Showing papers on "Synchrotron radiation published in 2002"
TL;DR: In this paper, the spectral energy distribution (SED) of electromagnetic radiation and the spectrum of high energy neutrinos from BL Lac objects in the context of the Synchrotron Proton Blazar Model were investigated.
Abstract: We calculate the spectral energy distribution (SED) of electromagnetic radiation and the spectrum of high energy neutrinos from BL Lac objects in the context of the Synchrotron Proton Blazar Model. In this model, the high energy hump of the SED is due to accelerated protons, while most of the low energy hump is due to synchrotron radiation by co-accelerated electrons. To accelerate protons to sufficiently high energies to produce the high energy hump, rather high magnetic fields are required. Assuming reasonable emission region volumes and Doppler factors, we then find that in low-frequency peaked BL Lacs (LBLs), which have higher luminosities than high-frequency peaked BL Lacs (HBLs), there is a significant contribution to the high frequency hump of the SED from pion photoproduction and subsequent cascading, including synchrotron radiation by muons. In contrast, in HBLs we find that the high frequency hump of the SED is dominated by proton synchrotron radiation. We are able to model the SED of typical LBLs and HBLs, and to model the famous 1997 flare of Markarian 501. We also calculate the expected neutrino output of typical BL Lac objects, and estimate the diffuse neutrino intensity due to all BL Lacs. Because pion photoproduction is inefficient in HBLs, as protons lose energy predominantly by synchrotron radiation, the contribution of LBLs dominates the diffuse neutrino intensity. We suggest that nearby LBLs may well be observable with future high-sensitivity TeV gamma-ray telescopes.
416 citations
TL;DR: Spontaneous radiation emitted from relativistic electrons undergoing betatron motion in a plasma-focusing channel is analyzed, and applications to plasma wake-field accelerator experiments and to the ion-channel laser (ICL) are discussed.
Abstract: Spontaneous radiation emitted from relativistic electrons undergoing betatron motion in a plasma focusing channel is analyzed and application to plasma wakefield accelerator experiments and to the ion channel laser (ICL) are discussed. Important similarities and differences between a free electron laser (FEL) and an ICL are delineated. It is shown that the frequency of spontaneous radiation is a strong function of the betatron strength parameter alpha-beta, which plays a similar role to that of the wiggler strength parameter in a conventional FEL. For alpha-beta > 1, radiation is emitted in numerous harmonics. Furthermore, alpha-beta is proportional to the amplitude of the betatron orbit, which varies for every electron in the beam. The radiation spectrum emitted from an electron beam is calculated by averaging the single electron spectrum over the electron distribution. This leads to a frequency broadening of the radiation spectrum, which places serious limits on the possibility of realizing an ICL.
302 citations
TL;DR: At BESSY II it is demonstrated that far-infrared coherent synchrotron radiation (CSR) can be generated by a controlled, steady-state process at storage rings, and the incoherent radiation remained below the background level.
Abstract: At BESSY II it is demonstrated that far-infrared coherent synchrotron radiation (CSR) can be generated by a controlled, steady-state process at storage rings. As an indication for coherent emission, the radiated power grows with the square of the beam current. The spectrum was analyzed by an interferometer in the 1-mm to 0.3-mm wavelength range. The CSR was enhanced more than 3000 times above background; the incoherent radiation remained below the background level. Steady-state and bursting CSR were discriminated by time resolved analysis from $\ensuremath{\mu}$ seconds to seconds.
211 citations
TL;DR: In this paper, the authors proposed an alternative mechanism for X-ray emission -synchrotron radiation by extremely high-energy protons -and discussed implications of this model for the extended jet features resolved by Chandra in several prominent radio galaxies and active galactic nuclei.
Abstract: The X-radiation of large-scale extragalactic jets poses a serious challenge for the conventional electron-synchrotron or inverse Compton models suggested to explain the overall non-thermal emission of the resolved knots and hotspots. In this paper I propose an alternative mechanism for X-ray emission - synchrotron radiation by extremely high-energy protons - and discuss implications of this model for the extended jet features resolved by Chandra in several prominent radio galaxies and active galactic nuclei (AGN) - Pictor A, 3C 120, PKS 0637-752 and 3C 273. I show that if protons are indeed accelerated to energies E p ≥ 10 1 8 eV, it is possible to construct a realistic model that allows an effective cooling of protons via synchrotron radiation on quite 'comfortable' time-scales of about 10 7 - 10 8 yr, i.e. on time-scales that provide effective propagation of protons over the jet structures on kpc scales. This explains quite naturally the diffuse character of the observed X-ray emission, as well as the broad range of spectral X-ray indices observed from different objects. Yet, as long as the proton synchrotron cooling time is comparable with both the particle escape time and the age of the jet, the proton-synchrotron model offers an adequate radiation efficiency. The model requires relatively large magnetic field of about 1 mG, and proton acceleration rates ranging from L p ∼ 10 4 3 to 10 4 6 erg s - 1 . These numbers could be reduced significantly if the jet structures are moving relativistically towards the observer. I discuss also possible contributions of synchrotron radiation by secondary electrons produced at interactions of relatively low energy (Ep ≤ 10 1 3 eV) protons with the compressed gas in the jet structures. This is an interesting possibility which however requires a very large product of the ambient gas density and total amount of accelerated protons. Therefore it could be treated as a viable working hypothesis only if one can reduce the intrinsic X-ray luminosities assuming that the regions of non-thermal radiation are relativistically moving condensations with Doppler factors δ j ≥ 1. The kpc scales of knots and hotspots are not sufficient for effective confinement of ≥ 10 1 9 eV protons. This suppresses the synchrotron radiation by secondary electrons produced at py interactions. At the same time the runaway protons, interacting with 2.7-K cosmic microwave background radiation, initiate non-negligible diffuse X- and γ-ray emission in the surrounding cluster environments. I discuss the spectral and angular characteristics of this radiation, which essentially depend on the strength of the ambient magnetic field.
195 citations
TL;DR: In this paper, the X-ray imaging spectroscopy of the jet of M87 at subarcsecond resolution with the Chandra Xray Observatory was reported, and it was shown that at least three knots are displaced from their radio/optical counterparts, being tens of parsecs closer to the nucleus at Xray than at radio or optical wavelengths.
Abstract: We report X-ray imaging spectroscopy of the jet of M87 at subarcsecond resolution with the Chandra X-ray Observatory. The galaxy nucleus and all the knots seen at radio and optical wavelengths, as far from the nucleus as knot C, are detected in the X-ray observations. There is a strong trend for the ratio of X-ray-to-radio, or optical, flux to decline with increasing distance from the nucleus. At least three knots are displaced from their radio/optical counterparts, being tens of parsecs closer to the nucleus at X-ray than at radio or optical wavelengths. The X-ray spectra of the nucleus and knots are well described by power laws absorbed by cold gas, with only the unresolved nucleus exhibiting intrinsic absorption. In view of the similar spectra of the nucleus and jet knots, and the high X-ray flux of the knots closest to the nucleus, we suggest that the X-ray emission coincident with the nucleus may actually originate from the parsec- or subparsec-scale jet rather than the accretion disk. Arguments are given that the X-ray emission process is unlikely to be inverse Compton scattering. Instead, we favor synchrotron radiation. Plotted as νSν, the spectra of the knots generally peak in or just above the optical-near-infrared band. However, the overall spectra of at least three knots cannot be described by simple models in which the spectral index monotonically increases with frequency, as would result from synchrotron losses or a high-energy cut-off to the injected electron spectrum. Instead, these spectra must turn down just above the optical band and then flatten in the X-ray band. In the context of a synchrotron model, this result suggests that either the X-ray-emitting electrons/positrons in these knots represent a separate "population" from those that emit the radio and optical radiation or that the magnetic field is highly inhomogeneous. If the former interpretation is correct, our results provide further support for the notion that radio galaxies produce a hard [γ 2-2.5, N(E) ∝ E-γ] spectrum of high-energy [ ~ 107-108] electrons and possibly positrons.
191 citations
TL;DR: In this article, high energy resolution (0.15 eV) along with high brightness level allows us to separate, unambiguously, on both Hf 4f and Si 2p core-level spectra, interfacial Hf-silicate bonds from bulk HfO2 and SiO2 contributions, thus making possible subsequent quantitative treatments and modeling of the interfacial layer structure.
Abstract: X-ray photoelectron spectroscopy using synchrotron radiation has been used to investigate the HfO2/SiO2 interface chemistry of high-quality 0.6 and 2.5 nm HfO2/0.6 nm SiO2/Si structures. The high energy resolution (0.15 eV) along with the high brightness level allows us to separate, unambiguously, on both Hf 4f and Si 2p core-level spectra, interfacial Hf–silicate bonds from bulk HfO2 and SiO2 contributions, thus making possible subsequent quantitative treatments and modeling of the interfacial layer structure. Careful assessment of the energy shift of the interfacial components shows that Si-rich Hf silicates are present. The underlying assumption that initial-state contribution dominates the observed Si 2p shift is briefly discussed.
186 citations
TL;DR: The availability of synchrotron radiation (SR) to the scientific community has literally revolutionized the way X-ray science is done in many disciplines, including low temperature geochemistry and environmental science.
Abstract: The availability of synchrotron radiation (SR) to the scientific community has literally revolutionized the way X-ray science is done in many disciplines, including low temperature geochemistry and environmental science. The key reason is that SR provides continuum vacuum ultraviolet (VUV) and X-ray radiation five to ten orders of magnitude brighter than that from standard sealed or rotating anode X-ray tubes (Winick 1987; Altarelli et al. 1998). Although SR was first observed indirectly by John Blewitt in 1945 (Blewitt 1946) and directly by Floyd Haber in 1946 at the General Electric 100-MeV Betatron in Schenectady, NY (see Elder et al. 1947; Baldwin 1975), it took 10 to 15 years before the first systematic applications of SR, which involved spectroscopic studies of the VUV absorption of selected elements (Tomboulian and Hartman 1956) using the 300-MeV synchrotron at Cornell University and of rare gases (Madden and Codling 1963) using the National Bureau of Standards SURF I synchrotron. As of September 2002, there are about 75 storage ring-based SR sources in operation, in construction, funded, or in advanced planning in 23 countries, with 10 fully dedicated SR storage ring facilities in the U.S.. A listing of these sources can be obtained at the following web site: http://www-ssrl.slac.stanford.edu/sr_sources.html .
The first SR experiments relevant to low temperature geochemistry and environmental science, although not performed on earth or environmental materials, were X-ray absorption fine structure (XAFS) spectroscopy measurements on amorphous and crystalline germanium oxide conducted on the SPEAR storage ring at the Stanford Synchrotron Radiation Project in 1971 by Dale Sayers, Farrel Lytle, and Edward Stern (Sayers et al. 1971). Prior to the availability of SR in the hard X-ray energy range (> 5 keV), XAFS spectroscopy measurements were impractical because of the high X-ray flux required and the need for a continuously tunable …
181 citations
Book•
01 Jan 2002
TL;DR: In this article, the authors present a user guide for synchrotron beamline design and beamline parameters, as well as three X-ray Reflectivity as a Probe of Mineral-Fluid Interfaces: A User Guide.
Abstract: ............................................................................................................................... 117 INTRODUCTION....................................................................................................................... 117 How does an electron emit light? ................................................................................... 118 Figures of merit .............................................................................................................. 120 SYNCHROTRON STORAGE RINGS....................................................................................... 120 History of synchrotron radiation .................................................................................... 123 Bending magnet radiation .............................................................................................. 128 INSERTION DEVICES .............................................................................................................. 130 Wiggler radiation............................................................................................................ 130 Undulator radiation......................................................................................................... 131 Important storage ring parameters.................................................................................. 134 BEAMLINE AND EXPERIMENTAL STATIONS................................................................... 139 Beamline design ............................................................................................................. 139 Synchrotron beamlines: general ..................................................................................... 139 OTHER CHARACTERISTICS OF SYNCHROTRON RADIATION ...................................... 140 Polarization..................................................................................................................... 140 Time structure................................................................................................................. 142 THE INTERACTION OF LIGHT WITH MATTER.................................................................. 142 Scattering........................................................................................................................ 142 Absorption...................................................................................................................... 143 The overall picture.......................................................................................................... 145 ACKNOWLEDGMENTS........................................................................................................... 147 REFERENCES............................................................................................................................ 147 3 X-ray Reflectivity as a Probe of Mineral-Fluid Interfaces: A User Guide
170 citations
TL;DR: The time-resolved diffraction technique described here is applicable to reversible light-driven processes in the crystalline solid state.
Abstract: X-ray crystallography has traditionally been limited to the study of the ground-state structure of molecules and solids. Recent technical advances are removing this limitation as demonstrated here by a time-resolved stroboscopic study of the photo-induced 50 µs lifetime excited triplet state of the [Pt2(pop)4]4− ion [pop = pyrophosphate, (H2P2O5)2−], performed at helium temperatures with synchrotron radiation. The shortening of the Pt—Pt bond by 0.28 (9) A upon excitation is compatible with the proposed mechanism involving promotion of a Pt—Pt antibonding dσ* electron to a weakly bonding p orbital. The contraction is accompanied by a 3° molecular rotation. The time-resolved diffraction technique described here is applicable to reversible light-driven processes in the crystalline solid state.
157 citations
TL;DR: The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films have been studied with circularly polarized synchrotron radiation and the ratio of orbital to spin magnetic moments varies considerably with cluster size, reflecting the dependence of magnetic properties on cluster size and geometry.
Abstract: The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films have been studied with circularly polarized synchrotron radiation. With the use of sum rules, orbital and spin magnetic moments have been extracted from x-ray magnetic circular dichroism spectra. The ratio of orbital to spin magnetic moments varies considerably with cluster size, reflecting the dependence of magnetic properties on cluster size and geometry. These variations can be explained in terms of enhanced orbital moments in small clusters.
150 citations
01 Aug 2002-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, an innovative technique for in-situ monitoring of a specific solidification phenomenon in real metallic systems has been presented, based on phase and amplitude contrast from the sample.
Abstract: Time-resolved direct-beam X-ray imaging, with intense, coherent, and monochromatic third-generation synchrotron radiation, and a high-resolution fast-readout detector system have been used for in-situ studies of dendritic and eutectic growth processes in Al-Cu alloys. Temporal and spatial resolutions down to 0.25 seconds and 2.5 μm, respectively, were obtained with a field of view up to 1.4×1.4 mm2. Solid-liquid interfaces and various phase-specific segregates could be observed, and their dynamics could be traced in a sequence of temporally resolved images formed by phase and amplitude contrast from the sample. This article does not present any detailed analysis of a specific solidification phenomenon; instead, it presents to the scientific community an innovative technique for in-situ monitoring of such a phenomenon in real metallic systems.
TL;DR: Observations made at the Advanced Light Source are consistent with the values predicted by the proposed microbunching model, demonstrating a new instability regime for high energy synchrotron radiation sources and could impact the design of future sources.
Abstract: Bursts of coherent synchrotron radiation at far-infrared and millimeter wavelengths have been observed at several storage rings. A microbunching instability has been proposed as the source for the bursts. However, the microbunching mechanism has yet to be elucidated. We provide the first evidence that the bursts are due to a microbunching instability driven by the emission of synchrotron radiation in the bunch. Observations made at the Advanced Light Source are consistent with the values predicted by the proposed microbunching model. These results demonstrate a new instability regime for high energy synchrotron radiation sources and could impact the design of future sources.
TL;DR: It is shown that resonant coupling of synchrotron beams into suitable nanostructures can be used for the generation of coherent x-ray point sources with a beam cross section in the nanometer range.
Abstract: We show that resonant coupling of synchrotron beams into suitable nanostructures can be used for the generation of coherent x-ray point sources. A two-dimensionally confining x-ray waveguide structure has been fabricated by e-beam lithography. By shining a parallel undulator beam onto the structure, a discrete set of resonant modes can be excited in the dielectric cavity, depending on the two orthogonal coupling angles between the beam and the waveguide interfaces. The resonant excitation of the modes is evidenced from the characteristic set of coupling angles as well as the observed far-field pattern. The x-ray nanostructure may be used as coherent x-ray point sources with a beam cross section in the nanometer range.
17 Oct 2002
TL;DR: In this article, the impact of Insertion Devices on macromolecular Crystallography was discussed and the choice of insertion device Optics and choice of Wavelengths End Station Instrumentation Area Detectors were discussed.
Abstract: UNDULATORS AND WIGGLERS Electron Beam Dynamics, L. Farvacque Generalities on the Synchrotron Radiation, P. Elleaume Undulator Radiation, P. Elleaume Bending Magnet and Wiggler Radiation, R.P. Walker Technology of Insertion Devices, J. Chavanne and P. Elleaume Polarizing Undulators and Wigglers, H. Onuki Undulators Wigglers Exotic Insertion Devices, S. Sasaki Free Electron Lasers, M.E. Couprie APPLICATIONS Impact of Insertion Devices on Macromolecular Crystallography, Wakatsuki Choice of Insertion Device Optics and Choice of Wavelengths End Station Instrumentation Area Detectors Data Acquisition and Data Analysis Ancillary Facilities New Operation Modes of Synchrotron Radiation Protein Crystallography Recent Results from Insertion Device Beam Lines Future Outlook Intravenous Coronary Angiography as an Example, W.R. Dix Polarization ModulationSpectroscopy by Polarizing Undulator, H, Onuki, T. Yamada, and K. Yagi-Watanbe Circular Dicroism (CD) Measurement and Two Dimensional CD Imaging Magnetic Circular Measurement Solid State Physics, T. Miyahara X-ray Optics, W.K. Lee, P. Fernandez, and D.M. Mills Metrological Applications, T. Saito
TL;DR: In this article, the authors formulate the general requirements, set by classical electrodynamics, on the sources of extremely high-energy cosmic rays (EHECRs), and show that the parameters of EHECR accelerators are strongly limited not only by the particle confinement in large-scale magnetic fields or by the difference in electric potentials (generalized Hillas criterion) but also by the synchrotron radiation, the electro-bremsstrahlung, or the curvature radiation of accelerated particles.
Abstract: We formulate the general requirements, set by classical electrodynamics, on the sources of extremely high-energy cosmic rays (EHECRs). It is shown that the parameters of EHECR accelerators are strongly limited not only by the particle confinement in large-scale magnetic fields or by the difference in electric potentials (generalized Hillas criterion) but also by the synchrotron radiation, the electro-bremsstrahlung, or the curvature radiation of accelerated particles. Optimization of these requirements in terms of an accelerator's size and magnetic field strength results in the ultimate lower limit to the overall source energy budget, which scales as the fifth power of attainable particle energy. Hard \ensuremath{\gamma} rays accompanying generation of EHECRs can be used to probe potential acceleration sites. We apply the results to several populations of astrophysical objects---potential EHECR sources---and discuss their ability to accelerate protons to ${10}^{20} \mathrm{eV}$ and beyond. The possibility of gain from ultrarelativistic bulk flows is addressed, with active galactic nuclei and gamma-ray bursts being the examples.
TL;DR: Observations of 13.8 GHz synchrotron emission that confirm the presence of electrons with energies up to 50 MeV are reported, collected during the Cassini fly-by of Jupiter.
Abstract: Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission1: thermal atmospheric emission and synchrotron emission2 from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements3,4 confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for electrons at energies up to 20 MeV. Although most radiation belt models predict electrons at higher energies5,6, adiabatic diffusion theory can account only for energies up to around 20 MeV. Unambiguous evidence for more energetic electrons is lacking. Here we report observations of 13.8 GHz synchrotron emission that confirm the presence of electrons with energies up to 50 MeV; the data were collected during the Cassini fly-by of Jupiter. These energetic electrons may be repeatedly accelerated through an interaction with plasma waves, which can transfer energy into the electrons. Preliminary comparison of our data with model results suggests that electrons with energies of less than 20 MeV are more numerous than previously believed.
TL;DR: It is shown that the wave vector and frequency profiles of this x-ray analogue of coherent Raman spectroscopy provide an excellent real-space probe that carries most valuable structural and dynamical information, not available from spontaneous Raman techniques.
Abstract: Nonlinear x-ray four-wave mixing experiments are becoming feasible due to rapid advances in high harmonic generation and synchrotron radiation coherent x-ray sources. By tuning the difference of two x-ray frequencies across the valence excitations, it is possible to probe the entire manifold of molecular electronic excitations. We show that the wave vector and frequency profiles of this x-ray analogue of coherent Raman spectroscopy provide an excellent real-space probe that carries most valuable structural and dynamical information, not available from spontaneous Raman techniques.
TL;DR: In this paper, the basic radiative transfer coefficients for polarized synchrotron radiation and apply them to the standard jet model for relativistic radio jets are presented, which can successfully explain the unusual circular and linear polarization of the Galactic Centre radio source Sgr A* and its sibling M 81*, and also can account for the circular polarization found in more luminous quasars and X-ray binaries.
Abstract: In inhomogeneous optically thick synchrotron sources a substantial part of the electron population at low energies can be hidden by self-absorption and overpowered by high energy electrons in optically thin emission. These invisible electrons produce Faraday rotation and conversion, leaving their footprints in the linear and circular polarized radiation of the source. An important factor is also the magnetic field structure, which can be characterized in most cases by a global magnetic field and a turbulent component. We present the basic radiative transfer coefficients for polarized synchrotron radiation and apply them to the standard jet model for relativistic radio jets. The model can successfully explain the unusual circular and linear polarization of the Galactic Centre radio source Sgr A* and its sibling M 81*. It also can account for the circular polarization found in jets of more luminous quasars and X-ray binaries. The high ratio of circular to linear polarization requires the presence of a significant fraction of hidden matter and low-energy electrons in these jets. The stable handedness of circular polarization requires stable global magnetic field components with non-vanishing magnetic flux along the jet, while the low degree of total polarization implies also a significant turbulent field. The most favoured magnetic field configuration is that of a helix, while a purely toroidal field is unable to produce significant circular polarization. If connected to the magnetosphere of the black hole, the circular polarization and the jet direction determine the magnetic poles of the system which is stable over long periods of time. This may also have implications for possible magnetic field configurations in accretion flows.
TL;DR: In this article, it was shown that the inferred relationship between the two spectral indices of observed gamma-ray burst spectra is inconsistent with the constraints from the simple optically thin synchrotron shock emission model.
Abstract: The current scenario for gamma-ray bursts (GRBs) involves internal shocks for the prompt GRB emission phase and external shocks for the afterglow phase. Assuming optically thin synchrotron emission from isotropically distributed energetic shocked electrons, GRB spectra observed with a low-energy power-law spectral index greater than -2/3 (for positive photon number indices E(exp alpha) indicate a problem with this model. For spectra that do not violate this condition, additional tests of the shock model can be made by comparing the low- and high-energy spectral indices, on the basis of the model's assertion that synchrotron emission from a single power-law distribution of electrons is responsible for both the low-energy and the high-energy power-law portions of the spectra. We find in most cases that the inferred relationship between the two spectral indices of observed GRB spectra is inconsistent with the constraints from the simple optically thin synchrotron shock emission model. In this sense, the prompt burst phase is different from the afterglow phase, and this difference may be related to anisotropic distributions of particles or to their continual acceleration in shocks during the prompt phase.
TL;DR: The free electron laser at Jefferson Laboratory is the first of a new generation of light sources based on a photoinjected energy recovered linac as discussed by the authors, which has a 40 MeV electron beam and an average current of 5 mA.
Abstract: The free electron laser at Jefferson Laboratory is the first of a new generation of light sources based on a photoinjected energy recovered linac. The present machine has a 40 MeV electron beam and an average current of 5 mA. The electron bunches are extremely short with full width at half maximum values that are in the few hundred femtosecond regime. These electron bunches pass a chicane around the optical cavity, and therefore, emit synchrotron radiation. In the far-IR region, the wavelength of the light being emitted approaches that of the electron bunch length, giving rise to multiparticle coherent enhancement. The result is a broadband spectrum whose average brightness is more than five orders of magnitude higher than can be obtained from conventional incoherent synchrotron IR sources. We will discuss preliminary measurements of this radiation, and applications to spectroscopy and imaging.
TL;DR: In this article, an X-ray synchrotron technique capable of mapping orientation and strain/stress in polycrystalline thin films with submicron spatial resolution is presented.
Abstract: The availability of high brilliance synchrotron sources, coupled with recent progress in achromatic focusing optics and large area 2D detector technology, have allowed us to develop an X-ray synchrotron technique capable of mapping orientation and strain/stress in polycrystalline thin films with submicron spatial resolution. To demonstrate the capabilities of this instrument, we have employed it to study the microstructure of aluminum thin film structures at the granular and subgranular level. Owing to the relatively low absorption of X-rays in materials, this technique can be used to study passivated samples, an important advantage over most electron probes given the very different mechanical behavior of buried and unpassivated materials.
TL;DR: Energy recovery linac (ERL) as mentioned in this paper uses the same superconducting linac as a decelerator of the electron beam after SR production, thereby recovering the beam energy for acceleration of new electrons.
Abstract: Practically all synchrotron x-ray sources to data are based on the use of storage rings to produce the high current electron (or positron) beams needed for synchrotron radiation (SR). The ultimate limitations on the quality of the electron beam, which are directly reflected in many of the most important characteristics of the SR beams, arise from the physics of equilibrium processes fundamental to the operation of storage rings. It is possible to produce electron beams with superior characteristics for SR via photoinjected electron sources and high-energy linacs; however, the energy consumption of such machines is prohibitive. This limitation can be overcome by the use of an energy recovery linac (ERL), which involves configuring the electron-beam path to use the same superconducting linac as a decelerator of the electron beam after SR production, thereby recovering the beam energy for acceleration of new electrons. ERLs have the potential to produce SR beams with brilliance, coherence, time structure, and source size and shape which are superior to even the best third-generation storage ring sources, while maintaining flexible machine operation and competitive costs. Here, we describe a project to produce a hard x-ray ERL SR source at Cornell University, with emphasis on the characteristics, promise, and challenges of such an ERL machine.
TL;DR: In this paper, the authors studied the instability of an initial density fluctuation with a characteristic length much shorter than the bunch length, which leads to microbunching of the beam and an increased coherent radiation at short wavelengths.
Abstract: A relativistic electron beam moving in a circular orbit in free space can radiate coherently if the wavelength of the synchrotron radiation exceeds the length of the bunch. In accelerators coherent synchrotron radiation of the bunch is usually suppressed by the shielding effect of the conducting walls of the vacuum chamber. However an initial density fluctuation with a characteristic length much shorter than the bunch length can radiate coherently. If the radiation reaction force results in the growth of the initial fluctuation, one can expect an instability which leads to microbunching of the beam and an increased coherent radiation at short wavelengths. Such an instability is studied theoretically in this paper.
TL;DR: In this paper, a synchrotron radiation based x-ray microprobe analytical technique, X-ray beam induced current (XBIC), is suggested and demonstrated at the Advanced Light Source at the Lawrence Berkeley National Laboratory.
Abstract: A synchrotron radiation based x-ray microprobe analytical technique, x-ray beam induced current (XBIC), is suggested and demonstrated at the Advanced Light Source at the Lawrence Berkeley National Laboratory. The principle of XBIC is similar to that of electron/laser beam induced current with the difference that minority carriers are generated by a focused x-ray beam. XBIC can be combined with any other x-ray microprobe tool, such as the x-ray fluorescence microprobe (μ-XRF), to complement chemical information with data on the recombination activity of impurities and defects. Since the XBIC signal, which carries information about the recombination activity of defects in the sample, and the μ-XRF signal, which contains data on their chemical nature, can be collected simultaneously, this combination offers a unique analytical capability of in situ analysis of the recombination activity of defects and their chemical origin with a high sensitivity and a micron-scale spatial resolution. Examples of an applicat...
TL;DR: A radiation chemical perspective on some of the physical and chemical processes that need to be considered in understanding potential pathways leading to the gradual degradation of protein samples by synchrotron radiation.
Abstract: Radiation-induced degradation of protein or DNA samples by synchrotron radiation is an inherent problem in X-ray crystallography, especially at the `brighter' light sources. This short review gives a radiation chemical perspective on some of the physical and chemical processes that need to be considered in understanding potential pathways leading to the gradual degradation of the samples. Under the conditions used for X-ray crystallography at a temperature of <100 K in the presence of cryoprotectant agents, the majority of radiation damage of the protein samples arises from direct ionization of the amino acid residues and their associated water molecules. Some of the chemical processes that may occur at these protein centres, such as bond scission, are discussed. Several approaches are discussed that may reduce radiation damage, using agents known from radiation chemistry to minimize radical-induced degradation of the sample.
TL;DR: This work has investigated the magnetic spin structure of a soft-magnetic film that is exchange-coupled to a hard- magnetic layer to form an exchange-spring layer system and found that the depth dependence of the magnetization direction was determined by nuclear resonant scattering of synchrotron radiation from ultrathin 57Fe probe layers.
Abstract: We have investigated the magnetic spin structure of a soft-magnetic film that is exchange-coupled to a hard-magnetic layer to form an exchange-spring layer system. The depth dependence of the magnetization direction was determined by nuclear resonant scattering of synchrotron radiation from ultrathin $^{\mathrm{57}}\mathrm{F}\mathrm{e}$ probe layers. In an external field a magnetic spiral structure forms that can be described within a one-dimensional micromagnetical model. The experimental method allows one to image vertical spin structures in stratified media with unprecedented accuracy.
01 Aug 2002
TL;DR: In this article, the authors considered the case when coherent synchrotron radiation of a bunch as a whole is suppressed by screening and is caused by microstructures with longitudinal dimensions small compared to the bunch length.
Abstract: A beam microwave instability induced by the coherent radiation of the density fluctuations is studied theoretically in this paper. We consider the case when coherent synchrotron radiation of a bunch as a whole is suppressed by screening and is caused by microstructures with longitudinal dimensions small compared to the bunch length. In this case, we can simplify consideration studying stability of a coasting beam with the line density equal to the local line density of the bunch.
TL;DR: X-ray micro-tomography, a non-destructive technique used to uncover the complex 3-D micro-architecture of a degradable polymer sponge designed for bone augmentation, elucidate that synchrotron radiation at the photon energy of 9 keV has an appropriate cross section for this low-weight material.
TL;DR: In this paper, the size effects on the crystal structure and phase transitions of BaTiO 3 fine particles of 700, 400, 300 and 100 nm were investigated by means of powder diffraction using synchrotron.
Abstract: The size effects on the crystal structure and phase transitions have been investigated for BaTiO 3 fine particles of 700, 400, 300 and 100 nm size, by means of powder diffraction using synchrotron ...
TL;DR: The results from a series of standard biological assays to evaluate any short- and/or long-term effects on cells exposed to the synchrotron radiation-based infrared (SR-IR) beam show no evidence of cytotoxic effects.
Abstract: Synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectromicroscopy is a newly emerging analytical tool capable of monitoring the biochemistry within an individual living mammalian cell in real time. This unique technique provides infrared (IR)spectra, hence chemical information, with high signal-to-noise at spatial resolutions as fine as 3 to 10 microns. Mid-IR photons are too low in energy (0.05-0.5 eV) to either break bonds or to cause ionization, and the synchrotron IR beam has been shown to produce minimal sample heating. However, an important question remains, ''Does the intense synchrotron beam induce any cytotoxic effects in living cells?'' In this work, we present the results from a series of standard biological assays to evaluate any short-and/or long-term effects on cells exposed to the synchrotron radiation-based infrared (SR-IR) beam. Cell viability was tested using alcian blue dye-exclusion and colony formation assays. Cell-cycle progression was tested with bromodeoxyuridine (BrdU) uptake during DNA synthesis. Cell metabolism was tested using an 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. All control, 5-, 10-, and 20-minute SR-IR exposure tests (267 total and over 1000 controls) show no evidence of cytotoxic effects. Concurrent infrared spectra obtained with each experiment confirm no detectable chemistry changes between control and exposed cells.