Showing papers on "Synchrotron radiation published in 1995"
TL;DR: In this paper, a straightforward experimental setup for phase contrast imaging is proposed and used to record holographic images from organic samples of 10-100 pm at energy lo-50 keV with the contrast up to 50%-100%.
Abstract: Coherent properties of the x-ray beam delivered at the ESRF allow the observation of very weak perturbations of the wave front, resulting in the phase contrast. A straightforward experimental setup for phase contrast imaging is proposed and used to record holographic images from organic samples of 10-100 pm at energy lo-50 keV with the contrast up to 50%-100%. The theory of phase contrast imaging is considered and some theoretical estimations are made to reveal the performance of the proposed technique in terms of resolution, sensitivity, geometrical requirements, and ehergy range applicability. It is found that for carbon-based fibers a detectable size with 2% contrast is 0.1 ,um for 10 keV and - 1 pm for 100 keV, It is demonstrated that the fine interference structure of the image is very sensitive to the shape, density variation, and internal structure of the sample. Some prospects for the practical use and future development of the new coherent techniques such as phase contrast microscopy, microtomography, holography, and interferometry at high energies are also discussed. 0 I995 American Institute of Physics.
1,413 citations
TL;DR: The phonon density of states was measured by observing the nuclear resonant fluorescence of {sup 57}Fe versus the energy of incident x rays from a synchrotron radiation beam.
Abstract: The phonon density of states was measured by observing the nuclear resonant fluorescence of ${}^{57}$Fe versus the energy of incident x rays from a synchrotron radiation beam. An energy resolution of 6 meV was achieved by use of high-resolution crystal optics for the incident beam. Extremely low background levels were obtained via time discrimination of the nuclear fluorescent radiation.
373 citations
TL;DR: The phonon energy spectrum of a polycrystalline o.
Abstract: The phonon energy spectrum of a polycrystalline o. -Fe foil was observed via nuclear resonant scattering of synchrotron radiation for the first time. The measured spectrum is in good agreement with earlier neutron inelastic scattering data. One of the advantageous features of this method is that excitation of only a specific element is possible. Our results show that this method is applicable to the study of lattice dynamics and open a new field of nuclear resonant scattering spectroscopy.
346 citations
TL;DR: In this article, the first numerical simulations of the parsec-scale synchrotron emission from hydrodynamic relativistic jets were presented, showing the existence of stationary quasi-periodic knots associated with internal oblique shocks.
Abstract: We present the first numerical simulations of the parsec-scale synchrotron emission from hydrodynamic relativistic jets. The jet structure is calculated using a relativistic time-dependent hydrodynamic code based on an approximate Riemann solver. The radio emission from the model jets is calculated by integrating the transfer equations of the synchrotron radiation, accounting for the appropriate opacity and relativistic effects, such as Doppler boosting and relativistic aberration. In order to study the influence of the external medium, we present two hydrodynamical jet simulations: one with a constant external pressure, and a second model with a decreasing external pressure. Multifrequency radio images of the synchrotron emission from these flows are presented, showing the existence of stationary quasi-periodic knots associated with internal oblique shocks. Whereas for the model with constant external pressure the knots remain almost constant in intensity and even in spacing, the model with decreasing external pressure shows stationary knots of progressively lower intensity and wider spacing as a function of distance down the jet.
133 citations
TL;DR: In this paper, the possibility of a coupled-bunch instability caused by beam-photoelectron interactions is discussed, and a simulation has shown that such an instability may be serious for positron storage rings with high current and multibunches.
Abstract: The possibility of a coupled-bunch instability caused by beam-photoelectron interactions is discussed. Very many photoelectrons are produced in a storage ring when photons emitted by synchrotron radiation hit the beam chamber. Since electrons are not trapped by a positron beam in ion-trapping theory, they are not considered to affect the beam. However, it is possible that an enormous number of photoelectrons would have sufficient density to cause a coupled-bunch instability. A simulation has shown that such an instability may be serious for positron storage rings with high current and multibunches.
130 citations
TL;DR: In this article, the authors extended the analysis of nonlinear Thomson scattering of intense laser from relativistic electron beams to describe off-axis scattering geometries and derived analytic expressions for the intensity distribution of the scattered radiation.
Abstract: Analysis of nonlinear Thomson scattering of intense lasers from relativistic electron beams is extended to describe off-axis scattering geometries. Electron trajectories are calculated for the case of a plane electromagnetic wave of arbitrary intensity, either circularly or linearly polarized, interacting with a relativistic electron beam at an arbitrary interaction angle. The trajectories are used to derive analytic expressions for the intensity distribution of the scattered radiation. These expressions are valid in the nonlinear regime (arbitrary laser intensity) and include the generation of harmonics. The effect of interaction angle on the intensity distribution is discussed and spectra are plotted numerically for the specific cases of head-on and transverse scattering. The dependence of x-ray frequency, pulse duration, and photon flux on interaction geometry are also examined. Applications to the laser synchrotron source are discussed. There are potential advantages of both head-on and transverse interaction geometries: head-on scattering results in the generation of higher frequencies and higher photon fluxes; normal incidence scattering can result in ultrashort x-ray pulses.
130 citations
TL;DR: X-ray synchrotron experiments with in situ laser heating of iron in a diamond-anvil cell show that the high-pressure ε phase, a hexagonal close-packed structure, transforms to another phase (possibly a polytype double-layer hcp) at a pressure of about 38 gigapascals and at temperatures between 1200 and 1500 kelvin.
Abstract: X-ray synchrotron experiments with in situ laser heating of iron in a diamond-anvil cell show that the high-pressure epsilon phase, a hexagonal close-packed (hcp) structure, transforms to another phase (possibly a polytype double-layer hcp) at a pressure of about 38 gigapascals and at temperatures between 1200 and 1500 kelvin. This information has implications for the phase relations of iron in Earth's core.
126 citations
TL;DR: In this paper, a Fourier transform infrared micro-spectrometer was interfaced with the National Synchrotron Light Source (NSLSTM) to provide high-quality IR spectra for probe diameters at the diffraction limit.
Abstract: When a Fourier transform infrared microspectrometer was first interfaced with the National Synchrotron Light Source in September 1993, there was an instant realization that the performance at the diffraction limit had increased 40–100 times. The synchrotron source transformed the IR microspectrometer into a true IR microprobe, providing high‐quality IR spectra for probe diameters at the diffraction limit. The combination of IR microspectroscopy and synchrotron radiation provides a powerful new tool for molecular spectroscopy. The ability to perform IR microspectroscopy with synchrotron radiation is still under development at Brookhaven National Laboratory, but several initial studies have been completed that demonstrate the broad‐ranging applications of this technology and its potential for materials characterization.
112 citations
TL;DR: A differential scanning calorimeter with a temperature range of 77 to 873 K was developed for use in combination with either time-resolved X-ray scattering or high-resolution energy-dispersive powder diffraction studies using synchrotron radiation as mentioned in this paper.
Abstract: A differential scanning calorimeter with a temperature range of 77 to 873 K has been developed for use in combination with either time-resolved X-ray scattering or high-resolution energy-dispersive powder diffraction studies using synchrotron radiation. The first results of successful experiments are briefly described.
107 citations
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01 Dec 1995
TL;DR: The basic characteristics of radiation scattering on individual particles equations of propagation of radiation polarization of radiation emitted by stars and stellar envelopes radiation of plasma in a strong magnetic field propagation.
Abstract: The basic characteristics of radiation scattering on individual particles equations of propagation of radiation polarization of radiation emitted by stars and stellar envelopes radiation of plasma in a strong magnetic field propagation and polarization of radiation in gaseous-dust cosmic media.
TL;DR: In this article, an analytic model of magnetic Compton scattering near the polar cap of isolated pulsar magnetospheres was proposed to model the pair cascade induced by relativistic electrons scattering photons through cyclotron resonance.
Abstract: Electrons accelerated to relativistic energies in pulsar magnetospheres will Compton scatter surface thermal emission and nonthermal optical, UV, and soft X-ray emission to gamma-ray energies, thereby initiating a pair cascade through synchrotron radiation and magnetic pair production. This process is proposed as the origin of the high-energy radiation that has been detected from six isolated pulsars. We construct an analytic model of magnetic Compton scattering near the polar cap of isolated pulsar magnetospheres and present approximate analytic derivations for scattered spectra, electron energy-loss rates, and photon luminosities. A Monte Carlo simulation is used to model the pair cascade induced by relativistic electrons scattering photons through the cyclotron resonance. For simplicity, the primary electrons are assumed to be monoenergetic and the nonresonant emission is omitted. Assuming that the angle phi(sub B) between the magnetic and spin axes is approximately equal to the polar-cap angle theta(sub pc), this model can produce both double-peaked and broad single-peaked pulse profiles and account for the trend of harder gamma-ray spectra observed from older pulsars.
TL;DR: In this article, the first time resolved X-ray photoelectron spectroscopy (XPS) experiments were performed at the Trieste SuperESCA beam line, where high quality high resolution (better than 0.3 eV) core level photoemission data from adsorbate species on metal samples can be acquired in a few seconds.
TL;DR: In this article, the quality of micromachining Teflon was found to be critically dependent on photon flux of the synchrotron radiation and the mass distribution of gaseous species formed upon this process suggested that photochemical processes rather than pyrolytic processes may still dominate.
Abstract: Micromachining Teflon was achieved by direct exposure to synchrotron radiation and the microstructures made had the smallest surface detail down to 20 μm with structural height of more than 200 μm, that is, aspect ratio on the order of 10. The quality of micromachining Teflon by this process was found to be critically dependent on photon flux of the synchrotron radiation. Analysis of the mass distribution of gaseous species formed upon this process suggested that photochemical processes rather than pyrolytic processes may still dominate.
TL;DR: In this paper, the energy dependences of nuclear forward scattering and nuclear 4π scattering of 14.4 keV synchrotron radiation were studied with an energy resolution of 6 meV.
Abstract: The energy dependences of nuclear forward scattering and nuclear 4π scattering of 14.4 keV synchrotron radiation were studied with an energy resolution of 6 meV. Nuclear 4π scattering resulted from internal conversion and therefore represents the energy dependence of resonant nuclear absorption. In the case of the [57Fe(bpp)2][BF4]2 sample the energy dependence of nuclear 4π scattering revealed a 13 meV inelastic broadening of the absorption line. This indicates an excitation of lattice motions in the nuclear absorption process. The technique allows the direct measurement of the energy distribution of nuclear recoil.
TL;DR: In this article, a general Monte Carlo code for the simulation of X-ray fluorescence spectrometers is extended to predict the spectral response of instruments employing polarized exciting radiation, which is used for quantitative analysis of intermediate and massive samples.
TL;DR: Early Mossbauer treatments and moment sum rules are extended to treat inelastic excitations measured in synchrotron experiments, with emphasis on the unique new conditions absent in neutron scattering and arising in resonance scattering.
Abstract: The availability of tunable synchrotron radiation sources with millivolt resolution has opened prospects for exploring dynamics of complex systems with Moessbauer spectroscopy. Early Moessbauer treatments and moment sum rules are extended to treat inelastic excitations measured in synchrotron experiments, with emphasis on the unique conditions absent in neutron scattering and arising in resonance scattering: prompt absorption, delayed emission, recoilfree transitions, and coherent forward scattering. The first moment sum rule normalizes the inelastic spectrum. Sum rules obtained for higher moments include the third moment proportional to the second derivative of the potential acting on the Moessbauer nucleus and independent of temperature in the harmonic approximation. Interesting information may be obtained on the behavior of the potential acting on this nucleus in samples not easily investigated with neutron scattering, e.g., small samples, thin films, time-dependent structures, and amorphous-metallic high pressure phases.
TL;DR: In this paper, the current status of photoelectron diffraction studies of surface structures is briefly reviewed, and several recent developments and proposals for future areas of application are then discussed, including the application of full-solid-angle diffraction data, together with simultaneous characterization by low energy electron diffraction and scanning tunnelling microscopy, to epitaxial growth.
TL;DR: The Super-ESCA beamline was designed for high resolution core level spectroscopy of adsorbates on single crystal surfaces using soft x-ray synchrotron radiation as discussed by the authors.
Abstract: The Super‐ESCA beamline has been designed for high resolution core level spectroscopy of adsorbates on single crystal surfaces using soft x‐ray synchrotron radiation. It receives the light from an 81 period undulator with 5.6 cm period and 4.5 m length in the storage ring ELETTRA. The tunability of this insertion device, at a storage ring electron energy of 2.0 GeV and the connected modified SX700 monochromator allows the performance of experiments at this beamline in the photon energy range 100–2000 eV. This beamline is now operational and first absorption spectra are presented which show available resolving powers varying from 8000 to 3000 for photon energies between 240 and 850 eV.
01 Jan 1995
TL;DR: In this paper, the authors present a survey of accelerator-based techniques in materials technology, including surface analysis techniques and laser beams in the context of Synchrotron Radiation and Accelerator-Based Techniques in Materials Technology.
Abstract: Preface. I: Fundamentals. II: Surface Analysis Techniques. III: Laser Beams in Materials Technology. IV: Accelerator-Based Techniques in Materials Technology. V: Materials Modification. VI: Synchrotron Radiation. Index.
TL;DR: In this article, a zone-plate microscope at beamline 6.1 of the ALS was used for high-resolution zone-plating at synchrotron radii.
Abstract: (1995). New high‐resolution zone‐plate microscope at beamline 6.1 of the ALS. Synchrotron Radiation News: Vol. 8, No. 3, pp. 29-33.
TL;DR: In this article, the results of an investigation of PbWO4 luminescence properties obtained by time-resolved techniques under VUV, X-ray synchrotron radiation and γ-radiation excitation are presented.
TL;DR: In this paper, a general Monte Carlo (MC) code was adapted to model the behavior of synchrotron radiation X-ray fluorescence (SR-XRF) spectrometers using polarized, polychromatic radiation as means of excitation.
02 May 1995-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, synchrotron radiation is applied to pattern several hundred micrometer thick resist layers, which are characterized by straight walls and a typical surface roughness in between 30 to 50 nm.
Abstract: In deep X-ray lithography, synchrotron radiation is applied to pattern several hundred micrometer thick resist layers. This technique has been used to obtain micro structures with an aspect ratio up to 100. The structures are characterized by straight walls and a typical surface roughness in between 30 to 50 nm, which are a consequence of the small divergence of synchrotron radiation and the high selectivity of the resist-developer system. The precision of the microstructures are affected by photoelectrons which are generated in the resist and by diffraction of the synchrotron radiation at the absorber structures. Secondary radiation which is generated during the irradiation in the X-ray mask and the substrat, as well as the heat load, which arises from the absorbed X-rays in the mask and the resist determines the quality of the micro structures.
TL;DR: A review of the performance of diamond single crystals as a high heat load optical component for synchrotron x rays is given in this paper, where it has been proven experimentally that the bandpass and the angular divergence of the monochromatic beam provided by a relatively thin diamond crystal used in an undulator beam are not degraded by thermal effects for a total power up to 280 W (8.7 W absorbed) at a heat flux up to 3.5 kW/mm2 (109 W/mm 2 absorbed).
Abstract: A review of the performance of diamond single crystals as a high heat load optical component for synchrotron x rays is given. It has been proven experimentally that the bandpass and the angular divergence of the monochromatic beam provided by a relatively thin diamond crystal used in an undulator beam are not degraded by thermal effects for a total power up to 280 W (8.7 W absorbed) at a heat flux up to 3.5 kW/mm2 (109 W/mm2 absorbed). These high heat load tests and model calculations have shown that edge-cooled diamond crystals at room temperature provide an easy and widely satisfactory solution to the heat load problems generated by undulator beams that are currently foreseen at the third-generation storage rings of the European Synchrotron Radiation Facility, the Advanced Photon Source, and the SPring-8 facilities. For this cooling geometry, diamond single crystals offer the additional advantage that beam multiplexing can be used. Currently available synthetic diamond crystals are sufficiently big for undulator beams and their crystalline perfection is adequate. Most of the crystals actually in use were prepared with their big surfaces (about 30 mm2 in size) oriented parallel to the (100) netplanes, but more recently bigger samples whose surfaces are parallel to the (111) lattice planes were obtained. Thus, diamond single crystals are superior to all other monochromator materials for undulators and for cases where a loss of a factor of 2 in flux combined with a similar gain in resolution (as compared to silicon) are compatible with the experiments.
TL;DR: A general theory of the time dependence of nuclear resonant forward scattering of synchrotron radiation in the presence of diffusive motion of nuclei is further developed and the scattering problem is solved for the two characteristic cases of Diffusive motion.
Abstract: A general theory of the time dependence of nuclear resonant forward scattering of synchrotron radiation in the presence of diffusive motion of nuclei is further developed. The scattering problem is solved for the two characteristic cases of diffusive motion. The first one is the continuous isotropic localized diffusion of a particle within a cage formed by a drift potential. The second case is the jump anisotropic unlimited diffusion of nuclei on a crystalline lattice. In both cases the frequency dependence of nuclear susceptibility has a complicated shape described by a superposition of Lorentzian functions having different weights and widths. Correspondingly several stages appear in the time evolution of the nuclear forward scattering which are characterized by different decay rates. In the thick absorber case the target can exhibit successively different partial thicknesses in the time evolution of forward scattering.
TL;DR: In this article, a silicon (840) channel cut crystal with a large asymmetry was used to linearly polarize synchrotron radiation generated by an undulator source at the 14.413 keV nuclear resonance of 57Fe.
Abstract: A silicon (840) channel‐cut crystal with a large asymmetry is used to linearly polarize synchrotron radiation generated by an undulator source at the 14.413 keV nuclear resonance of 57Fe. The resulting σ‐polarized radiation is then scattered from an 57Fe foil placed in a magnetic field that effects σ→π polarization conversion within the resonant bandwidth. A second crystal of the same type is placed in a crossed position to suppress the nonresonant radiation while transmitting the π‐polarized resonant radiation. A polarization suppression factor of 6×10−7 has been obtained. The suppression of the nonresonant radiation allowed monitoring the decay of the nuclear levels after 1 ns of their excitation.
TL;DR: In this article, the design and operation of a TOF mass spectrometer during single bunch operation of the Photon Factory 2.5 GeV storage ring is described, and the experimental results for H2O/Si(100), DCOOD/Si (100), polymethylmethacrylate and polymethyl acrylate thin films are demonstrated as examples of the capabilities of the apparatus.
Abstract: Photon stimulated ion desorption from small molecules on Si(100) surfaces and from polymer thin films was studied using time‐of‐flight (TOF) mass spectrometric techniques. The design and operation of a TOF mass spectrometer during single bunch operation of the Photon Factory 2.5 GeV storage ring is described. Experimental results for H2O/Si(100), DCOOD/Si(100), polymethylmethacrylate and polymethylacrylate thin films are demonstrated as examples of the capabilities of the apparatus.