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Witherspoon, Kenny C., Brian J. Cross i Mandi D. Hellested. "Combined Electron Excitation and X-Ray Excitation for Spectrometry in the SEM". Microscopy Today 21, nr 4 (lipiec 2013): 24–28. http://dx.doi.org/10.1017/s1551929513000709.
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Energy-dispersive X-ray spectrometry (EDS) is an analytical technique used to determine elemental composition. It is a powerful, easy-to-use, non-destructive technique that can be employed for a wide variety of materials. In this technique the electron beam of the scanning electron microscope (SEM) impinges on the sample and excites atomic electrons causing the production of characteristic X rays. These characteristic X rays have energies specific to elements in the sample. The EDS detector collects these X rays as a signal and produces a spectrum. Samples also can be excited by X rays. Collimated and focused X rays from an X-ray source produce characteristic X rays that can be detected by the same EDS detector. When X rays are used as the source of excitation, the method is then called X-ray fluorescence (XRF) or micro-XRF.
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Hlava, Paul F., i William F. Chambers. "Electron microprobe analysis: The upper limit of submicron spectroscopy". Proceedings, annual meeting, Electron Microscopy Society of America 44 (sierpień 1986): 744–47. http://dx.doi.org/10.1017/s0424820100145091.
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In the electron microprobe, a beam of high energy electrons is focussed to a fine point on the surface of a fairly thick specimen and the x rays produced are analyzed to determine the chemistry of the "point". The spa- cial resolution of this instrument for chemical analysis, then, is defined by the volume of material from which the x ray signal originates. This, in turn, is related to factors such as the diameter of the electron beam, the spreading of the electron beam as it penetrates into the sample and interacts with the atoms of the sample to generate x rays, and the extent to which these primary x rays penetrate beyond the region of electron beam interaction and generate secondary x rays by the process of fluorescence. Beam voltage, current, and diameter can all be easily controlled by the analyst. Once the electrons enter the specimen, however, the analyst loses control of their density. Each individual electron follows a unique, erratic path as it passes near, passes through, or collides with parts of the atoms in the specimen. Monte Carlo calculations are a means by which many investigators have tried to model the paths of individual electrons and the interation volume that large numbers of such electrons define.3 “* It is well known that the size and shape of the region into which the electron beam penetrates and expends its energy is controlled primarily by the average atomic number, atomic weight, and density of the specimen in the region of interest and the beam voltage.
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Falconer, Isobel. "Corpuscles, Electrons and Cathode Rays: J.J. Thomson and the ‘Discovery of the Electron’". British Journal for the History of Science 20, nr 3 (lipiec 1987): 241–76. http://dx.doi.org/10.1017/s0007087400023955.
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On 30 April, 1897, J. J. Thomson announced the results of his previous four months' experiments on cathode rays. The rays, he suggested, were negatively charged subatomic particles. He called the particles ‘corpuscles’. They have since been re-named ‘electrons’ and Thomson has been hailed as their ‘discoverer’. Contrary to the accounts of most later writers, I show that this discovery was not the outcome of a concern with the nature of cathode rays which had occupied Thomson since 1881 and had shaped the course of his experiments during the period 1881–1897. An examination of his work shows that he paid scant attention to cathode rays until late 1896.
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Carmichael, Stephen W. "An Electron Optical Achromat". Microscopy Today 5, nr 6 (sierpień 1997): 3–5. http://dx.doi.org/10.1017/s1551929500056029.
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Spherical and chromatic aberrations have been the bane of optical lenses ever since they were first ground from a piece of glass. As light travels through a convex (converging) lens, the rays at the center of the optical axis are refracted (bent) less than the peripheral rays, so that the central rays are focused behind the peripheral rays. This is the essence of spherical aberration. Light of differing wavelengths (colors) interact differently with the lens so that longer wavelengths (red) are focused behind shorter wavelengths (blue). This is chromatic aberration. In the early days of light microscopy, these two inherent flaws seriously limited the quality of images.
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Cao, Zhen, F. Aharonian, Q. An, Axikegu, L. X. Bai, Y. X. Bai, Y. W. Bao i in. "Peta–electron volt gamma-ray emission from the Crab Nebula". Science 373, nr 6553 (8.07.2021): 425–30. http://dx.doi.org/10.1126/science.abg5137.
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The Crab Nebula is a bright source of gamma rays powered by the Crab Pulsar’s rotational energy through the formation and termination of a relativistic electron-positron wind. We report the detection of gamma rays from this source with energies from 5 × 10−4 to 1.1 peta–electron volts with a spectrum showing gradual steepening over three energy decades. The ultrahigh-energy photons imply the presence of a peta–electron volt electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron’s size between 0.025 and 0.1 parsecs and the magnetic field to ≈110 microgauss. The production rate of peta–electron volt electrons, 2.5 × 1036 ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta–electron volt protons to the production of the highest-energy gamma rays.
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Moodie, A. F., i J. C. H. Spence. "John Maxwell Cowley 1923 - 2004". Historical Records of Australian Science 17, nr 2 (2006): 227. http://dx.doi.org/10.1071/hr06012.
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John Cowley contributed significantly to all of the fields that relate to electron diffraction and electron microscopy, and helped to found not a few of them. His name is associated in particular with n-beam dynamical theory, high-resolution electron microscopy, scanning transmission electron microscopy, instrumental design, and the application of the techniques of electron scattering to structure analysis. His experimental work was not, however, confined to the scattering of electrons: to take but one instance, his seminal work on the theory of short-range order was stimulated initially by his experiments using X-rays, and it was only later that he extended the technique to include electron diffraction. Finally, to all those who practise the techniques of scattering electrons, X-rays, or neutrons in the study of solids, liquids or gases, his book Diffraction Physics remains not only eminently readable but authoritative.
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Bednarik, Martin, David Manas, Miroslav Manas, Martin Ovsik, Jan Navratil i Ales Mizera. "Surface and Adhesive Properties of Low-Density Polyethylene after Radiation Cross-Linking". Key Engineering Materials 606 (marzec 2014): 265–68. http://dx.doi.org/10.4028/www.scientific.net/kem.606.265.
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Radiation cross-linking gives inexpensive commodity plastics and technical plastics the mechanical, thermal, and chemical properties of high-performance plastic. This upgrading of the plastics enables them to be used in conditions which they would not be able to with stand otherwise. The irradiation cross-linking of thermoplastic materials via electron beam or cobalt 60 (gammy rays) is performed separately, after processing. Generally, ionizing radiation includes accelerated electrons, gamma rays and X-rays. Radiation processing with an electron beam offers several distinct advantages when compared with other radiation sources, particularly γ-rays and x-rays. The process is very fast, clean and can be controlled with much precision. There is no permanent radioactivity since the machine can be switched off. In contrast to γ-rays and x-rays, the electron beam can steered relatively easily, thus allowing irradiation of a variety of physical shapes. The energy-rich beta rays trigger chemical reactions in the plastics which results in networking of molecules (comparable to the vulcanization of rubbers which has been in industrial use for so long). The energy from the rays is absorbed by the material and cleavage of chemical bonds takes place. This releases free radicals which in next phase from desired molecular bonds. This article describes the effect of radiation cross-linking on the surface and adhesive properties of low-density polyethylene.
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Vrakking, Marc J. J., i Thomas Elsaesser. "X-rays inspire electron movies". Nature Photonics 6, nr 10 (październik 2012): 645–47. http://dx.doi.org/10.1038/nphoton.2012.247.
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Shao, Tao, Victor F. Tarasenko, Cheng Zhang, Evgeni KH Baksht, Ping Yan i Yuliya V. Shut'Ko. "Repetitive nanosecond-pulse discharge in a highly nonuniform electric field in atmospheric air: X-ray emission and runaway electron generation". Laser and Particle Beams 30, nr 3 (25.05.2012): 369–78. http://dx.doi.org/10.1017/s0263034612000201.
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AbstractRepetitive nanosecond-pulse discharge with a highly inhomogeneous electric field was investigated in air at atmospheric pressure. Three repetitive nanosecond generators were used, and the rise times of the voltage pulses were 15, 1, and 0.2 ns, respectively. Under different experimental conditions, X-rays and runaway electron beams were directly measured using various setups. The variables affecting X-rays and runaway electrons, including gap distance, pulse repetition frequency, anode geometry, and material, were investigated. It was shown that it was significantly easier to record the X-rays than the runaway electrons in the repetitive nanosecond-pulse discharge. It was confirmed that a volume diffuse discharge was attributed to the generation of runaway electrons and the corresponding X-rays.
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Bell, David C., Anthony J. Garratt-Reed i Linn W. Hobbs. "RDF Analysis of Radiation-Amorphized SiC using a field Emission Scanning Electron Microscope". Microscopy and Microanalysis 4, S2 (lipiec 1998): 700–701. http://dx.doi.org/10.1017/s143192760002362x.
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AbstractFast electrons are a particularly useful chemical and structural probe for the small sample volumes associated with ion- or fast electron-irradiation-induced amorphization, because of their much stronger interaction with matter than for X-rays or neutrons, and also because they can be readily focused to small probes. Three derivative signals are particularly rich in information: the angular distribution of scattered electrons (which is utilized in both diffraction and imaging studies); the energy loss spectrum of scattered electrons (electron energy loss spectroscopy, or EELS); and the emission spectrum of characteristic X-rays resulting from ionization energy losses (energy dispersive X-ray spectroscopy, or EDXS). We have applied the first two to the study of three amorphized compounds (AIPO4, SiO2, SiC) using MIT's Vacuum Generators HB603 field-emission (FEG) scanning transmission electron microscope (STEM), operating at 250 kV and equipped with a Gatan digital parallel-detection electron energy-loss spectrometer (digiPEELS).
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Pettinato, Sara, Marco Girolami, Antonella Stravato, Valerio Serpente, Daniela Musio, Maria C. Rossi, Daniele M. Trucchi, Riccardo Olivieri i Stefano Salvatori. "A Highly Versatile X-ray and Electron Beam Diamond Dosimeter for Radiation Therapy and Protection". Materials 16, nr 2 (14.01.2023): 824. http://dx.doi.org/10.3390/ma16020824.
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Radiotherapy is now recognized as a pillar in the fight against cancer. Two different types are currently used in clinical practice: (1) external beam radiotherapy, using high-energy X-rays or electron beams, both in the MeV-range, and (2) intraoperative radiotherapy, using low-energy X-rays (up to 50 keV) and MeV-range electron beams. Versatile detectors able to measure the radiation dose independently from the radiation nature and energy are therefore extremely appealing to medical physicists. In this work, a dosimeter based on a high-quality single-crystal synthetic diamond sample was designed, fabricated and characterized under low-energy X-rays, as well as under high-energy pulsed X-rays and electron beams, demonstrating excellent linearity with radiation dose and dose-rate. Detector sensitivity was measured to be 0.299 ± 0.002 µC/Gy under 6 MeV X-ray photons, and 0.298 ± 0.004 µC/Gy under 6 MeV electrons, highlighting that the response of the diamond dosimeter is independent of the radiation nature. Moreover, in the case of low-energy X-rays, an extremely low limit of detection (23 nGy/s) was evaluated, pointing out the suitability of the device to radiation protection dosimetry.
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Aoshima, Keito, Masahiro Horita i Jun Suda. "Correlation between non-ionizing energy loss and production rate of electron trap at EC − (0.12–0.20) eV formed in gallium nitride by various types of radiation". Applied Physics Letters 122, nr 1 (2.01.2023): 012106. http://dx.doi.org/10.1063/5.0128709.
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Production rate (PR = trap concentration/incident fluence) of traps formed by energetic particles is important for predicting device degradation caused by radiation when developing radiation-resistant devices. We demonstrate a clear correlation between non-ionizing energy loss (NIEL) and PR of an electron trap at about 0.12–0.20 eV below the conduction band edge [ EC − (0.12–0.20) eV] for various types of energetic particles in gallium nitride (GaN). NIEL values in GaN for electrons, protons, and [Formula: see text]-rays were calculated using a screened-relativistic treatment, and NIEL values for gamma-rays were calculated by simulating slowed-down spectra due to shielding material. To obtain the PRs of the electron trap, 60Co gamma-rays with an average photon energy of 1.25 MeV and electron beams with energies from 137 keV to 2 MeV were irradiated onto n-type GaN Schottky barrier diodes. We measured the concentration of an electron trap at EC − (0.13–0.14) eV using deep-level transient spectroscopy. We also used the PRs of electron traps with similar energy levels of EC − (0.12–0.20) eV from previous studies on electrons, protons, and [Formula: see text]-rays irradiated on GaN. All the trap PRs were proportional to the NIEL in a range of eight orders of magnitude, which confirms that the energy levels formed by various energetic particles have the same origin of being generated by atomic displacements. The obtained relationship coefficient between the NIEL and PRs of the trap is useful for predicting the degradation of GaN-based devices due to traps formed by various kinds of radiation.
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Wittry, D. B. "Focusing x rays for microprobe x-ray fluorescence analysis". Proceedings, annual meeting, Electron Microscopy Society of America 50, nr 2 (sierpień 1992): 1730–31. http://dx.doi.org/10.1017/s042482010013328x.
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X-ray microprobes that use focused monochromatic x rays for fluorescence excitation have four significant advantages over electron microprobes that use focused electrons for direct excitation, namely: 1) less background radiation is produced, 2) there is little or no charging of insulating specimens, 3) less damage is caused to the specimen, and 4) the specimen often does not need a high vacuum environment. These advantages result from the difference in interaction of photon and electron beams with matter. In the first place, because the x-ray photon is uncharged, bremsstrahlung which is always obtained with electron bombardment, is not produced by photon bombardment; this results in higher signal/background ratio and can yield lower detection limits by a factor of about 10−2 of those obtained with electron microprobes. Also because the photon is uncharged, the only charging of insulating specimens is due to secondary effects. Second, x-ray photons preferentially excite inner shell electrons as is well known from the large increase in absorption coefficient when the photon energy exceeds the critical excitation energy; this results in less damage for a given number of characteristic x-rays produced in the specimen.
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ELIASSON, BENGT, i CHUAN SHENG LIU. "An electromagnetic gamma-ray free electron laser". Journal of Plasma Physics 79, nr 6 (9.08.2013): 995–98. http://dx.doi.org/10.1017/s0022377813000779.
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AbstractWe present a theoretical model for the generation of coherent gamma rays by a free electron laser, where a high-energy electron beam interacts with an electromagnetic wiggler. By replacing the static undulator with a 1-μm laser wiggler, the resulting radiation would go from X-rays currently observed in experiments, to gamma rays. Coherent light in the gamma-ray range would have wide-ranging applications in the probing of matter on sub-atomic scales.
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Winner, Georg, Christoph Pfrommer, Philipp Girichidis, Maria Werhahn i Matteo Pais. "Evolution and observational signatures of the cosmic ray electron spectrum in SN 1006". Monthly Notices of the Royal Astronomical Society 499, nr 2 (2.10.2020): 2785–802. http://dx.doi.org/10.1093/mnras/staa2989.
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ABSTRACT Supernova remnants (SNRs) are believed to be the source of Galactic cosmic rays (CRs). SNR shocks accelerate CR protons and electrons which reveal key insights into the non-thermal physics by means of their synchrotron and γ-ray emission. The remnant SN 1006 is an ideal particle acceleration laboratory because it is observed across all electromagnetic wavelengths from radio to γ-rays. We perform 3D magnetohydrodynamics (MHD) simulations where we include CR protons and follow the CR electron spectrum. By matching the observed morphology and non-thermal spectrum of SN 1006 in radio, X-rays, and γ-rays, we gain new insight into CR electron acceleration and magnetic field amplification. (1) We show that a mixed leptonic–hadronic model is responsible for the γ-ray radiation: while leptonic inverse-Compton emission and hadronic pion-decay emission contribute equally at GeV energies observed by Fermi, TeV energies observed by imaging air Cherenkov telescopes are hadronically dominated. (2) We show that quasi-parallel acceleration (i.e. when the shock propagates at a narrow angle to the upstream magnetic field) is preferred for CR electrons and that the electron acceleration efficiency of radio-emitting GeV electrons at quasi-perpendicular shocks is suppressed at least by a factor ten. This precludes extrapolation of current 1D plasma particle-in-cell simulations of shock acceleration to realistic SNR conditions. (3) To match the radial emission profiles and the γ-ray spectrum, we require a volume-filling, turbulently amplified magnetic field and that the Bell-amplified magnetic field is damped in the immediate post-shock region. Our work connects microscale plasma physics simulations to the scale of SNRs.
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Letaw, John R., J. H. Adams, Rein Silberberg i C. H. Tsao. "Electron capture decay of cosmic rays". Astrophysics and Space Science 114, nr 2 (wrzesień 1985): 365–79. http://dx.doi.org/10.1007/bf00653983.
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Wight, S. A., i C. J. Zeissler. "Phosphor Imaging Plate Measurement of Electron Scattering in the Environmental Scanning Electron Micrsoscope". Microscopy and Microanalysis 6, S2 (sierpień 2000): 798–99. http://dx.doi.org/10.1017/s1431927600036485.
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In this work, phosphor imaging plate technology is applied to measure electron scattering directly in the environmental scanning electron microscope (ESEM) specimen chamber. The scattering of electrons from the primary electron beam, under relatively high-pressure conditions (266 Pa) in the ESEM sample chamber, degrades the analytical accuracy of elemental analysis. The degree of this degradation is poorly known. To date, attempts to measure experimentally the spatial distribution of the scattered electrons have been limited to observing secondary effects such as the intensity of x-rays produced from copper targets positioned at various distances from the primary electron beam interaction point. A more accurate distribution of the scattered electron intensity can be obtained from a direct measurement of both the scattered and unscattered electrons over a large area with single electron sensitivity. Improvements to the accuracy of Monte Carlo models of the scattering process will be made possible by the direct measurement data.
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Liu, Yiheng, Kai He, Gang Wang, Guilong Gao, Xin Yan, Yanhua Xue, Ping Chen i in. "Simulation of the impact of using a novel neutron conversion screen on detector time characteristics and efficiency". AIP Advances 12, nr 4 (1.04.2022): 045206. http://dx.doi.org/10.1063/5.0073025.
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To directly measure the DT neutrons from inertial confinement fusion with a high time resolution, a new type of neutron conversion composed of a CH2 conversion layer, a metal moderation layer, and a CsI secondary electron emission layer is proposed. The conversion screen is based on the principle that recoil protons produced by elastic scattering of the neutrons in CH2 interact with CsI to generate secondary electrons. The moderation layer can filter the energy spectrum of protons to prevent low-energy protons from reaching CsI, which shortens the duration of the secondary electron pulse and improves the temporal resolution of the conversion screen. Based on the Monte Carlo method, both the neutron impulse and background γ-rays response of this conversion screen were calculated. The simulation indicates that the temporal resolution of the conversion screen can reach up to 4.9 ps when the thickness of the gold layer is 100 µm. The detection efficiency of secondary electrons/neutrons can reach 7.4 × 10−3. The detection efficiency of the neutron conversion screen for secondary electrons/γ-rays is an order of magnitude lower than the neutron impulse response, and the response time of γ-rays is 20 ps earlier than the neutron pulses. This means that using this conversion screen is beneficial to distinguish between neutrons and γ-rays and has a good signal-to-noise ratio.
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Yang, Qingyu, Yubo Wang, Yifei Cao, Jingwen Li i Youwei Tian. "Spatial radiation features of the off-axis collision between a relativistic electron and a tightly focused linearly polarized laser". Laser Physics Letters 20, nr 4 (14.02.2023): 045301. http://dx.doi.org/10.1088/1612-202x/acb91f.
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Abstract The collision between relativistic electrons and a tightly focused linearly polarized laser pulse produced nonlinear inverse Thomson scattering (NITS), which generates backward x-rays. The effects of the initial transverse position of electrons with varied initial energy on the angular distribution of radiation power and spectrum are studied through numerical simulation. For the electrons with low initial energy (i.e. 2.56 MeV ), the off-axis collision breaks the spatial symmetry of x-ray radiation compared with the axial collision, the radiation direction is also torqued towards the same off-axis direction. There exists an optimal initial transverse position of electrons, which means the electron emitted from this position obtains greater radiation power. For the high-energy ( \!\!\!10{\text{ MeV}}$?> > 10 MeV ) electrons, the effect of torsion is not significant. The impact of off-axial is mainly manifested in the high-order harmonic spectrum. These findings help obtain high quality x-rays and modulate NITS radiation symmetry by electron parameters.
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Østgaard, N., J. Stadsnes, K. Aarsnes, F. Søraas, K. Måseide, M. Smith i J. Sharber. "Simultaneous measurements of X-rays and electrons during a pulsating aurora". Annales Geophysicae 16, nr 2 (28.02.1998): 148–60. http://dx.doi.org/10.1007/s00585-998-0148-0.
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Abstract. The PULSAUR II rocket was launched from Andøya Rocket Range at 23.43 UT on 9 February 1994 into a pulsating aurora. In this paper we focus on the observations of precipitating electrons and auroral X-rays. By using models it is possible to deduce the electron energy spectrum from X-ray measurements. Comparisons are made between the deduced electron fluxes and the directly measured electron fluxes on the rocket. We found the shape of the observed and the deduced electron spectra to fit very well, with almost identical e-folding energies in the energy range from 10 ke V to ~60–80 ke V. For the integrated fluxes from 10.8 to 250 ke V, we found a discrepancy of 30% . By combining two models, we have found a good method of deducing the electron precipitation from X-ray measurements. The discrepancies between calculations and measurements are in the range of the uncertainties in the measurements.Key words. Ionospheric particle precipitation · Magnetospheric physics · Annual phenomena · Energetic particle
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M. MacRae, Colin, N. C. Wilson i M. Otsuki. "Holistic Mapping in an Electron Microprobe". Microscopy and Microanalysis 7, S2 (sierpień 2001): 146–47. http://dx.doi.org/10.1017/s1431927600026805.
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When an electron beam interacts with a solid target a number of interactions occur which produce electrons, x-rays and light. Typically in an electron microprobe analyser (EPMA) both the electron and x-ray signals are collected for analysis and imaging. However, if the EPMA is equipped with an optical spectrometer then all three signals can be collected. Commonly, the optical or CathodoLuminescence (CL) spectrometer is a monochromator type and can only collect a single frequency or small range of frequencies at a time. Simultaneous collection of the complete visible spectrum is not possible. The collection optics associated with the spectrometer often must be moved into place to start collection, this then obscures the other detectors and prevents simultaneous collection. At CSIRO Minerals an optical spectrometer has been integrated into a JEOL 8900R EPMA and allows simultaneous collect of all light, x-rays and electron signals. This form of mapping, termed Holistic Mapping, has significant advantages over traditional mapping in that it removes the need to have a priori knowledge about what the important frequencies are that will provide the solution to the problem at hand.
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Armstrong, John T., i Paul K. Carpenter. "X-ray spatial resolution in electron microbeam analysis". Proceedings, annual meeting, Electron Microscopy Society of America 49 (sierpień 1991): 462–63. http://dx.doi.org/10.1017/s0424820100086611.
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The spatial resolution of characteristic x-ray production from electron bombardment in thick specimens is dependent upon the rate of energy loss of the primary electrons, the degree of electron scattering, the degree of x-ray absorption by the matrix, and the extent of secondary fluorescence of the x-rays by higher energy characteristic and continuum x-rays. The x-ray spatial resolution in thick specimens is much coarser than the secondary or backscattered electron resolution, typically being of the order of a fraction of a μm to several μm when secondary fluorescence is not significant, or as much as 100 to 200 μm when it is. The size of the excited volume of x-ray production is dependent upon the accelerating potential of the electron beam, the critical excitation potential, and the sample density. The size of the excited volumes of different elements’ x-ray lines can be considerably different in the same matrix, due to differences in critical excitation potential; the emitting volumes can vary even more, due to differences in mass absorption.
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KAWATSURA, K., T. HASEGAWA, N. TERAZAWA, S. ARAI, M. SATAKA, H. NARAMOTO, K. KOMAKI i A. OOTUKA. "CONTINUUM X RAYS IN HIGHLY CHARGED ION-ATOM COLLISIONS". International Journal of PIXE 06, nr 03n04 (styczeń 1996): 441–45. http://dx.doi.org/10.1142/s0129083596000478.
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Continuous X rays produced by highly charged heavy ion-atom collisions have been studied experimentally. 2–5.5 MeV/u F, Si, S and Cl ions with zero or one electron were bombarded with a thin gas target of H 2 and He. Emitted X-ray spectra were measured by using a Si(Li) X-ray detector at 90°. The characteristic X rays and radiative electron capture X rays were observed clearly, which were superimposed on the continuum X rays. The continuum X rays can be well explained by two types of radiative processes: mainly quasi-free electron bremsstrahlung (QFEB), and partly atomic bremsstrahlung (AB). It should be noticed that QFEB is predominant at low X-ray energy region and AB at high X-ray energy region in highly charged heavy ion-atom collision process.
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Zhang, Jian, Tao Yi, Ming Su, Wei Ming Yang i Shen Ye Liu. "Ultrafast Electron Cascades in X-Rays Detector". Materials Science Forum 850 (marzec 2016): 226–29. http://dx.doi.org/10.4028/www.scientific.net/msf.850.226.
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A new detection method based on the ultrafast refractive index change of semiconductor was used for X-rays detection. Since temporal and spatial resolutions are important parameters of the ultrafast X-rays detector, the electron cascades in gallium arsenide and cadmium selenide were studied using Monte Carlo method. According to the calculations, the energy deposition time and scale are similar in gallium arsenide and cadmium selenide at low energy region, but different at high energy region. Electron cascades don’t have much impact on getting picosecond time resolution and high spatial resolution.
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Vij, K. K., i D. Venkatesan. "Propagation of bremsstrahlung X rays through the atmosphere". Canadian Journal of Physics 69, nr 8-9 (1.08.1991): 994–98. http://dx.doi.org/10.1139/p91-157.
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To understand auroral phenomena and associated magnetospheric processes, balloon-borne measurements of bremsstrahlung X rays produced by electrons precipitating in our atmosphere have been made by various scientists. Measurements made by balloon-borne payloads have an advantage over direct measurements of electrons by satellites or rockets as these measurements provide an intense coverage at one location. These observations are usually made between 30–35 km altitude, and to relate them to the parent electron flux at the top of the atmosphere, it is necessary to understand the effect of propagation of X rays through the terrestrial atmosphere from ~100 km to the detection altitude (~30 km).
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Yamamoto, Seiichi, Airi Hiramatsu, Yui Shimizu, Takuya Yabe, Katsunori Yogo i Jun Kataoka. "Three-dimensional (3D) optical imaging of electron beam and X-rays from medical linear accelerators (LINAC) using a plastic scintillator plate in water". Journal of Instrumentation 17, nr 08 (1.08.2022): P08015. http://dx.doi.org/10.1088/1748-0221/17/08/p08015.
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Abstract Although optical imaging of electron beams and X-rays from medical linear accelerators (LINAC) is a possible method for dose distribution measurements, it has been limited to two-dimensional (2D) projection images. For the precise measurement of an optical image of electron beams and X-rays, three-dimensional (3D) imaging is desired. To measure 3D dose distributions, we conducted imaging of electron beams and X-rays using a plastic scintillator plate set in a water phantom. When this plate was immersed in the water phantom, irradiation with electron beams or X-rays was carried out from along the plate's sides. Optical images of the scintillator plate were acquired using a charge-coupled device (CCD) camera from the side during irradiation with electron beams and X-rays. Measurements were conducted at 6 MeV, 9 MeV and 12 MeV for electron beams and at 6 MV and 10 MV for X-rays. The imaging system was set on the bed of the LINAC and moved at 10-mm steps perpendicular to the beam direction to acquire a set of sliced optical images of the beams. A set of these sliced images were stacked and interpolated to form 3D optical images. For the 3D images, after the correction of the Cherenkov-light component in the images, the relative depth and lateral doses were evaluated. From the relative depth doses of electron beams, the half-value depths could be evaluated within an error of 1.3 mm. Lateral widths could be evaluated within an error of less than 2 mm parallel to the plastic scintillator and less than 6.5 mm perpendicular to it. From the relative depth doses of X-rays, the average difference between the measured value and that by a planning system was within an error of 2 %. Lateral widths could be evaluated within an error of less than 0.68 mm parallel to the plastic scintillator and less than 2.6 mm perpendicular to it. We confirmed that 3D imaging of electron beams and X-rays using plastic scintillator plate is feasible and is a promising method for measuring dose images at any position.
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Tanaka, Motohiko, i K. Papadopoulos. "Creation of High-Energy Electron Tails by the Lower-Hybrid Waves and its Relevance to Type II and III Bursts". Symposium - International Astronomical Union 107 (1985): 505–8. http://dx.doi.org/10.1017/s0074180900076026.
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It is commonly anticipated that high-energy electrons play an important role for the wave emission in flare bursts. For instance, electrons with >100 KeV are considered to create microwave emissions through gyro-synchrotron process and hard x-rays may be due to bremstrahlung with >25 KeV electrons. However, electron acceleration mechanism itself is still in speculations.
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Thuillier, T., J. Benitez, S. Biri i R. Rácz. "X-ray diagnostics of ECR ion sources—Techniques, results, and challenges". Review of Scientific Instruments 93, nr 2 (1.02.2022): 021102. http://dx.doi.org/10.1063/5.0076321.
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The high magnetic confinement provided by the minimum-B structure of electron cyclotron resonance ion sources (ECRIS) hosts a non-equilibrium plasma, composed of cold multi-charged ions and hot electrons whose energy can expand up to ≈1 MeV. With a very limited accessibility, the ECR plasma is difficult to study. The x-ray photons generated by the interaction of the warm and hot electron populations within the plasma, as well as the photons generated by electrons lost to the chamber wall, are a signal of great interest as it gives an insight to the properties of the ECR plasma. After an introduction presenting the mechanism generating the x rays in ECRIS, this Review presents the methodology to measure x rays both for volumetric measurements and plasma imaging. The main insights of those measurements are presented. Prospects of x-ray measurements to better understand the plasma dynamics are finally highlighted.
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Jannis, Daen, Knut Müller-Caspary, Armand Béché i Jo Verbeeck. "Coincidence Detection of EELS and EDX Spectral Events in the Electron Microscope". Applied Sciences 11, nr 19 (28.09.2021): 9058. http://dx.doi.org/10.3390/app11199058.
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Recent advances in the development of electron and X-ray detectors have opened up the possibility to detect single events from which its time of arrival can be determined with nanosecond resolution. This allows observing time correlations between electrons and X-rays in the transmission electron microscope. In this work, a novel setup is described which measures individual events using a silicon drift detector and digital pulse processor for the X-rays and a Timepix3 detector for the electrons. This setup enables recording time correlation between both event streams while at the same time preserving the complete conventional electron energy loss (EELS) and energy dispersive X-ray (EDX) signal. We show that the added coincidence information improves the sensitivity for detecting trace elements in a matrix as compared to conventional EELS and EDX. Furthermore, the method allows the determination of the collection efficiencies without the use of a reference sample and can subtract the background signal for EELS and EDX without any prior knowledge of the background shape and without pre-edge fitting region. We discuss limitations in time resolution arising due to specificities of the silicon drift detector and discuss ways to further improve this aspect.
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Rigler, Mark, i William Longo. "High Voltage Scanning Electron Microscopy Theory and Applications". Microscopy Today 2, nr 5 (sierpień 1994): 12–13. http://dx.doi.org/10.1017/s1551929500066256.
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A variety of energy emissions occur as a result of primary beam interaction with the specimen surface. Secondary electrons, x-rays, visible photons, near IR photons, and Auger electrons are emitted during inelastic scattering of electrons. Backscattered electrons (BSE) are emitted during elastic scattering of primary electrons. Backscattered electrons are those electrons which pass through the electron cloud of an atom and change direction without much energy loss. BSEs may diffuse into the sample or may escape from the sample surface. In practice, the primary electron beam penetrates deeply into low Z (atomic number) materials and produces few BSEs while high Z materials retard primary beam penetration and emit large numbers of BSEs. According to Murata et al., the higher the atomic number, the smaller the mean free path between electron scattering events (i.e. 528 Å for Al vs. 50 Å for Au at 30 KeV) and the higher the probability of scattering.
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Zimek, Zbigniew. "Economical evaluation of radiation processing with high-intensity X-rays". Nukleonika 65, nr 3 (1.09.2020): 167–72. http://dx.doi.org/10.2478/nuka-2020-0027.
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AbstractX-rays application for radiation processing was introduced to the industrial practice, and in some circumstances is found to be more economically competitive, and offer more flexibility than gamma sources. Recent progress in high-power accelerators development gives opportunity to construct and apply reliable high-power electron beam to X-rays converters for the industrial application. The efficiency of the conversion process depends mainly on electron energy and atomic number of the target material, as it was determined in theoretical predictions and confirmed experimentally. However, the lower price of low-energy direct accelerators and their higher electrical efficiency may also have certain influence on process economy. There are number of auxiliary parameters that can effectively change the economical results of the process. The most important ones are as follows: average beam power level, spare part cost, and optimal shape of electron beam and electron beam utilization efficiency. All these parameters and related expenses may affect the unit cost of radiation facility operation and have a significant influence on X-ray process economy. The optimization of X-rays converter construction is also important, but it does not depend on the type of accelerator. The article discusses the economy of radiation processing with high-intensity of X-rays stream emitted by conversion of electron beams accelerated in direct accelerator (electron energy 2.5 MeV) and resonant accelerators (electron energy 5 MeV and 7.5 MeV). The evaluation and comparison of the costs of alternative technical solutions were included to estimate the unit cost of X-rays facility operation for average beam power 100 kW.
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Ritchie, Nicholas W. M. "Using DTSA-II to Simulate and Interpret Energy Dispersive Spectra from Particles". Microscopy and Microanalysis 16, nr 3 (20.04.2010): 248–58. http://dx.doi.org/10.1017/s1431927610000243.
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AbstractA high quality X-ray spectrum image of a 3.3 μm diameter sphere of K411 glass resting on a copper substrate was collected at 25 keV. The same sample configuration was modeled using the NISTMonte Monte Carlo simulation of electron and X-ray transport as is integrated into the quantitative X-ray microanalysis software package DTSA-II. The distribution of measured and simulated X-ray intensity compare favorably for all the major lines present in the spectra. The simulation is further examined to investigate the influence of angle-of-incidence, sample thickness, and sample diameter on the generated and measured X-ray intensity. The distribution of generated X-rays is seen to deviate significantly from a naive model which assumes that the distribution of generated X-rays is similar to bulk within the volume they share in common. It is demonstrated that the angle at which the electron beam strikes the sample has nonnegligible consequences. It is also demonstrated that within the volume that the bulk and particle share in common that electrons, which have exited and later reentered the particle volume, generate a significant fraction of the X-rays. Any general model of X-ray generation in particles must take into account the lateral spread of the scattered electron beam.
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Adischev, Yuri, Victor Zabaev, Valery Kaplin, Sergey Kuznetsov, Sergey Uglov i Vitaly Ivanov. "Coherent X-Rays Generated by Relativistic Electrons in a Tungsten Monocrystal". Advanced Materials Research 1084 (styczeń 2015): 217–20. http://dx.doi.org/10.4028/www.scientific.net/amr.1084.217.
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In an experiment conducted at the Tomsk synchrotron "Sirius", the photon yield of parametric X-ray radiation generated by 500 MeV electrons in a tungsten monocrystal in Bragg geometry has been studied. The (111) tungsten monocrystal, having a thickness of 1.7 mm and a surface mosaicity of not more than 80², was oriented at the Bragg angle θB= 45°to the direction of the electron beam. The photons were detected at the angle 2θB= 90° relative to the electron beam. A comparison of PXR angular distributions with calculations has been carried out with taking into account the actual conditions of the experiment.
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Kenik, E. A., i J. Bentley. "Influence of Tilt Angle on Hole Count and Secondary Fluorescence in x-ray Microanalysis". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 2 (12.08.1990): 462–63. http://dx.doi.org/10.1017/s0424820100135915.
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The spatial resolution and accuracy of X-ray microanalysis in an analytical electron microscope (AEM) are limited by a variety of factors, two of which are the hole count and secondary fluorescence. The hole count arises from uncollimated radiation, either electrons or X rays, which excites areas of the specimen other than that excited by the primary electron beam. This can result in X-ray generation even when the probe does not hit the specimen; hence the name hole count. Secondary fluorescence deals with X-ray generation resulting from radiation produced by the interaction of the incident probe with the specimen. This radiation may be either backscattered electrons spiraling in the magnetic field of the objective lens or high energy X rays, particularly forward-peaked bremsstrahlung radiation. As the interaction of both the uncollimated radiation and the secondary radiation with the specimen can be influenced by the tilt angle of the specimen, the variation of the hole count and secondary fluorescence with specimen tilt was investigated.
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Luccio, A., G. Matone, L. Miceli i G. Giordano. "Coherent backscattering in the soft X-ray region". Laser and Particle Beams 8, nr 3 (wrzesień 1990): 383–98. http://dx.doi.org/10.1017/s0263034600008636.
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Coherent X rays can be produced by Compton scattering of laser light on a relativistic electron beam, whose current is periodically modulated by the same laser radiation in a suitable miniundulator. If electron and laser photon energy are properly matched, the modulated electron beam acts as a moving diffraction grating and the X rays show a high degree of coherence. A practical implementation of this scheme is shown.
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Wang, Wei-Min, Zheng-Ming Sheng, Paul Gibbon, Li-Ming Chen, Yu-Tong Li i Jie Zhang. "Collimated ultrabright gamma rays from electron wiggling along a petawatt laser-irradiated wire in the QED regime". Proceedings of the National Academy of Sciences 115, nr 40 (17.09.2018): 9911–16. http://dx.doi.org/10.1073/pnas.1809649115.
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Even though high-quality X- and gamma rays with photon energy below mega-electron volt (MeV) are available from large-scale X-ray free electron lasers and synchrotron radiation facilities, it remains a great challenge to generate bright gamma rays over 10 MeV. Recently, gamma rays with energies up to the MeV level were observed in Compton scattering experiments based on laser wakefield accelerators, but the yield efficiency was as low as10−6, owing to low charge of the electron beam. Here, we propose a scheme to efficiently generate gamma rays of hundreds of MeV from submicrometer wires irradiated by petawatt lasers, where electron accelerating and wiggling are achieved simultaneously. The wiggling is caused by the quasistatic electric and magnetic fields induced around the wire surface, and these are so high that even quantum electrodynamics (QED) effects become significant for gamma-ray generation, although the driving lasers are only at the petawatt level. Our full 3D simulations show that directional, ultrabright gamma rays are generated, containing1012photons between 5 and 500 MeV within a 10-fs duration. The brilliance, up to1027photonss−1 mrad−2 mm−2per 0.1% bandwidth at an average photon energy of 20 MeV, is second only to X-ray free electron lasers, while the photon energy is 3 orders of magnitude higher than the latter. In addition, the gamma ray yield efficiency approaches 10%—that is, 5 orders of magnitude higher than the Compton scattering based on laser wakefield accelerators. Such high-energy, ultrabright, femtosecond-duration gamma rays may find applications in nuclear photonics, radiotherapy, and laboratory astrophysics.
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Heinrich, Kurt F. J. "Going Nondispersive". Microscopy and Microanalysis 4, S2 (lipiec 1998): 162–63. http://dx.doi.org/10.1017/s1431927600020936.
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In February 1968 Ray Fitzgerald, Klaus Keil and myself published in Science a communication titled “Solid-State Energy-Dispersion Spectrometer for Electron Microprobe X-ray Analysis”. The authors describe the use of a lithium-drifted silicon detector for the direct identification of x-rays, without a diffracting crystal, in an electron probe. The subject of this paper was to modify profoundly the development of x-ray microanalysis in the years to follow.Pulse-height analysis of gamma rays detected in scintillation counters was widely used at the time. For radiation of energies below 30 keV, gas proportional counters were also employed. In elementary analysis by x-rays the poor energy resolution of these detectors limited the application of such a procedure, although single-channel pulse height analysis was employed as an adjunct to crystal spectrometers.In 1951, Raymond Castaing in his thesis described his invention of the electron probe microanalyzer, created by adding to a transmission electron microscope a curved-crystal spectrometer which focused the x-rays emitted by the specimen into a Geiger-Muller counter.
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Tawara, H., P. Richard, U. I. Safronova, A. A. Vasilyev i M. Stockli. "M X-ray emission from low-energy, highly charged Taq+ (q = 4549) ions colliding with neutral atoms due to singly and doubly excited states formed through single-electron capture". Canadian Journal of Physics 80, nr 8 (1.08.2002): 821–35. http://dx.doi.org/10.1139/p02-014.
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M X-rays have been observed from 140 keV/u 181Taq+ (q = 4549) ions colliding with neutral Ar atoms under single collisions. The most dominant X-rays have been found to be due to transitions of 4p3d and 4f3d when the projectiles bring 3d-shell vacancies into collisions. Though much weaker, M X-rays also have been observed in collisions with Ta45+ ions that initially have no 3d-shell vacancy and are understood to originate from transitions of the doubly excited states 3d9nln'l' formed through strong electronelectron interactions after single-electron capture. The observed M X-ray spectra have been compared and reproduced nicely with the synthesized spectra. It has been confirmed that transitions of such doubly excited states also contribute to X-rays at the lower energy region observed even for higher charge ions with 3d vacancies. PACS Nos.: 32.30Rj, 32.70Cs, 32.80Rm, 34.70+e
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BACCI, A., C. MAROLI, V. PETRILLO, L. SERAFNI i M. FERRARIO. "STUDY OF TRANSVERSE EFFECTS IN THE PRODUCTION OF X-RAYS WITH A FREE-ELECTRON LASER BASED ON AN OPTICAL UNDULATOR". International Journal of Modern Physics A 22, nr 23 (20.09.2007): 4270–79. http://dx.doi.org/10.1142/s0217751x07037822.
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The interaction between high-brilliance electron beams and counter-propagating laser pulses produces X rays via Thomson back-scattering. If the laser source is long and intense enough, the electrons of the beam can bunch and a regime of collective effects can establish. In this case of dominating collective effects, the FEL instability can develop and the system behaves like a free-electron laser based on an optical undulator. Coherent X-rays can be irradiated, with a bandwidth very much thinner than that of the corresponding incoherent emission. The emittance of the electron beam and the distribution of the laser energy are the principal quantities that limit the growth of the X-ray signal. In this work we analyse with a 3-D code the transverse effects in the emission produced by a relativistic electron beam when it is under the action of an optical laser pulse and the X-ray spectra obtained. The scalings typical of the optical wiggler, characterized by very short gain lengths and overall time durations of the process make possible considerable emission also with emittance of the order of 1mm mrad.
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Sakurai, Y. "High-Energy Inelastic-Scattering Beamline for Electron Momentum Density Study". Journal of Synchrotron Radiation 5, nr 3 (1.05.1998): 208–14. http://dx.doi.org/10.1107/s0909049598002052.
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The advent of synchrotron radiation sources for well polarized and high-energy X-rays offers new opportunities for exploiting Compton scattering spectroscopy as a tool for investigating the electronic and magnetic structures of materials. Recent high-resolution Compton scattering experiments show the unique capability for the study of Fermiology-related issues and electron–electron correlation effects. Intense, high-energy and circularly polarized X-ray sources have improved magnetic Compton scattering spectroscopy from the point of statistical accuracy and momentum resolution. As a next advance, a high-energy inelastic scattering beamline dedicated to Compton scattering spectroscopies is being constructed at SPring-8. The light source is an elliptic multipole wiggler with a periodic length of 12 cm. The beamline includes two experimental stations: one is for high-resolution spectroscopy using 100–150 keV X-rays and the other is for magnetic Compton scattering experiments using circularly polarized 300 keV X-rays. The use of such high-energy X-rays makes it possible to carry out experiments efficiently on samples including heavier elements, such as high-T c superconductors and 4f and 5f magnetic materials.
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KRASNOHOLOVETS, VOLODYMYR, NICOLAI KUKHTAREV i TATIANA KUKHTAREVA. "HEAVY ELECTRONS: ELECTRON DROPLETS GENERATED BY PHOTOGALVANIC AND PYROELECTRIC EFFECTS". International Journal of Modern Physics B 20, nr 16 (30.06.2006): 2323–37. http://dx.doi.org/10.1142/s0217979206034662.
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Electron clusters, X-rays and nanosecond radio-frequency pulses are produced by 100 mW continuous-wave laser illuminating ferroelectric crystal of LiNbO 3. A long-living stable electron droplet with the size of about 100μ m has freely moved with the velocity ~0.5 cm/s in the air near the surface of the crystal experiencing the Earth gravitational field. The microscopic model of cluster stability, which is based on submicroscopic mechanics developed in the real physical space, is suggested. The role of a restraining force plays the inerton field, a substructure of the particles' matter waves, which a solitary one can elastically withstand the Coulomb repulsion of electrons. It is shown that electrons in the droplet are heavy electrons whose mass exceeds the rest mass of free electron at least 1 million of times. Application for X-ray imaging and lithography is discussed.
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Ebel, Horst, Robert Svagera, Maria F. Ebel i Norbert Zagler. "Total Electron Yield (TEY) A New Approach for Quantitative X-ray Analysis". Advances in X-ray Analysis 38 (1994): 325–35. http://dx.doi.org/10.1154/s0376030800017961.
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An irradiation of solid samples with x-rays causes an electron emission from the sample surface, owing to photoabsorption. These electrons can be detected under vacuum conditions and are photo, Auger and secondary electrons. Due to inelastic collisions most of these electrons have lost some of their original kinetic energy along the path from the atom of origin to the surface. With nondispersive electron detection the total electron yield (TEY) is observed. For measurements performed with a tunable x-ray monochromator information on the qualitative composition can be obtained by the following procedure. The photon energy has to be timed from below to above of one of the absorption edges of a given element. In case of its presence in the specimen an increase of the TEY-signal can be observed.
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Small, John A., Scott A. Wight, Robert L. Myklebust i Dale E. Newbury. "The measurement of the fluorescence of Si K x-rays by Au M x-rays". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 2 (12.08.1990): 198–99. http://dx.doi.org/10.1017/s0424820100134582.
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The characteristic fluorescence correction is used in electron probe microanalysis to account for the x-ray intensity excited in element “a” by the x-rays from the characteristic line of another element, “b”, in the sample. Since the excited intensity is not generated by the primary electron beam, it is necessary to apply the fluorescence correction for quantitative elemental analysis. This correction can be significant particularly when element “b” is a major component of the sample and the characteristic line for element “b” is slightly higher in energy than the critical excitation energy for the excited line of element “a”.The fluorescence correction, which is used in the various analytical programs, is described in equation 1.where I'*fa/I'*pa is the ratio of the emitted “a” intensity excited by “b” x-rays to the emitted intensity excited by the primary electron beam. The various parameters in this equation are accurately known for the K x-ray lines, but only very limited information is available for the M x-ray lines.
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Setthahirun, Suwitchaya, i Maneenate Wechakama. "Constraining the annihilation of dark matter via cosmic-ray positrons and electrons". Journal of Physics: Conference Series 2145, nr 1 (1.12.2021): 012007. http://dx.doi.org/10.1088/1742-6596/2145/1/012007.
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Abstract We aim to constrain the properties of dark matter particles by several measurements of positrons and electrons from cosmic-rays. We assume that collisions of dark matter particles and dark matter anti-particles can produce positrons and electrons. The electron-positron propagation is explained by a diffusion-loss equation including loss rates, diffusion, as well as source function. We use data of cosmic-ray positrons and electrons detected by PAMELA, H.E.S.S., AMS-02 and Fermi-LAT. We compare the observational data with the electron and positron spectrum from five annihilation channels in our model to derive constraining factors regarding the cross-section of the annihilation of dark matter. The tightest constraint is provided by cosmic-ray positrons of AMS-02 for the electron channel. Dark matter with mass below a few GeV gets excluded by the cosmic-ray positrons of AMS-02 for the electron, muon and tau channels.
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Chand, Bakhshish, Jatinder Goswamy, Devinder Mehta, Nirmal Singh i P. N. Trehan. "Study of the radioactive decays of 140Ba and 140La". Canadian Journal of Physics 69, nr 2 (1.02.1991): 90–101. http://dx.doi.org/10.1139/p91-014.
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The intensities of X rays and γ rays from the decays of 140Ba and 140La were measured precisely using Si(Li) and HPGe detectors. The L X-ray intensities in 140Ba decay are reported for the first time. The conversion electrons from these decays are investigated using a mini-orange electron spectrometer. The electron intensities for the (M + N.) conversion of 329, 487, 1596, and 1903 keV transitions in 140Ce were measured for the first time. From the present conversion-electron and γ-ray intensities, the conversion coefficients for various transitions in 140La and 140Ce were determined. Also, the γ–γ directional correlations for 15 cascades in,140Ce were studied using a HPGe–HPGe detector coincidence setup (time resolution = 7 ns). The 109–(329)– 487, 131–242, and 131–266 keV cascades in 140Ce were studied for the first time. The multipole mixing ratios for the 109, 131, 242, 266, 329, 432, 487, 751, 816, 868, 919, 925, and 951 keV transitions in 140Ce are deduced from the present directional correlation and conversion-coefficient measurements.
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Chen, Ye, Frank Brinker, Winfried Decking, Matthias Scholz, Lutz Winkelmann i Zihan Zhu. "Virtual commissioning of the European XFEL for advanced user experiments at photon energies beyond 25 keV using low-emittance electron beams". Journal of Physics: Conference Series 2420, nr 1 (1.01.2023): 012026. http://dx.doi.org/10.1088/1742-6596/2420/1/012026.
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Abstract Growing interests in ultra-hard X-rays are pushing forward the frontier of commissioning the European X-ray Free-Electron Laser (XFEL) for routine operation towards the sub-ångström regime, where a photon energy of 25 keV (0.5 Å) and above is desired. Such X-rays allow for larger penetration depths and enable the investigation of materials in highly absorbing environments. Delivering the requested X-rays to user experiments is of crucial importance for the XFEL development. Unique capabilities of the European XFEL are formed by combining a high energy linac and the long variable-gap undulator systems for generating intense X-rays at 25 keV and pushing the limit even further to 30 keV. However, the FEL performance relies on achievable electron bunch qualities. Low-emittance electron bunch production, and the associated start-to-end modelling of beam physics thus becomes a prerequisite to dig into the XFEL potentials. Here, we present the obtained simulation results from a virtual commissioning of the XFEL for the user experiments at 25 keV and beyond, including the optimized electron bunch qualities and corresponding FEL lasing performance. Experimental results at 30 keV from the first test run are presented.
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Gyani, Angeli K., Phillip McClusky, David S. Urch, M. Charbonnicr, F. Gaillard i M. Romand. "Non-Destructive Chemical-State Analysis of Thin Films and Surface Layers (1-1000 nm) by Low-Energy Electron-Induced X-ray Spectroscopy (LEEIXS)". Advances in X-ray Analysis 33 (1989): 247–59. http://dx.doi.org/10.1154/s0376030800019649.
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AbstractThe penetration depth of 1-12 keV electrons in most materials is less than one micron and the characteristic soft x-rays that are produced can be used to identify the elements present in the surface. Varying the energy of the incident electron beam enables the depth of analysis to be controlled.Soft x-rays often exhibit large 'chemical effects' (changes in peak profile and peak position) which can he correlated with chemical changes. A study of such effects for each element present in the sample surface, as a function of electron-beam energy, can in some cases, permit changes in the chemical state (valency - coordination number-spin state etc.) to be determined as a function of depth.Such analyses can be carried out either in a conventional x-ray spectrometer in which the x-ray tube has been replaced by a gas-discharge source, or in a spectrometer in which the sample is bombarded with electrons from a normal electron gun. In this paper these techniques are outlined and some applications reviewed:- the analysis of oxide layers on aluminium and steel, the analysis of aluminium-nitride layers produced by MOCVD on gallium arsenide, the analysis of silica fiims (with added boron and phosphorus oxides) on silicon and the analysis of zinc-oxide films on glass.
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Vergados, John D., Paraskevi C. Divari i Hiroyasu Ejiri. "Calculated Event Rates for Axion Detection via Atomic and Nuclear Processes". Advances in High Energy Physics 2022 (22.02.2022): 1–24. http://dx.doi.org/10.1155/2022/7373365.
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The possibility of detection of 5.5 MeV and 14.4 keV solar axions by observing axion-induced nuclear and atomic transitions is investigated. The presence of nuclear transitions between spin orbit partners can be manifested by the subsequent deexcitation via gamma ray emissions. The transition rates can also be studied in the context of radiative axion absorption by a nucleus. The elementary interaction is obtained in the context of the axion-quark couplings predicted by existing axion models. Then, these couplings will be transformed to the nucleon level utilizing reasonable existing models, which lead to effective transition operators. Using these operators, we calculate the needed nuclear matrix elements employing wave functions obtained in the context of the nuclear shell model. With these ingredients, we discuss possibilities of experimental observation of the axion-induced nuclear gamma rays. In the second part, we will examine the axion-induced production of X-rays (axion-photon conversion) or ionization from deeply bound electron orbits. In this case, the axion electron coupling is predicted by existing axion models; no renormalization is needed. The experimental signal is the observation of directly produced electrons and/or the emission of hard X-rays and Auger electrons, following the deexcitation of the final atom. Critical discussion is made on the experimental feasibility of detecting the solar axions by using multiton scale NaI detectors.
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Sei, Norihiro, Hiroshi Ogawa i QiKa Jia. "Multiple-Collision Free-Electron Laser Compton Backscattering for a High-Yield Gamma-Ray Source". Applied Sciences 10, nr 4 (20.02.2020): 1418. http://dx.doi.org/10.3390/app10041418.
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We observed multiple-collision free-electron laser (FEL)-Compton backscattering in which a multi-bunch electron beam makes head-on collisions with multi-pulse FELs in an optical cavity, using an infrared FEL system in the storage ring NIJI-IV. It was demonstrated that the measured spectrum of the multiple-collision FEL-Compton backscattering gamma rays was the summation of the spectra of the gamma rays generated at each collision point. Moreover, it was demonstrated that the spatial distribution of the multiple-collision FEL-Compton backscattering gamma rays was the summation of those of the gamma rays generated at each collision point. Our experimental results proved quantitatively that the multiple collisions in the FEL-Compton backscattering process are effective in increasing the yield of the gamma rays. By applying the multiple-collision FEL-Compton backscattering to high-repetition FEL devices such as energy recovery linac FELs, an unprecedented high-yield gamma-ray source with quasi-monochromaticity and wavelength tunability will be realized.
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Boamah, Mavis D., Kristal K. Sullivan, Katie E. Shulenberger, ChanMyae M. Soe, Lisa M. Jacob, Farrah C. Yhee, Karen E. Atkinson, Michael C. Boyer, David R. Haines i Christopher R. Arumainayagam. "Low-energy electron-induced chemistry of condensed methanol: implications for the interstellar synthesis of prebiotic molecules". Faraday Discuss. 168 (2014): 249–66. http://dx.doi.org/10.1039/c3fd00158j.
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In the interstellar medium, UV photolysis of condensed methanol (CH3OH), contained in ice mantles surrounding dust grains, is thought to be the mechanism that drives the formation of “complex” molecules, such as methyl formate (HCOOCH3), dimethyl ether (CH3OCH3), acetic acid (CH3COOH), and glycolaldehyde (HOCH2CHO). The source of this reaction-initiating UV light is assumed to be local because externally sourced UV radiation cannot penetrate the ice-containing dark, dense molecular clouds. Specifically, exceedingly penetrative high-energy cosmic rays generate secondary electrons within the clouds through molecular ionizations. Hydrogen molecules, present within these dense molecular clouds, are excited in collisions with these secondary electrons. It is the UV light, emitted by these electronically excited hydrogen molecules, that is generally thought to photoprocess interstellar icy grain mantles to generate “complex” molecules. In addition to producing UV light, the large numbers of low-energy (<20 eV) secondary electrons, produced by cosmic rays, can also directly initiate radiolysis reactions in the condensed phase. The goal of our studies is to understand the low-energy, electron-induced processes that occur when high-energy cosmic rays interact with interstellar ices, in which methanol, a precursor of several prebiotic species, is the most abundant organic species. Using post-irradiation temperature-programmed desorption, we have investigated the radiolysis initiated by low-energy (7 eV and 20 eV) electrons in condensed methanol at ∼ 85 K under ultrahigh vacuum (5 × 10−10 Torr) conditions. We have identified eleven electron-induced methanol radiolysis products, which include many that have been previously identified as being formed by methanol UV photolysis in the interstellar medium. These experimental results suggest that low-energy, electron-induced condensed phase reactions may contribute to the interstellar synthesis of “complex” molecules previously thought to form exclusively via UV photons.