg gratings

    Science.gov (United States)

    Fabian, M.; Borg Bartolo, J.; Ams, M.; Gerada, C.; Sun, T.; Grattan, K. T. V.

    2015-09-01

    In this paper a method to track the rotating force vector set up within the air-gap of radial flux rotating electrical machines using fibre Bragg gratings is reported. The proposed technique offers the potential for simultaneous rotor speed and position monitoring. This specific sensor design, together with other FBG-based multi-parameter measurements, is aimed to create an all-optical sensor solution for electrical machines, reducing the component count of existing systems and addressing noise issues traditionally associated with electrical sensors used. In this work, an optical fibre sensor system has been successfully integrated into an off-the-shelf four-pole 11kW induction motor.

  8. Fabrication of Dual-Wavelength Fiber Bragg Grating with a Longitudinal Stretch

    Institute of Scientific and Technical Information of China (English)

    JIANG Li; ZHANG Dong-sheng; ZHANG Wei-gang; KAI Gui-yun; DONG Xiao-yi

    2006-01-01

    A method of fabricating dual-wavelength fiber Bragg grating with a uniform phase mask is demonstrated.Theoretical analysis and numerical simulation using Matrix method arc given.The moving exposing technique is adopted.Good control over the grating's reflectivity and the separation of the two Bragg wavelengths is enabled by adjusting the stretch,the length of the grating,and the exposure.A grating with two equal transmission peaks of 19.5 dB is obtained by using this method,and the separation of the two Bragg wavelengths is 0.78 nm.

  9. Bragg-case section topography of growth defects in Si : Ge crystals

    International Nuclear Information System (INIS)

    The samples cut out from Si : Ge crystals with 3% and 1.2% of germanium were studied by means of synchrotron white beam Bragg-case section and projection topography as well as conventional transmission Lang topography. The obtained topographs revealed dominant contrast coming from the segregation of germanium. The use of Bragg-case section topography made possible to follow the shape of growth surfaces inside the crystal. The formation of contrast in Bragg-case section topographs for different orientation of growth surfaces with respect to the incident beam is discussed. The applied methods enabled also revealing growth surface instabilities occurring in some regions of Si : Ge crystals

  10. Planar waveguide tilted Bragg grating refractometer fabricated through physical micromachining and direct UV writing.

    Science.gov (United States)

    Holmes, Christopher; Carpenter, Lewis G; Rogers, Helen L; Sparrow, Ian J G; Gates, James C; Smith, Peter G R

    2011-06-20

    A set of rapid prototyping techniques are combined to construct a laterally-tilted Bragg grating refractometer in a novel planar geometry. The tilted Bragg grating is fabricated in a silica-on-silicon planar substrate using a dual beam direct UV writing (DUW) technique. Lateral cladding mode confinement is subsequently achieved by physically micromachining two trenches either side of the direct UV written waveguide. The resulting device is demonstrated as an effective refractometer, displaying a comparable sensitivity to tilted Bragg gratings in a fiber optical geometry, but with the added advantages of planar integration. PMID:21716485

  11. New imaging using pulsed neutron sources imaging of crystalline structural information by Bragg edge transmission spectroscopy

    International Nuclear Information System (INIS)

    Neutron imaging at a pulsed neutron source can simultaneously give position-dependent neutron transmission spectra of a material. 'Bragg edge' transmission pattern appears at low energy region of the spectrum. Since the Bragg edge transmission spectrum includes various crystalline structural information, e.g., crystal structure, crystalline phase, crystallographic texture, crystallite size and strain, the pulsed neutron imaging using a two-dimensional area detector can non-destructively visualize such the information over the wide area of a material. In this article, principles, features and experimental examples of the Bragg edge transmission imaging that is expected as a new analysis tool for materials science are presented. (author)

  12. Miniature fiber Bragg grating sensor interrogator (FBG-Transceiver) system

    Science.gov (United States)

    Mendoza, Edgar A.; Kempen, Cornelia; Lopatin, Craig

    2007-04-01

    This paper describes recent progress conducted towards the development of a miniature fiber Bragg grating sensor interrogator (FBG-Transceiver TM) system based on multi-channel integrated optic sensor (InOSense TM) microchip technology. The hybrid InOSense TM microchip technology enables the integration of all of the functionalities, both passive and active, of conventional bench top FBG sensor interrogator systems, packaged in a miniaturized, low power operation, 2-cm x 5-cm package suitable for the long-term structural health monitoring in applications where size, weight, and power are critical for operation. The FBG-Transceiver system uses active optoelectronic components monolithically integrated to the InOSense TM microchip, a microprocessor controlled signal processing electronics board capable of processing the FBG sensors signals related to stress-strain and temperature as well as vibration and acoustics. The FBG-Transceiver TM system represents a new, reliable, highly robust technology that can be used to accurately monitor the status of an array of distributed fiber optic Bragg grating sensors installed in critical infrastructures. Its miniature package, low power operation, and state-of-the-art data communications architecture, all at a very affordable price makes it a very attractive solution for a large number of SHM/NDI applications in aerospace, naval and maritime industry, civil structures like bridges, buildings and dams, the oil and chemical industry, and for homeland security applications. The miniature, cost-efficient FBG-Transceiver TM system is poised to revolutionize the field of structural health monitoring and nondestructive inspection market. The sponsor of this program is NAVAIR under a DOD SBIR contract.

  13. High-sensitivity temperature sensor based on Bragg grating in BDK-doped photosensitive polymer optical fiber

    Institute of Scientific and Technical Information of China (English)

    Xusheng Cheng; Weiwei Qiu; Wenxuan Wu; Yanhua Luo; Xiujie Tian; Qijin Zhang; Bing Zhu

    2011-01-01

    @@ A single-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) is fabricated and used for writing Bragg grating through the two-beam interference method. The Bragg wavelength of the grating is about 1570 nm, while the full-width at half-maximum (FWHM) of the reflection peak is 0.3 nm. The temperature response of POF Bragg grating is theoretically analyzed and experimentally measured in contrast to silica optical fiber Bragg grating (FBG). The result shows that the temperature character of POF Bragg grating is negative, which is opposite to the silica optical FBG. The absolute value of the temperature response of POF Bragg grating is one order of magnitude higher than that of the silica optical FBG, making POF Bragg grating appear to be very attractive for constructing temperature sensors with high resolution.%A single-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) is fabricated and used for writing Bragg grating through the two-beam interference method. The Bragg wavelength of the grating is about 1570 nm, while the full-width at half-maximum (FWHM) of the reflection peak is 0.3 nm. The temperature response of POF Bragg grating is theoretically analyzed and experimentally measured in contrast to silica optical fiber Bragg grating (FBG). The result shows that the temperature character of POF Bragg grating is negative, which is opposite to the silica optical FBG. The absolute value of the temperature response of POF Bragg grating is one order of magnitude higher than that of the silica optical FBG, making POF Bragg grating appear to be very attractive for constructing temperature sensors with high resolution.

  14. Diffractive optics and nanophotonics resolution below the diffraction limit

    CERN Document Server

    Minin, Igor

    2016-01-01

    In this book the authors present several examples of techniques used to overcome the Abby diffraction limit using flat and 3D diffractive optical elements, photonic crystal lenses, photonic jets, and surface plasmon diffractive optics. The structures discussed can be used in the microwave and THz range and also as scaled models for optical frequencies. Such nano-optical microlenses can be integrated, for example, into existing semiconductor heterostructure platforms for next-generation optoelectronic applications. Chapter 1 considers flat diffractive lenses and innovative 3D radiating structures including a conical millimeter-wave Fresnel zone plate (FZP) lens proposed for subwavelength focusing. In chapter 2 the subwavelength focusing properties of diffractive photonic crystal lenses are considered and it is shown that at least three different types of photonic crystal lens are possible.  With the aim of achieving subwavelength focusing, in chapter 3 an alternative mechanism to produce photonic jets at Tera...

  15. Computer Simulation of Diffraction Patterns.

    Science.gov (United States)

    Dodd, N. A.

    1983-01-01

    Describes an Apple computer program (listing available from author) which simulates Fraunhofer and Fresnel diffraction using vector addition techniques (vector chaining) and allows user to experiment with different shaped multiple apertures. Graphics output include vector resultants, phase difference, diffraction patterns, and the Cornu spiral…

  16. Measurements of transient electron density distributions by femtosecond X-ray diffraction; Messungen transienter Elektronendichteverteilungen durch Femtosekunden-Roentgenbeugung

    Energy Technology Data Exchange (ETDEWEB)

    Freyer, Benjamin

    2013-05-02

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  17. Surface plasmon-coupled emission on plasmonic Bragg gratings

    Czech Academy of Sciences Publication Activity Database

    Toma, M.; Toma, K.; Adam, Pavel; Homola, Jiří; Knoll, W.; Dostálek, J.

    2012-01-01

    Roč. 20, - (2012), s. 14042-14053. ISSN 1094-4087 Institutional support: RVO:67985882 Keywords : Surface plasmons * Fluorescence * Diffraction gratings Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 3.546, year: 2012

  18. Diffraction in Deep Inelastic Scattering

    CERN Document Server

    Hebecker, A

    2000-01-01

    Different theoretical methods used for the description of diffractive processes in small-x deep inelastic scattering are reviewed. The semiclassical approach, where a partonic fluctuation of the incoming virtual photon scatters off a superposition of target colour fields, is used to explain the basic physical effects. In this approach, diffraction occurs if the emerging partonic state is in a colour singlet, thus fragmenting independently of the target. Other approaches, such as the idea of the pomeron structure function and two gluon exchange calculations, are also discussed in some detail. Particular attention is paid to the close relation between the semiclassical approach and the method of diffractive parton distributions, which is linked to the relation between the target rest frame and the Breit frame point of view. While the main focus is on diffractive structure functions, basic issues in the diffractive production of mesons and of other less inclusive final states are also discussed. Models of the pr...

  19. New optical scheme for differential measurements of diffraction reflection intensity on X-radiation sliding incidence

    International Nuclear Information System (INIS)

    An X-ray optical scheme for differential measurements of X-ray diffraction under sliding incidence conditions is proposed and an attachment design realizng this scheme, using standard equipment, is described. The main feature of the scheme is the following: collimation according to the Bragg angle is carried out for the reflected beam rather than the incident one. Goniometers can be used from DRON, TRS, GS-5 and other spectrometers. The goniometer head carrying the sample is standard, it is a part of the DRON, TRS and DTS. The crystal analyzer is fixed on the attachment. The angular position of the crystal monochromator is controlled by an inductive sensor. The experimental differential curves of X-ray diffraction under conditions of sliding incidence, taken for a silicon crystal having the 111 orientation, are given as well

  20. Structural study on sodium choride by X-ray powder diffraction method

    International Nuclear Information System (INIS)

    The procedure for the crystal structure analysis by means of the X-ray powder diffraction method has been shown using the sodium chloride as a sample. The twelve X-ray diffraction intensity peaks for sodium chloride powder were collected rotating 2 THETA sub(hkl). Bragg angle of X-ray diffractometer from 20 to 160 degrees, in which Cu Ksub(α) radition filtered by nickel had been used. For assigning indices of each reflecting plane, the relationship between lattice parameter and interplanar spacing has been used. This result has shown that sodium chloride is face-centered cubic, space group F 4/m 3-2/m with until cell dimension a = 5.36 A and z = 4. The experimental and theoretical integrated intensities of the reflecting planes are in good agreement with each other. (author)

  1. Instrumentation components developed at NPI Rez, ILL and KURRI as used in focusing diffraction

    International Nuclear Information System (INIS)

    Complete text of publication follows. The use of neutron Bragg diffraction optics (NBDO) based on curved perfect crystals has proved to be a powerful way to increase luminosity and angular/energy resolution of some dedicated diffractometers or spectrometers installed at the steady state sources [1-3]. Although in the last several years many laboratories have used focusing instrumentation components permitting exploitation of NBDO in combination with PSD, there is a lack of publications describing them. This can be on e of the reasons why they are not used more extensively. Some results are presented of instrumentation developments, namely different types of horizontally and vertically focusing benders developed in the frame of collaboration. Furthermore, a unique tension/compression rig was introduced for in-situ strain investigations on 'samples of small dimensions' which is just the case where the Bragg diffraction optics appears enormously powerful. (author) [1] J. Kulda and J. Saroun, Nucl. Instrum. Methods in Phys. Research, A379 (1996) 155.; [2] P. Mikula et.al. Report PTB-N-26, PTB Braunschweig 1997, p. 1-53.; [3] M. Ono et.al, Proc, of EPDIC-6. August 22-25, 1998 Budapest, Hungary; Physica B, in print

  2. Study on Dual Bragg Wavelength Fiber Grating and Its Tuning Scheme

    Institute of Scientific and Technical Information of China (English)

    Dong Xingfa; Fu Shenggui; Zhang Hao; Kai Guiyun; Dong Xiaoyi

    2003-01-01

    Because of package, a single FBG has dual Bragg wavelength. One is sensitive to stress and the other is sensitive to temperature. By using the special mechanism, the wavelengths can be tuned by stress and temperature respectively.

  3. High Power Compact Single-Frequency Volume Bragg Er-Doped Fiber Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is based on successful results of Phase I project where it was shown that the use of volume Bragg gratings in PTR glass as selectors of transverse and...

  4. Impact of Saturable Gain/Loss on Bistability of Nonlinear Parity-Time Bragg Gratings

    CERN Document Server

    Phang, Sendy; Susanto, Hadi; Benson, Trevor M; Sewell, Phillip

    2014-01-01

    We report on the impact of realistic gain and loss models on the bistable operation of nonlinear parity-time Bragg gratings. In our model we include both dispersive and saturable gain and show that levels of gain/loss saturation can have significant impact on the bistable operation of a nonlinear PT Bragg grating based on GaAs material. The hysteresis of the nonlinear PT Bragg grating is analyzed for different levels of gain and loss and different saturation levels. We show that high saturation levels can improve the nonlinear operation by reducing the intensity at which the bistability occurs. However when the saturation intensity is low, saturation inhibits PT phenomena in a nonlinear PT Bragg grating.

  5. Fiber sensing system based on a bragg grating and optical time domain reflectometry

    OpenAIRE

    Chin, Sanghoon; Thévenaz, Luc

    2013-01-01

    Optic fiber sensor characterized in that the sensing fiber is provided with a continuous Bragg grating covering the entire fiber length which is dedicated to sensing and along which spatially resolved measurements are performed.

  6. Development of a Fibre Bragg Grating Sensor for Rock Deformation Monitoring

    Science.gov (United States)

    Kanopoulos, Patrick Paskalis

    This thesis examines the theoretical and experimental performance of a fibre Bragg grating sensor for static and dynamic strain measurement in hard rock. A literature review focuses on the fundamental theory of fibre Bragg gratings, various physical demodulation schemes used to interrogate Bragg sensors with an emphasis on charge coupled device spectrometry, as well as the aliasing behaviour of Bragg gratings as sensors. A coupled numerical-analytical analysis is conducted on various sensor configurations designed for borehole deployment in order to establish the response of the strain sensors under various strain conditions. The findings of an experimental investigation of two sensors subjected to uniaxial strain within a grout and a rock specimen are presented. The experimental data confirm the feasibility of using the proposed sensor as a part of an integrated optical strain sensing network.

  7. Analysis of Sampled Fiber Bragg Grating Based on the Photonic Crystal Theory

    Institute of Scientific and Technical Information of China (English)

    ZHU Dan-dan

    2009-01-01

    One of the most basic characteristics of photonic crystal is frequency band gap.When defects are introduced into the periodic photonic crystal,a number of defect modes appear in the stop band.In this paper,we exploit transfer matrix method based on photonic crystal theory,and assume the sampled fiber Bragg grating as one-dimensional dual photonic crystal with a large size defect.Characteristics of the sampled fiber Bragg grating are analyzed.Experimental results show that the sampled fiber Bragg grating has many reflective peaks.Its reflectivity,center wavelength,reflective peak intervals and band width all change with the grating parameters,including grating length,duty ratio of the material with high dielectric constant,and index modulation depth and period.Results agree with the conventional couple mode theory which can be used when analyzing other characteristics of the sampled fiber Bragg grating or applying it into practice.

  8. Extending Bragg peak of heavy ion beam and melanoma cell inactivation measurement

    Institute of Scientific and Technical Information of China (English)

    LiQiang; WeiZeng-Quan; 等

    1998-01-01

    A rotating range modulator was designed and manufactured.which is applied to extend Bragg peak of heavy ion beam.Bragg curves of 75MeV/u 16O and 75MeV/u 12C ion beams through this range modulator were measured respectively and two evident spread-out Bragg peaks corresponding to the modulated beams above are shown.In addition,inactivation effect of the modulated 75MeV/u 16O ion beam at nine different penetration depths on melanoma cells(B16) was measured.Results indicate that lethal effects at the spread-out Bragg peak region are larger than at the plateau of the particle beam entrance.

  9. Fiber Bragg Grating (FBG) sensors as flatness and mechanical stretching sensors

    CERN Document Server

    Abbaneo, D; Abbrescia, M.; Abdelalim, A.A.; Abi Akl, M.; Aboamer, O.; Acosta, D.; Ahmad, A.; Ahmed, W.; Ahmed, W.; Aleksandrov, A.; Aly, R.; Altieri, P.; Asawatangtrakuldee, C.; Aspell, P.; Assran, Y.; Awan, I.; Bally, S.; Ban, Y.; Banerjee, S.; Barashko, V.; Barria, P.; Bencze, G.; Beni, N.; Benussi, L.; Bhopatkar, V.; Bianco, S.; Bos, J.; Bouhali, O.; Braghieri, A.; Braibant, S.; Buontempo, S.; Calabria, C.; Caponero, M.; Caputo, C.; Cassese, F.; Castaneda, A.; Cauwenbergh, S.; Cavallo, F.R.; Celik, A.; Choi, M.; Choi, S.; Christiansen, J.; Cimmino, A.; Colafranceschi, S.; Colaleo, A.; Conde Garcia, A.; Czellar, S.; Dabrowski, M.M.; De Lentdecker, G.; De Oliveira, R.; De Robertis, G.; Dildick, S.; Dorney, B.; Elmetenawee, W.; Endroczi, G.; Errico, F.; Fenyvesi, A.; Ferry, S.; Furic, I.; Giacomelli, P.; Gilmore, J.; Golovtsov, V.; Guiducci, L.; Guilloux, F.; Gutierrez, A.; Hadjiiska, R.M.; Hassan, A.; Hauser, J.; Hoepfner, K.; Hohlmann, M.; Hoorani, H.; Iaydjiev, P.; Jeng, Y.G.; Kamon, T.; Karchin, P.; Korytov, A.; Krutelyov, S.; Kumar, A.; Kim, H.; Lee, J.; Lenzi, T.; Litov, L.; Loddo, F.; Madorsky, A.; Maerschalk, T.; Maggi, M.; Magnani, A.; Mal, P.K.; Mandal, K.; Marchioro, A.; Marinov, A.; Masod, R.; Majumdar, N.; Merlin, J.A.; Mitselmakher, G.; Mohanty, A.K.; Mohamed, S.; Mohapatra, A.; Molnar, J.; Muhammad, S.; Mukhopadhyay, S.; Naimuddin, M.; Nuzzo, S.; Oliveri, E.; Pant, L.M.; Paolucci, P.; Park, I.; Passeggio, G.; Passamonti, L.; Pavlov, B.; Philipps, B.; Piccolo, D.; Pierluigi, D.; Postema, H.; Puig Baranac, A.; Radi, A.; Radogna, R.; Raffone, G.; Ranieri, A.; Rashevski, G.; Riccardi, C.; Rodozov, M.; Rodrigues, A.; Ropelewski, L.; RoyChowdhury, S.; Russo, A.; Ryu, G.; Ryu, M.S.; Safonov, A.; Salva, S.; Saviano, G.; Sharma, A.; Sharma, A.; Sharma, R.; Shah, A.H.; Shopova, M.; Sturdy, J.; Sultanov, G.; Swain, S.K.; Szillasi, Z.; Talvitie, J.; Tatarinov, A.; Tuuva, T.; Tytgat, M.; Vai, I.; Van Stenis, M.; Venditti, R.; Verhagen, E.; Verwilligen, P.; Vitulo, P.; Volkov, S.; Vorobyev, A.; Wang, D.; Wang, M.; Yang, U.; Yang, Y.; Yonamine, R.; Zaganidis, N.; Zenoni, F.; Zhang, A.

    2016-01-01

    A novel approach which uses Fibre Bragg Grating (FBG) sensors has been utilised to assess and monitor the flatness of Gaseous Electron Multipliers (GEM) foils. The setup layout and preliminary results are presented.

  10. Trends and future of fiber Bragg grating sensing technologies: tailored draw tower gratings (DTGs)

    Science.gov (United States)

    Lindner, E.; Hartung, A.; Hoh, D.; Chojetzki, C.; Schuster, K.; Bierlich, J.; Rothhardt, M.

    2014-05-01

    Today fiber Bragg gratings are commonly used in sensing technology as well as in telecommunications. Numerous requirements must be satisfied for their application as a sensor such as the number of sensors per system, the measurement resolution and repeatability, the sensor reusability as well as the sensor costs. In addition current challenges need to be met in the near future for sensing fibers to keep and extend their marketability such as the suitability for sterilization, hydrogen darkening or the separation of strain and temperature (or pressure and temperature). In this contribution we will give an outlook about trends and future of the fiber Bragg gratings in sensing technologies. Specifically, we will discuss how the use of draw tower grating technology enables the production of tailored Bragg grating sensing fibers, and we will present a method of separating strain and temperature by the use of a single Bragg grating only, avoiding the need for additional sensors to realize the commonly applied temperature compensation.

  11. High-speed two-dimensional laser scanner based on Bragg gratings stored in photothermorefractive glass.

    Science.gov (United States)

    Yaqoob, Zahid; Arain, Muzammil A; Riza, Nabeel A

    2003-09-10

    A high-speed free-space wavelength-multiplexed optical scanner with high-speed wavelength selection coupled with narrowband volume Bragg gratings stored in photothermorefractive (PTR) glass is reported. The proposed scanner with no moving parts has a modular design with a wide angular scan range, accurate beam pointing, low scanner insertion loss, and two-dimensional beam scan capabilities. We present a complete analysis and design procedure for storing multiple tilted Bragg-grating structures in a single PTR glass volume (for normal incidence) in an optimal fashion. Because the scanner design is modular, many PTR glass volumes (each having multiple tilted Bragg-grating structures) can be stacked together, providing an efficient throughput with operations in both the visible and the infrared (IR) regions. A proof-of-concept experimental study is conducted with four Bragg gratings in independent PTR glass plates, and both visible and IR region scanner operations are demonstrated. PMID:14503693

  12. Fiber Bragg Grating (FBG) sensors as flatness and mechanical stretching sensors

    Science.gov (United States)

    Abbaneo, D.; Abbas, M.; Abbrescia, M.; Abdelalim, A. A.; Abi Akl, M.; Aboamer, O.; Acosta, D.; Ahmad, A.; Ahmed, W.; Ahmed, W.; Aleksandrov, A.; Aly, R.; Altieri, P.; Asawatangtrakuldee, C.; Aspell, P.; Assran, Y.; Awan, I.; Bally, S.; Ban, Y.; Banerjee, S.; Barashko, V.; Barria, P.; Bencze, G.; Beni, N.; Benussi, L.; Bhopatkar, V.; Bianco, S.; Bos, J.; Bouhali, O.; Braghieri, A.; Braibant, S.; Buontempo, S.; Calabria, C.; Caponero, M.; Caputo, C.; Cassese, F.; Castaneda, A.; Cauwenbergh, S.; Cavallo, F. R.; Celik, A.; Choi, M.; Choi, S.; Christiansen, J.; Cimmino, A.; Colafranceschi, S.; Colaleo, A.; Conde Garcia, A.; Czellar, S.; Dabrowski, M. M.; De Lentdecker, G.; De Oliveira, R.; De Robertis, G.; Dildick, S.; Dorney, B.; Elmetenawee, W.; Endroczi, G.; Errico, F.; Fenyvesi, A.; Ferry, S.; Furic, I.; Giacomelli, P.; Gilmore, J.; Golovtsov, V.; Guiducci, L.; Guilloux, F.; Gutierrez, A.; Hadjiiska, R. M.; Hassan, A.; Hauser, J.; Hoepfner, K.; Hohlmann, M.; Hoorani, H.; Iaydjiev, P.; Jeng, Y. G.; Kamon, T.; Karchin, P.; Korytov, A.; Krutelyov, S.; Kumar, A.; Kim, H.; Lee, J.; Lenzi, T.; Litov, L.; Loddo, F.; Madorsky, A.; Maerschalk, T.; Maggi, M.; Magnani, A.; Mal, P. K.; Mandal, K.; Marchioro, A.; Marinov, A.; Masod, R.; Majumdar, N.; Merlin, J. A.; Mitselmakher, G.; Mohanty, A. K.; Mohamed, S.; Mohapatra, A.; Molnar, J.; Muhammad, S.; Mukhopadhyay, S.; Naimuddin, M.; Nuzzo, S.; Oliveri, E.; Pant, L. M.; Paolucci, P.; Park, I.; Passeggio, G.; Passamonti, L.; Pavlov, B.; Philipps, B.; Piccolo, D.; Pierluigi, D.; Postema, H.; Puig Baranac, A.; Radi, A.; Radogna, R.; Raffone, G.; Ranieri, A.; Rashevski, G.; Riccardi, C.; Rodozov, M.; Rodrigues, A.; Ropelewski, L.; RoyChowdhury, S.; Russo, A.; Ryu, G.; Ryu, M. S.; Safonov, A.; Salva, S.; Saviano, G.; Sharma, A.; Sharma, A.; Sharma, R.; Shah, A. H.; Shopova, M.; Sturdy, J.; Sultanov, G.; Swain, S. K.; Szillasi, Z.; Talvitie, J.; Tatarinov, A.; Tuuva, T.; Tytgat, M.; Vai, I.; Van Stenis, M.; Venditti, R.; Verhagen, E.; Verwilligen, P.; Vitulo, P.; Volkov, S.; Vorobyev, A.; Wang, D.; Wang, M.; Yang, U.; Yang, Y.; Yonamine, R.; Zaganidis, N.; Zenoni, F.; Zhang, A.

    2016-07-01

    A novel approach which uses Fiber Bragg Grating (FBG) sensors has been utilized to assess and monitor the flatness of Gaseous Electron Multipliers (GEM) foils. The setup layout and preliminary results are presented.

  13. Anomalous longitudinal mode hops in GaAs/AlGaAs distributed Bragg reflector lasers

    OpenAIRE

    Hofstetter, Daniel; Zappe, H. P.

    2008-01-01

    We investigate normal and anomalous longitudinal mode hops in GaAs/AlGaAs-based distributed Bragg reflector (DBR) lasers; anomalous mode hops are defined as those which move toward shorter wavelengths with increasing temperature, which is unexpected. The two-section DBR lasers discussed in this letter, consisting of a gain section and an unpumped Bragg reflector, typically exhibit one mode hop in a 10 K temperature range. Although the longer wavelength modes are expected to start lasing when ...

  14. Fiber-optical accelerometers based on polymer optical fiber Bragg gratings

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Stefani, Alessio; Bang, Ole;

    2010-01-01

    Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer.......Fiber-optical accelerometers based on polymer optical fiber Bragg gratings (FBGs) are reported. We have written 3mm FBGs for 1550nm operation, characterized their temperature and strain response, and tested their performance in a prototype accelerometer....

  15. An experimental approach to quantify strain transfer efficiency of fibre bragg grating sensors to host structures

    OpenAIRE

    C. Y. Wei; Ye, Chen-Chun; James, Stephen W.; Tatam, Ralph P.; Irving, Phil E.

    2001-01-01

    This paper developed a method to evaluate the strain transfer efficiency of fibre Bragg grating sensors to host structures. Various coatings were applied to fibre Bragg grating sensors after being fabricated. They were epoxy, silane agent and polypropylene, representing different surface properties. A neat epoxy resin plate was used as the host in which the coated fibre sensors were embedded in the central layer. The tensile strain output from the FBGs was compared with that...

  16. Uniform Fiber Bragg Grating modeling and simulation used matrix transfer method

    Directory of Open Access Journals (Sweden)

    Abdallah Ikhlef

    2012-01-01

    Full Text Available This paper presents the modeling and simulation of an optical fiber Bragg grating for maximum reflectivity, minimum side lobe. Gating length represents as one of the critical parameters in contributing to a high performance fiber Bragg grating. The reflection spectra and side lobes strength were analyzed with different lengths .The side lobes have been suppressed using raised cosine apodization while maintaining the peak reflectivity. Such simulations are based on solving coupled mode equations by transfer matrix method.

  17. Ionoacoustic tomography of the proton Bragg peak in combination with ultrasound and optoacoustic imaging

    OpenAIRE

    Stephan Kellnberger; Walter Assmann; Sebastian Lehrack; Sabine Reinhardt; Peter Thirolf; Daniel Queirós; George Sergiadis; Günther Dollinger; Katia Parodi; Vasilis Ntziachristos

    2016-01-01

    Ions provide a more advantageous dose distribution than photons for external beam radiotherapy, due to their so-called inverse depth dose deposition and, in particular a characteristic dose maximum at their end-of-range (Bragg peak). The favorable physical interaction properties enable selective treatment of tumors while sparing surrounding healthy tissue, but optimal clinical use requires accurate monitoring of Bragg peak positioning inside tissue. We introduce ionoacoustic tomography based ...

  18. Strain and temperature sensors using multimode optical fiber Bragg gratings and correlation signal processing

    OpenAIRE

    Lim, J; Yang, QP; Jones, BE; Jackson, PR

    2002-01-01

    Multimode fiber optic Bragg grating sensors for strain and temperature measurements using correlation signal processing methods have been developed. Two multimode Bragg grating sensors were fabricated in 62/125 m graded-index silica multimode fiber; the first sensor was produced by the holographic method and the second sensor by the phase mask technique. The sensors have signal reflectivity of approximately 35% at peak wavelengths of 835 nm and 859 nm, respectively. Strain testing...

  19. A temperature insensitive Bragg grating sensor - using orthogonal polar polarisation modes for in situ temperature compensation

    OpenAIRE

    Parker, R M; J.C.Gates; Grossel, M. C.; P.G.R.Smith

    2010-01-01

    An exposed Bragg grating incorporated into a planar waveguide forms an optical device that acts as a refractive index sensor. The exposed evanescent field causes the Bragg peak to be sensitive to the refractive index of its surroundings and can be used to detect changes in this environment. The method reported is able to provide accurate temperature compensation by applying a scaling factor derived from measurement of the birefringence of the transverse electric (TE) and transverse magnetic (...

  20. Karakterisasi Fiber Bragg Grating (FBG) Untuk Pengembangan Sistem Sensor Strain Tanah

    OpenAIRE

    Sinuhaji, Depi Santi

    2010-01-01

    Fiber Bragg Grating (FBG) is a periodic change of refractive index which is the length of optical fiber. Has been developed Fiber Bragg Grating (FBG)-based laser diodes for monitoring landslide-prone areas. This sensor has been developed because high sensitivity and is not affected by electromagnetic induction that can be placed at a distance from the location where the power supply and monitor. FBG transmission peak will shift when the grating is change resulting from a change in temperature...

  1. Practical biological spread-out Bragg peak design of carbon beam

    OpenAIRE

    Kim, Chang Hyeuk; Lee, Hwa-Ryun; Chang, Seduk; Jang, Hong Suk; Kim, Jeong Hwan; Park, Dong Wook; Hwang, Won Taek; Yang, Tea-Keun

    2015-01-01

    The carbon beams show more advantages on the biological properties compared with proton beams in radiation therapy. The carbon beam shows high linear energy transfer (LET) to medium and it increases the relative biological effectiveness (RBE). To design spread-out Bragg peak (SOBP) of biological dose using carbon beam, a practical method was purposed by using the linear-quadratic (LQ) model and Geant4 based Monte Carlo simulation code. The various Bragg peak profiles and LET was calculated fo...

  2. 100 GHz electrically tunable planar Bragg gratings via liquid crystal overlay

    OpenAIRE

    Adikan, F.R.Mahamd; J.C.Gates; Snow, B.D.; Dyadyusha, A.; Major, H.E.; Gawith, C.B.E.; Kaczmarek, M.; P.G.R.Smith

    2007-01-01

    We demonstrate 114GHz electrically tunable liquid crystal Bragg gratings using 170Vpp voltage. The devices were made using direct UV grating writing and use evanescent coupling into an electrically tuned nematic liquid crystal. Reconfigurable integrated optical devices are essential in today's dense and complex telecommunication meshes. A commonly employed component on the silica platform fulfilling the above role is a planar Bragg grating. The ability to tune the reflection peak of these gra...

  3. Uniform Fiber Bragg Grating modeling and simulation used matrix transfer method

    OpenAIRE

    Abdallah Ikhlef; Rachida Hedara; Mohamed Chikh-Bled

    2012-01-01

    This paper presents the modeling and simulation of an optical fiber Bragg grating for maximum reflectivity, minimum side lobe. Gating length represents as one of the critical parameters in contributing to a high performance fiber Bragg grating. The reflection spectra and side lobes strength were analyzed with different lengths .The side lobes have been suppressed using raised cosine apodization while maintaining the peak reflectivity. Such simulations are based on ...

  4. Numerical Analysis of Thermal Dependence of the Spectral Response of Polymer Optical Fiber Bragg Gratings

    OpenAIRE

    Hisham K. Hisham

    2016-01-01

    The thermal dependence of the spectral response (i.e. transmission, reflection and time delay (r) responses) of uniform polymer optical fiber (POF) Bragg gratings has been investigated. In addition to the temperature dependence, the effects of grating strength (kLg) and fiber index modulation (n) have been investigated. Besides high capability of tunable wavelength due to the unique large and negative thermo-optic coefficient of POF, the spectral response for POF Bragg gratings sh...

  5. Floquet-Bloch vs. Nicolson-Ross-Weir Extraction for Magneto-Dielectric Bragg Stacks

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav

    We extract and compare the permittivity and permeability from a dielectric and a magnetodielectric Bragg stack with the Floquet-Bloch (FB) method for the infinite stack and the Nicolson-Ross- Weir (NRW) method for the finite stack. While the extracted propagation constants are identical, the wave...... impedances are different. Moreover, the NRWmethod yields magnetic effects for the dielectric Bragg stack, while the FB method gives the expected vacuum permeability, also in the bandgab....

  6. Fiber Bragg Gratings in Small-Core Ge-Doped Photonic Crystal Fibers

    Institute of Scientific and Technical Information of China (English)

    Yiping Wang; Hartmut Bartelt; Wolfgang Ecke; Reinhardt Willsch; Jens Kobelke; Michael Kautz; Sven Brueckner; Manfred Rothhardt

    2008-01-01

    This paper reports fiber Bragg gratings (FBGs) inscribed in a small-core Ge-doped photonic crystal fibers with a UV laser and a Talbot inter-ferometer. The responses of such FBGs to temper-ature, strain, bending, and transverse-loading were systematically investigated. The Bragg wavelength of the FBGs shifts toward longer wavelengths with increasing temperature, tensile strain, and trans-verse-loading. The bending and transverse- loading properties of the FBGs are sensitive to the fiber orientations.

  7. Efectos rotacionales en redes de Bragg en fibras ópticas

    OpenAIRE

    Arce Diego, José Luis; Muriel Fernández, Miguel Ángel; López Ruisánchez, Roberto; López Higuera, José Miguel

    1997-01-01

    The periodic mode coupling between the right and left circular polarization modes that is induced by a photoinduced fiber grating, with or without lineal birefringence, and with a magnetic field or a twist rate applied to it, is studied and analyzed through the use of the generalized coupled-mode theory. Several novel application of such devices as a fiber Bragg grating twist rate probe, a tuneable optical fiber based on twisted fiber Bragg grating, and an optical filter tuned by magnetic fie...

  8. Computer-Generated Holograms for Recording Multiple-Phase-Shifte Fiber Bragg Grating Corrugations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new method of fabricating multiple-phase-shifte fiber Bragg grating by CGHs is proposed. The authors present an example of such CGH by which a section multiple-phase-shifte fiber Bragg grating with two π/2 phase shifts and grating length L=21.2 μm was produced. The authors describe the production process and finally give an example of a reconstructed fiber grating with two phase-shifts.

  9. Temperature sensor based on injection fiber Bragg grating laser with wavelength and temporal domain demodulation

    Science.gov (United States)

    Li, Qi; Huang, Kaiqiang; Chen, Haiyan

    2015-08-01

    A novel temperature sensor based on injection fiber Bragg grating laser with wavelength and temporal domain demodulation is proposed and demonstrated experimentally. The proof of concept device consists of a DFB laser modulated by a RF signal as injection light, a fiber Bragg grating laser, an optical spectrum analyzer, and a digital oscilloscope. The dynamic range of the proposed sensor is explored. The results demonstrate the new concept of temperature sensors and the technical feasibility for temperature measurement.

  10. Comparison of spatial harmonics in infinite and finite Bragg stacks for metamaterial homogenization

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav

    2014-01-01

    Metamaterial homogenization may be based on the dominance of a single Floquet-Bloch spatial harmonic in an infinite periodic structure - with the dominance quantified in terms of the relative magnitude of the associated spatial harmonic Poynting vector. For the corresponding finite structure...... of the corresponding infinite Bragg stack. This is even the case for finite Bragg stacks having only two unit cells; thus, the number of unit cells does not influence the homogenizability of this type of configuration. ©...

  11. Preparation of Zn-Ni-Fe-Cr Ferrites and characterisation by X-ray diffraction

    International Nuclear Information System (INIS)

    Four samples of the spinel oxide ZnxNi1-xFeCrO4 with x=0.2, 0.4, 0.6 and 0.8 have been prepared using the conventional solid state sintering technique. The stoichiometric mixture of high purity (99.99%) oxides of ZnO, NiO, Fe2O3 and Cr2O3 were taken as starting materials. The samples were pre-sintered at a temperature of 1000oC for 6 hours and then sintered at a temperature of 1250''oC for 8 hours. X-ray diffraction experiments on all the specimens were performed using an X-ray diffractometer (Shimadzu XRD-6000, Japan) with CuK α radiation of wavelength λ =1.540598 A0. For all the samples X-ray diffraction patterns were recorded in the angular range 10o ≤ 2θ ≤ 90o. The diffraction patterns thus obtained showed sharp lines corresponding to the single phase cubic spinel structure. The Bragg diffraction peaks in the pattern could be indexed corresponding to the indexing scheme of the spinel structure. The prepared samples were thus characterized to be spinel structure. The prepared samples were thus characterized to be spinel ferrites. The cell parameters have been calculated from the diffraction patterns which increases with increasing diamagnetic Zn2+ substitution in the system

  12. Experimental and theoretical aspects of ab initio structure determination using powder diffraction techniques

    International Nuclear Information System (INIS)

    Neutron powder diffraction has, over the past two decades, developed into a powerful technique for the refinement of moderately complex crystal structures. The advent of a new generation of ultra-high resolution X-ray and neutron powder diffractometers, however, not only permits the refinement of more complex materials but also opens up new areas of research. Perhaps the most exciting development in powder diffraction techniques associated with high resolution is the ab initio determination of crystal structures. This has until recently been possible, in a routine way, only by single crystal studies. The compression of three dimensions of diffraction data to the one dimension of a powder diffraction pattern leads to an unavoidable loss of information. For many, but not all, crystal symmetries high resolution minimises this loss thus allowing the intensities of a sufficient number of resolved Bragg reflections from moderately complex materials to be extracted for use in structure solution by direct methods of phase determination and by Patterson methods. Recent structure determination using the high resolution powder diffractometer, HRPD, at ISIS will be presented. The inherent limitations resulting from crystal and instrumental resolution are discussed along with maximum entropy techniques that seek to optimise the information content of a powder diffraction pattern. (author) 36 refs., 1 fig., 3 tabs

  13. ENDIX. A computer program to simulate energy dispersive X-ray and synchrotron powder diffraction diagrams

    International Nuclear Information System (INIS)

    A Fortran 77 computer program is described which allows the simulation of energy dispersive X-ray and synchrotron powder diffraction diagrams. The input consists of structural data (space group, unit cell dimensions, atomic positional and displacement parameters) and information on the experimental conditions (chosen Bragg angle, type of X-ray tube and applied voltage or operating power of synchrotron radiation source). The output consists of the normalized intensities of the diffraction lines, listed by increasing energy (in keV), and of an optional intensity-energy plot. The intensities are calculated with due consideration of the wave-length dependence of both the anomalous dispersion and the absorption coefficients. For a better agreement between observed and calculated spectra provision is made to optionally superimpose, on the calculated diffraction line spectrum, all additional lines such as fluorescence and emission lines and escape peaks. The different effects which have been considered in the simulation are discussed in some detail. A sample calculation of the energy dispersive powder diffraction pattern of UPt3 (Ni3Sn structure type) is given. Warning: the user of ENDIX should be aware that for a successful application it is necessary to adapt the program to correspond to the actual experimental conditions. Even then, due to the only approximately known values of certain functions, the agreement between observed and calculated intensities will not be as good as for angle dispersive diffraction methods

  14. Femtosecond X-ray diffraction from two-dimensional protein crystals

    Directory of Open Access Journals (Sweden)

    Matthias Frank

    2014-03-01

    Full Text Available X-ray diffraction patterns from two-dimensional (2-D protein crystals obtained using femtosecond X-ray pulses from an X-ray free-electron laser (XFEL are presented. To date, it has not been possible to acquire transmission X-ray diffraction patterns from individual 2-D protein crystals due to radiation damage. However, the intense and ultrafast pulses generated by an XFEL permit a new method of collecting diffraction data before the sample is destroyed. Utilizing a diffract-before-destroy approach at the Linac Coherent Light Source, Bragg diffraction was acquired to better than 8.5 Å resolution for two different 2-D protein crystal samples each less than 10 nm thick and maintained at room temperature. These proof-of-principle results show promise for structural analysis of both soluble and membrane proteins arranged as 2-D crystals without requiring cryogenic conditions or the formation of three-dimensional crystals.

  15. The early development of neutron diffraction: science in the wings of the Manhattan Project

    International Nuclear Information System (INIS)

    Early neutron diffraction experiments performed in 1944 using the first nuclear reactors are described. Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool

  16. Dynamical X-ray Diffraction from In x Ga1- x As Heterostructures with Dislocations

    Science.gov (United States)

    Rago, P. B.; Ayers, J. E.

    2013-08-01

    High-resolution x-ray diffraction is an important nondestructive tool for structural characterization of semiconductor heterostructures, and the diffraction intensity profiles contain information on the depth profiles of strain, composition, and defect densities in device heterostructures. Much of this information remains inaccessible because the lack of phase information prevents direct inversion of the rocking curves. The current practice is to use dynamical simulations in conjunction with a curve-fitting procedure to indirectly extract the profiles of strain and composition, but such dynamical simulations have been based on perfect, dislocation-free laminar crystals, which renders the analysis inapplicable to highly mismatched structures containing dislocation densities greater than about 106 cm-2. In this work we present a dynamical model for Bragg x-ray diffraction in semiconductor device structures with nonuniform composition, strain, and dislocation density, which is based on the Takagi-Taupin equation for distorted crystals and accounts for the diffuse scattering arising from the strain mosaicity and angular mosaicity associated with dislocations. We show theoretically that the x-ray diffraction profiles from In x Ga1- x As/GaAs (001) heterostructures are strongly affected by the depth distribution of the dislocation density as well as the composition and strain, so that in principle all three distributions may be obtained by the analysis of the measured diffraction profiles.

  17. Keyhole electron diffractive imaging (KEDI).

    Science.gov (United States)

    De Caro, Liberato; Carlino, Elvio; Vittoria, Fabio Alessio; Siliqi, Dritan; Giannini, Cinzia

    2012-11-01

    Electron diffractive imaging (EDI) relies on combining information from the high-resolution transmission electron microscopy image of an isolated kinematically diffracting nano-particle with the corresponding nano-electron diffraction pattern. Phase-retrieval algorithms allow one to derive the phase, lost in the acquisition of the diffraction pattern, to visualize the actual atomic projected potential within the specimen at sub-ångström resolution, overcoming limitations due to the electron lens aberrations. Here the approach is generalized to study extended crystalline specimens. The new technique has been called keyhole electron diffractive imaging (KEDI) because it aims to investigate nano-regions of extended specimens at sub-ångström resolution by properly confining the illuminated area. Some basic issues of retrieving phase information from the EDI/KEDI measured diffracted amplitudes are discussed. By using the generalized Shannon sampling theorem it is shown that whenever suitable oversampling conditions are satisfied, EDI/KEDI diffraction patterns can contain enough information to lead to reliable phase retrieval of the unknown specimen electrostatic potential. Hence, the KEDI method has been demonstrated by simulations and experiments performed on an Si crystal cross section in the [112] zone-axis orientation, achieving a resolution of 71 pm. PMID:23075611

  18. Numerical Analysis of Thermal Dependence of the Spectral Response of Polymer Optical Fiber Bragg Gratings

    Directory of Open Access Journals (Sweden)

    Hisham K. Hisham

    2016-06-01

    Full Text Available The thermal dependence of the spectral response (i.e. transmission, reflection and time delay (r responses of uniform polymer optical fiber (POF Bragg gratings has been investigated. In addition to the temperature dependence, the effects of grating strength (kLg and fiber index modulation (n have been investigated. Besides high capability of tunable wavelength due to the unique large and negative thermo-optic coefficient of POF, the spectral response for POF Bragg gratings show high stability and larger spectrum bandwidth with temperature variation compare with the silica optical fiber (SOF Bragg gratings, especially with the increase of the kLg value. It was found that by increasing kLg, the peak reflectance value increases and the bandwidth of the Bragg reflector become narrower. Also it’s shown by increasing the kLg value, r deceasing significantly and reach its minimum value at the designed wavelength (B. Furthermore, the r for POF Bragg gratings is less than that for SOF Bragg gratings at the same value of kLg. Also it’s found that the peak reflectivity value increases to around 60% when the n value increases from 110-4 to 510-4.

  19. Formularization and simulation of Bragg selectivity of readout signals in angular-multiplexing holographic data storage.

    Science.gov (United States)

    Ide, Tatsuro

    2016-04-01

    Bragg selectivity of readout signals in angular-multiplexing holographic data storage was investigated. The effects of degrading factors, namely, volume change, refractive-index change, and positional change (tilt and rotation) of a hologram, and the effects of compensating variables, namely, wavelength shift and reference-beam-angle shift, on Bragg selectivity were evaluated. Deviation of wave vectors of recovered pixels of a hologram from the Bragg condition under degrading factors and compensating variables, namely, Bragg mismatch, Δσ, was mathematically derived. Approximating Δσ by using the first-order Maclaurin series with respect to degrading factors and compensating variables revealed their effects on Bragg selectivity. The extent to which wavelength and angle of reference beam should be shifted to compensate for the degrading factors were determined. Then, readout images were simulated under multiple degrading factors and compensating variables. These simulated images were found to agree well with the experimentally obtained ones, which reveals the validity of the formalization of Bragg selectivity. PMID:27139671

  20. The Functionality of Fiber Bragg Grating Sensor Compared to that of Foil Gauge

    Directory of Open Access Journals (Sweden)

    Bashir A. Tahir

    2005-01-01

    Full Text Available Technology such as Fiber Bragg Grating (FBG sensors are widely accepted in almost all industries. FBG are being investigated for their applicability in other markets such as smart structures. Fiber optic sensors can also be used in many different applications. Fiber optic sensors are available in several types; among them, the Bragg grating sensor is being studied in this research. For this research work, the main focus was the use of fiber Bragg grating sensors for measuring strain. The key objective of this research; to determine the functionality of fiber Bragg grating sensors compared to that of conventional foil gauges. Fiber Bragg grating sensors were chosen for this research because they have a high potential for various uses in the monitoring of smart structures. The major incentives for this type of research are the current deterioration of civil structures in west Malaysia. The laboratory tests are being reported in this research work including tests of steel straps and an aluminum test specimen. In all the tests, strain was measured using the fiber Bragg grating sensors and compared to values from a conventional foil gauge. The results are being discussed in details. It was inferred that the use of fiber optic technology for the monitoring of civil structures is very promising and the future is sure to bring further advancements and improvements.

  1. Heavy ion induced damage to plasmid DNA: plateau region vs. spread out Bragg-peak

    Science.gov (United States)

    Dang, H. M.; van Goethem, M. J.; van der Graaf, E. R.; Brandenburg, S.; Hoekstra, R.; Schlathölter, T.

    2011-08-01

    We have investigated the damage of synthetic plasmid pBR322 DNA in dilute aqueous solutions induced by fast carbon ions. The relative contribution of indirect damage and direct damage to the DNA itself is expected to vary with linear energy transfer along the ion track, with the direct damage contribution increasing towards the Bragg peak. Therefore, 12C ions at the spread-out Bragg peak (dose averaged LET∞ = 189 ± 15 keV/ μm) and in the plateau region of the Bragg curve (LET = 40 keV/ μm) were employed and the radical scavenger concentration in the plasmid solution was varied to quantify the indirect effect. In order to minimize the influence of 12C break-up fragments, a relatively low initial energy of 90 MeV/nucleon was employed for the carbon ions. DNA damage has been quantified by subsequent electrophoresis on agarose gels. We find that strand breaks due to both indirect and direct effects are systematically higher in the plateau region as compared to the Bragg peak region with the difference being smallest at high scavenging capacities. In view of the fact that the relative biological effectiveness for many biological endpoints is maximum at the Bragg peak our findings imply that DNA damage at the Bragg peak is qualitatively most severe.

  2. Development of Bragg Gratings as Shear Stress Monitors in Aerodynamic >Facilities

    Science.gov (United States)

    Parmar, Devandra S.

    1998-04-01

    Two Bragg gratings centered at 1289.565 nm and 1299.432 nm were co-written in the core of a 9/125 telecommunications fiber doped with 10 weight percent germanium. The fiber was mounted in a 126 deep groove, with a 127 diameter semicircular bottom, etched in a flat metal plate used as the test model. A 1 thick epoxy layer bonded the fiber to the metal plate. A thermocouple was also attached to the metal plate in the vicinity of the Bragg fiber. The metal plate was next mounted in the test section of a subsonic wind tunnel. A skin friction balance was also mounted on the wall of the test section. As the wind speed in the tunnel was increased from 0 to 90 m/sec, reflected Bragg wavelengths and the fiber temperatures were recorded continuously. At a windspeed of 38.89 m/sec, the tunnel flow experienced a fan-induced turbulence registered by the skin friction balance as well as the Bragg signals. This commonality of the turbulence signal registration provided a unique calibration datum for the modulus of rigidity of the Bragg fiber assembly. This value of h has been used to calculate the values of shear stress at various tunnel speeds on the basis of Bragg wavelength changes at those speeds.

  3. Heavy ion induced damage to plasmid DNA: plateau region vs. spread out Bragg-peak

    Energy Technology Data Exchange (ETDEWEB)

    Dang, H.M.; Van Goethem, M.J.; Van der Graaf, E.R.; Brandenburg, S.; Hoekstra, R.; Schlatholtera, T. [KVI University of Groningen, Zernikelaan 25, 9747AA Groningen (Netherlands)

    2011-08-15

    We have investigated the damage of synthetic plasmid pBR322 DNA in dilute aqueous solutions induced by fast carbon ions. The relative contribution of indirect damage and direct damage to the DNA itself is expected to vary with linear energy transfer along the ion track, with the direct damage contribution increasing towards the Bragg peak. Therefore, {sup 12}C ions at the spread-out Bragg peak (dose averaged LET{sub {infinity} }= (189 {+-} 15) keV/{mu}m) and in the plateau region of the Bragg curve (LET = 40 keV/{mu}m) were employed and the radical scavenger concentration in the plasmid solution was varied to quantify the indirect effect. In order to minimize the influence of {sup 12}C break-up fragments, a relatively low initial energy of 90 MeV/nucleon was employed for the carbon ions. DNA damage has been quantified by subsequent electrophoresis on agarose gels. We find that strand breaks due to both indirect and direct effects are systematically higher in the plateau region as compared to the Bragg peak region with the difference being smallest at high scavenging capacities. In view of the fact that the relative biological effectiveness for many biological endpoints is maximum at the Bragg peak our findings imply that DNA damage at the Bragg peak is qualitatively most severe. (authors)

  4. Heavy ion induced damage to plasmid DNA: plateau region vs. spread out Bragg-peak

    International Nuclear Information System (INIS)

    We have investigated the damage of synthetic plasmid pBR322 DNA in dilute aqueous solutions induced by fast carbon ions. The relative contribution of indirect damage and direct damage to the DNA itself is expected to vary with linear energy transfer along the ion track, with the direct damage contribution increasing towards the Bragg peak. Therefore, 12C ions at the spread-out Bragg peak (dose averaged LET∞ = (189 ± 15) keV/μm) and in the plateau region of the Bragg curve (LET = 40 keV/μm) were employed and the radical scavenger concentration in the plasmid solution was varied to quantify the indirect effect. In order to minimize the influence of 12C break-up fragments, a relatively low initial energy of 90 MeV/nucleon was employed for the carbon ions. DNA damage has been quantified by subsequent electrophoresis on agarose gels. We find that strand breaks due to both indirect and direct effects are systematically higher in the plateau region as compared to the Bragg peak region with the difference being smallest at high scavenging capacities. In view of the fact that the relative biological effectiveness for many biological endpoints is maximum at the Bragg peak our findings imply that DNA damage at the Bragg peak is qualitatively most severe. (authors)

  5. Diffractive Bremsstrahlung in Hadronic Collisions

    Directory of Open Access Journals (Sweden)

    Roman Pasechnik

    2015-01-01

    Full Text Available Production of heavy photons (Drell-Yan, gauge bosons, Higgs bosons, and heavy flavors, which is treated within the QCD parton model as a result of hard parton-parton collision, can be considered a bremsstrahlung process in the target rest frame. In this review, we discuss the basic features of the diffractive channels of these processes in the framework of color dipole approach. The main observation is a dramatic breakdown of diffractive QCD factorisation due to the interplay between soft and hard interactions, which dominates these processes. This observation is crucial for phenomenological studies of diffractive reactions in high energy hadronic collisions.

  6. Diffractive bremsstrahlung in hadronic collisions

    CERN Document Server

    Pasechnik, Roman; Potashnikova, Irina

    2015-01-01

    Production of heavy photons (Drell-Yan), gauge bosons, Higgs bosons, heavy flavors, which is treated within the QCD parton model as a result of hard parton-parton collision, can be considered as a bremsstrahlung process in the target rest frame. In this review, we discuss the basic features of the diffractive channels of these processes in the framework of color dipole approach. The main observation is a dramatic breakdown of diffractive QCD factorisation due to the interplay between soft and hard interactions, which dominates these processes. This observation is crucial for phenomenological studies of diffractive reactions in high-energy hadronic collisions.

  7. Arbitrary shape surface Fresnel diffraction.

    Science.gov (United States)

    Shimobaba, Tomoyoshi; Masuda, Nobuyuki; Ito, Tomoyoshi

    2012-04-01

    Fresnel diffraction calculation on an arbitrary shape surface is proposed. This method is capable of calculating Fresnel diffraction from a source surface with an arbitrary shape to a planar destination surface. Although such calculation can be readily calculated by the direct integral of a diffraction calculation, the calculation cost is proportional to O(N²) in one dimensional or O(N⁴) in two dimensional cases, where N is the number of sampling points. However, the calculation cost of the proposed method is O(N log N) in one dimensional or O(N² log N) in two dimensional cases using non-uniform fast Fourier transform. PMID:22513646

  8. Arbitrary shape surface Fresnel diffraction

    CERN Document Server

    Shimobaba, Tomoyoshi; Ito, Tomoyoshi

    2012-01-01

    Fresnel diffraction calculation on an arbitrary shape surface is proposed. This method is capable of calculating Fresnel diffraction from a source surface with an arbitrary shape to a planar destination surface. Although such calculation can be readily calculated by the direct integral of a diffraction calculation, the calculation cost is proportional to $O(N^2)$ in one dimensional or $O(N^4)$ in two dimensional cases, where $N$ is the number of sampling points. However, the calculation cost of the proposed method is $O(N \\log N)$ in one dimensional or $O(N^2 \\log N)$ in two dimensional cases using non-uniform fast Fourier transform.

  9. Neutron diffraction investigation of structural deviations in cement clinker

    International Nuclear Information System (INIS)

    Full text: The effects of refining the atomic positions in cement clinker phases using Rietveld analysis of neutron powder diffraction data was investigated. Changes in phase quantification and Bragg-R factors of phases after atomic position refinement are reported. A previous x-ray study, briefly reported that less than a 1% (average) alteration to bond distances in a refinement resulted in an approximately 25% improvement in the fits of a tricalcium silicate phase. In this neutron study, relatively minor adjustments to the structures resulted in decreased R-Bragg factors of tricalcium silicate phases, with very little changes to the overall bond distances. Rietveld refinement is commonly used for the phase quantification of cement clinker, which is difficult due to the complexity of component phases. Phases typically present in cement clinker are tricalcium silicate (Ca3SiO5), dicalcium silicate (Ca2SiO4), tricalcium aluminate (Ca3AI2O6), and tetracalcium aluminoferrite (Ca2(AI2O3)x(Fe2O3)i-x. Rietveld analysis is complicated by the polymorphic modification of these phases. At least seven tricalcium silicate polymorphs exist, three of which have structures that are commonly used in the Rietveld analysis of clinkers. Only one dicalcium silicate type has been shown likely to be present. Tricalcium aluminate has three polymorphs, all found in clinker, whilst tetracalcium aluminoferrite can appear with a varying AI:Fe ratio. Full-profile Rietveld methods have the ability to define the tricalcium silicate form. It is usual to include a polymorph of tricalcium silicate in each of the three crystal systems encountered when beginning a refinement of clinker data, and then exclude the crystal system(s) not found. Care must be taken so as not to enable one crystal system to alter itself to compensate for another. Quantification by diffraction methods of the tricalcium and dicalcium silicate phases in mixtures, such as in clinker, is further complicated by the wide range of

  10. Palladium coated fibre Bragg grating based hydrogen sensor

    International Nuclear Information System (INIS)

    Detection of steam generator leaks in fast nuclear reactors is carried out by monitoring hydrogen in argon cover-gas. Hydrogen released during sodium cleaning of fast reactor components is required to be monitored. Hydrogen sensors with good sensitivity, stability and response time are required for all the above applications. We report a new type of hydrogen sensor with a Fibre Bragg Grating (FBG) coated with palladium thin film which is used to detect the leak of hydrogen gas in the Steam Generator (SG) module of the Fast Breeder Reactor (FBR). If water leaks into sodium, it results in sodium-water reaction. In this reaction hydrogen and sodium hydroxide are formed. Due to the explosive risk of hydrogen system, hydrogen sensors are of great interest in this case. It is known that hydrogen forms an explosive mixture with air once its concentration exceeds beyond the explosion limit of four percent. The advantages of FBG based hydrogen sensor over the other hydrogen sensors are its inherent property of safety from sparking, immunity to ambient electromagnetic interference. The sensing mechanism in this device is based on mechanical strain that is induced in the palladium coating when it absorbs hydrogen. This process physically stretches the grating and causes the grating period and grating's refractive index, to change. The Bragg wavelength shift is directly proportional to the strain induced and can be directly related to the percentage of hydrogen exposure. The online monitoring of palladium thin film coating on FBG is carried out and recorded the wavelength change and strain induced on the FBG. A hydrogen sensor set up have been fabricated which consists of SS vessel of capacity 10 litres, provided with pressure gauge, Argon filling line with a valve, Hydrogen injection line with flange, a vent line with valve and Hydrogen sensor fixing point. The Palladium coated FBG based Hydrogen sensor is tested in this experimental facility in the exposure of hydrogen in

  11. Diffraction of multilayer gratings and zone plates in the x-ray region using the Born approximation

    International Nuclear Information System (INIS)

    New devices combining the Bragg reflection from periodic multilayer structures with Fraunhofer or Fresnel diffraction arising from lateral patterning of the multilayer are now available for x-ray optics. Using Green's-function method, the authors establish an integral equation for the scattered amplitude that is valid in the framework of both Fraunhofer and Fresnel diffraction. The scattered amplitude is given in the first and the second Born approximations for multilayer mirrors, laminar and sawtooth-profile multilayer gratings, and linear multilayer zone plates. The main diffractive properties of these devices are deduced. The efficiencies are computed in the first and/or in the second Born approximation and are compared with efficiencies obtained from a rigorous electromagnetic theory when they are available. 18 refs., 10 figs., 1 tab

  12. Electrically-programmable diffraction grating

    Science.gov (United States)

    Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

    1998-05-26

    An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

  13. High pressure diffraction at ISIS

    International Nuclear Information System (INIS)

    The development of the high pressure diffraction programme at ISIS is reviewed. Along with general accounts of the technique and the pressure cells used, examples of science carried out in this field are given. (author)

  14. Experimental studies of diffractive phenomena

    International Nuclear Information System (INIS)

    The coherent inelastic scattering process, usually called inclusive diffraction dissociation, is discussed. Topics include: t and M/sub x/ dependence, factorization, finite mass sum rule and charged particle multiplicities. 6 references, 14 figures

  15. Femtosecond single-electron diffraction

    Directory of Open Access Journals (Sweden)

    S. Lahme

    2014-05-01

    Full Text Available Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration.

  16. Diffractive and rising cross sections

    International Nuclear Information System (INIS)

    The energy dependence of the diffractive component of the proton-proton cross section is discussed and its contribution to the rise of the total cross section at high energies is examined. 17 refs., 9 figs

  17. Phase Aberrations in Diffraction Microscopy

    OpenAIRE

    Marchesini, S.; Chapman, H. N.; Barty, A.; Cui, C.; Howells, M. R.; Spence, J. C. H.; Weierstall, U.; Minor, A.M.

    2005-01-01

    In coherent X-ray diffraction microscopy the diffraction pattern generated by a sample illuminated with coherent x-rays is recorded, and a computer algorithm recovers the unmeasured phases to synthesize an image. By avoiding the use of a lens the resolution is limited, in principle, only by the largest scattering angles recorded. However, the imaging task is shifted from the experiment to the computer, and the algorithm's ability to recover meaningful images in the presence of noise and limit...

  18. Texture determination by neutron diffraction

    International Nuclear Information System (INIS)

    Application of neutron diffraction to crystallographic texture determination shows many advantages: possibility of an important grain size, the quantity of material contributing to diffraction is more important than with X rays, good accuracy and complete pole figures are obtained by transmission only eliminating corrections needed with X rays. Texture determination allows control and improvement of material quality. Texture studies give good informations on mechanisms occuring in deformation or recrystallization of polycrystals and on anisotropy of physical and mechanical properties

  19. Fresnel diffraction by spherical obstacles

    Science.gov (United States)

    Hovenac, Edward A.

    1989-01-01

    Lommel functions were used to solve the Fresnel-Kirchhoff diffraction integral for the case of a spherical obstacle. Comparisons were made between Fresnel diffraction theory and Mie scattering theory. Fresnel theory is then compared to experimental data. Experiment and theory typically deviated from one another by less than 10 percent. A unique experimental setup using mercury spheres suspended in a viscous fluid significantly reduced optical noise. The major source of error was due to the Gaussian-shaped laser beam.

  20. Accuracy of needle position measurements using fiber Bragg gratings.

    Science.gov (United States)

    Henken, Kirsten; Van Gerwen, Dennis; Dankelman, Jenny; Van Den Dobbelsteen, John

    2012-11-01

    Accurate placement of the needle tip is essential in percutaneous therapies such as radiofrequency ablation (RFA) of liver tumors. Use of a robotic system for navigating the needle could improve the targeting accuracy. Real-time information on the needle tip position is needed, since a needle deflects during insertion in tissue. Needle shape can be reconstructed based on strain measurements within the needle. In the current experiment we determined the accuracy with which the needle tip position can be derived from strain measurements using Fiber Bragg Gratings (FBGs). Three glass fibers equipped with two FBGs each were incorporated in a needle. The needle was clamped at one end and deformed by applying static radial displacements at one or two locations. The FBG output was used for offline estimation of the needle shape and tip position. During deflections of the needle tip up to 12.5 mm, the tip position was estimated with a mean accuracy of 0.89 mm (std 0.42 mm). Adding a second deflection resulted in an error of 1.32 mm (std 0.48 mm). This accuracy is appropriate for applications such as RFA of liver tumors. The results further show that the accuracy can be improved by optimizing the placement of FBGs. PMID:22455615

  1. Investigation on Thermal-Induced Decay of Fiber Bragg Grating

    Science.gov (United States)

    Zhang, Peng; Ding, Pinyi; Liu, Li

    2015-06-01

    A fiber Bragg grating (FBG), with advantages such as high anti-interference ability, a simple structure, and multiplexing, is widely used as a core component in numerous applications to monitor adverse environments of high temperature and air pressure. When FBGs are exposed to these extreme conditions, especially high temperature, performance decay may occur, bringing serious impact on the stability and reliability of the instruments. Therefore, it is necessary to make a detailed analysis on the mechanism of the thermal-induced decay of a FBG. One commonly used theory is proposed by Erdogn, which is based on a power function and aging curve method. However, these empirical equations are limited in application because only one single type of FBG can be analyzed this way. This paper focuses on the mechanism of a FBG, and presents a detailed analysis on the theory of the thermal-induced decay of a FBG using the electron dipole mode. Theoretical relationships between reflectivity and time or temperature were obtained, and a corresponding thermal-induced decay testing system was designed. The experimental and theoretical reflectivity decline under different temperatures of and are plotted, and the curves of reduction derived from the theoretical model fit the experimental data well. Thus, this model can be applied to predict the performance decay of FBGs at high temperature.

  2. Perimeter security alarm system based on fiber Bragg grating

    Science.gov (United States)

    Zhang, Cui; Wang, Lixin

    2010-11-01

    With the development of the society and economy and the improvement of living standards, people need more and more pressing security. Perimeter security alarm system is widely regarded as the first line of defense. A highly sensitive Fiber Bragg grating (FBG) vibration sensor based on the theory of the string vibration, combined with neural network adaptive dynamic programming algorithm for the perimeter security alarm system make the detection intelligently. Intelligent information processing unit identify the true cause of the vibration of the invasion or the natural environment by analyzing the frequency of vibration signals, energy, amplitude and duration. Compared with traditional perimeter security alarm systems, such as infrared perimeter security system and electric fence system, FBG perimeter security alarm system takes outdoor passive structures, free of electromagnetic interference, transmission distance through optical fiber can be as long as 20 km It is able to detect the location of event within short period of time (high-speed response, less than 3 second).This system can locate the fiber cable's breaking sites and alarm automatically if the cable were be cut. And the system can prevent effectively the false alarm from small animals, birds, strong wind, scattering things, snowfalls and vibration of sensor line itself. It can also be integrated into other security systems. This system can be widely used in variety fields such as military bases, nuclear sites, airports, warehouses, prisons, residence community etc. It will be a new force of perimeter security technology.

  3. Fiber Bragg grating sensors for strain monitoring of steelwork

    Science.gov (United States)

    Wang, Tao; He, Dawei; Yang, Fan; Wang, Yongsheng

    2009-11-01

    Over the last few years, fiber Bragg grating (FBG) sensors have attracted a lot of interest and they are being used in various applications. This paper describes the FBG sensors used for strain monitoring of bogie and other steelworks. FBG sensors and resistance strain gauges are set on different position of steel girder, and weight is loaded on the steel girder. Strain value of the steel girder can be caught by two kinds of sensors when weight loaded is changed. Result of experiment shows that strain value obtained by resistance strain gauges and FBG sensor is coinciding. There is a linear correlation between value of strain and the weight loaded on the steel girder. FBG sensors with different encapsulations are set on bogie by acrylic plastic materials in order to monitor its dynamic strains. When sinusoidal load with its frequency from 0.15Hz to 2Hz was set on the bogie, FBG sensor system with data sampling rate of 20Hz were used to monitoring the dynamic strains. Strain data caught by FBG sensor system can offer accurate description of dynamic strain, and value of strain provided by FBG sensor suits theoretical values well. The experimental observations show that FBG sensors can be set on steelworks easily, and can monitor both static strain and dynamic strains well.

  4. Integrated waveguide Bragg gratings for microwave photonics signal processing.

    Science.gov (United States)

    Burla, Maurizio; Cortés, Luis Romero; Li, Ming; Wang, Xu; Chrostowski, Lukas; Azaña, José

    2013-10-21

    Integrated Microwave photonics (IMWP) signal processing using Photonic Integrated Circuits (PICs) has attracted a great deal of attention in recent years as an enabling technology for a number of functionalities not attainable by purely microwave solutions. In this context, integrated waveguide Bragg grating (WBG) devices constitute a particularly attractive approach thanks to their compactness and flexibility in producing arbitrarily defined amplitude and phase responses, by directly acting on coupling coefficient and perturbations of the grating profile. In this article, we review recent advances in the field of integrated WBGs applied to MWP, analyzing the advantages leveraged by an integrated realization. We provide a perspective on the exciting possibilities offered by the silicon photonics platform in the field of MWP, potentially enabling integration of highly-complex active and passive functionalities with high yield on a single chip, with a particular focus on the use of WBGs as basic building blocks for linear filtering operations. We demonstrate the versatility of WBG-based devices by proposing and experimentally demonstrating a novel, continuously-tunable, integrated true-time-delay (TTD) line based on a very simple dual phase-shifted WBG (DPS-WBG). PMID:24150355

  5. Opto-acoustic behavior of coated fiber Bragg gratings.

    Science.gov (United States)

    Moccia, Massimo; Pisco, Marco; Cutolo, Antonello; Galdi, Vincenzo; Bevilacqua, Pierantonio; Cusano, Andrea

    2011-09-26

    In this paper, we present the study of the acousto-optic behavior of underwater-acoustic sensors constituted by fiber Bragg gratings (FBGs) coated by ring-shaped overlays. Via full-wave numerical simulations, we study the complex opto-acousto-mechanical interaction among an incident acoustic wave traveling in water, the optical fiber surrounded by the ring shaped coating, and the FBG inscribed the fiber, focusing on the frequency range 0.5-30 kHz of interest for SONAR applications. Our results fully characterize the mechanical behavior of an acoustically driven coated FBG, and highlight the key role played by the coating in enhancing significantly its sensitivity by comparison with a standard uncoated configuration. Furthermore, the hydrophone sensitivity spectrum exhibits characteristic resonances, which strongly improve the sensitivity with respect to its background (i.e., away from resonances) level. Via a three-dimensional modal analysis, we verify that the composite cylindrical structure of the sensor acts as an acoustic resonator tuned at the frequencies of its longitudinal vibration modes. In order to evaluate the sensor performance, we also carry out a comprehensive parametric analysis by varying the geometrical and mechanical properties of the coating, whose results also provide a useful design tool for performance optimization and/or tailoring for specific SONAR applications. Finally, a preliminary validation of the proposed numerical analysis has been carried out through experimental data obtained using polymeric coated FBGs sensors revealing a good agreement and prediction capability. PMID:21996827

  6. Photonic hydrophones based on coated fiber Bragg gratings

    International Nuclear Information System (INIS)

    The development of underwater acoustic sensors with performances competitive with conventional piezoelectric hydrophones would overcome intrinsic limitations related to the piezoceramic technology. Optical fiber technology represents a valid platform to implement acoustic sensors for underwater scenarios. Here we report on recent numerical and experimental results obtained with photonic hydrophones based on fiber-Bragg-grating (FBG) with ring shaped coatings. Our numerical results fully characterize the opto-acoustic response of the optical hydrophone, and highlight the key role played by the coating in enhancing significantly its sensitivity by comparison with a standard uncoated configuration. Furthermore, the analysis reveals that the hydrophone sensitivity spectrum exhibits characteristic resonances, which strongly improve the sensitivity with respect to its background level. Our experimental results confirmed the expected resonant behavior of such devices and are in good agreement with the numerical predictions. Optical hydrophones based on coated FBG exhibited an excellent capability to detect acoustic waves in the acoustic frequency range, with extremely high sensitivities. By comparison with bare FBGs, sensitivity enhancements of up to three orders of magnitude were found, demonstrating the effectiveness of polymeric coatings in tailoring the acoustic response of FBG-based hydrophones.

  7. Pipeline corrosion assessment using embedded Fiber Bragg grating sensors

    Science.gov (United States)

    Liang, Xiao; Huang, Ying; Galedari, Sahar Abuali; Azarmi, Fardad

    2015-04-01

    Corrosion is a leading cause of failure in metallic transmission pipelines. It significantly impacts the reliability and safety of metallic pipelines. An accurate assessment of corrosion status of the pipelines would contribute to timely pipeline maintenance and repair and extend the service life of the associated pipelines. To assess pipeline corrosion, various technologies have been investigated and the pipe-to-soil voltage potential measurement was commonly applied. However, remote and real-time corrosion assessment approaches are in urgent needs but yet achieved. Fiber optic sensors, especially, fiber Bragg gating (FBG) sensors, with unique advantages of real-time sensing, compactness, immune to EMI and moisture, capability of quasi-distributed sensing, and long life cycle, will be a perfect candidate for longterm pipeline corrosion assessment. In this study, FBG sensors are embedded inside pipeline external coating for corrosion monitoring of on-shore buried metallic transmission pipelines. Detail sensing principle, sensor calibration and embedment are introduced in this paper together with experimental corrosion evaluation testing ongoing. Upon validation, the developed sensing system could serve the purpose of corrosion monitoring to the numerous metallic pipelines across nation and would possibly reduce the pipeline corrosion induced tragedies.

  8. Composite scarf repair monitoring using fiber Bragg grating sensors

    Science.gov (United States)

    Li, Henry C. H.; Herszberg, Israel; Davis, Claire E.; Stoddart, Paul R.

    2007-04-01

    Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair efficacy. This paper describes an SHM technique for the detection of debonding in composite scarf repairs using fibre optic Bragg grating strain sensors. A typical composite sandwich structure with a scarf repair on one surface is examined in this paper. A finite element study was conducted which showed that the strain in the debonded region changed significantly compared to the undamaged state. A differential strain approach was used to facilitate the detection of debonds, where two sensors were strategically positioned so that their strain differential increased as the damage propagated. With the use of matching gratings, this technique greatly reduced the support equipment requirement by converting the spectral information into an intensity-modulated signal, thus allowing a compact photodetector to be used for sensor interrogation. An experimental investigation was conducted to validate the theoretically predicted results. The experimental measurements agreed well with the numerical findings qualitatively, indicating that the proposed scheme has great potential as a simple and effective monitoring technique for composite scarf repairs.

  9. Multiplexed Volume Bragg Gratings in Narrowand Broad-band Spectral Systems: Analysis and Application

    Science.gov (United States)

    Ingersoll, Gregory B.

    Volume Bragg gratings (VBGs) are important holographic optical elements in many spectral systems. Using multiple volume gratings, whether multiplexed or arranged sequentially, provides advantages to many types of systems in overall efficiency, dispersion performance, flexibility of design, etc. However, the use of multiple gratings---particularly when the gratings are multiplexed in a single holographic optical element (HOE)---is subject to inter-grating coupling effects that ultimately limit system performance. Analyzing these coupling effects requires a more complex mathematical model than the straightforward analysis of a single volume grating. We present a matrix-based algorithm for determining diffraction efficiencies of significant coupled waves in these multiplexed grating holographic optical elements (HOEs). Several carefully constructed experiments with spectrally multiplexed gratings in dichromated gelatin verify our conclusions. Applications of this theory to broad- and narrow-band systems are explored in detailed simulations. Broadband systems include spectrum splitters for diverse-bandgap photovoltaic (PV) cells. Volume Bragg gratings can serve as effective spectrum splitters, but the inherent dispersion of a VBG can be detrimental given a broad-spectrum input. The performance of a holographic spectrum splitter element can be improved by utilizing multiple volume gratings, each operating in a slightly different spectral band. However, care must be taken to avoid inter-grating coupling effects that limit ultimate performance. We explore broadband multi-grating holographic optical elements (HOEs) in sandwiched arrangements where individual single-grating HOEs are placed in series, and in multiplexed arrangements where multiple gratings are recorded in a single HOE. Particle swarm optimization (PSO) is used to tailor these systems to the solar spectrum taking into account both efficiency and dispersion. Both multiplexed and sandwiched two-grating systems

  10. Fiber Optic Fabry-Perot Current Sensor Integrated with Magnetic Fluid Using a Fiber Bragg Grating Demodulation

    OpenAIRE

    Ji Xia; Qi Wang; Xu Liu; Hong Luo

    2015-01-01

    An optical fiber current sensor based on Fabry-Perot interferometer using a fiber Bragg grating demodulation is proposed. Magnetic fluid is used as a sensitive medium in fiber optical Fabry-Perot (F-P) cavity for the optical characteristic of magnetic-controlled refractive index. A Fiber Bragg grating (FBG) is connected after the F-P interferometer which is used to reflect the optical power at the Bragg wavelength of the interference transmission spectrum. The corresponding reflective power o...

  11. Misfit strain of oxygen precipitates in Czochralski silicon studied with energy-dispersive X-ray diffraction

    International Nuclear Information System (INIS)

    Annealed Czochralski Silicon wafers containing SiOx precipitates have been studied by high energy X-ray diffraction in a defocused Laue setup using a laboratory tungsten tube. The energy dispersive evaluation of the diffracted Bragg intensity of the 220 reflection within the framework of the statistical dynamical theory yields the static Debye-Waller factor E of the crystal, which gives access to the strain induced by the SiOx precipitates. The results are correlated with precipitate densities and sizes determined from transmission electron microscopy measurements of equivalent wafers. This allows for the determination of the constrained linear misfit ε between precipitate and crystal lattice. For samples with octahedral precipitates the values ranging from ε = 0.39 (+0.28/−0.12) to ε = 0.48 (+0.34/−0.16) indicate that self-interstitials emitted into the matrix during precipitate growth contribute to the lattice strain. In this case, the expected value calculated from literature values is ε = 0.26 ± 0.05. Further, the precise evaluation of Pendellösung oscillations in the diffracted Bragg intensity of as-grown wafers reveals a thermal Debye-Waller parameter for the 220 reflection B220(293 K) of 0.5582 ± 0.0039 Å2 for a structure factor based on spherically symmetric scattering contributions.

  12. Influence of relativistic electron beam divergence on angular characteristics of PXR and DTR generated in a single-crystal plate in bragg scattering geometry

    International Nuclear Information System (INIS)

    A dynamical theory of coherent X-ray radiation generated in a single-crystal target by the finite divergence beam of relativistic electrons has been developed in the scattering Bragg geometry. Coherent X-ray emission is considered in general case of asymmetric reflection for electron Coulomb field in the form of two emission mechanism contributions: parametric X-ray radiation (PXR) and diffracted transition radiation (DTR). The method of averaging radiation cross section over the angular electrons distribution is used. The influence of electron beam divergence on both spectral and angular characteristics of coherent radiation has been studied. The significant difference of the effects of electron beam divergence in PXR and DTR is shown. The possibilities of practical use of DTR from a single-crystal target for indication of beam divergence of ultrarelativistic electrons are investigated

  13. Application of the entropy maximum method for processing of X-ray diffraction patterns and gamma spectra of amorphous minerals

    International Nuclear Information System (INIS)

    Opportunities of the maximum entropy method (MEM) for processing of X-ray and gamma spectra of amorphous minerals are considered. MEM is the modern method of solving the reverse Rayleigh problem permitting to exclude the effect of the apparatus response function. The X-ray diffraction of quartz and schungite is carried out at the installation DRON-4 in the Bragg geometry. Initial data and processing results including the fine spectral structure (locations and intensities of peaks) are presented. The accuracy of the least square method and MEM is compared for the fine structure of amorphous sulfate-phosphates

  14. Performances of synchrotron X-ray monochromators under heat load. Part 2. Application of the Takagi-Taupin diffraction theory

    CERN Document Server

    Mocella, V; Freund, A K; Hoszowska, J; Zhang, L; Epelboin, Y

    2001-01-01

    The aim of this work is to generate the rocking curves of monochromators exposed to heat load in synchrotron radiation beams with a computer code performing diffraction calculations based on the theory of Takagi and Taupin. The model study starts with the calculation of deformation by finite element analysis and from an accurate characterization of the incident wave and includes the simulation of the wavefront propagation between the first and the second crystal (analyzer) of a double crystal monochromator. A monochromatic plane wave as well as a polychromatic spherical wave approach is described. The theoretical predictions of both methods are compared with experimental data measured in Bragg geometry and critically discussed.

  15. Transformations in neutron powder diffraction

    International Nuclear Information System (INIS)

    The major milestone in neutron powder diffraction occurred thirty years ago with the advent of the Rietveld method of structure refinement. The combination of advances in both instrumentation and computing power allowed moderately complex low-symmetry structures to be analysed by powder methods for the first time. Over the past five years there have been further transformations in neutron powder diffraction again resulting from combined developments in instrumentation and data analysis methods. In this paper we shall focus on high resolution, high intensity time-of-flight neutron powder diffraction and the impact that this technique has had on our understanding of the structural aspects of phase transitions and phase transformations. The essentially constant Δd/d resolution that is intrinsic to a time-of-flight diffractometry implies that peak splittings arising from a structural phase transition are observed with equal resolution at all orders of reflection, thus maximising the information content associated with structural distortions. Additionally, the fixed diffraction geometry permits the use of sophisticated sample environments such as high pressure cells and special atmosphere furnaces without contamination of the sample diffraction pattern. (orig.)

  16. High energy x-ray diffraction/x-ray fluorescence spectroscopy for high-throughput analysis of composition spread thin films

    International Nuclear Information System (INIS)

    High-throughput crystallography is an important tool in materials research, particularly for the rapid assessment of structure-property relationships. We present a technique for simultaneous acquisition of diffraction images and fluorescence spectra on a continuous composition spread thin film using a 60 keV x-ray source. Subsequent noninteractive data processing provides maps of the diffraction profiles, thin film fiber texture, and composition. Even for highly textured films, our diffraction technique provides detection of diffraction from each family of Bragg reflections, which affords direct comparison of the measured profiles with powder patterns of known phases. These techniques are important for high throughput combinatorial studies as they provide structure and composition maps which may be correlated with performance trends within an inorganic library.

  17. X-Ray Powder Diffraction with Guinier - Haegg Focusing Cameras

    International Nuclear Information System (INIS)

    The Guinier - Haegg focusing camera is discussed with reference to its use as an instrument for rapid phase analysis. An actual camera and the alignment procedure employed in its setting up are described. The results obtained with the instrument are compared with those obtained with Debye - Scherrer cameras and powder diffractometers. Exposure times of 15 - 30 minutes with compounds of simple structure are roughly one-sixth of those required for Debye - Scherrer patterns. Coupled with the lower background resulting from the use of a monochromatic X-ray beam, the shorter exposure time gives a ten-fold increase in sensitivity for the detection of minor phases as compared with the Debye - Scherrer camera. Attention is paid to the precautions taken to obtain reliable Bragg angles from Guinier - Haegg film measurements, with particular reference to calibration procedures. The evaluation of unit cell parameters from Guinier - Haegg data is discussed together with the application of tests for the presence of angle-dependent systematic errors. It is concluded that with proper calibration procedures and least squares treatment of the data, accuracies of the order of 0.005% are attainable. A compilation of diffraction data for a number of compounds examined in the Active Central Laboratory at Studsvik is presented to exemplify the scope of this type of powder camera

  18. Variable Depth Bragg Peak Method for Single Event Effects Testing

    Science.gov (United States)

    Buchner, S.; Kanyogoro, N.; Foster, C.; O'Neill, P.

    2011-01-01

    Traditionally, accelerator SEE testing is accomplished by removing the tops of packages so that the IC chips are accessible to heavy ions. However, ICs in some advanced packages cannot be de-lidded so a different approach is used that involves grinding and/or chemically etching away part of the package and the chip from the back side. The parts are then tested from the back side with ions having sufficient range to reach the sensitive volume. More recently, the entire silicon substrate in an SOI/SRAM was removed, making it possible to use low-energy ions with shorter ranges. Where removal of part of the package is not possible, facilities at Michigan State, NASA Space Radiation Laboratory, GANIL (France) and GSI (Germany) offer high-energy heavy ions with long ranges so that the ions can reach the devices' sensitive volumes without much change in the LET. Unfortunately, a run will typically involve only one ion species having a single energy and LET due to the long time it takes to tune a new energy. The Variable Depth Bragg Peak (VDBP) method is similar to the above method in that it involves the use of high-energy heavy ions that are able to pass through the packaging material and reach the device, obviating the need to remove the package. However, the method provides a broad range of LETs from a single ion by inserting degraders in the beam that modify the ion energy and, therefore, the LET. The crux of the method involves establishing a fiduciary point for degrader thickness, i.e., where the Bragg peak is located precisely at the sensitive volume in the device, for which the measured SEU cross-section and the ion LET are both also maxima and can be calculated using a Monte-Carlo program, TRIM. Once the fiduciary point has been established, calibrated high density polyethylene (HDPE) degraders are inserted into or removed from the beam to vary the ion LET at the device in a known manner. After each change of degrader thickness, the SEU cross-section is measured

  19. Determination of interplanar distances starting from diffraction spectra for the Cyber computer of the ININ

    International Nuclear Information System (INIS)

    To identify a compound by means of diffraction it is required to obtain it spectrum or diffractogram that it is not more than a graphic I/Io vs. 2 θ. Since this analysis type is carried out on samples of glasses, it is expected that when impacting the radiation on the sample and to vary the angles θ and 2 θ, and when being completed the Bragg law, constructive interference it exists among all the radiation beams that emerge of the sample and take place the diffraction. In this work the diffractogram is identified by means of a graph equipment (x,t) that directly obtains the graphic I/Io vs. 2 θ and in this it has to be carried out angular measurement of the present peaks and later on with the data 2 θi it was proceeds to compare with the totally identified patterns as the contents in the Powder Diffraction File of the Joint Committee on Powder Diffraction Standards (JCPDS). (Author)

  20. Beam characteristics of polychromatic diffracted neutrons used for prompt gamma activation analysis

    International Nuclear Information System (INIS)

    The neutron beam is fully characterized for the prompt gamma activation analysis facility at Hanaro in the Korea Atomic Energy Research Institute(KAERI). The facility uses thermal neutrons which are diffracted vertically from a horizontal beam port by a set of pyrolytic graphite(PG) crystals positioned at the Bragg angle of 45 .deg.. Neutron spectra, neutron flux and Cd-ratio are determined for the three extraction modes of diffracted beam by means of the theoretical and experimental efforts. To obtain theoretical result, the reflectivity of pyrolytic graphite is calculated in the diffraction model for mosaic crystal and the angular divergence after diffraction by mosaic crystal is estimated from Monte Carlo simulation. The time-of-flight spectrometer and gold activation wire are used for measuring the neutron spectra. Both the calculated and measured spectra have proven that the unique feature of polychromatic beam obtained by PG crystals are useful for PGAA. The thermal neutron flux of 7.9 x 107 n/cm2s and the Cd-ratio of 266 for gold have been achieved at the sample position while the reactor operates at 24MW. The uniformity of beam flux is 12% in the central 1 x 1 cm2 area. Finally, the beam is briefly characterized by the effective velocity and temperature which are determined by measuring the prompt γ-ray spectra for thin and thick boron samples

  1. The Scherrer equation and the dynamical theory of X-ray diffraction.

    Science.gov (United States)

    Muniz, Francisco Tiago Leitão; Miranda, Marcus Aurélio Ribeiro; Morilla Dos Santos, Cássio; Sasaki, José Marcos

    2016-05-01

    The Scherrer equation is a widely used tool to determine the crystallite size of polycrystalline samples. However, it is not clear if one can apply it to large crystallite sizes because its derivation is based on the kinematical theory of X-ray diffraction. For large and perfect crystals, it is more appropriate to use the dynamical theory of X-ray diffraction. Because of the appearance of polycrystalline materials with a high degree of crystalline perfection and large sizes, it is the authors' belief that it is important to establish the crystallite size limit for which the Scherrer equation can be applied. In this work, the diffraction peak profiles are calculated using the dynamical theory of X-ray diffraction for several Bragg reflections and crystallite sizes for Si, LaB6 and CeO2. The full width at half-maximum is then extracted and the crystallite size is computed using the Scherrer equation. It is shown that for crystals with linear absorption coefficients below 2117.3 cm(-1) the Scherrer equation is valid for crystallites with sizes up to 600 nm. It is also shown that as the size increases only the peaks at higher 2θ angles give good results, and if one uses peaks with 2θ > 60° the limit for use of the Scherrer equation would go up to 1 µm. PMID:27126115

  2. Indexing amyloid peptide diffraction from serial femtosecond crystallography: new algorithms for sparse patterns

    Energy Technology Data Exchange (ETDEWEB)

    Brewster, Aaron S. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Sawaya, Michael R. [University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); Rodriguez, Jose [University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); Hattne, Johan; Echols, Nathaniel [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); McFarlane, Heather T. [University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); Cascio, Duilio [University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); Adams, Paul D. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); University of California, Berkeley, CA 94720 (United States); Eisenberg, David S. [University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); University of California, Los Angeles, CA 90095-1570 (United States); Sauter, Nicholas K., E-mail: nksauter@lbl.gov [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2015-02-01

    Special methods are required to interpret sparse diffraction patterns collected from peptide crystals at X-ray free-electron lasers. Bragg spots can be indexed from composite-image powder rings, with crystal orientations then deduced from a very limited number of spot positions. Still diffraction patterns from peptide nanocrystals with small unit cells are challenging to index using conventional methods owing to the limited number of spots and the lack of crystal orientation information for individual images. New indexing algorithms have been developed as part of the Computational Crystallography Toolbox (cctbx) to overcome these challenges. Accurate unit-cell information derived from an aggregate data set from thousands of diffraction patterns can be used to determine a crystal orientation matrix for individual images with as few as five reflections. These algorithms are potentially applicable not only to amyloid peptides but also to any set of diffraction patterns with sparse properties, such as low-resolution virus structures or high-throughput screening of still images captured by raster-scanning at synchrotron sources. As a proof of concept for this technique, successful integration of X-ray free-electron laser (XFEL) data to 2.5 Å resolution for the amyloid segment GNNQQNY from the Sup35 yeast prion is presented.

  3. Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic Temperature

    Science.gov (United States)

    Wu, Meng-Chou; Prosser, William H.; Rogowski, Robert S.; DeHaven, Stanton L.

    2003-01-01

    By using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.

  4. Effects of Coating and Diametric Load on Fiber Bragg Gratings as Cryogenic Temperature Sensors

    Science.gov (United States)

    Wu, meng-Chou; Pater, Ruth H.; DeHaven, Stanton L.

    2008-01-01

    Cryogenic temperature sensing was demonstrated using pressurized fiber Bragg gratings (PFBGs) with polymer coating of various thicknesses. The PFBG was obtained by applying a small diametric load to a regular fiber Bragg grating (FBG). The Bragg wavelengths of FBGs and PFBG were measured at temperatures from 295 K to 4.2 K. The temperature sensitivities of the FBGs were increased by the polymer coating. A physical model was developed to relate the Bragg wavelength shifts to the thermal expansion coefficients, Young's moduli, and thicknesses of the coating polymers. When a diametric load of no more than 15 N was applied to a FBG, a pressure-induced transition occurred at 200 K during the cooling cycle. The pressure induced transition yielded PFBG temperature sensitivities three times greater than conventional FBGs for temperatures ranging from 80 to 200 K, and ten times greater than conventional fibers for temperatures below 80 K. PFBGs were found to produce an increased Bragg wavelength shift of 2.2 nm compared to conventional FBGs over the temperature range of 4.2 to 300 K. This effect was independent of coating thickness and attributed to the change of the fiber thermo-optic coefficient.

  5. Adaptive Integrated Optical Bragg Grating in Semiconductor Waveguide Suitable for Optical Signal Processing

    Science.gov (United States)

    Moniem, T. A.

    2016-05-01

    This article presents a methodology for an integrated Bragg grating using an alloy of GaAs, AlGaAs, and InGaAs with a controllable refractive index to obtain an adaptive Bragg grating suitable for many applications on optical processing and adaptive control systems, such as limitation and filtering. The refractive index of a Bragg grating is controlled by using an external electric field for controlling periodic modulation of the refractive index of the active waveguide region. The designed Bragg grating has refractive indices programmed by using that external electric field. This article presents two approaches for designing the controllable refractive indices active region of a Bragg grating. The first approach is based on the modification of a planar micro-strip structure of the iGaAs traveling wave as the active region, and the second is based on the modification of self-assembled InAs/GaAs quantum dots of an alloy from GaAs and InGaAs with a GaP traveling wave. The overall design and results are discussed through numerical simulation by using the finite-difference time-domain, plane wave expansion, and opto-wave simulation methods to confirm its operation and feasibility.

  6. The influence of adhesive on fiber Bragg grating strain sensor

    Science.gov (United States)

    Chen, Jixuan; Gong, Huaping; Jin, Shangzhong; Li, Shuhua

    2009-08-01

    A fiber Bragg grating (FBG) sensor was fixed on the uniform strength beam with three adhesives, which were modified acrylate, glass glue and epoxy resin. The influence of adhesive on FBG strain sensor was investigated. The strain of FBG sensor was varied by loading weight to the uniform strength beam. The wavelength shift of the FBG sensor fixed by the three kinds of adhesive were measured with different weight at the temperatures 0°C, 10°C, 20°C, 30°C, 40°C. The linearity, sensitivity and their stability at different temperature of FBG sensor which fixed by every kind of adhesives were analyzed. The results show that, the FBG sensor fixed by the modified acrylate has a high linearity, and the linear correlation coefficient is 0.9996. It also has a high sensitivity which is 0.251nm/kg. The linearity and the sensitivity of the FBG sensor have a high stability at different temperatures. The FBG sensor fixed by the glass glue also has a high linearity, and the linear correlation coefficient is 0.9986, but it has a low sensitivity which is only 0.041nm/kg. The linearity and the sensitivity of the FBG sensor fixed by the glass glue have a high stability at different temperatures. When the FBG sensor is fixed by epoxy resin, the sensitivity and linearity is affected significantly by the temperature. When the temperature changes from 0°C to 40°C, the sensitivity decreases from 0.302nm/kg to 0.058nm/kg, and the linear correlation coefficient decreases from 0.9999 to 0.9961.

  7. Aberrations of diffracted wave fields.

    Science.gov (United States)

    Harvey, J E; Shack, R V

    1978-09-15

    This paper is an attempt to provide new insight into the behavior of near-field scalar diffraction phenomena by showing that the Rayleigh-Sommerfeld diffraction integral is equivalent to the Fourier transform integral of a generalized pupil function which includes a term that represents phase errors in the aperture. This term can be interpreted as describing a conventional wavefront aberration function. The resulting aberration coefficients are calculated and expressed in terms of the aperture diameter, observation distance, and appropriate field parameter for several different geometrical configurations of incident beam and observation space. These aberrations, which are inherently associated with the diffraction process, are precisely the effects ignored when making the usual Fresnel and Fraunhofer approximations. PMID:20203910

  8. Detonation diffraction through different geometries

    Science.gov (United States)

    Sorin, Rémy; Zitoun, Ratiba; Khasainov, Boris; Desbordes, Daniel

    2009-04-01

    We performed the study of the diffraction of a self-sustained detonation from a cylindrical tube (of inner diameter d) through different geometric configurations in order to characterise the transmission processes and to quantify the transmission criteria to the reception chamber. For the diffraction from a tube to the open space the transmission criteria is expressed by d c = k c · λ (with λ the detonation cell size and k c depending on the mixture and on the operture configuration, classically 13 for alkane mixtures with oxygen). The studied geometries are: (a) a sharp increase of diameter ( D/ d > 1) with and without a central obstacle in the diffracting section, (b) a conical divergent with a central obstacle in the diffracting section and (c) an inversed intermediate one end closed tube insuring a double reflection before a final diffraction between the initiator tube and the reception chamber. The results for case A show that the reinitiation process depends on the ratio d/ λ. For ratios below k c the re-ignition takes place at the receptor tube wall and at a fixed distance from the step, i.e. closely after the diffracted shock reflection shows a Mach stem configuration. For ratios below a limit ratio k lim (which depends on D/ d) the re-ignition distance increases with the decrease of d/λ. For both case A and B the introduction of a central obstacle (of blockage ratio BR = 0.5) at the exit of the initiator tube decreases the critical transmission ratio k c by 50%. The results in configuration C show that the re-ignition process depends both on d/ λ and the geometric conditions. Optimal configuration is found that provides the transmission through the two successive reflections (from d = 26 mm to D ch = 200 mm) at as small d/ λ as 2.2 whatever the intermediate diameter D is. This configuration provides a significant improvement in the detonation transmission conditions.

  9. The use of net analyte signal orthogonalization in the separation of multi-component diffraction patterns obtained from X-ray powder diffraction of intact compacts.

    Science.gov (United States)

    Moore, Michael D; Cogdill, Robert P; Short, Steven M; Hair, Colleen R; Wildfong, Peter L D

    2008-06-01

    X-ray powder diffraction (XRPD) analysis of intact multi-component consolidated mixtures has significant potential owing to the ability to non-destructively quantify and discriminate between solid phases in composite bodies with minimal sample preparation. There are, however, limitations to the quantitative power using traditional univariate methods on diffraction data containing features from all components in the system. The ability to separate multi-component diffraction data into patterns representing single constituents allows both composition as well as physical phenomena associated with the individual components of complex systems to be probed. Intact, four-component compacts, consisting of two crystalline and two amorphous constituents were analyzed using XRPD configured in both traditional Bragg-Brentano reflectance geometry and parallel-beam transmission geometry. Two empirical, model-based methods consisting of a multiple step net analyte signal (NAS) orthogonalization are presented as ways to separate multi-component XRPD patterns into single constituent patterns. Multivariate figures of merit (FOM) were calculated for each of the isolated constituents to compare method-specific parameters such as sensitivity, selectivity, and signal-to-noise, enabling quantitative comparisons between the two modes of XRPD analysis. PMID:18294800

  10. Acoustooptic Diffraction in Borate Crystals

    CERN Document Server

    Martynyuk-Lototska, I; Krupych, O; Adamiv, V; Smirnov, Ye; Vlokh, R

    2004-01-01

    The efficiency of acoustooptic (AO) diffraction in a-BaB2O4 and Li2B4O7 crystals is studied experimentally. The crystals are shown to be quite good AO materials. The efficiency of AO diffraction in a-BaB2O4 reaches h=30% at the electric signal power of P=0.7W for the transverse acoustic wave and 15% at the power of P=0.56W for the longitudinal wave. The same parameter for Li2B4O7 reaches h=21% at P=0,81W for the longitudinal acoustic wave.

  11. Diffractive dissociation and new quarks

    International Nuclear Information System (INIS)

    We argue that the chiral limit of QCD can be identified with the strong (diffractive dissociation) coupling limit of reggeon field theory. Critical Pomeron scaling at high energy must then be directly related to an infra-red fixed-point of massless QCD and so requires a large number of flavors. This gives a direct argument that the emergence of diffraction-peak scaling, KNO scaling etc. at anti p-p colliders are evidence of a substantial quark structure still to be discovered

  12. Numerical investigation of slow solitons in Bragg gratings with a hyperbolic tangent apodization

    Institute of Scientific and Technical Information of China (English)

    Wang Kui-Ru; Cheng Jie-Lin; Sang Xin-Zhu; Chen Gong

    2011-01-01

    This paper numerically and analytically investigates the formation and propagation motion of optical soliton in the Bragg grating. We choose the fibre Bragg grating with hyperbolic tangent apodization in the middle section in order to obtain slower solitons. Optical fibre soliton but not Bragg grating soliton is used as input pulse in the discussion, which is much more approximate to the light source for the practical purpose. We discuss in detail the effects of the soliton's velocity with some parameters in the process of transmission. The results show that by choosing special parameters, one can make the soliton slow-down with a little distortion and energy decay and obtain tunable time-delay on a small scale.

  13. Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

    Science.gov (United States)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

    A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

  14. Design of a Label-Free, Distributed Bragg Grating Resonator Based Dielectric Waveguide Biosensor

    Directory of Open Access Journals (Sweden)

    Florian Kehl

    2015-01-01

    Full Text Available In this work, we present a resonant, dielectric waveguide device based on distributed Bragg gratings for label-free biosensing applications. The refractive index sensitive optical transducer aims at improving the performance of planar waveguide grating sensor systems with limited Q-factor and dynamic range by combing the advantages of resonant cavities, such as a multitude of resonance peaks with high finesse, with the manageable complexity of waveguide grating couplers. The general sensor concept is introduced and supported by theoretical considerations as well as numerical simulations based on Coupled Mode Theory. In contrast to a single Bragg grating reflector, the presented Fabry-Pérot type distributed Bragg resonator exhibits an extended measurement range as well as relaxed fabrication tolerances. The resulting, relatively simple sensor structure can be fabricated with standard lithographic means and is independent of expensive light-sources and/or detectors, making an affordable but sensitive device, potentially suitable for point-of-care applications.

  15. Bragg band gaps tunability in an homogeneous piezoelectric rod with periodic electrical boundary conditions

    Science.gov (United States)

    Degraeve, S.; Granger, C.; Dubus, B.; Vasseur, J. O.; Pham Thi, M.; Hladky-Hennion, A.-C.

    2014-05-01

    An homogeneous piezoelectric rod is shown to exhibit Bragg band gaps when an electrical boundary condition is applied periodically with the help of metallic electrodes. An analytical model is developed which formulation depends on the applied electric boundary condition and reveals that Bragg band gaps occurring in this very peculiar phononic crystal are related to the electric charge located on the electrodes. Moreover, via an accurate boundary condition (electrodes connected in short circuit, in open circuit, or through an external capacitance), full tunability of the Bragg band gaps can be achieved. Measurements of ultrasonic transmission present an overall excellent agreement with the theoretical results. This phononic crystal can be easily manufactured and presents many potential applications as frequency filters especially for radio frequency telecommunications.

  16. A novel dual-wavelength fiber Bragg grating and its application in fiber ring laser

    Institute of Scientific and Technical Information of China (English)

    姜莉; 张东生; 董兴法; 开桂云; 董孝义

    2004-01-01

    A novel method for fabricating dual-wavelength fiber Bragg gratings (FBGs) by using one phase mask is developed. The method is based on a double-exposure technique. Our technique lends itself to writing gratings with controllable reflectivity and separation of two Bragg wavelengths. A grating with two equal transmission peaks of 20.25 dB is obtained by this method and the separation of the two Bragg wavelengths is about 0.8 nm. With the grating, we demonstrate a dual-wavelength erbium-doped fiber ring laser whose interval of the two peaks is 0.8 nm. The laser's peak powers can get 3.1 mW above and have a good stability.

  17. Characteristics of Bragg Gratings in All-Solid Photonic Bandgap Fiber

    Institute of Scientific and Technical Information of China (English)

    Bai-Ou Guan; Zhi Wang; Yang Zhang; Da Chen

    2008-01-01

    We report on fiber Bragg gratings in all-solid photonie bandgap fiber that was composed of a triangular array of high-index Ge-doped rods in pure silica background with fluorine-doped index-depressed layer surrounding the Ge-doped rod. Fiber Bragg gratings were photowritten with 193 nm ArF excimer laser and characterized for their response to strain, temperature, bending, and torsion. These gratings couple light from the forward core mode to not only backward core mode but also backward rod modes. This results in multiple resonance peaks in the reflection spectrum. All resonance wavelengths exhibited the same temperature and strain response with coefficient similar to that of Bragg gratings in standard single-mode fiber. The strength of the resonance peaks corresponding to the backward rod modes showed high sensitivity to bending and torsion.

  18. A Bragg beam splitter for hard x-ray free-electron lasers.

    Science.gov (United States)

    Osaka, Taito; Yabashi, Makina; Sano, Yasuhisa; Tono, Kensuke; Inubushi, Yuichi; Sato, Takahiro; Matsuyama, Satoshi; Ishikawa, Tetsuya; Yamauchi, Kazuto

    2013-02-11

    We report a Bragg beam splitter developed for utilization of hard x-ray free-electron lasers. The splitter is based on an ultrathin silicon crystal operating in the symmetric Bragg geometry to provide high reflectivity and transmissivity simultaneously. We fabricated frame-shaped Si(511) and (110) crystals with thicknesses below 10 μm by a reactive dry etching method using atmospheric-pressure plasma. The thickness variation over an illuminated area is less than 300 nm peak-to-valley. High crystalline perfection was verified by topographic and diffractometric measurements. The crystal thickness was evaluated from the period of the Pendellösung beats measured with a highly monochromatic and collimated x-ray probe. The crystals provide two replica pulses with uniform wavefront [(<1/50)λ] and low spatial intensity variation (<5%). These Bragg beam splitters will play an important role in innovating XFEL applications. PMID:23481739

  19. Bragg prism monochromator and analyser for super ultra-small angle neutron scattering studies

    Indian Academy of Sciences (India)

    Apoorva G Wagh; Sohrab Abbas; Markus Strobl; Wolfgang Treimer

    2008-11-01

    We have designed, fabricated and operated a novel Bragg prism monochromator–analyser combination. With a judicious choice of the Bragg reflection, its asymmetry and the apex angle of the silicon single crystal prism, the monochromator has produced a neutron beam with sub-arcsec collimation. A Bragg prism analyser with the opposite asymmetry has been tailored to accept a still sharper angular profile. With this optimized monochromator–analyser pair, we have attained the narrowest and sharpest neutron angular profile to date. At this facility, we have recorded the first SUSANS spectra spanning wave vector transfers ∼ 10−6 Å-1 to characterize samples containing agglomerates up to tens of micrometres in size.

  20. Development of tilted fibre Bragg gratings using highly coherent 255 nm radiation

    Indian Academy of Sciences (India)

    O Prakash; J Kumar; R Mahakud; U Kumbhkar; S V Nakhe; S K Dixit

    2014-02-01

    This paper reports the study on development of tilted fibre Bragg gratings using highly coherent 255 nm radiation, obtained from the second harmonic generation (SHG) of copper vapour laser (CVL). The transmission and reflection spectra of the tilted fibre Bragg gratings (TFBG) were studied for the tilt angles of 0° (normal FBG), 1°, 3° and 4° between the fibre axis and the interference fringe plane. It was observed that as the angle of fibre axis and phase mask increased, the main Bragg peak shifted towards the higher wavelength and transmission dip decreased. The transmission dip of the cladding mode first increased and then decreased after reaching a maximum with the increase in the tilt angle.