Showing papers on "Synchrotron radiation published in 2000"
TL;DR: In this article, a new study of the diUuse Galactic c-ray continuum radiation is presented, using a cosmic-ray propa- gation model which includes nucleons, antiprotons, electrons, positrons, and synchrotron radiation.
Abstract: A new study of the diUuse Galactic c-ray continuum radiation is presented, using a cosmic-ray propa- gation model which includes nucleons, antiprotons, electrons, positrons, and synchrotron radiation. Our treatment of the inverse Compton scattering includes the eUect of anisotropic scattering in the Galactic interstellar radiation —eld (ISRF) and a new evaluation of the ISRF itself. Models based on locally mea- sured electron and nucleon spectra and synchrotron constraints are consistent with c-ray measurements in the 30¨500 MeV range, but outside this range excesses are apparent. A harder nucleon spectrum is considered but —tting to c-rays causes it to violate limits from positrons and antiprotons. A harder inter- stellar electron spectrum allows the c-ray spectrum to be —tted above 1 GeV as well, and this can be further improved when combined with a modi—ed nucleon spectrum which still respects the limits imposed by antiprotons and positrons. A large electron/inverse Compton halo is proposed which repro- duces well the high-latitude variation of c-ray emission; this is taken as support for the halo size for nucleons deduced from studies of cosmic-ray composition. Halo sizes in the range 4¨10 kpc are favored by both analyses. The halo contribution of Galactic emission to the high-latitude c-ray intensity is large, with implications for the study of the diUuse extragalactic component and signatures of dark matter. The constraints provided by the radio synchrotron spectral index do not allow all of the c-ray emission at less than 30 MeV to be explained in terms of a steep electron spectrum unless this takes the form of a sharp upturn below 200 MeV. This leads us to prefer a source population as the origin of the excess low-energy c-rays, which can then be seen as a continuation of the hard X-ray continuum measured by OSSE, Ginga, and RXT E. Subject headings: cosmic raysdiUuse radiationGalaxy: generalgamma rays: observations ¨ gamma rays: theoryISM: general
635 citations
TL;DR: Femtosecond synchrotron pulses were generated directly from an electron storage ring and offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter.
Abstract: Femtosecond synchrotron pulses were generated directly from an electron storage ring. An ultrashort laser pulse was used to modulate the energy of electrons within a 100-femtosecond slice of the stored 30-picosecond electron bunch. The energy-modulated electrons were spatially separated from the long bunch and used to generate ∼300-femtosecond synchrotron pulses at a bend-magnet beamline, with a spectral range from infrared to x-ray wavelengths. The same technique can be used to generate ∼100-femtosecond x-ray pulses of substantially higher flux and brightness with an undulator. Such synchrotron-based femtosecond x-ray sources offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter.
571 citations
TL;DR: In this paper, it was shown that if protons are accelerated at the maximum possible rate, i.e. tacc=η(rg/c) with so-called gyro-factor η∼1, the synchrotron cooling of protons could not only dominate over other radiative and non-radiative losses, but also provide good fits (within uncertainties introduced by extragalactic γ-ray extinction) to the γradiation of two firmly established TeV blazars.
488 citations
TL;DR: In this article, a variation of the Synchrotron Proton Blazar model is proposed, in which the low energy part of the spectral energy distribution is mainly synchoretron radiation by electrons co-accelerated with protons, and the high energy part is mainly asproton synchron radiation.
Abstract: (abr.) The spectral energy distribution (SED) of blazars typically has a double-humped appearance usually interpreted in terms of synchrotron self-Compton models. In proton blazar models, the SED is instead explained in terms of acceleration of protons and subsequent cascading. We discuss a variation of the Synchrotron Proton Blazar model, first proposed by Mucke & Protheroe (1999), in which the low energy part of the SED is mainly synchrotron radiation by electrons co-accelerated with protons which produce the high energy part of the SED mainly asproton synchrotron radiation. Using a Monte Carlo/numerical technique to simulate the interactions and subsequent cascading of the accelerated protons, we are able to fit the observed SED of Markarian 501 during the April 1997 flare. We find that the emerging cascade spectra initiated by gamma-rays from $\pi^0$ decay and by $e^\pm$ from $\mu^\pm$ decay turn out to be relatively featureless. Synchrotron radiation produced by $\mu^\pm$ from $\pi^\pm$ decay, and even more importantly by protons, and subsequent synchrotron-pair cascading, is able to reproduce well the high energy part of the SED. For this fit we find that synchrotron radiation by protons dominates the TeV emission, pion photoproduction being less important with the consequence that we predict a lower neutrino flux than in other proton blazar models.
319 citations
TL;DR: In this paper, a quantitative analytical theory of jitter radiation was developed, which was applied to internal shocks of γ-ray bursts (GRBs), and it was shown that the emergent spectrum is determined by statistical properties of the magnetic field.
Abstract: We demonstrate that the radiation emitted by ultrarelativistic electrons in highly nonuniform, small-scale magnetic fields is different from synchrotron radiation if the electron's transverse deflections in these fields are much smaller than the beaming angle. A quantitative analytical theory of this radiation, which we refer to as jitter radiation, is developed. It is shown that the emergent spectrum is determined by statistical properties of the magnetic field. The jitter radiation theory is then applied to internal shocks of γ-ray bursts (GRBs). The model of a magnetic field in GRBs proposed by Medvedev & Loeb in 1999 is used. The spectral power distribution of radiation produced by the power-law-distributed electrons with a low-energy cutoff is well described by a sharply broken power law: P(ω) ∝ ω1 for ω ωjm and P(ω) ∝ ω-(p-1)/2 for ω ωjm, where p is the electron power-law index and ωjm is the jitter break frequency, which is independent of the field strength but depends on the electron density in the ejecta, ωjm ∝ n1/2, as well as on the shock energetics and kinematics. The total emitted power of jitter radiation is, however, equal to that of synchrotron radiation. Since large-scale fields may also be present in the ejecta, we construct a two-component, jitter + synchrotron spectral model of the prompt γ-ray emission. Quite surprisingly, this model seems to be readily capable of explaining several properties of time-resolved spectra of some GRBs, such as (1) the violation of the constraint on the low-energy spectral index called the synchrotron "line of death," (2) the sharp spectral break at the peak frequency, inconsistent with the broad synchrotron bump, (3) the evidence for two spectral subcomponents, and (4) possible existence of emission features called "GRB lines." We believe these facts strongly support both the existence of small-scale magnetic fields and the proposed radiation mechanism from GRB shocks. As an example, we use the composite model to analyze GRB 910503, which has two spectral peaks. At last, we emphasize that accurate GRB spectra may allow precise determination of fireball properties as early as several minutes after the explosion.
277 citations
TL;DR: The authors evaluated the effect on mammographic examinations of the use of synchrotron radiation to detect phase-perturbation effects, which are higher than absorption effects for soft tissue in the energy range of 15-25 keV.
Abstract: The authors evaluated the effect on mammographic examinations of the use of synchrotron radiation to detect phase-perturbation effects, which are higher than absorption effects for soft tissue in the energy range of 15-25 keV. Detection of phase-perturbation effects was possible because of the high degree of coherence of synchrotron radiation sources. Synchrotron radiation images were obtained of a mammographic phantom and in vitro breast tissue specimens and compared with conventional mammographic studies. On the basis of grades assigned by three reviewers, image quality of the former was considerably higher, and the delivered dose was fully compatible.
276 citations
TL;DR: The high brilliance of third-generation synchrotron radiation sources allows new applications in x-ray microdiffraction and micro-small-angle scattering as discussed by the authors, and beam sizes down to about one µm are routinely used and sub-µm beam sizes are becoming available.
Abstract: The high brilliance of third-generation synchrotron radiation sources allows new applications in x-ray microdiffraction and microsmall-angle scattering. Beam sizes down to about one µm are routinely used and sub-µm beam sizes are becoming available. Scanning diffractometry can be used to examine samples like single fibres without the necessity for sectioning, as is required for transmission electron scattering experiments. Examples are taken principally from weakly scattering polymers and biopolymers. In single-crystal diffraction, sub-µm3 crystal volumes have been reached for inorganic crystals. Protein crystallography has been demonstrated for a few tenths of µm linear crystal size, which reduces the crystallization time for many proteins.
204 citations
TL;DR: In this paper, the authors investigated synchrotron emission models as the source of gamma-ray burst (GRB) spectra and derived the expected distribution of α from a spurious correlation between spectral parameters, including the value of the peak of the νFν spectrum, Ep, and the low-energy photon spectral index α.
Abstract: We investigate synchrotron emission models as the source of gamma-ray burst (GRB) spectra. We show that including the possibility for synchrotron self-absorption, a "smooth cutoff" to the electron energy distribution, and an anisotropic distribution for the electron pitch angles produces a whole range of low-energy spectral behavior. In addition, we show that the procedure of spectral fitting to GRB data over a finite bandwidth can introduce a spurious correlation between spectral parameters—in particular, the value of the peak of the νFν spectrum, Ep, and the low-energy photon spectral index α (the lower Ep is, the lower [softer] the fitted value of α will be). From this correlation and knowledge of the Ep distribution, we show how to derive the expected distribution of α. We show that optically thin synchrotron models with an isotropic electron pitch angle distribution can explain the distribution of α below α = - . This agreement is achieved if we relax the unrealistic assumption of the presence of a sharp low-energy cutoff in the spectrum of accelerated electrons and allow for a more gradual break. We show that this low-energy portion of the electron spectrum can be at most flat. We also show that optically thin synchrotron models with an anisotropic electron pitch angle distribution can explain all bursts with - α 0. The very few bursts with low-energy spectral indices that fall above α = 0 may be due to the presence of a synchrotron self-absorption frequency entering the lower end of the BATSE window. Our results also predict a particular relationship between α and Ep during the temporal evolution of a GRB. We give examples of spectral evolution in GRBs and discuss how its behavior is consistent with the above models.
186 citations
TL;DR: The detection of linear polarization from Sgr A* at 750, 850, 1350, and 2000 µm which confirms the contribution of synchrotron radiation and implies that the excess arises in an extremely compact source of approximately 2 Schwarzschild radii.
Abstract: We report the detection of linear polarization from Sgr A* at 750, 850, 1350, and 2000 µm which confirms the contribution of synchrotron radiation. From the lack of polarization at longer wavelengths, it appears to arise in the millimeter/submillimeter excess. There are large position angle changes between the millimeter and submillimeter results, and these are discussed in terms of a polarized dust contribution in the submillimeter and various synchrotron models. In the model that best explains the data, the synchrotron radiation from the excess is self-absorbed in the millimeter region and becomes optically thin in the submillimeter. This implies that the excess arises in an extremely compact source of approximately 2 Schwarzschild radii.
186 citations
TL;DR: In this paper, the authors reported on the excellent performance of a newly constructed soft x-ray helical undulator beamline BL25SU of SPring-8 for photon energies 500-1800 eV.
Abstract: We report on the excellent performance of a newly constructed soft x-ray helical undulator beamline BL25SU of SPring-8 for photon energies 500–1800 eV The full beamline was designed to perform very high resolution soft x-ray spectroscopy of solids with using high brilliance, highly circularly polarized undulator radiation The grazing incidence monochromator employs varied-line-spacing plane gratings which operate in convergent light from a spherical mirror and focuses monochromatic light onto the exit slit A resolving power in excess of 15 000 was measured at 540 and 870 eV for a grating with a central groove density of 600 lines/mm from the photoemission spectra of Au A resolving power of more than 20 000 is estimated near 870 eV for a grating with a central groove density of 1000 lines/mm A photon flux of more than 1×1011 photons/s/100 mA/002% bw is supplied onto the sample between 500 and 1800 eV with very low amount of higher-order light The low heat load from the twin-helical undulator gives
172 citations
TL;DR: In this paper, Chandra X-ray observations of the powerful radio galaxy Cygnus A with the X-Ray Observatory were reported, showing that the magnetic field in each of the brighter hot spots is 1.5 × 10^(-4) G, with an uncertainty of a few tens of percent.
Abstract: We report X-ray observations of the powerful radio galaxy Cygnus A with the Chandra X-Ray Observatory. This Letter focuses on the radio hot spots, all four of which are detected in X-rays with a very similar morphology to their radio structure. X-ray spectra have been obtained for the two brighter hot spots (A and D). Both are well described by a power law with photon index Γ = 1.8 ± 0.2 absorbed by the Galactic column in the direction of Cygnus A. Thermal X-ray models require too high gas densities and may be ruled out. The images and spectra strongly support synchrotron self-Compton models of the X-ray emission, as proposed by Harris, Carilli, & Perley on the basis of ROSAT imaging observations. Such models indicate that the magnetic field in each of the brighter hot spots is 1.5 × 10^(-4) G, with an uncertainty of a few tens of percent. This value is close to the equipartition field strengths assuming no protons are present. The possibility that the X-rays are synchrotron radiation is briefly discussed but not favored. We speculate that production of the γ ~ 107 electrons necessary for X-ray synchrotron radiation from hot spots is inhibited when the external gas density is high, as is the case when the radio galaxy is within a cooling flow.
TL;DR: In this article, the authors describe state-of-the-art experimental techniques using the beamline BM29 of the European Synchrotron Radiation Facility (ESRF) using Si(111), Si(311), and Si(511) crystal pairs.
Abstract: We describe state-of-the-art experimental techniques using the beamline BM29 of the European Synchrotron Radiation Facility (ESRF). This station exploits the unique characteristics of an ESRF bending magnet source to provide a tunable, collimated, x-ray beam to perform high quality x-ray absorption spectroscopy within the energy range of E=5–75 keV using Si(111), Si(311), and Si(511) crystal pairs. Energy scans can be performed over this wide energy range with excellent reproducibility, stability and resolution, usually better than ΔE/E≃5×10−5. The experimental setup has been exploited to study condensed matter under extreme conditions. We describe here two sample environment devices; the L’ Aquila–Camerino oven for high-temperature studies up to 3000 K in high vacuum and the Paris–Edinburgh press suitable for high-pressure high-temperature studies in the range 0.1–7 GPa and temperatures up to 1500 K. These devices can be integrated in an experimental setup which combines various control and detection sys...
TL;DR: The structural anisotropy of poly(alkylthiophene) films has been studied by X-ray diffraction, using both conventional methods and synchrotron radiation at grazing incidence as discussed by the authors.
Abstract: The structural anisotropy of various poly(alkylthiophene) films have been studied by X-ray diffraction, using both conventional methods and synchrotron radiation at grazing incidence. Solution-cast ...
TL;DR: In this article, the relevant relationships of the dynamical theory of X-ray diffraction are used to explain basic concepts of monochromatization and are combined with ray-tracing techniques to design high-energy-resolution synchromators.
Abstract: An introduction to monochromatization of synchrotron radiation in the energy range of 5‐30 keV is presented for applications involving nuclear resonant scattering. The relevant relationships of the dynamical theory of X-ray diffraction are used to explain basic concepts of monochromatization. These relations are combined with ray-tracing techniques to design high-energy-resolution monochromators. Transmission-optimized and energyresolution-optimized designs that achieve high energy resolutions (10 6
TL;DR: In this article, a planar parabolic lens with minimized absorption was fabricated by a combination of photolithography and dry-etching techniques at the European Synchrotron Radiation Facility.
Abstract: Silicon refractive planar parabolic lenses with minimized absorption were fabricated by a combination of photolithography and dry-etching techniques. Focusing and spectral properties of the lenses were studied with synchrotron radiation in the energy range 8–25 keV at the European Synchrotron Radiation Facility. A focal spot of 1.8 μm with a gain of 18.5 and transmission of more then 80% was measured at 15.6 keV. The spectral characteristics were analyzed taking into account material dispersion and photon-energy attenuation in the hard x-ray range.
TL;DR: In this article, the volume of periclase (MgO) was measured by monochromatic X-ray diffraction in a laser-heated diamond anvil cell up to a pressure of 53 GPa and a temperature of 2500 K. In order to take thermal pressure effect into account, pressure was measured using an internal pressure calibrant (platinum).
Abstract: The volume of periclase (MgO) has been measured by monochromatic X-ray diffraction in a laser-heated diamond anvil cell up to a pressure of 53 GPa and a temperature of 2500 K. The X-ray source was synchrotron radiation at the European Synchrotron Radiation Facility (Grenoble, France). In addition to laser heating, the use of argon as a pressure transmitting medium provided quasi-hydrostatic conditions in the cell assembly. In order to take thermal pressure effect into account, pressure was measured using an internal pressure calibrant (platinum). By analysis of the experimental P-V-T data set the following parameters were obtained: at ambient temperature, K′0 = 3.94 ± 0.2 when K0 is fixed to 161 GPa (with a Birch-Murnaghan equation of state); under high temperature, α(P = 0,T) = (3.0 + 0.0012T) × 10−5 K−1; (∂KT/∂T)P = −0.022(3) GPa K−1. The quasi-harmonic Debye model appears to describe correctly the temperature dependence of the volume at high pressure within experimental errors, with the following parameters: θD0 = 800 K, γ0 = 1.45 (Gruneisen parameter under ambient conditions), and q = 0.8 ± 0.5.
TL;DR: In this paper, a low photon energy-pass filter has been designed and built, ensuring a high spectral purity on the vacuum ultraviolet (VUV) SU5 beamline at Super-ACO.
Abstract: In order to separate the fundamental synchrotron radiation from the high harmonics emitted by an undulator, a low photon energy-pass filter has been designed and built, ensuring a high spectral purity on the vacuum ultraviolet (VUV) SU5 beamline at Super-ACO. It consists of an absorption cell filled with rare gases and separated from the ultrahigh vacuum of the storage ring and of the beamline by a double differential pumping obtained with thin capillaries. Its conception has been optimized by numerical computation of pumping speed. Admission pressures in the range of 100 Pa in the central part of the filter have been used without any degradation of the upstream or downstream ultrahigh vacuum. The measured attenuation factors above the energy cutoff are above 105 and 102 (and certainly above 103 with ultimate pressure of Ne) for argon and neon absorbing gases, respectively, with no measurable attenuation of fundamental radiation. A sophisticated numerical simulation of the pressure distribution, taking in...
31 Jul 2000
TL;DR: In this article, the design and operation of a gas aggregation source is described, which combines the attributes of high-temperature operation (enabling preparation of transition metal clusters), mass selection, ultrahigh vacuum compatibility, and transportability.
Abstract: The design and operation of a gas aggregation source is described. The source combines the attributes of high-temperature operation (enabling preparation of transition metal clusters), mass selection, ultrahigh vacuum compatibility, and transportability. This makes it ideally suited to in situ studies such as scanning tunneling microscope or synchrotron radiation experiments. Data are presented to illustrate the performance of the source; recent results obtained in synchrotron radiation studies are highlighted.
TL;DR: In this paper, a synchrotron X-ray transmission technique was applied to study the internal load transfer and micromechanical damage in molybdenum particle-reinforced copper matrix composites during plastic deformation.
Abstract: A synchrotron X-ray transmission technique was applied to study the internal load transfer and micromechanical damage in molybdenum particle-reinforced copper matrix composites during plastic deformation. Mechanically loaded, 1.5-mm-thick specimens were irradiated with a monochromatic beam of 65 keV X-rays. Low-index diffraction rings of both phases were recorded with a high-resolution two-dimensional detector. By means of newly developed data processing routines, we could quantify as a function of applied stress both the ring distortion (from which the volume-averaged elastic strains in the two phases were calculated), and the ring graininess (which is related to the Bragg peak broadening). Based on this information, the deformation and damage processes in these alloys were studied in detail. As compared to conventional neutron diffraction methods, the photon transmission technique yielded similar precision but at much reduced measurement times. The main sources of experimental errors were identified and strategies to minimize these errors were developed.
TL;DR: In this article, the authors investigated the process of synchrotron radiation from thermal electrons at semirelativistic and relativistic temperatures and derived an analytic expression for the emission coefficient for random magnetic fields with an accuracy significantly higher than those derived previously.
Abstract: We investigate the process of synchrotron radiation from thermal electrons at semirelativistic and relativistic temperatures. We find an analytic expression for the emission coefficient for random magnetic fields with an accuracy significantly higher than those derived previously. We also present analytic approximations to the synchrotron turnover frequency, treat Comptonization of self-absorbed synchrotron radiation, and give simple expressions for the spectral shape and the emitted power. We also consider modifications of the above results by bremsstrahlung.
We then study the importance of Comptonization of thermal synchrotron radiation in compact X-ray sources. We first consider emission from hot accretion flows and active coronae above optically thick accretion discs in black hole binaries and active galactic nuclei (AGNs). We find that for plausible values of the magnetic field strength, this radiative process is negligible in luminous sources, except for those with hardest X-ray spectra and stellar masses. Increasing the black hole mass results in a further reduction of the maximum Eddington ratio from this process. Then, X-ray spectra of intermediate-luminosity sources, e.g. low-luminosity AGNs, can be explained by synchrotron Comptonization only if they come from hot accretion flows, and X-ray spectra of very weak sources are always dominated by bremsstrahlung. On the other hand, synchrotron Comptonization can account for power-law X-ray spectra observed in the low states of sources around weakly magnetized neutron stars.
TL;DR: In this paper, the authors performed detailed temporal and spectral studies of a purely cooling plasma system using parameters appropriate to blazars, and found that the SSC process contributes strongly to electron cooling and that the whole system is nonlinear; thus, simultaneously solving electron and photon kinetic equations is necessary.
Abstract: Multiwavelength observations of blazars such as Mrk 421 and Mrk 501 show that they exhibit strong short time variabilities in flarelike phenomena. Working from the homogeneous synchrotron self-Compton (SSC) model and assuming that time variability of the emission is initiated by changes in the injection of nonthermal electrons, we perform detailed temporal and spectral studies of a purely cooling plasma system using parameters appropriate to blazars. One important parameter is the total injected energy , and we show how the synchrotron and Compton components respond as varies. When the synchrotron and SSC components have comparable peak fluxes, we find that the SSC process contributes strongly to the electron cooling and that the whole system is nonlinear; thus, simultaneously solving electron and photon kinetic equations is necessary. In the limit of the injection-dominated situation when the cooling timescale is long, we find a unique set of model parameters that are fully constrained by observable quantities. In the limit of the cooling-dominated situation, TeV emissions arise mostly from a cooled electron distribution and the Compton scattering process is always in the Klein-Nishina regime, which gives the TeV spectrum a large curvature. Furthermore, even in a single-injection event, the multiwavelength light curves do not necessarily track each other because the electrons that are responsible for those emissions might have quite different lifetimes. We discuss in detail how one could infer important physical parameters using the observed spectra. In particular, we could infer the size of the emission region by looking for exponential decay in the light curves. We could also test the basic assumption of the SSC model by measuring the difference in the rate of peak energy changes of synchrotron and SSC peaks. We also show that the trajectory in the photon index-flux plane evolves clockwise or counterclockwise depending on the value of and the observed energy bands.
TL;DR: A simple interferometric technique for hard x-ray spatial coherence characterization, recording a Fresnel interference pattern produced by a round fiber or a slit, derived analytical formulas that give a direct relation between a visibility of interference fringes and either the source size or the transverse coherence length.
Abstract: We propose a simple interferometric technique for hard x-ray spatial coherence characterization, recording a Fresnel interference pattern produced by a round fiber or a slit. We have derived analytical formulas that give a direct relation between a visibility of interference fringes and either the source size or the transverse coherence length. The technique is well suited to third-generation synchrotron radiation sources and was experimentally applied to determine the spatial coherence length and the source size at the European Synchrotron Radiation Facility.
TL;DR: In this article, the authors considered the excitation and decay of a core hole in an isolated atom or molecule as a scattering process and treated the whole phenomenon in a one-step picture, where the bandwidth of the exciting radiation is narrower than the core hole lifetime broadening of the neutral core-excited state.
TL;DR: In this paper, a one-zone, shocked wind model is developed for the X-ray luminosity of pulsar nebulae, where the electrons and positrons are cooled rapidly by synchrotron radiation and the initial particle spectrum is similar to the Crab Nebula.
Abstract: A one-zone, shocked wind model is developed for the X-ray luminosity of pulsar nebulae. If the electrons and positrons cool rapidly by synchrotron radiation and the initial particle spectrum is similar to that of the Crab Nebula, the X-ray luminosity is produced from the pulsar power with high efficiency and is insensitive to the model parameters. If the electrons are not in the cooling regime, the X-ray luminosity is produced with lower efficiency, as appears to be the case for the compact nebula around the Vela pulsar. The observed X-ray spectral index is an indicator for which case applies and thus plays a role in estimating the pulsar power needed to produce an observed X-ray luminosity.
TL;DR: In this article, the ASCA (Advanced Satellite for Cosmology and Astrophysics) results of RCW 86, a shell-like supernova remnant (SNR), were reported.
Abstract: We report the ASCA (Advanced Satellite for Cosmology and Astrophysics) results of RCW 86, a shell-like supernova remnant (SNR). The bright region in the X-ray band traces the radio clumpy shell, although details of the structure are different. The X-ray spectrum from each part of the shell can not be fitted to a thin thermal plasma model, but requires, at least three components: a low temperature plasma of 0.3 keV, high temperature plasma of > several keV, and a power-law component with a photon index = 3. The abundances of O, Ne, Mg and Si are significantly higher than that of Fe, indicating that RCW 86 is a type II SNR. The absorption column of 3e21 H cm^-2 indicates the distance to the SNR to be several kpc. The power-law component can be interpreted to be synchrotron radiation of high energy electrons. Assuming energy density equipartition between the magnetic field and the electrons, and using the radio and X-ray spectra, we argue that high energy electrons are accelerated up to 20 TeV. The acceleration efficiency is, however, different from shell to shell.
TL;DR: In this paper, the authors performed an in situ X-ray diffraction study on a Li 1−xCoO2 cathode in a Li|Li1−xCOO2 cell, which was charged at a C/10 rate from 3.5 to 5.2 V.
TL;DR: There are numerous advantages of using synchrotron radiation for protein crystallography: rapid data collection, use of smaller crystals than with conventional X-ray sources, and the ability to conduct measurements at multiple wavelengths.
TL;DR: To design therapy parameters for tumour treatments, the newly upgraded LSCAT (Low energy SCATtering) package of the EGS4 Monte Carlo simulation code was adapted to develop an accurate self-written user code for calculating microbeam radiation dose profiles with a precision of 1 microm.
Abstract: Microbeam therapy is established as a general concept for brain tumour treatment A synchrotron based x-ray source was chosen for experimental research into microbeam therapy, and therefore new simulations were essential for investigating the therapy parameters with a proper description of the synchrotron radiation characteristics To design therapy parameters for tumour treatments, the newly upgraded LSCAT (Low energy SCATtering) package of the EGS4 Monte Carlo simulation code was adapted to develop an accurate self-written user code for calculating microbeam radiation dose profiles with a precision of 1 microm LSCAT is highly suited to this purpose due to its ability to simulate low-energy x-ray transport with detailed photon interactions (including bound electron incoherent scattering functions, and linear polarized coherent scattering) The properties of the synchrotron x-ray microbeam, including its polarization, source spectrum and beam penumbra, were simulated by the new user codes Two concentric spheres, an inner sphere, defined as a brain, and a surrounding sphere, defined as a skull, represented the phantom The microbeam simulation was tested using a 3 x 3 cm array beam for small treatment areas and a 6 x 6 cm array for larger ones, with different therapy parameters, such as beam width and spacing The results showed that the microbeam array retained an adequate peak-to-valley ratio, of five times at least, at tissue depths suitable for radiation therapy Dose measurements taken at 1 microm resolution with an 'edge-on' MOSFET validated the basics of the user code for microplanar radiation therapy
TL;DR: In this paper, an account of developments in instrumentation for soft X-ray emission spectroscopy (SXES) based on synchrotron radiation is presented, and a brief discussion on future developments in SXES instrumentation is included.
TL;DR: The current best detection limit achieved at the Stanford Synchrotron Radiation Laboratory (SSRL) for Ni is 8×10 7 atoms/cm 2 which is a factor of 50 better than what can be achieved using laboratory-based sources as mentioned in this paper.