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Sample records for low energy electron diffraction

  1. LEED (Low Energy Electron Diffraction)

    International Nuclear Information System (INIS)

    Aberdam, M.

    1973-01-01

    The various types of systems studied by LEED, and for which the geometry of diffraction patterns is exploited, are reviewed, intensity profiles being another source of information. Two representative approaches of the scattering phenomenon are examined; the band structure theory and the T matrix approach [fr

  2. Introduction to the theory of low-energy electron diffraction

    International Nuclear Information System (INIS)

    Fingerland, A.; Tomasek, M.

    1975-01-01

    An elementary introduction to the basic principles of the theory of low-energy electron diffraction is presented. General scattering theory is used to classify the hitherto known approaches to the problem (optical potential and one-electron approximation; formal scattering theory: Born expansion and multiple scattering; translational symmetry: Ewald construction; classification of LEED theories by means of the T matrix; pseudokinematical theory for crystal with clean surface and with an adsorbed monomolecular layer; dynamical theory; inclusion of inelastic collisions; discussion of a simple example by means of the band-structure approach)

  3. Interpretation of diffuse low-energy electron diffraction intensities

    International Nuclear Information System (INIS)

    Saldin, D.K.; Pendry, J.B.; Van Hove, M.A.; Somorjai, G.A.

    1985-01-01

    It is shown that the diffuse low-energy electron diffraction (LEED) that occurs between sharp LEED beams can be used to determine the local bonding configuration near disordered surface atoms. Two approaches to the calculation of diffuse LEED intensities are presented for the case of lattice-gas disorder of an adsorbate on a crystalline substrate. The capabilities of this technique are most similar to those of near-edge extended x-ray absorption fine structure, but avoid the restrictions due to the use of photons

  4. Low-energy electron diffraction and induced damage in hydrated DNA

    International Nuclear Information System (INIS)

    Orlando, Thomas M.; Oh, Doogie; Chen Yanfeng; Aleksandrov, Alexandr B.

    2008-01-01

    Elastic scattering of 5-30 eV electrons within the B-DNA 5 ' -CCGGCGCCGG-3 ' and A-DNA 5 ' -CGCGAATTCGCG-3 ' DNA sequences is calculated using the separable representation of a free-space electron propagator and a curved wave multiple scattering formalism. The disorder brought about by the surrounding water and helical base stacking leads to a featureless amplitude buildup of elastically scattered electrons on the sugar and phosphate groups for all energies between 5 and 30 eV. However, some constructive interference features arising from diffraction are revealed when examining the structural waters within the major groove. These appear at 5-10, 12-18, and 22-28 eV for the B-DNA target and at 7-11, 12-18, and 18-25 eV for the A-DNA target. Although the diffraction depends on the base-pair sequence, the energy dependent elastic scattering features are primarily associated with the structural water molecules localized within 8-10 A spheres surrounding the bases and/or the sugar-phosphate backbone. The electron density buildup occurs in energy regimes associated with dissociative electron attachment resonances, direct electronic excitation, and dissociative ionization. Since diffraction intensity can be localized on structural water, compound H 2 O:DNA states may contribute to energy dependent low-energy electron induced single and double strand breaks

  5. Diffraction of high energy electrons

    International Nuclear Information System (INIS)

    Bourret, A.

    1981-10-01

    The diffraction of electrons by a crystal is examined to study its structure. As the electron-substance interaction is strong, it must be treated in a dynamic manner. Using the N waves theory and physical optics the base equations giving the wave at the outlet are deduced for a perfect crystal and their equivalence is shown. The more complex case of an imperfect crystal is then envisaged in these two approaches. In both cases, only the diffraction of high energy electrons ( > 50 KeV) are considered since in the diffraction of slow electrons back scattering cannot be ignored. Taking into account an increasingly greater number of beams, through fast calculations computer techniques, enables images to be simulated in very varied conditions. The general use of the Fast Fourier Transform has given a clear cut practical advantage to the multi-layer method [fr

  6. Reciprocal space mapping by spot profile analyzing low energy electron diffraction

    International Nuclear Information System (INIS)

    Meyer zu Heringdorf, Frank-J.; Horn-von Hoegen, Michael

    2005-01-01

    We present an experimental approach for the recording of two-dimensional reciprocal space maps using spot profile analyzing low energy electron diffraction (SPA-LEED). A specialized alignment procedure eliminates the shifting of LEED patterns on the screen which is commonly observed upon variation of the electron energy. After the alignment, a set of one-dimensional sections through the diffraction pattern is recorded at different energies. A freely available software tool is used to assemble the sections into a reciprocal space map. The necessary modifications of the Burr-Brown computer interface of the two Leybold and Omicron type SPA-LEED instruments are discussed and step-by-step instructions are given to adapt the SPA 4.1d software to the changed hardware. Au induced faceting of 4 deg. vicinal Si(001) is used as an example to demonstrate the technique

  7. Low-energy electron diffraction experiment, theory and surface structure determination

    CERN Document Server

    Hove, Michel A; Chan, Chi-Ming

    1986-01-01

    Surface crystallography plays the same fundamental role in surface science which bulk crystallography has played so successfully in solid-state physics and chemistry. The atomic-scale structure is one of the most important aspects in the understanding of the behavior of surfaces in such widely diverse fields as heterogeneous catalysis, microelectronics, adhesion, lubrication, cor­ rosion, coatings, and solid-solid and solid-liquid interfaces. Low-Energy Electron Diffraction or LEED has become the prime tech­ nique used to determine atomic locations at surfaces. On one hand, LEED has yielded the most numerous and complete structural results to date (almost 200 structures), while on the other, LEED has been regarded as the "technique to beat" by a variety of other surface crystallographic methods, such as photoemission, SEXAFS, ion scattering and atomic diffraction. Although these other approaches have had impressive successes, LEED has remained the most productive technique and has shown the most versatility...

  8. Surface structure of VN0.89(100) determined by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Gauthier, Y.; Joly, Y.; Rundgren, J.; Johansson, L.I.; Wincott, P.

    1990-01-01

    The structure of the (100) surface of substoichiometric vanadium nitride was studied by low-energy electron diffraction on a VN 0.89 (100) sample. A simple 1x1 (100) diffractogram was observed. To describe the electron scattering in substoichiometric VN we apply the averaged t-matrix approximation to the nitrogen atoms. We find that the best structural model is one having no nitrogen vacancies in the surface region. It turns out that the first layer is rippled with the N atoms displaced 0.17 A above the subplane of V atoms, that the spacing between this subplane and the second layer is 1.92 A, and that the spacing between the second and the third layer is 2.08 A. In relation to the (100) spacing of the bulk, 2.06 A, these spacings are 6.8% contracted and 1% expanded, respectively. The Debye temperature of VN is found to be 660 K in good agreement with a prediction from entropy data and from neutron diffraction and helium-ion channeling experiments

  9. Low-energy positron and electron diffraction and positron-stimulated secondary electron emission from Cu(100)

    International Nuclear Information System (INIS)

    Weiss, A.H.

    1983-01-01

    The results of two series of experiments are reported. In the first, an electrostatically guided beam of low-energy (40-400 eV) positrons, delta/sub p/ was used to study low-energy positron diffraction (LEPD) from a Cu(100) surface under ultrahigh-vacuum conditions. Low-energy electron diffraction (LEED) data were obtained from the same sample in the same apparatus. Comparison of LEPD and LEED intensity versus energy data with model calculations made using computer programs developed by C.B. Duke and collaborators indicated that: LEPD data is adequately modeled using potentials with no exchange-correlation term. The inelastic mean free path, lambda/sub ee/, is shorter for positrons than for electrons at low (< approx.80 eV). LEED is better than LEPD at making a determination of the first-layer spacing of Cu(100) for the particular data set reported. In the second set of experiments, the same apparatus and sample were used to compare positron- and electron-stimulated secondary-electron emission (PSSEE and ESSEE). The results were found to be consistent with existing models of secondary-electron production for metals. The energy distributions of secondary-electrons had broad low-energy (<10 eV) peaks for both positron and electron stimulation. But the PSEE distribution showed no elastic peak. Measurements of secondary-electron angular distributions, found to be cosine-like in both the PSSEE and ESSEE case, were used to obtain total secondary yield ratios, delta, at four beam energies ranging from 40-400 eV. The secondary yield ratio for primary positrons and the yield for primary electrons, delta/sub e/, were similar at these energies. For 400-eV primary particles the secondary yields were found to be delta/sub p/ = 0.94 +/- 0.12 and delta/sub e/ = 0.94 +/- 0./12, giving a ratio of unity for positron-stimulated secondary yield to electron-stimulated secondary yield

  10. High-energy electron diffraction and microscopy

    CERN Document Server

    Peng, L M; Whelan, M J

    2011-01-01

    This book provides a comprehensive introduction to high energy electron diffraction and elastic and inelastic scattering of high energy electrons, with particular emphasis on applications to modern electron microscopy. Starting from a survey of fundamental phenomena, the authors introduce the most important concepts underlying modern understanding of high energy electron diffraction. Dynamical diffraction in transmission (THEED) and reflection (RHEED) geometries is treated using ageneral matrix theory, where computer programs and worked examples are provided to illustrate the concepts and to f

  11. Structure of ultrathin Pd films determined by low-energy electron microscopy and diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Santos, B; De la Figuera, J [Centro de Microanalisis de Materiales, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Puerta, J M; Cerda, J I [Instituto de Ciencia de Materiales, CSIC, Madrid 28049 (Spain); Herranz, T [Instituto de Quimica-Fisica ' Rocasolano' , CSIC, Madrid 28006 (Spain); McCarty, K F [Sandia National Laboratories, Livermore, CA 94550 (United States)], E-mail: benitosantos001@gmail.com

    2010-02-15

    Palladium (Pd) films have been grown and characterized in situ by low-energy electron diffraction (LEED) and microscopy in two different regimes: ultrathin films 2-6 monolayers (ML) thick on Ru(0001), and {approx}20 ML thick films on both Ru(0001) and W(110). The thinner films are grown at elevated temperature (750 K) and are lattice matched to the Ru(0001) substrate. The thicker films, deposited at room temperature and annealed to 880 K, have a relaxed in-plane lattice spacing. All the films present an fcc stacking sequence as determined by LEED intensity versus energy analysis. In all the films, there is hardly any expansion in the surface-layer interlayer spacing. Two types of twin-related stacking sequences of the Pd layers are found on each substrate. On W(110) the two fcc twin types can occur on a single substrate terrace. On Ru(0001) each substrate terrace has a single twin type and the twin boundaries replicate the substrate steps.

  12. Surface structure of Bi2Se3(111) determined by low-energy electron diffraction and surface x-ray diffraction

    DEFF Research Database (Denmark)

    dos Reis, Diogo Duarte; Barreto, Lucas; Bianchi, Marco

    2013-01-01

    The surface structure of the prototypical topological insulator Bi2Se3 is determined by low-energy electron diffraction and surface x-ray diffraction at room temperature. Both approaches show that the crystal is terminated by an intact quintuple layer. Specifically, an alternative termination by ...... by a bismuth bilayer is ruled out. Surface relaxations obtained by both techniques are in good agreement with each other and found to be small. This includes the relaxation of the van der Waals gap between the first two quintuple layers....

  13. Quantitative low-energy electron diffraction analysis of the GaN(000-1) (1×1) reconstruction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Jiříček, Petr; Paskova, T.

    2012-01-01

    Roč. 606, 7-8 (2012), s. 740-743 ISSN 0039-6028 R&D Projects: GA ČR GPP204/10/P028 Institutional research plan: CEZ:AV0Z10100521 Keywords : gallium nitride * semiconductor surfaces * quantitative low-energy electron diffraction * LEED Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.838, year: 2012

  14. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  15. Oxygen adsorption on Cu-9 at. %Al(111) studied by low energy electron diffraction and Auger electron spectroscopy

    Science.gov (United States)

    Yoshitake, Michiko; Bera, Santanu; Yamauchi, Yasuhiro; Song, Weijie

    2003-07-01

    Cu-based alloys have been used for electric cables for long time. In the field of microelectronics, Al had been used for electrical wiring. However, it became clear that electromigration occurs in Al that causes breaking of wires in minute wirings. Due to this problem, Cu wiring is used in most advanced microprocessors. Cu metal is more corrosive than Al and Cu-based alloys with a small amount of Al is expected to solve problems both on electromigration and corrosion. The initial stage of corrosion is oxygen adsorption. We studied surface segregation of Al on Cu-9% Al(111) and oxygen adsorption on the surface with/without Al segregation in ultrahigh vacuum by low energy electron diffraction (LEED) and Auger electron spectroscopy. It was found that Al segregates on the surface to form (√3×√3)R30° structure and the structure vanishes above 595 K to give (1×1) structure while Al still segregates. The specimen was exposed to oxygen at different temperatures. The amount of oxygen uptake was not structure dependent but temperature dependent. Below 595 K, only a small amount of oxygen adsorbed. Between 595 and 870 K, oxygen adsorbed surface showed amorphous LEED pattern. The specimen was annealed at 1070 K after oxygen exposure. When the specimen was exposed oxygen below 870 K, the oxygen Auger intensity decreased significantly by annealing and the annealed surface showed (√3×√3)R30° structure at room temperature. When the specimen was exposed to oxygen at 870 K, diffused spots developed newly in LEED pattern but the pattern disappeared after 1070 K annealing while oxygen Auger intensity remained almost constant. Exposing the specimen to oxygen at 995 K resulted in clear spots in the LEED pattern, which were attributed to the (7/√3×7√3)R30° structure.

  16. Structure determination of disordered organic molecules on surfaces from the Bragg spots of low-energy electron diffraction and total energy calculations

    International Nuclear Information System (INIS)

    Poon, H.C.; Weinert, M.; Saldin, D.K.; Stacchiola, D.; Zheng, T.; Tysoe, W.T.

    2004-01-01

    We show that an analysis of the intensity versus energy variation of Bragg spots due to low-energy electron diffraction from a disordered overlayer of molecules on a crystal surface allows a much more convenient method of determining the local adsorption geometries of such molecules than previously analyzed weak diffuse diffraction patterns. For the case of methanol on Pd(111), we show that the geometry determined by this means from experimental diffraction data is in excellent agreement with the predictions of density functional total energy calculations

  17. Temperature-dependent surface structure, composition, and electronic properties of the clean SrTiO3(111) crystal face: Low-energy-electron diffraction, Auger-electron spectroscopy, electron energy loss, and ultraviolet-photoelectron spectroscopy studies

    International Nuclear Information System (INIS)

    Lo, W.J.; Somorjai, G.A.

    1978-01-01

    Low-energy-electron diffraction, Auger-electron spectroscopy, electron-energy-loss, and ultraviolet-photoelectron spectroscopies were used to study the structure, composition, and electron energy distribution of a clean single-crystal (111) face of strontium titanate (perovskite). The dependence of the surface chemical composition on the temperature has been observed along with corresponding changes in the surface electronic properties. High-temperature Ar-ion bombardment causes an irreversible change in the surface structure, stoichiometry, and electron energy distribution. In contrast to the TiO 2 surface, there are always significant concentrations of Ti 3+ in an annealed ordered SrTiO 3 (111) surface. This stable active Ti 3+ monolayer on top of a substrate with large surface dipole potential makes SrTiO 3 superior to TiO 2 when used as a photoanode in the photoelectrochemical cell

  18. Structure of solid surfaces and of adsorbates by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Somorjai, G.A.

    1977-01-01

    LEED theory has developed to the point where the diffraction beam intensities can be computed using the locations of the surface atoms as the only adjustable parameters. The position of atoms in many clean monatomic solid surfaces and the surface structures of ordered monolayers of adsorbed atoms have been determined this way. Surface crystallography studies are now extended to small hydrocarbon molecules that are adsorbed on metal surfaces. These studies are reviewed

  19. Atmospheric deterioration of clean surface of epitaxial (001)-YBaCuO films studied by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Ohara, Tomoyuki; Sakuta, Ken; Kamishiro, Makio; Kobayashi, Takeshi

    1991-01-01

    The effects of gas exposure on the clean surface of the epitaxial YBaCuO thin films were closely investigated using the low-energy electron diffraction (LEED) method. The clean surface was obtained by in-vacuum annealing at 500degC. Once the clean surface was exposed to air, even at room temperature, the LEED spots disappeared or sometimes became faint. To ensure the degradation mechanism of the YBaCuO clean surface, the specimens were exposed to pure O 2 and N 2 gases separately and measured by LEED. As a result, it was found that O 2 is very safe but N 2 serves as a poisonous gas for the YBaCuO clean surface. (author)

  20. Holography and coherent diffraction with low-energy electrons: A route towards structural biology at the single molecule level.

    Science.gov (United States)

    Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2015-12-01

    The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2Å has been achieved revealing the 660.000 unit cells of the graphene sheet from a single data set. Once applied to individual biomolecules the method shall ultimately allow for non-destructive imaging and imports the potential to distinguish between different conformations of proteins with atomic resolution. Copyright © 2015. Published by Elsevier B.V.

  1. 1D chain formation by coadsorption of Pb and Bi on Cu(001): Determination using low energy electron diffraction

    Science.gov (United States)

    Kabiruzzaman, Md; Ahmed, Rezwan; Nakagawa, Takeshi; Mizuno, Seigi

    2017-10-01

    Coadsorption of two heavy metals, Pb and Bi, on Cu(001) at room temperature has been studied using low energy electron diffraction (LEED). c(4 × 4), c(2 × 2), and c(9√{ 2}×√{ 2}) phases are obtained at different coverages; here, we have determined the best-fit structure of c(4 × 4) phase. This structure can be described as a 1D substitutional chain arrangement of Pb and Bi atoms between the Cu rows along the [110] direction. The unit cell in the two-dimensional (2D) surface consists of one Bi atom, two Pb atoms, and four Cu atoms with one vacancy at the center. The optimal structure parameters demonstrate that Bi atoms are located at fourfold-hollow sites and that Pb atoms are laterally displaced by 0.78 Å from the fourfold-hollow site toward the vacancy. The reasons for the formation of the c(4 × 4) structure upon deposition of Pb and Bi on Cu(001) are discussed in comparison with a similar structure formed by the individual adsorption of Pb on the same substrate.

  2. High energy electron multibeam diffraction and imaging

    International Nuclear Information System (INIS)

    Bourret, Alain.

    1980-04-01

    The different theories of dynamical scattering of electrons are firstly reviewed with special reference to their basis and the validity of the different approximations. Then after a short description of the different experimental set ups, structural analysis and the investigation of the optical potential by means of high energy electrons will be surveyed

  3. In situ observation of low temperature growth of Ge on Si(1 1 1) by reflection high energy electron diffraction

    International Nuclear Information System (INIS)

    Grimm, Andreas; Fissel, Andreas; Bugiel, Eberhard; Wietler, Tobias F.

    2016-01-01

    Highlights: • Investigation of the initial stages of epitaxial growth of Ge on Si(1 1 1) in situ by RHEED. • Impact of growth temperature on strain evolution for temperatures between 200 °C and 400 °C. • Epitaxy with a high degree of structural perfection already at growth temperature of 200 °C. • Ordered interfacial dislocation networks already at 200 °C. • Tensile strain contribution of Si(1 1 1) 7 × 7-surface reconstruction to strain relaxation process for epitaxial growth of Ge. - Abstract: In this paper we investigate the initial stages of epitaxial growth of Ge on Si(1 1 1) and the impact of growth temperature on strain evolution in situ by reflection high energy electron diffraction (RHEED) for temperatures between 200 °C and 400 °C. The change in surface morphology from a flat wetting layer to subsequent islanding that is characteristic for Stranski–Krastanov growth is monitored by spot intensity analysis. The corresponding critical layer thickness is determined to 3.1 < d c < 3.4 ML. In situ monitoring of the strain relaxation process reveals a contribution of the Si(1 1 1) 7 × 7-surface reconstruction to the strain relaxation process. High resolution transmission electron microscopy confirms that the Ge islands exhibit a high degree of structural perfection and an ordered interfacial misfit dislocation network already at a growth temperature of 200 °C is established. The temperature dependency of island shape, density and height is characterized by atomic force microscopy and compared to the RHEED investigations.

  4. Surface structure of Bi2Sr2CaCu2O(8+delta) high-temperature superconductors studied using low-energy electron diffraction

    Science.gov (United States)

    Lindberg, P. A. P.; Shen, Z.-X.; Wells, B. O.; Mitzi, D. B.; Lindau, I.

    1988-12-01

    The surface structure of Bi2Sr2CaCu2O(8+delta) has been studied using low-energy electron diffraction (LEED). Sharp diffraction spots indicative of a well-ordered surface are observed. The LEED patterns unequivocally show that this type of material preferentially cleaves along the a-b planes of the nearly tetragonal unit cell. A superstructure extending along one of the axes in the a-b plane (b) is found to have a periodicity of 27 + or - 0.5 A, in good agreement with earlier studies of the three-dimensional crystal structure. The superstructure at the surface is nonlocal in character and reflects the long-range superlattice of the bulk along the b axis. Intensity modulations of the diffraction spots oriented along the b axis are also reported and discussed in terms of the cell dimension of the unit cell along the b axis.

  5. Surface structure of Bi2Sr2CaCu2O/sub 8+//sub δ high-temperature superconductors studied using low-energy electron diffraction

    International Nuclear Information System (INIS)

    Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1988-01-01

    The surface structure of Bi 2 Sr 2 CaCu 2 O/sub 8+//sub δ has been studied using low-energy electron diffraction (LEED). Sharp diffraction spots indicative of a well-ordered surface are observed. The LEED patterns unequivocally show that this type of material preferentially cleaves along the a-b planes of the nearly tetragonal unit cell. A superstructure extending along one of the axes in the a-b plane (b) is found to have a periodicity of 27 +- 0.5 A, in good agreement with earlier studies of the three-dimensional crystal structure. We conclude that the superstructure at the surface is nonlocal in character and reflects the long-range superlattice of the bulk along the b axis. Intensity modulations of the diffraction spots oriented along the b axis are also reported and discussed in terms of the cell dimension of the unit cell along the b axis

  6. Non-destructive assessment of the polarity of GaN nanowire ensembles using low-energy electron diffraction and x-ray photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Fernández-Garrido, S.; Jiříček, Petr; Bartoš, Igor; Geelhaar, L.; Brandt, O.; Paskova, T.

    2015-01-01

    Roč. 106, č. 2 (2015), "021602-1"-"021602-4" ISSN 0003-6951 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN nanowires * X-ray photoelectron diffraction * LEED I-V * GaN polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.142, year: 2015

  7. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Directory of Open Access Journals (Sweden)

    M. Guevara-Bertsch

    2016-03-01

    Full Text Available We investigate the variation of the oscillation frequency of the Mg2+ and O2− ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  8. Structure determination of the ordered (2 × 1) phase of NiSi surface alloy on Ni(111) using low-energy electron diffraction

    Science.gov (United States)

    Sazzadur Rahman, Md.; Amirul Islam, Md.; Saha, Bidyut Baran; Nakagawa, Takeshi; Mizuno, Seigi

    2015-12-01

    The (2 × 1) structure of the two-dimensional nickel silicide surface alloy on Ni(111) was investigated using quantitative low-energy electron diffraction analysis. The unit cell of the determined silicide structure contains one Si and one Ni atom, corresponding to a chemical formula of NiSi. The Si atoms adopt substitutional face-centered cubic hollow sites on the Ni(111) substrate. The Ni-Si bond lengths were determined to be 2.37 and 2.34 Å. Both the alloy surface and the underlying first layers of Ni atoms exhibit slight corrugation. The Ni-Si interlayer distance is smaller than the Ni-Ni interlayer distance, which indicates that Si atoms and underlying Ni atoms strongly interact.

  9. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Bertsch, M.; Avendaño, E. [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Ramírez-Hidalgo, G. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Sección de Física Teórica, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Chavarría-Sibaja, A.; Araya-Pochet, J. A. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Herrera-Sancho, O. A., E-mail: oscar-andrey.herrera@uibk.ac.at [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstr. 21a, 6020 Innsbruck (Austria)

    2016-03-15

    We investigate the variation of the oscillation frequency of the Mg{sup 2+} and O{sup 2−} ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  10. Studies of the surface structures of molecular crystals and of adsorbed molecular monolayers on the (111) crystal faces of platinum and silver by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Firment, L.E.

    1977-01-01

    The structures of molecular crystal surfaces were investigated for the first time by the use of low-energy electron diffraction (LEED). The experimental results from a variety of molecular crystals were examined and compared as a first step towards understanding the properties of these surfaces on a microscopic level. The method of sample preparation employed, vapor deposition onto metal single-crystal substrates at low temperatures in ultrahigh vacuum, allowed concurrent study of the structures of adsorbed monolayers on metal surfaces and of the growth processes of molecular films on metal substrates. The systems investigated were ice, ammonia, naphthalene, benzene, the n-paraffins (C 3 to C 8 ), cyclohexane, trioxane, acetic acid, propionic acid, methanol, and methylamine adsorbed and condensed on both Pt(111) and Ag(111) surfaces. Electron-beam-induced damage of the molecular surfaces was observed after electron exposures of 10 -4 A sec cm -2 at 20 eV. Aromatic molecular crystal samples were more resistant to damage than samples of saturated molecules. The quality and orientation of the grown molecular crystal films were influenced by substrate preparation and growth conditions. Forty ordered monolayer structures were observed. 110 figures, 22 tables, 162 references

  11. Interface structure and stabilization of metastable B2-FeSi/Si(111) studied with low-energy electron diffraction and density functional theory

    International Nuclear Information System (INIS)

    Walter, S; Blobner, F; Krause, M; Mueller, S; Heinz, K; Starke, U

    2003-01-01

    We present a combined experimental and theoretical investigation of the interface between a B2-type FeSi film and Si(111). Using an ultra-thin B2-FeSi film grown on Si(111), the interface is still reached by electrons, so quantitative low-energy electron diffraction (LEED) could be applied to determine the bonding geometry experimentally. As a result, the local configuration at the shallow buried interface is characterized by near-substrate Fe atoms being 8-fold coordinated to Si atoms and by the silicide unit cell being rotated by 180 deg. with respect to the Si unit cell (B8 configuration). The interface energetics were explored by total-energy calculations using density functional theory (DFT). The B8-type interface proves to be the most stable one, consistent with the experimental findings. The atomic geometries obtained experimentally (LEED) and theoretically (DFT) agree within the limits of errors. Additionally, the calculations explain the stabilization of the B2 phase, which is unstable as bulk material: the analysis of the elastic behaviour reveals a reversed energy hierarchy of B2 and the bulk stable B20 phase when epitaxial growth on Si(111) is enforced

  12. Low energy electron diffraction (LEED) and sum frequency generation (SFG) vibrational spectroscopy studies of solid-vacuum, solid-air and solid-liquid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoffer, Saskia [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Electron based surface probing techniques can provide detailed information about surface structure or chemical composition in vacuum environments. The development of new surface techniques has made possible in situ molecular level studies of solid-gas interfaces and more recently, solid-liquid interfaces. The aim of this dissertation is two-fold. First, by using novel sample preparation, Low Energy Electron Diffraction (LEED) and other traditional ultra high vacuum (UHV) techniques are shown to provide new information on the insulator/vacuum interface. The surface structure of the classic insulator NaCl has been determined using these methods. Second, using sum frequency generation (SFG) surface specific vibrational spectroscopy studies were performed on both the biopolymer/air and electrode/electrolyte interfaces. The surface structure and composition of polyetherurethane-silicone copolymers were determined in air using SFG, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). SFG studies of the electrode (platinum, gold and copper)/electrolyte interface were performed as a function of applied potential in an electrochemical cell.

  13. Detailed low-energy electron diffraction analysis of the (4×4) surface structure of C60 on Cu(111): Seven-atom-vacancy reconstruction

    Science.gov (United States)

    Xu, Geng; Shi, Xing-Qiang; Zhang, R. Q.; Pai, Woei Wu; Jeng, H. T.; Van Hove, M. A.

    2012-08-01

    A detailed and exhaustive structural analysis by low-energy electron diffraction (LEED) is reported for the C60-induced reconstruction of Cu(111), in the system Cu(111) + (4 × 4)-C60. A wide LEED energy range allows enhanced sensitivity to the crucial C60-metal interface that is buried below the 7-Å-thick molecular layer. The analysis clearly favors a seven-Cu-atom vacancy model (with Pendry R-factor Rp = 0.376) over a one-Cu-atom vacancy model (Rp = 0.608) and over nonreconstructed models (Rp = 0.671 for atop site and Rp = 0.536 for hcp site). The seven-Cu-atom vacancy forms a (4 × 4) lattice of bowl-like holes. In each hole, a C60 molecule can nestle by forming strong bonds (shorter than 2.30 Å) between 15 C atoms of the molecule and 12 Cu atoms of the outermost and second Cu layers.

  14. Low-kilovolt coherent electron diffractive imaging instrument based on a single-atom electron source

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Yueh [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Chang, Wei-Tse; Chen, Yi-Sheng; Hwu, En-Te; Chang, Chia-Seng; Hwang, Ing-Shouh, E-mail: ishwang@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China); Hsu, Wei-Hao [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2016-03-15

    In this work, a transmission-type, low-kilovolt coherent electron diffractive imaging instrument was constructed. It comprised a single-atom field emitter, a triple-element electrostatic lens, a sample holder, and a retractable delay line detector to record the diffraction patterns at different positions behind the sample. It was designed to image materials thinner than 3 nm. The authors analyzed the asymmetric triple-element electrostatic lens for focusing the electron beams and achieved a focused beam spot of 87 nm on the sample plane at the electron energy of 2 kV. High-angle coherent diffraction patterns of a suspended graphene sample corresponding to (0.62 Å){sup −1} were recorded. This work demonstrated the potential of coherent diffractive imaging of thin two-dimensional materials, biological molecules, and nano-objects at a voltage between 1 and 10 kV. The ultimate goal of this instrument is to achieve atomic resolution of these materials with high contrast and little radiation damage.

  15. Lateral ordering of PTCDA on the clean and the oxygen pre-covered Cu(100) surface investigated by scanning tunneling microscopy and low energy electron diffraction.

    Science.gov (United States)

    Gärtner, Stefan; Fiedler, Benjamin; Bauer, Oliver; Marele, Antonela; Sokolowski, Moritz M

    2014-01-01

    We have investigated the adsorption of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) on the clean and on the oxygen pre-covered Cu(100) surface [referred to as (√2 × 2√2)R45° - 2O/Cu(100)] by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Our results confirm the (4√2 × 5√2)R45° superstructure of PTCDA/Cu(100) reported by A. Schmidt et al. [J. Phys. Chem. 1995, 99,11770-11779]. However, contrary to Schmidt et al., we have no indication for a dissociation of the PTCDA upon adsorption, and we propose a detailed structure model with two intact PTCDA molecules within the unit cell. Domains of high lateral order are obtained, if the deposition is performed at 400 K. For deposition at room temperature, a significant density of nucleation defects is found pointing to a strong interaction of PTCDA with Cu(100). Quite differently, after preadsorption of oxygen and formation of the (√2 × 2√2)R45° - 2O/Cu(100) superstructure on Cu(100), PTCDA forms an incommensurate monolayer with a structure that corresponds well to that of PTCDA bulk lattice planes.

  16. Lateral ordering of PTCDA on the clean and the oxygen pre-covered Cu(100 surface investigated by scanning tunneling microscopy and low energy electron diffraction

    Directory of Open Access Journals (Sweden)

    Stefan Gärtner

    2014-09-01

    Full Text Available We have investigated the adsorption of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA on the clean and on the oxygen pre-covered Cu(100 surface [referred to as (√2 × 2√2R45° – 2O/Cu(100] by scanning tunneling microscopy (STM and low energy electron diffraction (LEED. Our results confirm the (4√2 × 5√2R45° superstructure of PTCDA/Cu(100 reported by A. Schmidt et al. [J. Phys. Chem. 1995, 99,11770–11779]. However, contrary to Schmidt et al., we have no indication for a dissociation of the PTCDA upon adsorption, and we propose a detailed structure model with two intact PTCDA molecules within the unit cell. Domains of high lateral order are obtained, if the deposition is performed at 400 K. For deposition at room temperature, a significant density of nucleation defects is found pointing to a strong interaction of PTCDA with Cu(100. Quite differently, after preadsorption of oxygen and formation of the (√2 × 2√2R45° – 2O/Cu(100 superstructure on Cu(100, PTCDA forms an incommensurate monolayer with a structure that corresponds well to that of PTCDA bulk lattice planes.

  17. Surface structures of normal paraffins and cyclohexane monolayers and thin crystals grown on the (111) crystal face of platinum. A low-energy electron diffraction study

    International Nuclear Information System (INIS)

    Firment, L.E.; Somorjai, G.A.

    1977-01-01

    The surfaces of the normal paraffins (C 3 --C 8 ) and cyclohexane have been studied using low-energy electron diffraction (LEED). The samples were prepared by vapor deposition on the (111) face of a platinum single crystal in ultrahigh vacuum, and were studied both as thick films and as adsorbed monolayers. These molecules form ordered monolayers on the clean metal surface in the temperature range 100--220 K and at a vapor flux corresponding to 10 -7 Torr. In the adsorbed monolayers of the normal paraffins (C 4 --C 8 ), the molecules lie with their chain axes parallel to the Pt surface and Pt[110]. The paraffin monolayer structures undergo order--disorder transitions as a function of temperature. Multilayers condensed upon the ordered monolayers maintained the same orientation and packing as found in the monolayers. The surface structures of the growing organic crystals do not corresond to planes in their reported bulk crystal structures and are evidence for epitaxial growth of pseudomorphic crystal forms. Multilayers of n-octane and n-heptane condensed upon disordered monolayers have also grown with the (001) plane of the triclinic bulk crystal structures parallel to the surface. n-Butane has three monolayer structures on Pt(111) and one of the three is maintained during growth of the crystal. Cyclohexane forms an ordered monolayer, upon which a multilayer of cyclohexane grows exhibiting the (001) surface orientation of the monoclinic bulk crystal structure. Surface structures of saturated hydrocarbons are found to be very susceptible to electron beam induced damage. Surface charging interferes with LEED only at sample thicknesses greater than 200 A

  18. Absorptive form factors for high-energy electron diffraction

    International Nuclear Information System (INIS)

    Bird, D.M.; King, Q.A.

    1990-01-01

    The thermal diffuse scattering contribution to the absorptive potential in high-energy electron diffraction is calculated in the form of an absorptive contribution to the atomic form factor. To do this, the Einstein model of lattice vibrations is used, with isotropic Debye-Waller factors. The absorptive form factors are calculated as a function of scattering vector s and temperature factor M on a grid which enables polynomial interpolation of the results to be accurate to better than 2% for much of the ranges 0≤Ms 2 ≤6 and 0≤M≤2 A 2 . The computed values, together with an interpolation routine, have been incorporated into a Fortran subroutine which calculates both the real and absorptive form factors for 54 atomic species. (orig.)

  19. Energy-weighted dynamical scattering simulations of electron diffraction modalities in the scanning electron microscope.

    Science.gov (United States)

    Pascal, Elena; Singh, Saransh; Callahan, Patrick G; Hourahine, Ben; Trager-Cowan, Carol; Graef, Marc De

    2018-04-01

    Transmission Kikuchi diffraction (TKD) has been gaining momentum as a high resolution alternative to electron back-scattered diffraction (EBSD), adding to the existing electron diffraction modalities in the scanning electron microscope (SEM). The image simulation of any of these measurement techniques requires an energy dependent diffraction model for which, in turn, knowledge of electron energies and diffraction distances distributions is required. We identify the sample-detector geometry and the effect of inelastic events on the diffracting electron beam as the important factors to be considered when predicting these distributions. However, tractable models taking into account inelastic scattering explicitly are lacking. In this study, we expand the Monte Carlo (MC) energy-weighting dynamical simulations models used for EBSD [1] and ECP [2] to the TKD case. We show that the foil thickness in TKD can be used as a means of energy filtering and compare band sharpness in the different modalities. The current model is shown to correctly predict TKD patterns and, through the dictionary indexing approach, to produce higher quality indexed TKD maps than conventional Hough transform approach, especially close to grain boundaries. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  20. Electron spin polarization effects in low energy electron diffraction, ion neutralization and metastable atom deexcitation at solid surfaces. Progress report No. 4, 1 January-31 December 1984

    International Nuclear Information System (INIS)

    1984-01-01

    In the present contract year, a GaAs polarized electron source has been used to undertake a polarized LEED study of order-disorder transformations at Cu 3 Au (100) and (111) surfaces. A polarized LEED study of Cu (100) has also been initiated. A polarized MDS study of Ni(110) surface magnetism has been completed. Spin dependences in the Auger electron yield were observed that provide a measure of the surface magnetism and were used to probe the dependence of surface magnetism on temperature and adsorbate coverage. A similar study using a ferromagnetic glass is now underway. A Mott polarization analyzer, constructed to measure the ESP of the ejected electrons, is also being installed on the apparatus. Such measurements provide direct information concerning the dynamics of secondary electron ejection and the details of adsorbate-substrate bonding

  1. Low temperature electron microscopy and electron diffraction of the purple membrane of Halobacterium halobium

    International Nuclear Information System (INIS)

    Hayward, S.B.

    1978-09-01

    The structure of the purple membrane of Halobacterium halobium was studied by high resolution electron microscopy and electron diffraction, primarily at low temperature. The handedness of the purple membrane diffraction pattern with respect to the cell membrane was determined by electron diffraction of purple membranes adsorbed to polylysine. A new method of preparing frozen specimens was used to preserve the high resolution order of the membranes in the electron microscope. High resolution imaging of glucose-embedded purple membranes at room temperature was used to relate the orientation of the diffraction pattern to the absolute orientation of the structure of the bacteriorhodopsin molecule. The purple membrane's critical dose for electron beam-induced damage was measured at room temperature and at -120 0 C, and was found to be approximately five times greater at -120 0 C. Because of this decrease in radiation sensitivity, imaging of the membrane at low temperature should result in an increased signal-to-noise ratio, and thus better statistical definition of the phases of weak reflections. Higher resolution phases may thus be extracted from images than can be determined by imaging at room temperature. To achieve this end, a high resolution, liquid nitrogen-cooled stage was built for the JEOL-100B. Once the appropriate technology for taking low dose images at very high resolution has been developed, this stage will hopefully be used to determine the high resolution structure of the purple membrane

  2. Electron spin polarization effects in low-energy electron diffraction, ion neutralization, and metastable-atom deexcitation at solid surfaces. Progress report No. 3, January 1-December 31, 1983

    International Nuclear Information System (INIS)

    Walters, G.K.; Dunning, F.B.

    1983-01-01

    The importance of electron spin polarization (ESP) effects in the various spectroscopies used to study solid surfaces has become increasingly apparent in recent years. Recent low energy electron diffraction (LEED) investigations in this laboratory and elsewhere have shown that a great deal of new information contributing to the understanding of the geometrical arrangements of atoms at a surface can be obtained if the polarization of the various LEED beams is measured, or if the incident electron beam is polarized. Polarized LEED studies have shown large polarization features that are very sensitive to the presence of adsorbed layers, surface reconstruction, etc. In addition, theory suggests that polarization measurements can provide a more sensitive test of many of the parameters used in a surface model than can conventional LEED intensity measurements alone. Polarized LEED has also been applied to the study of surface magnetism. In the present contract year, polarized LEED has been used, together with Auger analysis and LEED intensity measurements, as a diagnostic to characterize Ni(001) surfaces produced by laser annealing

  3. Scattering of polarized low-energy electrons by ferromagnetic metals

    International Nuclear Information System (INIS)

    Helman, J.S.

    1981-01-01

    A source of spin polarized electrons with remarkable characteristics based on negative electron affinity (NEA) GaAs has recently been developed. It constitutes a unique tool to investigate spin dependent interactions in electron scattering processes. The characteristics and working principles of the source are briefly described. Some theoretical aspects of the scattering of polarized low-energy electrons by ferromagnetic metals are discussed. Finally, the results of the first polarized low-energy electron diffraction experiment using the NEA GaAs source are reviewed; they give information about the surface magnetization of ferromagnetic Ni (110). (Author) [pt

  4. Surface sterilization by low energy electron beams

    International Nuclear Information System (INIS)

    Sekiguchi, Masayuki; Tabei, Masae

    1989-01-01

    The germicidal effectiveness of low energy electron beams (175 KV) against bacterial cells was investigated. The dry spores of Bacillus pumilus ATCC 27142 and Bacillus globigii ATCC 9372 inoculated on carrier materials and irradiated by gamma rays showed the exponential type of survival curves whereas they showed sigmoidal ones when exposed to low energy electron beams. When similarly irradiated, the wet spores inoculated on membrane filter showed the same survival curves as the dry spores inoculated on carrier materials. The wet vegetative cells of Escherichia coli ATCC 25922 showed exponential curves when exposed to gamma and electron beam irradiation. Low energy electron beams in air showed little differences from nitrogen stream in their germicidal effectiveness against dry spores of B. pumilus. The D values of B. pumilus spores inoculated on metal plates decreased as the amounts of backscattering electrons from the plates increased. There was adequate correlation between the D value (linear region of survival curve), average D value (6D/6) and 1% survival dose and backscattering factor. Depth dose profile and backscatterig dose of low energy electron beams were measured by radiochromic dye film dosimeter (RCD). These figures were not always in accord with the observed germicidal effectiveness against B. pumilus spores because of varying thickness of RCD and spores inoculated on carrier material. The dry spores were very thin and this thinness was useful in evaluating the behavior of low energy electrons. (author)

  5. Food irradiation by low energy electrons

    International Nuclear Information System (INIS)

    Bird, J.R.

    1985-01-01

    For some special cases, the use of low energy electrons has advantages over the use of gamma-rays or higher energy electrons for the direct irradiation of food. These advantages arise from details of the interaction processes which are responsible for the production of physical, chemical and biological effects. Factors involved include depth of penetration, dose distribution, irradiation geometry, the possible production of radioactivity and costs

  6. A summary of the low angle x-ray atomic scattering factors which have been measured by the critical voltage effect in High Energy Electron Diffraction (HEED)

    International Nuclear Information System (INIS)

    Fox, A.G.; Fisher, R.M.

    1987-08-01

    A tabulated summary of all the accurate (/approximately/0.1%) low-angle x-ray atomic scattering (form) factors which have been determined by the systematic critical voltage technique in HEED is presented. For low atomic number elements (Z/approx lt/40) the low angle form factors can be significantly different to best free atom values, and so the best band structure calculated and/or x-ray measured form factors consistent with the critical voltage measurements are also indicated. At intermediate atomic numbers Z≅40→50 only the very low-angle form factors appear to be different to the best free atom values, and even then only by a small amount. For heavy elements (Z/approx lt/70) the best free atom form factors appear to agree very closely with the critical voltage measured values and so, in this case, critical voltage measurements give very accurate measurements of Debye-Waller factors. 48 refs

  7. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Messahel, Lyria

    2012-11-12

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage {Theta}{sub Cu,Ag,Au}=2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The

  8. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Messahel, Lyria

    2012-01-01

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage Θ Cu,Ag,Au =2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The structure

  9. Low energy electron scattering from fuels

    International Nuclear Information System (INIS)

    Lopes, M. Cristina A.; Silva, Daniel G.M.; Coelho, Rafael F.; Duque, Humberto V.; Santos, Rodrigo R. dos; Ribeiro, Thiago M.

    2011-01-01

    Full text. Accurate and precise values of absolute total cross section (TCS) represent important information in many scientific and technological applications. In our case, for example, we are motivated to provide such information for electron-fuel collision processes which are specifically relevant to modeling spark ignition in alcohol-fuelled internal combustion engines. Many electron scattering TCS measurements are presently available for a diverse range of atomic and molecular targets. However, lack of data for important bio-molecular targets still remains. Disagreements between the available TCS data for the alcohols have prompted several studies of electron scattering collision of slow electrons with these molecules which are currently important in applications as bio- fuels. This relevance, which has attracted much attention, has been one of the subjects of a recent collaboration between experimental and theoretical groups in the USA and Brazil. Recently this collaboration reported first measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering by several primary alcohols. In this work we address methanol and ethanol TCSs at low energy range and report additional studies of resonant structure in ethanol using the detection of metastable states produced by electron impact excitation with high energy resolution. We have recently constructed a TCS apparatus in our laboratory at Universidade Federal de Juiz de Fora, Brazil, based on the well-known linear transmission technique. The experimental setup is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the atoms or molecules to be studied at a given pressure. It consists essentially of an electron gun, a gas cell and an electron energy analyzer composed of an array of decelerating electrostatic lenses, a cylindrical dispersive 127o analyzer and a Faraday cup. To our knowledge, there exist

  10. Low energy electron scattering from fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, M. Cristina A.; Silva, Daniel G.M.; Coelho, Rafael F.; Duque, Humberto V.; Santos, Rodrigo R. dos; Ribeiro, Thiago M. [Universidade Federal de Juiz de Fora (UFJF), MG (Brazil). Dept. de Fisica; Yates, Brent; Hong, Ling; Khakoo, Murtadha A. [California State University at Fullerton, CA (US). Physics Department; Bettega, Marcio H.F. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Fisica; Costa, Romarly F. da [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Lima, Marco A.P. [Laboratorio Nacional de Ciencia e Tecnologia do Bioetanol (CTBE/CNPEM), Campinas, SP (Brazil)

    2011-07-01

    Full text. Accurate and precise values of absolute total cross section (TCS) represent important information in many scientific and technological applications. In our case, for example, we are motivated to provide such information for electron-fuel collision processes which are specifically relevant to modeling spark ignition in alcohol-fuelled internal combustion engines. Many electron scattering TCS measurements are presently available for a diverse range of atomic and molecular targets. However, lack of data for important bio-molecular targets still remains. Disagreements between the available TCS data for the alcohols have prompted several studies of electron scattering collision of slow electrons with these molecules which are currently important in applications as bio- fuels. This relevance, which has attracted much attention, has been one of the subjects of a recent collaboration between experimental and theoretical groups in the USA and Brazil. Recently this collaboration reported first measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering by several primary alcohols. In this work we address methanol and ethanol TCSs at low energy range and report additional studies of resonant structure in ethanol using the detection of metastable states produced by electron impact excitation with high energy resolution. We have recently constructed a TCS apparatus in our laboratory at Universidade Federal de Juiz de Fora, Brazil, based on the well-known linear transmission technique. The experimental setup is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the atoms or molecules to be studied at a given pressure. It consists essentially of an electron gun, a gas cell and an electron energy analyzer composed of an array of decelerating electrostatic lenses, a cylindrical dispersive 127o analyzer and a Faraday cup. To our knowledge, there exist

  11. On a semiclassical analysis of high energy electron diffraction by imperfect crystals: the stacking fault

    International Nuclear Information System (INIS)

    Smith, A.E.; Chadderton, L.T.; Johnson, E.

    1978-01-01

    Electron diffraction amplitudes at the lower surface of a displaced sandwich crystal are obtained for the high energy limit in the real space formulation. Using semiclassical methods analytical approximations to a resulting overlap integral - central to the problem - are derived. (Auth.)

  12. Electron-ion recombination at low energy

    International Nuclear Information System (INIS)

    Andersen, L.H.

    1993-01-01

    The work is based on results obtained with a merged-beams experiment. A beam of electronics with a well characterized density and energy distribution was merged with a fast, monoenergetic ion beam. Results have been obtained for radiative recombination and dielectronic recombination at low relative energies (0 to ∼70eV). The obtained energy resolution was improved by about a factor of 30. High vacuum technology was used to suppress interactions with electrons from the environments. The velocity distribution of the electron beam was determined. State-selective dielectronic-recombination measurements were performable. Recombination processes were studied. The theoretical background for radiative recombination and Kramers' theory are reviewed. The quantum mechanical result and its relation to the semiclassical theory is discussed. Radiative recombination was also measured with several different non-bare ions, and the applicability of the semiclassical theory to non-bare ions was investigated. The use of an effective charge is discussed. For dielectronic recombination, the standard theoretical approach in the isolated resonance and independent-processes approximation is debated. The applicability of this method was tested. The theory was able to reproduce most of the experimental data except when the recombination process was sensitive to couplings between different electronic configurations. The influence of external perturbing electrostatic fields is discussed. (AB) (31 refs.)

  13. Energy loss and thermalization of low-energy electrons

    International Nuclear Information System (INIS)

    LaVerne, J.A.; Mozumder, A.; Notre Dame Univ., IN

    1984-01-01

    Various processes involved in the moderation of low-energy electrons (< 10 keV in energy) have been delineated in gaseous and liquid media. The discussion proceeds in two stages. The first stage ends and the second stage begins when the electron energy equals the first excitation potential of the medium. The second stage ends with thermalization. Cross sections for electronic excitation and for the excitation (and de-excitation) of sub-electronic processes have been evaluated and incorporated in suitable stopping power and transport theories. Comparison between experiment and theory and intercomparisons between theories and experiments have been provided where possible. (author)

  14. Contrast of HOLZ lines in energy-filtered convergent-beam electron diffraction patterns from silicon

    International Nuclear Information System (INIS)

    Lehmpfuhl, G.; Krahl, D.; Uchida, Y.

    1995-01-01

    Higher-order Laue-zone (HOLZ) lines were investigated in convergent-beam electron diffraction patterns from silicon near the low-indexed zone axes [100], [110] and [111]. The visibility of these lines depends on the effective structure potentials of the reflections from the first Laue zone depending on their Debye-Waller factor. The contrast of the HOLZ lines is strongly reduced by inelastically scattered electrons. They can be excluded by an imaging Ω filter for energy losses above 2 eV. The diffraction patterns were compared with many-beam calculations. Without absorption, an excellent agreement could be achieved for the [111] and [100] zone axes, while the simulation of the [110] zone-axis pattern needed a calculation with absorption. The reason for this observation is explained in the Bloch-wave picture. Calculations with absorption, however, lead to artefacts in the intensity distribution of the [100] HOLZ pattern. In order to obtain agreement with the experiment, the Debye-Waller factor had to be modified in different ways for the different zone axes. This corresponds to a strong anisotropy of the Debye-Waller factor. To confirm this observation, the temperature dependence of the itensity distributions of the HOLZ patterns was investigated between 50 and 680 K. At room temperature, the parameter D in the Debye-Waller factor exp(-Ds 2 ) was determined as 0.13, 0.26 and 0.55 A 2 for the zone axes [100], [111] and [110], respectively. The reliability of the conclusions is discussed. (orig.)

  15. Medipix 2 detector applied to low energy electron microscopy

    International Nuclear Information System (INIS)

    Gastel, R. van; Sikharulidze, I.; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, S.J. van der

    2009-01-01

    Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy. Here, we report on a successful test series using a solid state hybrid pixel detector, Medipix 2, in LEEM and PEEM. Medipix 2 is a background-free detector with an infinite dynamic range, making it very promising for both real-space imaging and spectroscopy. We demonstrate a significant enhancement of both image contrast and resolution, as compared to MCPs. Since aging of the Medipix 2 detector is negligible for the electron energies used in LEEM/PEEM, we expect Medipix to become the detector of choice for a new generation of systems.

  16. Medipix 2 detector applied to low energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gastel, R. van, E-mail: R.vanGastel@utwente.nl [University of Twente, MESA Institute for Nanotechnology, P.O. Box 217, NL-7500 AE Enschede (Netherlands); Sikharulidze, I. [Leiden University, Leiden Institute of Chemistry, P.O. Box 9502, NL-2300 RA Leiden (Netherlands); Schramm, S. [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands); Abrahams, J.P. [Leiden University, Leiden Institute of Chemistry, P.O. Box 9502, NL-2300 RA Leiden (Netherlands); Poelsema, B. [University of Twente, MESA Institute for Nanotechnology, P.O. Box 217, NL-7500 AE Enschede (Netherlands); Tromp, R.M. [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands); IBM Research Division, T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Molen, S.J. van der [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands)

    2009-12-15

    Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy. Here, we report on a successful test series using a solid state hybrid pixel detector, Medipix 2, in LEEM and PEEM. Medipix 2 is a background-free detector with an infinite dynamic range, making it very promising for both real-space imaging and spectroscopy. We demonstrate a significant enhancement of both image contrast and resolution, as compared to MCPs. Since aging of the Medipix 2 detector is negligible for the electron energies used in LEEM/PEEM, we expect Medipix to become the detector of choice for a new generation of systems.

  17. Can Low Energy Electrons Affect High Energy Physics Accelerators?

    International Nuclear Information System (INIS)

    Cimino, Roberto

    2004-01-01

    The properties of the electrons participating in the build up of an electron cloud (EC) inside the beam-pipe have become an increasingly important issue for present and future accelerators whose performance may be limited by this effect. The EC formation and evolution are determined by the wall-surface properties of the accelerator vacuum chamber. Thus, the accurate modeling of these surface properties is an indispensible input to simulation codes aimed at the correct prediction of build-up thresholds, electron-induced instability or EC heat load. In this letter, we present the results of surface measurements performed on a prototype of the beam screen adopted for the Large Hadron Collider (LHC), which presently is under construction at CERN. We have measured the total secondary electron yield (SEY) as well as the related energy distribution curves (EDC) of the secondary electrons as a function of incident electron energy. Attention has been paid, for the first time in this context, to the probability at which low-energy electrons (<∼ 20 eV) impacting on the wall create secondaries or are elastically reflected. It is shown that the ratio of reflected to true-secondary electrons increases for decreasing energy and that the SEY approaches unity in the limit of zero primary electron energy

  18. Low Energy Electron Cooler for NICA Booster

    CERN Document Server

    Denisov, A P

    2017-01-01

    BINP has developed an electron cooler to increase the ion accumulation efficiency in the NICA (Nuclotron-based Ion Collider fAcility) heavy ion booster (JINR, Dubna). Adjustment of the cooler magnetic system provides highly homogeneous magnetic field in the cooling section B trans/B long ≤ 4∙10-5 which is vital for efficient electron cooling. First experiments with an electron beam performed at BINP demonstrated the target DC current of 500 mA and electron energy 6 keV.

  19. Low energy electron transport in furfural

    Science.gov (United States)

    Lozano, Ana I.; Krupa, Kateryna; Ferreira da Silva, Filipe; Limão-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, Darryl B.; Brunger, Michael J.; García, Gustavo

    2017-09-01

    We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed.

  20. Low energy electron transport in furfural

    International Nuclear Information System (INIS)

    Lozano, A.I.; Garcia, G.; Krupa, K.; Ferreira da Silva, F.; Limao-Vieira, P.; Blanco, F.; Munoz, A.; Jones, D.B.; Brunger, M.J.

    2017-01-01

    The cyclic configuration of the furfural molecule is similar to the 5-membered ring structure constituting the sugar units of the DNA helix, hence its importance in biology. In this paper, we report on an initial investigation into the transport of electrons through a gas cell containing 1 mtorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed

  1. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    International Nuclear Information System (INIS)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2√3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (√3 x √3) reconstruction on the (111) face of the α-CuAl alloy has been determined

  2. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

  3. Electron polarimetry at low energies in Hall C at JLab

    International Nuclear Information System (INIS)

    Gaskell, D.

    2013-01-01

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered

  4. The interaction of low-energy electrons with fructose molecules

    Science.gov (United States)

    Chernyshova, I. V.; Kontrosh, E. E.; Markush, P. P.; Shpenik, O. B.

    2017-11-01

    Using a hypocycloidal electronic spectrometer, the interactions of low energy electrons (0-8.50 eV) with fructose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of fructose molecules occurs effectively even at an electron energy close to zero. In the total electron-scattering cross section by molecules, resonance features (at energies 3.10 and 5.00 eV) were first observed near the formation thresholds of light ion fragments OH- and H-. The correlation of the features observed in the cross sections of electron scattering and dissociative attachment is analyzed.

  5. Big-data reflection high energy electron diffraction analysis for understanding epitaxial film growth processes.

    Science.gov (United States)

    Vasudevan, Rama K; Tselev, Alexander; Baddorf, Arthur P; Kalinin, Sergei V

    2014-10-28

    Reflection high energy electron diffraction (RHEED) has by now become a standard tool for in situ monitoring of film growth by pulsed laser deposition and molecular beam epitaxy. Yet despite the widespread adoption and wealth of information in RHEED images, most applications are limited to observing intensity oscillations of the specular spot, and much additional information on growth is discarded. With ease of data acquisition and increased computation speeds, statistical methods to rapidly mine the data set are now feasible. Here, we develop such an approach to the analysis of the fundamental growth processes through multivariate statistical analysis of a RHEED image sequence. This approach is illustrated for growth of La(x)Ca(1-x)MnO(3) films grown on etched (001) SrTiO(3) substrates, but is universal. The multivariate methods including principal component analysis and k-means clustering provide insight into the relevant behaviors, the timing and nature of a disordered to ordered growth change, and highlight statistically significant patterns. Fourier analysis yields the harmonic components of the signal and allows separation of the relevant components and baselines, isolating the asymmetric nature of the step density function and the transmission spots from the imperfect layer-by-layer (LBL) growth. These studies show the promise of big data approaches to obtaining more insight into film properties during and after epitaxial film growth. Furthermore, these studies open the pathway to use forward prediction methods to potentially allow significantly more control over growth process and hence final film quality.

  6. Low energy electron transport in furfural

    OpenAIRE

    Lozano, Ana I.; Krupa, K.; Ferreira da Silva, F.; Limao-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, D. B.; Brunger, M. J.; García, Gustavo

    2017-01-01

    We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulat...

  7. Electron emission from materials at low excitation energies

    International Nuclear Information System (INIS)

    Urma, N.; Kijek, M.; Millar, J.J.

    1996-01-01

    Full text: An experimental system has been designed and developed with the purpose of measuring the total electron emission yield from materials at low energy excitation. In the first instance the reliability of the system was checked by measuring the total electron emission yield for a well defined surface (aluminium 99.45%). The obtained data was in the expected range given by the literature, and consequently the system will be used further for measuring the total electron yield for a range of materials with interest in the instrumentation industry. We intend to measure the total electron emission yield under electron bombardment as a function of incident electron energy up to 1200 eV, angle of incidence, state of the surface and environment to which the surface has been exposed. Dependence of emission on total electron irradiated dose is also of interest. For many practical application of the 'Secondary Electron Emission', the total electron yield is desired to be as large as possible. The above phenomenon has practical applicability in electron multiplier tube and Scanning electron microscopy - when by means of the variation of the yield of the emitted electrons one may produce visible images of small sample areas. The electron multiplier tube, is a device which utilises the above effect to detect and amplify both single particles and low currents streams of charged particles. The majority of electron tubes use electrons with low energy, hundreds of eV. Not a lot has been published in the literature about this regime and also about the emission when the impinging electrons have small energy, up to 1 KeV. The information obtained from the experimental measurements concerning the total electron emission yield is used to asses the investigated materials as a potential electron emitting surfaces or dynodes in an electron multiplier tube

  8. Low energy intense electron beams with extra-low energy spread

    International Nuclear Information System (INIS)

    Aleksandrov, A.V.; Calabrese, R.; Ciullo, G.; Dikansky, N.S.; Guidi, V.; Kot, N.C.; Kudelainen, V.I.; Lamanna, G.; Lebedev, V.A.; Logachov, P.V.; Tecchio, L.; Yang, B.

    1994-01-01

    Maximum achievable intensity for low energy electron beams is a feature that is not very often compatible with low energy spread. We show that a proper choice of the source and the acceleration optics allows one to match them together. In this scheme, a GaAs photocathode excited by a single-mode infrared laser and adiabatic acceleration in fully magnetised optics enables the production of a low-energy-spread electron beam with relatively high intensity. The technological problems associated with the method are discussed together with its limitations. (orig.)

  9. Scanning transmission low-energy electron microscopy

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Hovorka, Miloš; Konvalina, Ivo; Unčovský, M.; Frank, Luděk

    2011-01-01

    Roč. 55, č. 4 (2011), 2:1-6 ISSN 0018-8646 R&D Projects: GA AV ČR IAA100650902; GA MŠk ED0017/01/01 Institutional research plan: CEZ:AV0Z20650511 Keywords : TEM * STEM * SEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.723, year: 2011

  10. Ultra-low-energy wide electron exposure unit

    International Nuclear Information System (INIS)

    Yonago, Akinobu; Oono, Yukihiko; Tokunaga, Kazutoshi; Kishimoto, Junichi; Wakamoto, Ikuo

    2001-01-01

    Heat and ultraviolet ray processes are used in surface dryness of paint, surface treatment of construction materials and surface sterilization of food containers. A process using a low-energy wide-area electron beam (EB) has been developed that features high speed and low drive cost. EB processing is not widespread in general industry, however, due to high equipment cost and difficult maintenance. We developed an ultra-low-energy wide-area electron beam exposure unit, the Mitsubishi Wide Electron Exposure Unit (MIWEL) to solve these problems. (author)

  11. Low-energy electron microdosimetry of CS-137

    International Nuclear Information System (INIS)

    Paschoa, A.S.; Wrenn, M.E.

    1980-09-01

    The mass of tissue irradiated by an internal emitter depends upon the distribution of the radionuclide within the organism and the type of radiation emitted. The range (95% absorption) of low-energy electron effectively defines the sensitive volume in which the energy of the emitted electron is deposited. Accordingly, in the case of Auger electron microdosimetry of internal emitters the correct definition of the sensitive volume is of paramount importance. The amount of energy delivered by the monoenergetic electrons emitted by the decay system 137 Cs → sup(137m)Ba to spherical volumes of water-like tissue media of radii equivalent to the estimated ranges of those electrons in water is calculated and discussed as far as the variations of the estimated ranges of electrons as a function of the initial energy of emission are concerned. Although there are still many uncertainties on the actual ranges of low-energy electrons, one can state confidently that the ranges of the Auger electrons of the decay system 137 Cs → 137 sup(m) Ba → 137 Ba can be considered to be in the same order of magnitude of the diameter of a cell. The energy deposition in spherical volumes of water-like tissue media, considered equivalent to the sensitive volumes for the Auger electrons of the decay system 137 Cs → 137 sub(m) Ba → 137 Ba, range for several orders of magnitude from 10 2 to about 10 10 times higher than the energy deposition in similar media by the internal conversion electrons of this decay system. If equivalent variations of energy deposition per unit mass occur when the masses considered are cellular, and subcellular structures, then the effects into the sensitive volume should be taken into biological consideration as far as the microdosimetry of low-energy electrons (approximately equal to 10 keV) is considered, whenever there is internal localization of Auger emitters. (Author) [pt

  12. Electron diffraction from carbon nanotubes

    International Nuclear Information System (INIS)

    Qin, L-C

    2006-01-01

    The properties of a carbon nanotube are dependent on its atomic structure. The atomic structure of a carbon nanotube can be defined by specifying its chiral indices (u, v), that specify its perimeter vector (chiral vector), with which the diameter and helicity are also determined. The fine electron beam available in a modern transmission electron microscope (TEM) offers a unique probe to reveal the atomic structure of individual nanotubes. This review covers two aspects related to the use of the electron probe in the TEM for the study of carbon nanotubes: (a) to understand the electron diffraction phenomena for inter-pretation of the electron diffraction patterns of carbon nanotubes and (b) to obtain the chiral indices (u, v), of the carbon nanotubes from the electron diffraction patterns. For a nanotube of a given structure, the electron scattering amplitude from the carbon nanotube is first described analytically in closed form using the helical diffraction theory. From a known structure as given by the chiral indices (u, v), its electron diffraction pattern can be calculated and understood. The reverse problem, i.e. assignment of the chiral indices from an electron diffraction pattern of a carbon nanotube, is approached from the relationship between the electron scattering intensity distribution and the chiral indices (u, v). We show that electron diffraction patterns can provide an accurate and unambiguous assignment of the chiral indices of carbon nanotubes. The chiral indices (u, v) can be read indiscriminately with a high accuracy from the intensity distribution on the principal layer lines in an electron diffraction pattern. The symmetry properties of electron diffraction from carbon nanotubes and the electron diffraction from deformed carbon nanotubes are also discussed in detail. It is shown that 2mm symmetry is always preserved for single-walled carbon nanotubes, but it can break down for multiwalled carbon nanotubes under some special circumstances

  13. Can low energy electrons affect high energy physics accelerators?

    CERN Document Server

    Cimino, R; Furman, M A; Pivi, M; Ruggiero, F; Rumolo, Giovanni; Zimmermann, Frank

    2004-01-01

    The properties of the electrons participating in the build up of an electron cloud (EC) inside the beam-pipe have become an increasingly important issue for present and future accelerators whose performance may be limited by this effect. The EC formation and evolution are determined by the wall-surface properties of the accelerator vacuum chamber. Thus, the accurate modeling of these surface properties is an indispensible input to simulation codes aimed at the correct prediction of build-up thresholds, electron-induced instability or EC heat load. In this letter, we present the results of surface measurements performed on a prototype of the beam screen adopted for the Large Hadron Collider (LHC), which presently is under construction at CERN. We have measured the total secondary electron yield (SEY) as well as the related energy distribution curves (EDC) of the secondary electrons as a function of incident electron energy. Attention has been paid, for the first time in this context, to the probability at whic...

  14. Degradation of vitamin C by low-energy electrons

    Science.gov (United States)

    Abdoul-Carime, Hassan; Illenberger, Eugen

    2004-06-01

    We report on the degradation of gas phase vitamin C (ascorbic acid, AA) induced by low-energy electrons. In the energy range of (0-12) eV, different negatively charged fragments, attributed to the dehydro-ascorbic acid anion ((AA-H) -), OH -, O - and H -, are observed. The yield functions indicate that these ions are formed via dissociative electron attachment, DEA. While the formation of (AA-H) - is exclusively observed at sub-excitation energies (<1.5 eV), the other fragments arise from resonance features at higher energies. Possible implications of these observations for radiation damage and food treatment by high energy radiation are considered.

  15. Charge-coupled device area detector for low energy electrons

    Czech Academy of Sciences Publication Activity Database

    Horáček, Miroslav

    2003-01-01

    Roč. 74, č. 7 (2003), s. 3379 - 3384 ISSN 0034-6748 R&D Projects: GA ČR GA102/00/P001 Institutional research plan: CEZ:AV0Z2065902 Keywords : low energy electrons * charged-coupled device * detector Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.343, year: 2003

  16. Utilization of low-energy electron accelerators in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byung Cheol [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2003-02-01

    There are more than 20 electron accelerators in Korea. Most of those are installed in factories for heat-resistant cables, heat-shrinkable cables, radial tires, foams, tube/ films, curing, etc. Four low-energy electron accelerators are in operation for research purposes such as polymer modification, purification of flue gas, waste water treatment, modification of semiconductor characteristics, etc. (author)

  17. Utilization of low-energy electron accelerators in Korea

    International Nuclear Information System (INIS)

    Lee, Byung Cheol

    2003-01-01

    There are more than 20 electron accelerators in Korea. Most of those are installed in factories for heat-resistant cables, heat-shrinkable cables, radial tires, foams, tube/ films, curing, etc. Four low-energy electron accelerators are in operation for research purposes such as polymer modification, purification of flue gas, waste water treatment, modification of semiconductor characteristics, etc. (author)

  18. Very low energy scanning electron microscopy in nanotechnology

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Hovorka, Miloš; Mika, Filip; Mikmeková, Eliška; Mikmeková, Šárka; Pokorná, Zuzana; Frank, Luděk

    2012-01-01

    Roč. 9, 8/9 (2012), s. 695-716 ISSN 1475-7435 R&D Projects: GA MŠk OE08012; GA MŠk ED0017/01/01; GA AV ČR IAA100650902 Institutional research plan: CEZ:AV0Z20650511 Keywords : scanning electron microscopy * very low energy electrons * cathode lens * grain contrast * strain contrast * imaging of participates * dopant contrast * very low energy STEM * graphene Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.087, year: 2012

  19. Low energy positron diffraction from Cu(111): Importance of surface loss processes at large angles of incidence

    International Nuclear Information System (INIS)

    Lessor, D.L.; Duke, C.B.; Lippel, P.H.; Brandes, G.R.; Canter, K.F.; Horsky, T.N.

    1990-10-01

    Intensities of positrons specularly diffracted from Cu(111) were measured at the Brandeis positron beam facility and analyzed in the energy range 8eV i = 4eV. At lower energies strong energy dependences occur associated both with multiple elastic scattering phenomena within atomic layers of Cu parallel to the surface and with the thresholds of inelastic channels (e.g., plasmon creation). Use of the free electron calculation of V i shows that energy dependence of inelastic processes is necessary to obtain a satisfactory description of the absolute magnitude of the diffracted intensities below E = 50eV. Detailed comparison of the calculated and observed diffraction intensities reveals the necessity of incorporating surface loss processes explicitly into the model in order to achieve a quantitative description of the measured intensities for E 40 degree. 30 refs., 5 figs., 1 tab

  20. Diffraction at collider energies

    International Nuclear Information System (INIS)

    Frankfurt, L.L.

    1992-01-01

    Lessons with ''soft'' hadron physics to explain (a) feasibility to observe and to investigate color transparency, color opacity effects at colliders; (b) significant probability and specific features of hard diffractive processes; (c) feasibility to investigate components of parton wave functions of hadrons with minimal number of constituents. This new physics would be more important with increase of collision energy

  1. Low Energy Electron Gun on Board a Scientific Satellite GEOTAIL

    OpenAIRE

    TSUTSUI, Minoru; ONISHI, Yoshiaki; MATSUMOTO, Hiroshi; KIMURA, Iwane; 筒井, 稔; 大西, 嘉昭; 松本, 紘; 木村, 磐根

    1988-01-01

    A low energy electron gun to be used for beam-plasma interaction experiments by a scientific satellite GEOTAIL has been designed and manufactured. Electrodes of the gun have been modified from the Pierce type gun because of the use of a directly heated cathode. Spatial density distributions of beam electrons emitted from the new gun have been measured in a large vacuum chamber, and characteristic curves of emission currents for some beam energies and cathode powers have been checked repeatedl...

  2. Axial channeling in electron diffraction

    International Nuclear Information System (INIS)

    Ichimiya, A.; Lehmpfuhl, G.

    1978-01-01

    Kossel patterns from Silicon and Niobium were obtained with a convergent electron beam. An intensity maximum in the direction of the zone axes [001] and [111] of Nb was interpreted as axial channeling. The intensity distribution in Kossel patterns was calculated by means of the Bloch wave picture of the dynamical theory of electron diffraction. Particularly zone axis patterns were calculated for different substance-energy combinations and they were compared with experimental observations. The intensity distribution in the calculated Kossel patterns was very sensitive to the model of absorption and it was found that a treatment of the absorption close to the model of Humphreys and Hirsch [Phil. Mag. 18, 115 (1968)] gave the best agreement with the experimental observations. Furthermore it is shown which Bloch waves are important for the intensity distribution in the Kossel patterns, how they are absorbed and how they change with energy. (orig.) [de

  3. Elastic scattering of low-energy electrons with Sr atoms

    International Nuclear Information System (INIS)

    Yuan, J.; Zhang, Z.; Wan, H.

    1990-01-01

    Static-exchange, plus correlation-polarization-potential calculations are performed for elastic low-energy electron scattering from Sr atoms while paying attention to the low-lying shape resonances. The correlation potential is calculated both with and without a scaling factor. A 2 D-shape resonance is produced at 1.0 eV with a parameter-free, and at 1.25 eV with a scaled, correlation potential. No 2 P-shape resonances are predicted, but evidence to support the existence of a stable negative ion Sr - in the 5s 2 5p electron configuration is given from the viewpoint of electron scattering. The bound energy of the extra electron in the negative ion is estimated by transforming the phase shift of the corresponding partial wave into the polarization quantum-defect number and extrapolating the number from positive to negative energies

  4. A semiclassical analysis of high energy electron diffraction by stacking faults: arrival at the classical limit

    International Nuclear Information System (INIS)

    Smith, A.E.; Chadderton, L.T.

    1978-01-01

    In a recent note the authors summarised results for an extension of Berry's theory to cover the one-dimensional problem of systematic reflections (planes) for a thin crystal sandwich consisting of two identical slabs of lattice parameter 'a' with a relative horizontal displacement 'f'. The diffraction amplitudes at the lower surface of the crystal were shown to depend on a double summation over the various transverse energy states in the upper and lower slab respectively, and on the transitions between them. In this report the authors demonstrate the arrival at the classical limit for the problem and, in particular, indicate briefly the nature of the topologically different classical paths. (Auth.)

  5. Low Energy Electrons in the Mars Plasma Environment

    Science.gov (United States)

    Link, Richard

    2001-01-01

    The ionosphere of Mars is rather poorly understood. The only direct measurements were performed by the Viking 1 and 2 landers in 1976, both of which carried a Retarding Potential Analyzer. The RPA was designed to measure ion properties during the descent, although electron fluxes were estimated from changes in the ion currents. Using these derived low-energy electron fluxes, Mantas and Hanson studied the photoelectron and the solar wind electron interactions with the atmosphere and ionosphere of Mars. Unanswered questions remain regarding the origin of the low-energy electron fluxes in the vicinity of the Mars plasma boundary. Crider, in an analysis of Mars Global Surveyor Magnetometer/Electron Reflectometer measurements, has attributed the formation of the magnetic pile-up boundary to electron impact ionization of exospheric neutral species by solar wind electrons. However, the role of photoelectrons escaping from the lower ionosphere was not determined. In the proposed work, we will examine the role of solar wind and ionospheric photoelectrons in producing ionization in the upper ionosphere of Mars. Low-energy (internal (photoelectron) sources of ionization, and accounts for Auger electron production. The code will be used to analyze Mars Global Surveyor measurements of solar wind and photoelectrons down to altitudes below 200 km in the Mars ionosphere, in order to determine the relative roles of solar wind and escaping photoelectrons in maintaining plasma densities in the region of the Mars plasma boundary.

  6. A Low-Temperature Electron Microscopy and Electron Diffraction Study of La1.84Sr0.16CuO4

    Science.gov (United States)

    Onozuka, Takashi; Omori, Mamoru; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-10-01

    A high-Tc superconducting compound, La1.84Sr0.16CuO4, has been investigated by electron microscopy and electron diffraction in the range from 10 K to ambient temperature. The tetragonal K2NiF4-type structure undergoes an orthorhombic distortion below about 130 K. In the low-temperature phase, extra diffraction spots and twin lamellae are observed reversibly on cooling and heating in situ. Based on the observed results, a plausible structure model with orthorhombic distortion is proposed.

  7. A low-temperature electron microscopy and electron diffraction study of La1.84Sr0.16CuO4

    International Nuclear Information System (INIS)

    Onozuka, Takashi; Omori, Mamoru; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-01-01

    A high-T c superconducting compound, La 1.84 Sr 0.16 CuO 4 , has been investigated by electron microscopy and electron diffraction in the range from 10 K to ambient temperature. The tetragonal K 2 NiF 4 -type structure undergoes an orthorhombic distortion below about 130 K. In the low-temperature phase, extra diffraction spots and twin lamellae are observed reversibly on cooling and heating in situ. Based on the observed results, a plausible structure model with orthorhombic distortion is proposed. (author)

  8. Low-temperature electron microscopy and electron diffraction study of La/sub 1. 84/Sr/sub 0. 16/CuO/sub 4/

    Energy Technology Data Exchange (ETDEWEB)

    Onozuka, Takashi; Omori, Mamoru; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-10-01

    A high-T/sub c/ superconducting compound, La/sub 1.84/Sr/sub 0.16/CuO/sub 4/, has been investigated by electron microscopy and electron diffraction in the range from 10 K to ambient temperature. The tetragonal K/sub 2/NiF/sub 4/-type structure undergoes an orthorhombic distortion below about 130 K. In the low-temperature phase, extra diffraction spots and twin lamellae are observed reversibly on cooling and heating in situ. Based on the observed results, a plausible structure model with orthorhombic distortion is proposed

  9. Charge-coupled device area detector for low energy electrons

    International Nuclear Information System (INIS)

    Horacek, Miroslav

    2003-01-01

    A fast position-sensitive detector was designed for the angle- and energy-selective detection of signal electrons in the scanning low energy electron microscope (SLEEM), based on a thinned back-side directly electron-bombarded charged-coupled device (CCD) sensor (EBCCD). The principle of the SLEEM operation and the motivation for the development of the detector are explained. The electronics of the detector is described as well as the methods used for the measurement of the electron-bombarded gain and of the dark signal. The EBCCD gain of 565 for electron energy 5 keV and dynamic range 59 dB for short integration time up to 10 ms at room temperature were obtained. The energy dependence of EBCCD gain and the detection efficiency are presented for electron energy between 2 and 5 keV, and the integration time dependence of the output signals under dark conditions is given for integration time from 1 to 500 ms

  10. Quantitative investigation of precipitate growth during ageing of Al-(Mg,Si) alloys by energy-filtered electron diffraction

    DEFF Research Database (Denmark)

    Wollgarten, M.; Chang, C. S. T.; Duchstein, Linus Daniel Leonhard

    2011-01-01

    Besides other application fields, light-weight Al-(Mg, Si) (6XXX series) alloys are of substantial importance in automotive industries where they are used for the production of car body panels. The material gains its strength by precipitation of metastable Mg-Si-based phases. Though the general...... accepted that the early stages of precipitate growth are important for the understanding of this peculiar behaviour. During these stages, electron diffraction patterns of Al-(Mg, Si) alloys show diffuse features (Figure 1 (a) and (b)) which can be traced back to originate from β'' Mg5Si6 precipitates [5......-7]. In this paper, we use energy-filtered electron diffraction to determine dimensions of the β'' Mg5Si6 precipitates along their a, b and c-axes as a function of ageing time and alloy composition. In our contribution, we first derive that there is an optimal zone axis - - from the view point of practicability. We...

  11. Elastic scattering of low energy electrons by hydrogen molecule

    International Nuclear Information System (INIS)

    Freitas, L.C.G.; Mu-Tao, L.; Botelho, L.F.

    1987-01-01

    The coherent version of the Renormalized Multiple-Centre Potential Model (RMPM) has been extended to treat the elastic scattering of low energy electrons by H2 molecule. The intramolecular Multiple Scattering (MS) effect has also been included. The comparison against the experimental data shows that the inclusion of the MS improves significantly with experiment. The extension of the present method to study electron-polyatomic molecule interaction is also discussed. (author) [pt

  12. Reactions induced by low energy electrons in cryogenic films

    International Nuclear Information System (INIS)

    Bass, A.D.; Sanche, L.

    2003-01-01

    We review recent research on reactions (including dissociation) initiated by low-energy electron bombardment of monolayer and multilayer molecular solids at cryogenic temperatures. With incident electrons of energies below 20 eV, dissociation is observed by the electron stimulated desorption (ESD) of anions from target films and is attributed to the processes of dissociative electron attachment (DEA) and to dipolar dissociation. It is shown that DEA to condensed molecules is sensitive to environmental factors such as the identity of co-adsorbed species and film morphology. The effects of image-charge induced polarization on cross-sections for DEA to CH3Cl are also discussed. Taking as examples, the electron-induced production of CO within multilayer films of methanol and acetone, it is shown that the detection of electronic excited states by high resolution electron energy loss spectroscopy can be used to monitor electron beam damage. In particular, the incident energy dependence of the CO indicates that below 19 eV, dissociation proceeds via the decay of transient negative ions (TNI) into electronically excited dissociative states. The electron induced dissociation of biomolecular targets is also considered, taking as examples the ribose analog tetrahydrofuran and DNA bases adenine and thymine, cytosine and guanine. The ESD of anions from such films also show dissociation via the formation of TNI. In multilayer molecular solids, fragment species resulting from dissociation, may react with neighboring molecules, as is demonstrated in anion ESD measurements from films containing O 2 and various hydrocarbon molecules. X-ray photoelectron spectroscopy measurements reported for electron irradiated monolayers of H 2 O and CF 4 on a Si - H passivated surface further show that DEA is an important initial step in the electron-induced chemisorption of fragment species

  13. Electron microscopy and diffraction

    International Nuclear Information System (INIS)

    Gjoennes, J.; Olsen, A.

    1986-01-01

    This report is a description of research activities and plans at the electron microscopy laboratorium, Physics Department, University of Oslo. Since the first electron microscope was installed in 1968, the research has covered inorganic structures, physical metallurgy, as well as theory of electron scattering and the development of methods in this field. The current plans involve efforts in the development of crystallographic and spectroscopic methods

  14. Development of real-time low energy electron calorimeter

    International Nuclear Information System (INIS)

    Noriah Mod Ali; Smith, F.A.

    1999-01-01

    A low energy electron beam calorimeter with a thin film window has been fabricated to facilitate a reliable method of dose assessment for electron beam energies down to 200 keV. The system was designed to incorporate a data-logger in order that it could be used on the self-shielded 200 keV facility at MINT. In use, the calorimeter started logging temperature a short time before it passed under the beam and it continued taking data until well after the end of the irradiation. Data could be retrieved at any time after the calorimeter had emerged from the irradiator

  15. Treatment of surfaces with low-energy electrons

    Czech Academy of Sciences Publication Activity Database

    Frank, Luděk; Mikmeková, Eliška; Lejeune, M.

    2017-01-01

    Roč. 407, JUN 15 (2017), s. 105-108 ISSN 0169-4332 R&D Projects: GA TA ČR(CZ) TE01020118; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : Low- energy electrons * Electron beam induced release * Graphene * Ultimate cleaning of surfaces Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Nano-processes (applications on nano-scale) Impact factor: 3.387, year: 2016

  16. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    Science.gov (United States)

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Monitoring non-pseudomorphic epitaxial growth of spinel/perovskite oxide heterostructures by reflection high-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Schütz, P.; Pfaff, F.; Scheiderer, P.; Sing, M.; Claessen, R. [Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, Am Hubland, D-97074 Würzburg (Germany)

    2015-02-09

    Pulsed laser deposition of spinel γ-Al{sub 2}O{sub 3} thin films on bulk perovskite SrTiO{sub 3} is monitored by high-pressure reflection high-energy electron diffraction (RHEED). The heteroepitaxial combination of two materials with different crystal structures is found to be inherently accompanied by a strong intensity modulation of bulk diffraction patterns from inelastically scattered electrons, which impedes the observation of RHEED intensity oscillations. Avoiding such electron surface-wave resonance enhancement by de-tuning the RHEED geometry allows for the separate observation of the surface-diffracted specular RHEED signal and thus the real-time monitoring of sub-unit cell two-dimensional layer-by-layer growth. Since these challenges are essentially rooted in the difference between film and substrate crystal structure, our findings are of relevance for the growth of any heterostructure combining oxides with different crystal symmetry and may thus facilitate the search for novel oxide heterointerfaces.

  18. Diagnosis and dynamics of low energy electron beams using DIADYN

    International Nuclear Information System (INIS)

    Marghitu, S.; Oproiu, C.; Toader, D.; Ruset, C.; Grigore, E.; Marghitu, O.; Vasiliu, M.

    2008-01-01

    The paper presents original results concerning electron beam diagnosis and dynamics using DIADYN, a low energy (10 - 50 kV), medium intensity (0.1 - 1 A) laboratory equipment. A key stage in the operation of DIADYN is the beam diagnosis, performed by the non-destructive, modified three-gradient method (MTGM). We concentrate on the better use of experimental and computational techniques, in order to improve the consistency of the results. At present, DIADYN is equipped with a hot filament vacuum electron source (VES), consisting of a convergent Pierce diode, working in a pulse mode. Since the plasma electron sources (PES) have a longer lifetime and produce higher beam currents, we discuss the possibility to replace the VES with a PES. Special attention is given to VES results in a functioning regime typical for a low energy glow discharge PES. (authors)

  19. Diagnosis and dynamics of low energy electron beams using DIADYN

    Energy Technology Data Exchange (ETDEWEB)

    Marghitu, S [Electrostatica, ICPE-CA S.A., Spaiul Unirii 313, Sector 3, RO-74204 Bucharest (Romania); Oproiu, C; Toader, D; Ruset, C; Grigore, E [National Institute for Laser, Plasma and Radiation Physics, PO Box MG-36, 409 Atomistilor Street, RO-76900 Bucharest-Magurele (Romania); Marghitu, O [Institute for Space Sciences, INCDLPFR, PO Box MG-23, RO-76911 Bucharest-Magurele (Romania); Vasiliu, M [Politehnica University, 313 Splaiul Independentei, RO-060032, Bucharest (Romania)

    2008-07-01

    The paper presents original results concerning electron beam diagnosis and dynamics using DIADYN, a low energy (10 - 50 kV), medium intensity (0.1 - 1 A) laboratory equipment. A key stage in the operation of DIADYN is the beam diagnosis, performed by the non-destructive, modified three-gradient method (MTGM). We concentrate on the better use of experimental and computational techniques, in order to improve the consistency of the results. At present, DIADYN is equipped with a hot filament vacuum electron source (VES), consisting of a convergent Pierce diode, working in a pulse mode. Since the plasma electron sources (PES) have a longer lifetime and produce higher beam currents, we discuss the possibility to replace the VES with a PES. Special attention is given to VES results in a functioning regime typical for a low energy glow discharge PES. (authors)

  20. Radiation degradation of marine polysaccharides by low energy electron beam

    International Nuclear Information System (INIS)

    Yoshii, Fumio; Nagasawa, Naotsugu; Kume, Tamikazu

    2003-01-01

    The radiation degradations of marine polysaccharides by both gamma Co-60 and electron beam irradiations are investigated. Polysaccharides and oligosaccharides can be produced by degradation of corresponding polysaccharides including marine polysaccharides such as alginates, chitin chitosan and carrageenan. The viscosity of alginate, chitosan and carrageenan solution decreases markedly with increase of the low energy electron beam irradiation time and the beam current. Furthermore, the viscosity is reduced sharply in short time for polysaccharide solution with low concentration, for instance carrageenan solution of 1%. (author)

  1. Monitoring the growth of SrTiO{sub 3} and La{sub 0.66}Sr{sub 0.33}MnO{sub 3} thin films using a low-pressure Reflection High Energy Electron Diffraction system

    Energy Technology Data Exchange (ETDEWEB)

    Mercey, Bernard; David, Adrian; Copie, Olivier; Prellier, Wilfrid, E-mail: wilfrid.prellier@ensicaen.fr

    2016-12-15

    Oxides display a variety of electronic phenomena, including ferroelectricity, magnetism or multiferroicity. Recently, a large interest has raised from the interfaces between two oxides of few unit cells, which show unexpected electronic properties such as superconductivity or magnetism. Thus, the structural quality of interfaces as well as a precise control of the thickness are main challenges for researchers who grow oxide films. To achieve such a high quality interface and a careful control of the growth, Reflection High Energy Electron Diffraction in-situ monitoring, is often used and mounted in a pulsed laser ablation system. While high pressure is widely utilized, low pressure is rarely utilized for oxides except when coupled to a molecular beam epitaxy (MBE) chamber. Here, the preparation of high-quality oxide thin films is reported and the different factors which affect the reliability of such an approach are presented, i.e. the correlation between the observed intensity oscillations and the deposited thickness. It is shown that oxides thin films grown on SrTiO{sub 3} single crystals, in a low-pressure environment with the laser-MBE system, possess extremely high physical characteristics (magnetoresistance, ferroelectricity, ferromagnetism, metal/insulating transition) very close to the bulk values and that the interface is nearly perfect, of the same quality as found for semiconductors.

  2. Low energy electron beam processing of YBCO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chromik, Š., E-mail: stefan.chromik@savba.sk [Institute of Electrical Engineering, SAS, Dúbravská cesta 9, 841 04 Bratislava (Slovakia); Camerlingo, C. [CNR-SPIN, Istituto Superconduttori, Materiali Innovativi e Dispositivi, via Campi Flegrei 34, 80078 Pozzuoli (Italy); Sojková, M.; Štrbík, V.; Talacko, M. [Institute of Electrical Engineering, SAS, Dúbravská cesta 9, 841 04 Bratislava (Slovakia); Malka, I.; Bar, I.; Bareli, G. [Department of Physics, Ben Gurion University of the Negev, P.O.B. 653, 84105 Beer Sheva (Israel); Jung, G. [Department of Physics, Ben Gurion University of the Negev, P.O.B. 653, 84105 Beer Sheva (Israel); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)

    2017-02-15

    Highlights: • Improvement of superconducting properties of irradiated bridges under certain conditions. • 30 keV irradiation influence CuO{sub 2} planes as well as oxygen chains. • Direct confirmation of changes in oxygen chains using micro-Raman spectroscopy. • Possibility of electron writing. - Abstract: Effects of low energy 30 keV electron irradiation of superconducting YBa{sub 2}Cu{sub 3}O{sub 7−δ} thin films have been investigated by means of transport and micro-Raman spectroscopy measurements. The critical temperature and the critical current of 200 nm thick films initially increase with increasing fluency of the electron irradiation, reach the maximum at fluency 3 − 4 × 10{sup 20} electrons/cm{sup 2}, and then decrease with further fluency increase. In much thinner films (75 nm), the critical temperature increases while the critical current decreases after low energy electron irradiation with fluencies below 10{sup 20} electrons/cm{sup 2}. The Raman investigations suggest that critical temperature increase in irradiated films is due to healing of broken Cu−O chains that results in increased carrier’s concentration in superconducting CuO{sub 2} planes. Changes in the critical current are controlled by changes in the density of oxygen vacancies acting as effective pinning centers for flux vortices. The effects of low energy electron irradiation of YBCO turned out to result from a subtle balance of many processes involving oxygen removal, both by thermal activation and kick-off processes, and ordering of chains environment by incident electrons.

  3. Detectors for low energy electron cooling in RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Carlier, F. S. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-02-15

    Low-energy operation of RHIC is of particular interest to study the location of a possible critical point in the QCD phase diagram. The performance of RHIC at energies equal to or lower than 10 GV/nucleon is limited by nonlinearities, Intra-BeamScattering (IBS) processes and space-charge effects. To successfully address the luminosity and ion store lifetime limitations imposed by IBS, the method of electron cooling has been envisaged. During electron cooling processes electrons are injected along with the ion beam at the nominal ion bunch velocities. The velocity spread of the ion beam is reduced in all planes through Coulomb interactions between the cold electron beam and the ion beam. The electron cooling system proposed for RHIC will be the first of its kind to use bunched beams for the delivery of the electron bunches, and will therefore be accompanied by the necessary challenges. The designed electron cooler will be located in IP2. The electron bunches will be accelerated by a linac before being injected along side the ion beams. Thirty consecutive electron bunches will be injected to overlap with a single ion bunch. They will first cool the yellow beam before being extracted, turned by 180-degrees, and reinjected into the blue beam for cooling. As such, both the yellow and blue beams will be cooled by the same ion bunches. This will pose considerable challenges to ensure proper electron beam quality to cool the second ion beam. Furthermore, no ondulator will be used in the electron cooler so radiative recombination between the ions and the electrons will occur.

  4. A real-time low energy electron calorimeter

    International Nuclear Information System (INIS)

    Mod Ali, N.; Smith, F.A.

    1999-01-01

    A real-time low energy electron calorimeter with a thin film window has been designed and fabricated to facilitate a reliable method of dose assessment for electron beam energies down to 200 keV. The work was initiated by the Radiation Physics Group of Queen Mary and Westfield College in collaboration with the National Physical Laboratory (NPL), Teddington. Irradiations were performed on the low and medium electron energy electron accelerators at the Malaysian Institute for Nuclear Technology Research (MINT). Calorimeter response was initially tested using the on-line temperature measurements for a 500-keV electron beam. The system was later redesigned by incorporating a data-logger to use on the self-shielded 200-keV beam. In use, the final version of the calorimeter could start logging temperature a short time before the calorimeter passed under the beam and continue measurements throughout the irradiation. Data could be easily retrieved at the end of the exposure. (author)

  5. Low-Energy Electron Scattering by Sugarcane Lignocellulosic Biomass Molecules

    Science.gov (United States)

    Oliveira, Eliane; Sanchez, Sergio; Bettega, Marcio; Lima, Marco; Varella, Marcio

    2012-06-01

    The use of second generation (SG) bioethanol instead of fossil fuels could be a good strategy to reduce greenhouse gas emissions. However, the efficient production of SG bioethanol has being a challenge to researchers around the world. The main barrier one must overcome is the pretreatment, a very important step in SG bioethanol aimed at breaking down the biomass and facilitates the extraction of sugars from the biomass. Plasma-based treatment, which can generate reactive species, could be an interesting possibility since involves low-cost atmospheric-pressure plasma. In order to offer theoretical support to this technique, the interaction of low-energy electrons from the plasma with biomass is investigated. This study was motived by several works developed by Sanche et al., in which they understood that DNA damage arises from dissociative electron attachment, a mechanism in which electrons are resonantly trapped by DNA subunits. We will present elastic cross sections for low-energy electron scattering by sugarcane biomass molecules, obtained with the Schwinger multichannel method. Our calculations indicate the formation of π* shape resonances in the lignin subunits, while a series of broad and overlapping σ* resonances are found in cellulose and hemicellulose subunits. The presence of π* and σ* resonances could give rise to direct and indirect dissociation pathways in biomass. Then, theoretical resonance energies can be useful to guide the plasma-based pretreatment to break down specific linkages of interest in biomass.

  6. Growth and intercalation of graphene on silicon carbide studied by low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Speck, Florian; Ostler, Markus; Wanke, Martina; Seyller, Thomas [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Technische Physik, Erlangen (Germany); Technische Universitaet Chemnitz, Institut fuer Physik (Germany); Besendoerfer, Sven [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Technische Physik, Erlangen (Germany); Krone, Julia [Technische Universitaet Chemnitz, Institut fuer Physik (Germany)

    2017-11-15

    Based on its electronic, structural, chemical, and mechanical properties, many potential applications have been proposed for graphene. In order to realize these visions, graphene has to be synthesized, grown, or exfoliated with properties that are determined by the targeted application. Growth of so-called epitaxial graphene on silicon carbide by sublimation of silicon in an argon atmosphere is one particular method that could potentially lead to electronic applications. In this contribution we summarize our recent work on different aspects of epitaxial graphene growth and interface manipulation by intercalation, which was performed by a combination of low-energy electron microscopy, low-energy electron diffraction, atomic force microscopy and photoelectron spectroscopy. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Dose controlled low energy electron irradiator for biomolecular films.

    Science.gov (United States)

    Kumar, S V K; Tare, Satej T; Upalekar, Yogesh V; Tsering, Thupten

    2016-03-01

    We have developed a multi target, Low Energy Electron (LEE), precise dose controlled irradiator for biomolecular films. Up to seven samples can be irradiated one after another at any preset electron energy and dose under UHV conditions without venting the chamber. In addition, one more sample goes through all the steps except irradiation, which can be used as control for comparison with the irradiated samples. All the samples are protected against stray electron irradiation by biasing them at -20 V during the entire period, except during irradiation. Ethernet based communication electronics hardware, LEE beam control electronics and computer interface were developed in house. The user Graphical User Interface to control the irradiation and dose measurement was developed using National Instruments Lab Windows CVI. The working and reliability of the dose controlled irradiator has been fully tested over the electron energy range of 0.5 to 500 eV by studying LEE induced single strand breaks to ΦX174 RF1 dsDNA.

  8. Dose controlled low energy electron irradiator for biomolecular films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. V. K., E-mail: svkk@tifr.res.in; Tare, Satej T.; Upalekar, Yogesh V.; Tsering, Thupten [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India)

    2016-03-15

    We have developed a multi target, Low Energy Electron (LEE), precise dose controlled irradiator for biomolecular films. Up to seven samples can be irradiated one after another at any preset electron energy and dose under UHV conditions without venting the chamber. In addition, one more sample goes through all the steps except irradiation, which can be used as control for comparison with the irradiated samples. All the samples are protected against stray electron irradiation by biasing them at −20 V during the entire period, except during irradiation. Ethernet based communication electronics hardware, LEE beam control electronics and computer interface were developed in house. The user Graphical User Interface to control the irradiation and dose measurement was developed using National Instruments Lab Windows CVI. The working and reliability of the dose controlled irradiator has been fully tested over the electron energy range of 0.5 to 500 eV by studying LEE induced single strand breaks to ΦX174 RF1 dsDNA.

  9. Studies on functional polymer films utilizing low energy electron beam

    International Nuclear Information System (INIS)

    Ando, Masayuki

    1992-01-01

    Also in adhesives and tackifiers, with the expansion of the fields of application, the required characteristics have become high grade and complex. As one of them, the instantaneous hardening of adhesives can be taken up. In the field of lamination works, the low energy type electron beam accelerators having the linear filament of accelerating voltage below 300 kV were developed in 1970s, and the interest in the development of electron beam-handened adhesives has heightend. The authors have carried out research aiming at heightening the functions of the polymer films obtained by electron beam hardening reaction, and developed the adhesives. In this report, the features of electron beam hardening reaction, the structure and properties of electron beam-hardened polymer films and the molecular design of electron beam-hardened monomer oligomers are described. The feature of electron beam hardening reaction is the cross-linking of high degree as the structure of oligomers is maintained. By controlling the structure at the time of electron beam hardening, the heightening of the functions of electron beam-hardened polymer films is feasible. (K.I.)

  10. Vibrational excitation of D2 by low energy electrons

    International Nuclear Information System (INIS)

    Buckman, S.J.; Phelps, A.V.

    1985-01-01

    Excitation coefficients for the production of vibrationally exicted D 2 by low energy electrons have been determined from measurements of the intensity of infrared emission from mixtures of D 2 and small concentrations of CO 2 or CO. The measurements were made using the electron drift tube technique and covered electric field to gas density ratios (E/n) from (5 to 80) x 10 -21 V m 2 , corresponding to mean electron energies between 0.45 and 4.5 eV. The CO 2 and CO concentrations were chosen to allow efficient excitation transfer from the D 2 to the carbon containing molecule, but to minimize direct excitation of the CO 2 or CO. The measured infrared intensities were normalized to predicted values for N 2 --CO 2 and N 2 --CO mixtures at E/n where the efficiency of vibrational excitation is known to be very close to 100%. The experimental excitation coefficients are in satisfactory agreement with predictions based on electron--D 2 cross sections at mean electron energies below 1 eV, but are about 50% too high at mean energies above about 2 eV. Application of the technique to H 2 did not yield useful vibrational excitation coefficients. The effective coefficients in H 2 --CO 2 mixtures were a factor of about 3 times the predicted values. For our H 2 --CO mixtures the excitation of CO via excitation transfer from H 2 is small compared to direct electron excitation of CO molecules. Published experiments and theories on electron--H 2 and electron--D 2 collisions are reviewed to obtain the cross sections used in the predictions

  11. Wettability Modification of Nanomaterials by Low-Energy Electron Flux

    Directory of Open Access Journals (Sweden)

    Torchinsky I

    2009-01-01

    Full Text Available Abstract Controllable modification of surface free energy and related properties (wettability, hygroscopicity, agglomeration, etc. of powders allows both understanding of fine physical mechanism acting on nanoparticle surfaces and improvement of their key characteristics in a number of nanotechnology applications. In this work, we report on the method we developed for electron-induced surface energy and modification of basic, related properties of powders of quite different physical origins such as diamond and ZnO. The applied technique has afforded gradual tuning of the surface free energy, resulting in a wide range of wettability modulation. In ZnO nanomaterial, the wettability has been strongly modified, while for the diamond particles identical electron treatment leads to a weak variation of the same property. Detailed investigation into electron-modified wettability properties has been performed by the use of capillary rise method using a few probing liquids. Basic thermodynamic approaches have been applied to calculations of components of solid–liquid interaction energy. We show that defect-free, low-energy electron treatment technique strongly varies elementary interface interactions and may be used for the development of new technology in the field of nanomaterials.

  12. Challenges in validating radiation sterilization with low energy electron irradiation

    International Nuclear Information System (INIS)

    Miller, A.; Helt-Hansen, J.

    2011-01-01

    Complete text of publication follows. Low energy electron irradiation (80-300 keV) is used increasingly for sterilization or decontamination in connection with isolators for aseptic filling lines in the pharmaceutical industry. It is not defined how validation for this process shall be carried out. A method can be derived from the medical device standard for radiation sterilization, ISO 11137, because the principles described in this standard can be applied to almost any industrial irradiation process. The validations elements are: Process definition, concerning specification of the dose required for the process and the maximum acceptable dose for the product. Installation qualification, concerning acceptance the irradiation facility. Operational qualification, concerning characterization of the facility. Performance qualification, concerning setting up the process. Process control, concerning routine monitoring. The limited penetration of the low energy electrons leads to problems with respect to executing these validation steps. This paper discusses these problems, and shows with examples how they can be solved.

  13. High-energy particle diffraction

    International Nuclear Information System (INIS)

    Barone, V.; Predazzi, E.

    2002-01-01

    This monograph gives a comprehensive and up-to-date overview of soft and hard diffraction processes in strong interaction physics. The first part covers the general formalism (the optical analogy, the eikonal picture, high-energy kinematics, S-matrix theory) and soft hadron-hadron scattering (including the Regge theory) in a complete and mature presentation. It can be used as a textbook in particle physics classes. The remainder of the book is devoted to the 'new diffraction': the pomeron in QCD, low-x physics, diffractive deep inelastic scattering and related processes, jet production etc. It presents recent results and experimental findings and their phenomenological interpretations. This part addresses graduate students as well as researchers. (orig.)

  14. Radiation from silver films bombarded by low-energy electrons

    International Nuclear Information System (INIS)

    Chung, M.S.; Callcott, T.A.; Kretschmann, E.; Arakawa, E.T.

    1980-01-01

    Emission spectra from Ag films irradiated by low energy electrons (20-1500 eV) have been measured, and the results compared with theory. For relatively smooth films, two peaks in the spectra are resolved. One at 3.73 eV, the volume plasmon energy, is attributed to transition radiation and/or bremsstrahlung. The second, at about 3.60 eV, is very sensitive to surface roughness in both position and magnitude and is produced by roughness-coupled radiation from surface plasmons. For rough films, the roughness-coupled radiation dominates the emission. In addition to spectral shapes, the polarization of the radiation and its intensity as a function of electron energy were measured. The experimental results are compared with new calculations of roughness-coupled emission which account for most of our observations. They indicate that high wavevector roughness components play the dominant role in the emission process. (orig.)

  15. Low-energy electron scattering from molecules, biomolecules and surfaces

    CERN Document Server

    Carsky, Petr

    2011-01-01

    Since the turn of the 21st century, the field of electron molecule collisions has undergone a renaissance. The importance of such collisions in applications from radiation chemistry to astrochemistry has flowered, and their role in industrial processes such as plasma technology and lighting are vital to the advancement of next generation devices. Furthermore, the development of the scanning tunneling microscope highlights the role of such collisions in the condensed phase, in surface processing, and in the development of nanotechnology.Low-Energy Electron Scattering from Molecules, Biomolecule

  16. Low energy electron beams for industrial and environmental applications

    CERN Document Server

    Skarda, Vlad

    2017-01-01

    EuCARD-2 Workshop, 8-9 December 2016, Warsaw, Poland. Organizers: Science and Technology Facilities Council, UK CERN - The European Organization for Nuclear Research, Switzerland, Institute of Nuclear Chemistry and Technology, Poland, Fraunhofer Institute for Electron Beam and Plasma Technology, Germany, Warsaw University of Technology, Poland. An article presents short information about EuCARD-2 Workshop “Low energy electron beams for industrial and environmental applications”, which was held in December 2016 in Warsaw. Objectives, main topics and expected output of meeting are described. List of organizers is included.

  17. Practical Use of Scanning Low Energy Electron Microscope (SLEEM)

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Mikmeková, Eliška; Mikmeková, Šárka; Konvalina, Ivo; Frank, Luděk

    2016-01-01

    Roč. 22, S3 (2016), s. 1650-1651 ISSN 1431-9276 R&D Projects: GA TA ČR(CZ) TE01020118; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : scanning low energy * SLEEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.891, year: 2016

  18. Application of low energy electron beam to precoated steel plates

    International Nuclear Information System (INIS)

    Koshiishi, Kenji

    1989-01-01

    Recently in the fields of home electric appliances, machinery and equipment and interior building materials, the needs for the precoated steel plates having the design and function of high class increase rapidly. In order to cope with such needs, the authors have advanced the examination on the application of electron beam hardening technology to precoated steel plates, and developed the precoated steel plates of high grade and high design 'Super Tecstar EB Series' by utilizing low energy electron beam. The features of this process are (1) hardening can be done at room temperature in a short time-thermally weak films can be adhered, (2) high energy irradiation-the hardening of thick enamel coating and the adhesion of colored films are feasible, (3) the use of monomers of low molecular weight-by high crosslinking, the performance of high sharpness, high hardness, anti-contamination property and so on can be given. The application to precoated steel plate production process is the coating and curing of electron beam hardening type paints, the coating of films with electron beam hardening type adhesives, and the reforming of surface polymer layers by impregnating monomers and causing graft polymerization with electron beam irradiation. The outline of the Super Tecstar EB Series is described. (K.I.)

  19. Uniting Electron Crystallography and Powder Diffraction

    CERN Document Server

    Shankland, Kenneth; Meshi, Louisa; Avilov, Anatoly; David, William

    2012-01-01

    The polycrystalline and nanocrystalline states play an increasingly important role in exploiting the properties of materials, encompassing applications as diverse as pharmaceuticals, catalysts, solar cells and energy storage. A knowledge of the three-dimensional atomic and molecular structure of materials is essential for understanding and controlling their properties, yet traditional single-crystal X-ray diffraction methods lose their power when only polycrystalline and nanocrystalline samples are available. It is here that powder diffraction and single-crystal electron diffraction techniques take over, substantially extending the range of applicability of the crystallographic principles of structure determination.  This volume, a collection of teaching contributions presented at the Crystallographic Course in Erice in 2011, clearly describes the fundamentals and the state-of-the-art of powder diffraction and electron diffraction methods in materials characterisation, encompassing a diverse range of discipl...

  20. Radiation processing of natural polymers using low energy electron beam

    International Nuclear Information System (INIS)

    Kume, Tamikazu

    2004-01-01

    Radiation processing is widely used in Japan and the economic scale of radiation application amounted to about 71 b$ (ratio relative to GDP: 1.7%) in total. It consisted of 60 b$ (85%) in industry, 10 b$ (14%) in medicine and 1 b$ (1%) in agriculture. Irradiation using gamma-ray from 60 Co and electron beam is commercially used for the sterilization and modification of materials. Utilization of natural polymers by radiation has been investigated for recycling the natural resources and reducing the environmental pollution. Polysaccharides such as chitosan, sodium alginate, carrageenan, cellulose, pectin were easily degraded by irradiation and induced various kinds of biological activities, i.e. anti-bacterial activity, elicitor activity, plant growth promotion, suppression of environmental stress on plants. Radiation degraded chitosan was effective to enhance the growth of plants in tissue culture. Low energy electron beam (EB) irradiation has a variety of applications and good safety. A self-shielded low energy electron accelerator system needs an initial investment much lower than a 60 Co facility. It was demonstrated that the liquid sample irradiation system using low energy EB was effective not only for the preparation of degraded polysaccharides but also for radiation vulcanization of natural rubber latex (RVNRL). Some carbohydrate derivatives, carboxymethylcellulose (CMC), carboxymethyl-starch and carboxymethyl-chitin/chitosan, can be crosslinked under certain radiation condition and produced the biodegradable hydrogel for medical and agricultural use. Treatment of soybean seeds by low energy EB enhanced the growth and the number of rhizobia on the root. (author)

  1. Secondary electron emission yield in the limit of low electron energy

    CERN Document Server

    Andronov, A.N.; Kaganovich, I.D.; Startsev, E.A.; Raitses, Y.; Demidov, V.I.

    2013-04-22

    Secondary electron emission (SEE) from solids plays an important role in many areas of science and technology.1 In recent years, there has been renewed interest in the experimental and theoretical studies of SEE. A recent study proposed that the reflectivity of very low energy electrons from solid surface approaches unity in the limit of zero electron energy2,3,4, If this was indeed the case, this effect would have profound implications on the formation of electron clouds in particle accelerators,2-4 plasma measurements with electrostatic Langmuir probes, and operation of Hall plasma thrusters for spacecraft propulsion5,6. It appears that, the proposed high electron reflectivity at low electron energies contradicts to numerous previous experimental studies of the secondary electron emission7. The goal of this note is to discuss possible causes of these contradictions.

  2. Silicon passivation study under low energy electron irradiation conditions

    International Nuclear Information System (INIS)

    Cluzel, R.

    2010-01-01

    Backside illuminated thinned CMOS (Complementary Metal Oxide Semiconductor) imaging system is a technology developed to increase the signal to noise ratio and the sensibility of such sensors. This configuration is adapted to the electrons detection from the energy range of [1 - 12 keV]. The impinging electron creates by multiplication several hundreds of secondary electrons close to the surface. A P ++ highly-doped passivation layer of the rear face is required to reduce the secondary electron surface recombination rate. Thanks to the potential barrier induced by the P ++ layer, the passivation layer increases the collected charges number and so the sensor collection gain. The goal of this study is to develop some experimental methods in order to determine the effect of six different passivation processes on the collection gain. Beforehand, the energy profile deposited by an incident electron is studied with the combination of Monte-Carlo simulations and some analytical calculations. The final collection gain model shows that the mirror effect from the passivation layer is a key factor at high energies whereas the passivation layer has to be as thin as possible at low energies. A first experimental setup which consists in irradiating P ++ /N large diodes allows to study the passivation process impacts on the surface recombinations. Thanks to a second setup based on a single event upset directly on thinned CMOS sensor, passivation techniques are discriminated in term of mirror effect and the implied spreading charges. The doping atoms activation laser annealing is turn out to be a multiplication gain inhomogeneity source impacting directly the matrix uniformity. (author)

  3. Radiation processing of liquid with low energy electron accelerator

    International Nuclear Information System (INIS)

    Makuuchi, Keizo

    2003-01-01

    Radiation induced emulsion polymerization, radiation vulcanization of NR latex (RVNRL) and radiation degradation of natural polymers were selected and reviewed as the radiation processing of liquid. The characteristic of high dose rate emulsion polymerization is the occurrence of cationic polymerization. Thus, it can be used for the production of new materials that cannot be obtained by radical polymerization. A potential application will be production of polymer emulsion that can be used as water-borne UV/EB curing resins. The technology of RVNRL by γ-ray has been commercialized. RVNRL with low energy electron accelerator is under development for further vulcanization cost reduction. Vessel type irradiator will be favorable for industrial application. Radiation degradation of polysaccharides is an emerging and promising area of radiation processing. However, strict cost comparison between liquid irradiation with low energy EB and state irradiation with γ-ray should be carried out. (author)

  4. Radiation processing of liquid with low energy electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Makuuchi, Keizo [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    2003-02-01

    Radiation induced emulsion polymerization, radiation vulcanization of NR latex (RVNRL) and radiation degradation of natural polymers were selected and reviewed as the radiation processing of liquid. The characteristic of high dose rate emulsion polymerization is the occurrence of cationic polymerization. Thus, it can be used for the production of new materials that cannot be obtained by radical polymerization. A potential application will be production of polymer emulsion that can be used as water-borne UV/EB curing resins. The technology of RVNRL by {gamma}-ray has been commercialized. RVNRL with low energy electron accelerator is under development for further vulcanization cost reduction. Vessel type irradiator will be favorable for industrial application. Radiation degradation of polysaccharides is an emerging and promising area of radiation processing. However, strict cost comparison between liquid irradiation with low energy EB and state irradiation with {gamma}-ray should be carried out. (author)

  5. Generation of Low-Energy High-Current Electron Beams in Plasma-Anode Electron Guns

    Science.gov (United States)

    Ozur, G. E.; Proskurovsky, D. I.

    2018-01-01

    This paper is a review of studies on the generation of low-energy high-current electron beams in electron guns with a plasma anode and an explosive-emission cathode. The problems related to the initiation of explosive electron emission under plasma and the formation and transport of high-current electron beams in plasma-filled systems are discussed consecutively. Considerable attention is given to the nonstationary effects that occur in the space charge layers of plasma. Emphasis is also placed on the problem of providing a uniform energy density distribution over the beam cross section, which is of critical importance in using electron beams of this type for surface treatment of materials. Examples of facilities based on low-energy high-current electron beam sources are presented and their applications in materials science and practice are discussed.

  6. Study and realization of an electron gun at low energy

    International Nuclear Information System (INIS)

    Camus, P.

    1977-01-01

    This work presents the theoretical concepts and experimental design of an electron gun. This gun is working in the weak energy range and the focus position is independant of electron energy measurements and analysis methods of the electron beam are described [fr

  7. Piezoelectric energy harvesting for powering low power electronics

    Energy Technology Data Exchange (ETDEWEB)

    Leinonen, M.; Palosaari, J.; Hannu, J.; Juuti, J.; Jantunen, H. (Univ. of Oulu, Dept. of Electrical and Information Engineering (Finland)). email: jajuu@ee.oulu.fi

    2009-07-01

    Although wireless data transmission techniques are commonly used in electronic devices, they still suffer from wires for the power supply or from batteries which require charging, replacement and other maintenance. The vision for the portable electronics and industrial measurement systems of the future is that they are intelligent and independent on their energy supply. The major obstacle in this path is the energy source which enables all other functions and 'smartness' of the systems as the computing power is also restricted by the available energy. The development of long-life energy harvesters would reduce the need for batteries and wires thus enabling cost-effective and environment friendlier solutions for various applications such as autonomous wireless sensor networks, powering of portable electronics and other maintenance-free systems. One of the most promising techniques is mechanical energy harvesting e.g. by piezoelectric components where deformations produced by different means is directly converted to electrical charge via direct piezoelectric effect. Subsequently the electrical energy can be regulated or stored for further use. The total mechanical energy in vibration of machines can be very large and usually only a fraction of it can be transformed to electrical energy. Recently, piezoelectric vibration based energy harvesters have been developed widely for different energy consumption and application areas. As an example for low energy device an piezoelectric energy harvester based on impulse type excitations has been developed for active RFID identification. Moreover, piezoharvester with externally leveraged mechanism for force amplification was reported to be able to generate mean power of 0.4 mW from backpack movement. Significantly higher power levels are expected from larger scale testing in Israel, where piezoelectric material is embedded under active walking street, road, airport or railroad. The energy is harvested from human or

  8. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Musumeci, P. [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA 90095-1547 (United States)], E-mail: musumeci@physics.ucla.edu; Moody, J.T.; Scoby, C.M. [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA 90095-1547 (United States)

    2008-10-15

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10{sup 7}-10{sup 8} electrons packed in bunches of {approx}100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics.

  9. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory

    International Nuclear Information System (INIS)

    Musumeci, P.; Moody, J.T.; Scoby, C.M.

    2008-01-01

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10 7 -10 8 electrons packed in bunches of ∼100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics

  10. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory.

    Science.gov (United States)

    Musumeci, P; Moody, J T; Scoby, C M

    2008-10-01

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10(7)-10(8) electrons packed in bunches of approximately 100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics.

  11. Low energy electron-driven damage in biomolecules

    International Nuclear Information System (INIS)

    Sanche, L.

    2005-01-01

    The damage induced by the impact of low energy electrons (LEE) on biomolecules is reviewed from a radiobiological perspective with emphasis on transient anion formation. The major type of experiments, which measure the yields of fragments produced as a function of incident electron energy (0.1 - 30 eV), are briefly described. Theoretical advances are also summarized. Several examples are presented from the results of recent experiments performed in the gas-phase and on bio-molecular films bombarded with LEE under ultra-high vacuum conditions. These include the results obtained from DNA films and those obtained from the fragmentation of elementary components of the DNA molecule (i.e., the bases, sugar and phosphate group analogs and oligonucleotides) and of proteins (e.g. amino acids). By comparing the results from different experiments and theory, it is possible to determine fundamental mechanisms that are involved in the dissociation of the biomolecules and the production of single- and double-strand breaks in DNA. Below 15 eV, electron resonances (i.e., the formation of transient anions) play a dominant role in the fragmentation of all biomolecules investigated. These transient anions fragment molecules by decaying into dissociative electronically excited states or by dissociating into a stable anion and a neutral radical. These fragments can initiate further reactions within large biomolecules or with nearby molecules and thus cause more complex chemical damage. Dissociation of a transient anion within DNA may occur by direct electron attachment at the location of dissociation or by electron transfer from another subunit. Damage to DNA is dependent on the molecular environment, topology, type of counter ion, sequence context and chemical modifications. (author)

  12. Design, development and characterization of tetrode type electron gun system for generation of low energy electrons

    International Nuclear Information System (INIS)

    Deore, A.V.; Bhoraskar, V.N.; Dhole, S.D.

    2011-01-01

    A tetrode type electron gun system for the generation of low energy electrons was designed, developed and characterized. An electron gun having four electrodes namely cathode, focusing electrode, control electrode and anode has been designed for the irradiation experiments. This electron gun is capable to provide electrons of energy over the range of 1 keV to 20 keV, with current maximum upto 100 μA. The electron gun and a faraday cup are mounted in the evacuated cylindrical chamber. The samples are fixed on the faraday cup and irradiated with low energy electrons at a pressure around 10 -6 mbar. In this electron gun system, at any electron energy over the entire range, the electron beam diameter can be varied from 5 to 120 mm on the Faraday cup mounted at a distance of 200 mm from the anode in the chamber. Also, the circular shape of the beam spot was maintained, even though the beam current and beam diameter are varied. The uniformity of the electron beam over the entire beam area was measured with a multi electrode assembly and found to be well within 15%. This system is being used for the synthesis and diffusion of metal and semiconductor nanoparticles in polymeric materials. (author)

  13. Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction.

    Science.gov (United States)

    Sokolowski-Tinten, K; Shen, X; Zheng, Q; Chase, T; Coffee, R; Jerman, M; Li, R K; Ligges, M; Makasyuk, I; Mo, M; Reid, A H; Rethfeld, B; Vecchione, T; Weathersby, S P; Dürr, H A; Wang, X J

    2017-09-01

    We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.

  14. High energy diffraction

    International Nuclear Information System (INIS)

    Berger, C.

    1995-11-01

    Recent experiments on total hadronic cross sections are reviewed together with results on photo- and electroproduction of vector mesons. New data on diffractive deep inelastic scattering shed light on the nature of the pomeron. (orig.)

  15. Cost analysis of low energy electron accelerator for film curing

    International Nuclear Information System (INIS)

    Ochi, Masafumi

    2003-01-01

    Low energy electron accelerators are recognized as one of the advanced curing means of converting processes for films and papers. In the last three years the price of the accelerator equipment has been greatly reduced. The targeted application areas are mainly processes of curing inks, coatings, and adhesives to make packaging materials. The operating cost analyses were made for electron beam (EB) processes over the conventional ones without EB. Then three new proposals for cost reduction of EB processes are introduced. Also being developed are new EB chemistries such as coatings, laminating adhesives and inks. EB processes give instantaneous cure and EB chemistries are basically non solvent causing less VOC emission to the environment. These developments of both equipment and chemistries might have a potential to change conventional packaging film industries. (author)

  16. New development for low energy electron beam processor

    International Nuclear Information System (INIS)

    Takei, Taro; Goto, Hitoshi; Oizumi, Matsutoshi; Hirakawa, Tetsuya; Ochi, Masafumi

    2003-01-01

    Newly developed low-energy electron beam (EB) processors that have unique designs and configurations compared to conventional ones enable electron-beam treatment of small three-dimensional objects, such as grain-like agricultural products and small plastic parts. As the EB processor can irradiate the products from the whole angles, the uniform EB treatment can be achieved at one time regardless the complex shapes of the product. Here presented are two new EB processors: the first system has cylindrical process zone, which allows three-dimensional objects to be irradiated with one-pass treatment. The second is a tube-type small EB processor, achieving not only its compactor design, but also higher beam extraction efficiency and flexible installation of the irradiation heads. The basic design of each processor and potential applications with them will be presented in this paper. (author)

  17. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    Science.gov (United States)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    hitting anything solid, they will create secondary electrons. These electrons are in fact the energy source needed to run interstellar chemistry. Slow electrons can in principle trigger three different primary processes in a molecule. The first is ionisation by electron impact (EI), which is used to create ions in mass spectrometry. In this process an electron hits a molecule M and knocks an outer shell electron to create a cation. This occurs whenever the electron energy is above the ionisation threshold of the target molecule. Another possibility is the attachment of a slow electron to a molecule to create an anion. This can occur at sharply defined resonance energies specific to the molecule M. A third possibility is to excite the molecule M to a neutral state M∗ .[9] M + e- -> M+ + 2 e- (Electron impact ionisation) M + e- -> M- (Electron attachment) M + e- -> M∗ + e- (Neutral excitation) The created states M+ , M- and M∗ are usually not stable states so they very often dissociate into ions and radicals, which can then further react with neighbouring molecules to form new chemical species. In these chemical reactions some products can be formed even at very low temperatures that would otherwise require a lot of thermal energy and/or special catalysts. The formation of ethylamine from ethylene and ammonia by hydroamination is one such example. The reaction is characterized by a high activation barrier caused by the electronic repulsion between the electron density rich C=C double bound and the lone pair electrons of ammo-nia. The reaction also has a highly negative entropy, so it becomes less favourable at higher temperatures, ruling out heat as a means to facilitate the reaction. In classical chemistry this problem is overcome by the use of catalysts. Unfortunately there still is no general catalyst for this kind of reaction. Recently it was shown that the reaction can efficiently be induced by low energy electron radiation.[10] One of the reaction partners is

  18. Shape resonances in low-energy-electron collisions with halopyrimidines

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Alessandra Souza; Bettega, Márcio H. F., E-mail: bettega@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná (Brazil)

    2013-12-07

    We report calculated cross sections for elastic collisions of low-energy electrons with halopyrimidines, namely, 2-chloro, 2-bromo, and 5-bromopyrimidine. We employed the Schwinger multichannel method with pseudopotentials to compute the cross sections in the static-exchange and static-exchange plus polarization levels of approximation for energies up to 10 eV. We found four shape resonances for each molecule: three of π* nature localized on the ring and one of σ* nature localized along the carbon–halogen bond. We compared the calculated positions of the resonances with the electron transmission spectroscopy data measured by Modelli et al. [J. Phys. Chem. A 115, 10775 (2011)]. In general the agreement between theory and experiment is good. In particular, our results show the existence of a π* temporary anion state of A{sub 2} symmetry for all three halopyrimidines, in agreement with the dissociative electron attachment spectra also reported by Modelli et al. [J. Phys. Chem. A 115, 10775 (2011)].

  19. A low energy electron microscopy study of the initial growth, structure and thermal stability of BDA-domains on Cu(001)

    NARCIS (Netherlands)

    Khokhar, F.S.; van Gastel, Raoul; Schwarz, Daniel; Schwarz, Daniel; Zandvliet, Henricus J.W.; Poelsema, Bene

    2011-01-01

    The growth of 4,4′-biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene

  20. Low energy electron point source microscopy: beyond imaging

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Andre; Goelzhaeuser, Armin [Physics of Supramolecular Systems and Surfaces, University of Bielefeld, Postfach 100131, 33501 Bielefeld (Germany)

    2010-09-01

    Low energy electron point source (LEEPS) microscopy has the capability to record in-line holograms at very high magnifications with a fairly simple set-up. After the holograms are numerically reconstructed, structural features with the size of about 2 nm can be resolved. The achievement of an even higher resolution has been predicted. However, a number of obstacles are known to impede the realization of this goal, for example the presence of electric fields around the imaged object, electrostatic charging or radiation induced processes. This topical review gives an overview of the achievements as well as the difficulties in the efforts to shift the resolution limit of LEEPS microscopy towards the atomic level. A special emphasis is laid on the high sensitivity of low energy electrons to electrical fields, which limits the structural determination of the imaged objects. On the other hand, the investigation of the electrical field around objects of known structure is very useful for other tasks and LEEPS microscopy can be extended beyond the task of imaging. The determination of the electrical resistance of individual nanowires can be achieved by a proper analysis of the corresponding LEEPS micrographs. This conductivity imaging may be a very useful application for LEEPS microscopes. (topical review)

  1. Low energy electron microscopy imaging using Medipix2 detector

    International Nuclear Information System (INIS)

    Sikharulidze, I.; Gastel, R. van; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, S.J. van der

    2011-01-01

    Low Energy Electron Microscopy (LEEM) and Photo-Emission Electron Microscopy (PEEM) predominantly use a combination of microchannel plate (MCP), phosphor screen and optical camera to record images formed by 10-20 keV electrons. We have tested the performance of a LEEM/PEEM instrument with a Medipix2 hybrid pixel detector using an Ir(1 1 1) sample with graphene flakes grown on its surface. We find that Medipix2 offers a number of advantages over the MCP. The adjustable threshold settings allow Medipix2 to operate as a noiseless detector, offering an improved signal-to-noise ratio for the same amount of signal compared to the MCP. At the same magnification Medipix2 images exhibit superior resolution and can handle significantly higher electron current densities than an MCP, offering the prospect of substantially higher frame rates in LEEM imaging. These factors make Medipix2 an excellent candidate to become the detector of choice for LEEM/PEEM applications.

  2. Low energy electron microscopy imaging using Medipix2 detector

    Energy Technology Data Exchange (ETDEWEB)

    Sikharulidze, I., E-mail: irakli@chem.leidenuniv.nl [Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300RA Leiden (Netherlands); Gastel, R. van [MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Schramm, S. [Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300RA Leiden (Netherlands); Abrahams, J.P. [Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300RA Leiden (Netherlands); Poelsema, B. [MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Tromp, R.M. [Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300RA Leiden (Netherlands); IBM Research Division, T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Molen, S.J. van der [Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300RA Leiden (Netherlands)

    2011-05-15

    Low Energy Electron Microscopy (LEEM) and Photo-Emission Electron Microscopy (PEEM) predominantly use a combination of microchannel plate (MCP), phosphor screen and optical camera to record images formed by 10-20 keV electrons. We have tested the performance of a LEEM/PEEM instrument with a Medipix2 hybrid pixel detector using an Ir(1 1 1) sample with graphene flakes grown on its surface. We find that Medipix2 offers a number of advantages over the MCP. The adjustable threshold settings allow Medipix2 to operate as a noiseless detector, offering an improved signal-to-noise ratio for the same amount of signal compared to the MCP. At the same magnification Medipix2 images exhibit superior resolution and can handle significantly higher electron current densities than an MCP, offering the prospect of substantially higher frame rates in LEEM imaging. These factors make Medipix2 an excellent candidate to become the detector of choice for LEEM/PEEM applications.

  3. Degradation of carrageenan by low energy electron accelerator

    International Nuclear Information System (INIS)

    Relleve, L.; Aranilla, C.; Abad, L.; Dela Rosa, A.; Nagasawa, Naotsugu; Yagi, Toshiaki; Kume, Tamikazu; Yoshii, Fumio

    2004-01-01

    Degradation of κ-carrageenan using vessel-type low energy electron accelerator was investigated. Carrageenan with different molecular weights were obtained from irradiation of high molecular weight (HMW) and low molecular weight (LMW) κ-carrageenan. Other results presented were obtained from degradation studies of carrageenan by gamma rays. The decrease in molecular weight was accompanied by partial desulfation. From comparison of radiation degradation yield (Gd), it was found that the susceptibility to radiation of the three types of carrageenans in aqueous/gel forms follows the order of λ->ι->>κ- and could have been influenced by their conformational state. κ-carrageenan with molecular weight of ca. 10,000 showed strong growth promotion effect for potato in tissue culture. (author)

  4. On the energy dependence of DIS in the diffraction region of low x

    Energy Technology Data Exchange (ETDEWEB)

    Schildknecht, D. [Bielefeld, Univ., Fakultat fur Physik (Germany)

    2005-07-01

    The energy dependence of the virtual photoabsorption cross-section in deep inelastic scattering (DIS) at low x = Q{sup 2}/W{sup 2} < 0.1 may be described in terms of the saturation scale that in our approach depends on the energy, {lambda}{sup 2}{sub sat} = {lambda}{sup 2}{sub sat}(W{sup 2}). We briefly summarize our recent findings that allow us to predict the exponent C{sub 2} of {lambda}{sup 2}{sub sat}(W{sup 2}) {approx} (W{sup 2}){sup C{sub 2}} in agreement with the previous result obtained from fitting the experimental data. The exponent C{sub 2} depending on the relative magnitude of the longitudinal and transverse contribution to the structure function, direct measurements of the longitudinal part are urgently needed. (author)

  5. Low-energy electron point projection microscopy of suspended graphene, the ultimate 'microscope slide'

    International Nuclear Information System (INIS)

    Mutus, J Y; Livadaru, L; Urban, R; Salomons, M H; Cloutier, M; Wolkow, R A; Robinson, J T

    2011-01-01

    Point projection microscopy (PPM) is used to image suspended graphene by using low-energy electrons (100-205 eV). Because of the low energies used, the graphene is neither damaged nor contaminated by the electron beam for doses of the order of 10 7 electrons per nm 2 . The transparency of graphene is measured to be 74%, equivalent to electron transmission through a sheet twice as thick as the covalent radius of sp 2 -bonded carbon. Also observed is rippling in the structure of the suspended graphene, with a wavelength of approximately 26 nm. The interference of the electron beam due to diffraction off the edge of a graphene knife edge is observed and is used to calculate a virtual source size of 4.7±0.6 A for the electron emitter. It is demonstrated that graphene can serve as both the anode and the substrate in PPM, thereby avoiding distortions due to strong field gradients around nanoscale objects. Graphene can be used to image objects suspended on the sheet using PPM and, in the future, electron holography.

  6. Low energy elastic electron scattering from polyatomic targets

    International Nuclear Information System (INIS)

    Khakoo, M A

    2008-01-01

    New differential cross-section measurements for elastic electron scattering from ethylene (C 2 H 4 ), three primary alcohols, methanol (CH 3 OH), ethanol (C 2 H 5 OH) and propanol (C 3 H 7 OH) are reported. The measurements are obtained using the relative flow method with a thin aperture as the collimating target gas source. The relative flow method is applied without the molecular diameters restriction imposed by the relative flow pressure condition on helium (the calibrating gas) and the unknown gases (the primary alcohols). The experimental data were taken at incident electron energies of 1eV, 2eV, 5eV, 10eV, 15eV, 20eV, 30eV, 50eV and 100eV, but only a brief survey of these results will be made here. The experimental results are compared to theoretical differential cross-sections are obtained by using the variational multi-channel Schwinger method. Initial comparisons between theory and experiment show that present theory is well-able to model low electron scattering from these polyatomic targets.

  7. Low-energy electron collisions with metal clusters: Electron capture and cluster fragmentation

    International Nuclear Information System (INIS)

    Kresin, V.V.; Scheidemann, A.; Knight, W.D.

    1993-01-01

    The authors have carried out the first measurement of absolute cross sections for the interaction between electrons and size-resolved free metal clusters. Integral inelastic scattering cross sections have been determined for electron-Na n cluster collisions in the energy range from 0.1 eV to 30 eV. At energies ≤1 eV, cross sections increase with decreasing impact energies, while at higher energies they remain essentially constant. The dominant processes are electron attachment in the low-energy range, and collision-induced fragmentation at higher energies. The magnitude of electron capture cross sections can be quantitatively explained by the effect of the strong polarization field induced in the cluster by the incident electron. The cross sections are very large, reaching values of hundreds of angstrom 2 ; this is due to the highly polarizable nature of metal clusters. The inelastic interaction range for fragmentation collisions is also found to considerably exceed the cluster radius, again reflecting the long-range character of electron-cluster interactions. The important role played by the polarization interaction represents a bridge between the study of collision processes and the extensive research on cluster response properties. Furthermore, insight into the mechanisms of electron scattering is important for understanding production and detection of cluster ions in mass spectrometry and related processes

  8. New directions in low energy electron molecule collision calculations

    International Nuclear Information System (INIS)

    Burke, P.G.; Noble, C.J.

    1982-01-01

    New theoretical and computational methods for studying low energy electron molecule collisions are discussed. Having considered the fixed-nuclei approximation and the form of the expansion of the total collision wavefunction, the various approximations which have been made are examined, including the static plus model exchange approximation, the static exchange approximation and the close coupling approximation, particular attention being paid to methods of including the molecular charge polarisation. Various ways which have been developed to solve the resultant equations are discussed and it is found that there is increasing emphasis being given to methods which combine the advantages of discrete multi-centre analytic bases with single centre numerical bases. (U.K.)

  9. Low-energy electron irradiation assisted diffusion of gold nanoparticles in polymer matrix

    International Nuclear Information System (INIS)

    Deore, Avinash V.; Bhoraskar, V.N.; Dhole, S.D.

    2014-01-01

    A simple and controllable method to synthesize nanoparticles in the surface region of polymers was used by low energy electron irradiation. Using this method, gold nanoparticles have been synthesized by irradiating gold coated PVA (Polyvinyl Alcohol) sheets. This method was easy in operation and even period of few minutes was sufficient to obtain the nanoparticles. The coatings (∼10 μm) made from a mixture of ethanol and HAuCl 4 on PVA sheets (∼150 μm) by simple drop cast method were irradiated with 30 keV electrons, at room temperature and 10 −6 mbar vacuum level. The electron fluence was varied from coating to coating in the range of 0 to 24×10 15 e/cm 2 . The irradiated samples were characterized by the UV–Vis, XRD, SEM and RBS techniques. The plasmon absorption peak at ∼539 nm in UV–Vis spectra was an evidence for the initiation of the growth of gold nanoparticles. The X-ray diffraction results and the blue shift in the plasmon absorption peak reveal that the size of nanoparticles could be tailored in the range from 58 to 40 nm by varying the electron fluence. The diffusion of gold in the PVA was confirmed by the Rutherford backscattering spectroscopy and scanning electron microscopy techniques. This method of synthesis of metal nanoparticles by low energy electron beam irradiation has the key importance in the development of new fabrication techniques for nanomaterials. - Highlights: • The results indicate that low energy electrons can effectively be used for the synthesis of nanoparticles of different sizes. • This study leads to a definite conclusion that gold nanoparticles have been synthesized in surface region of the PVA sheet. • The size of nanoparticles decreases with increasing electron fluence. • The depth of diffusion of Au atoms at maximum fluence was found to be ∼1.5 μm

  10. Fine structure characterization of martensite/austenite constituent in low-carbon low-alloy steel by transmission electron forward scatter diffraction.

    Science.gov (United States)

    Li, C W; Han, L Z; Luo, X M; Liu, Q D; Gu, J F

    2016-11-01

    Transmission electron forward scatter diffraction and other characterization techniques were used to investigate the fine structure and the variant relationship of the martensite/austenite (M/A) constituent of the granular bainite in low-carbon low-alloy steel. The results demonstrated that the M/A constituents were distributed in clusters throughout the bainitic ferrite. Lath martensite was the main component of the M/A constituent, where the relationship between the martensite variants was consistent with the Nishiyama-Wassermann orientation relationship and only three variants were found in the M/A constituent, suggesting that the variants had formed in the M/A constituent according to a specific mechanism. Furthermore, the Σ3 boundaries in the M/A constituent were much longer than their counterparts in the bainitic ferrite region. The results indicate that transmission electron forward scatter diffraction is an effective method of crystallographic analysis for nanolaths in M/A constituents. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  11. Vibrational and electronic excitation of hexatriacontane thin films by low energy electron impact

    International Nuclear Information System (INIS)

    Vilar, M.R.; Schott, M.; Pfluger, P.

    1990-01-01

    Thin polycrystalline films of hexatriacontane (HTC) were irradiated with low energy (E=0.5--15 eV) electrons, and off-specular backscattered electron spectra were measured. Below E∼7 eV, single and multiple vibrational excitations only are observed, which relax the electrons down to the bottom of the HTC conduction band. Due to the negative electron affinity of HTC, thermal electrons are emitted into vacuum. Structure in the backscattered electron current at kinetic energies about 1.5 and 4 eV are associated to conduction band density of states. Above E∼7 eV, the dominant losses correspond to electronic excitations, excitons, or above a threshold (energy of the electron inside the HTC film) at 9.2±0.1 eV, electron--hole pair generation. The latter process is very efficient and reaches a yield of the order of one ∼11 eV. Evidence for chemical reaction above E∼4 eV is observed

  12. Observation of second harmonics in laser-electron scattering using low energy electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Iinuma, Masataka [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan)]. E-mail: iinuma@hiroshima-u.ac.jp; Matsukado, Koji [Venture Business Laboratory, Hiroshima University, 1-313 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527 (Japan); Endo, Ichita [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Hashida, Masaki [Institute for chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Hayashi, Kenji [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Kohara, Akitsugu [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Matsumoto, Fumihiko [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Nakanishi, Yoshitaka [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Sakabe, Shuji [Institute for chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Shimizu, Seiji [Institute for chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Tauchi, Toshiaki [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Yamamoto, Ken [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Takahashi, Tohru [ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan)

    2005-10-17

    We observed photon generation in the second harmonic region in collisions of 10 keV free electrons and the intense laser beam with the peak intensity of 4.0x10{sup 15} W/cm{sup 2}. Observed photon yield was 3 orders of magnitude higher than expectation from the nonlinear Compton scattering. The observation indicates necessity of further investigation for the interaction between the intense laser field and the low energy electron beam.

  13. Low energy electron attachment to the uracil molecule

    International Nuclear Information System (INIS)

    Hanel, G.; Gstir, B.; Denifl, S.; Scheier, P.; Maerk, T.D.; Farizon, B.; Farizon, M.

    2002-01-01

    Using a recently constructed high resolution crossed beam apparatus involving a hemispherical electron monochromator, electron attachment to the uracil molecule C 4 H 4 N 2 O 2 was studied. The electron energy range investigated was in the region between 0 and 12 eV. What will happen when slow electrons are colliding with the cellular RNA compound uracil was the objective of this investigation. The following anion fragments were detected: (C 4 H 3 N 2 O 2 ) - , OCN - , (H 2 C 3 NO) - , CN - , O - . The most important result was that within the detection efficiency any traces of the parent anion were observed. The most intense fragment anion appeared on a mass to charge ratio 111 amu., it corresponds to a uracil molecule missing one hydrogen. Another observation was whereas the parent minus H anion is observed at zero electron energy, all other fragments appear in other range. (nevyjel)

  14. High-Resolution Measurements of Low-Energy Conversion Electrons

    CERN Multimedia

    Gizon, A; Putaux, J

    2002-01-01

    Measurements of low-energy internal conversion electrons have been performed with high energy resolution in some N = 105 odd and odd-odd nuclei using a semi-circular spectrograph associated to a specific tape transport system. These experiments aimed to answer the following questions~: \\begin{itemize} \\item Do M3 isomeric transitions exist in $^{183}$Pt and $^{181}$Os, isotones of $^{184}$Au~? \\item Are the neutron configurations proposed to describe the isomeric and ground states of $^{184}$Au right or wrong~? \\item Does it exist an isomeric state in $^{182}$Ir, isotone of $^{181}$Os, $^{183}$Pt and $^{184}$Au~? \\item What are the spin and parity values of the excited states of $^{182}$Ir~? \\end{itemize} In $^{183}$Pt, the 35.0 keV M3 isomeric transition has been clearly observed and the reduced transition probability has been determined. The deduced hindrance factor is close to that observed in the neighbouring odd-odd $^{184}$Au nucleus. This confirms the neutron configurations previously proposed for the ...

  15. Surface segregation of InGaAs films by the evolution of reflection high-energy electron diffraction patterns

    International Nuclear Information System (INIS)

    Zhou Xun; Luo Zi-Jiang; Guo Xiang; Zhang Bi-Chan; Shang Lin-Tao; Zhou Qing; Deng Chao-Yong; Ding Zhao

    2012-01-01

    Surface segregation is studied via the evolution of reflection high-energy electron diffraction (RHEED) patterns under different values of As 4 BEP for InGaAs films. When the As 4 BEP is set to be zero, the RHEED pattern keeps a 4×3/(n × 3) structure with increasing temperature, and surface segregation takes place until 470 °C. The RHEED pattern develops into a metal-rich (4 × 2) structure as temperature increases to 495 °C. The reason for this is that surface segregation makes the In inside the InGaAs film climb to its surface. With the temperature increasing up to 515 °C, the RHEED pattern turns into a GaAs(2 × 4) structure due to In desorption. While the As 4 BEP comes up to a specific value (1.33 × 10 -4 Pa−1.33 × 10 -3 Pa), the surface temperature can delay the segregation and desorption. We find that As 4 BEP has a big influence on surface desorption, while surface segregation is more strongly dependent on temperature than surface desorption. (condensed matter: structural, mechanical, and thermal properties)

  16. Low-energy electron inelastic mean free path in materials

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen-Truong, Hieu T., E-mail: nguyentruongthanhhieu@tdt.edu.vn [Theoretical Physics Research Group & Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 756636 (Viet Nam)

    2016-04-25

    We show that the dielectric approach can determine electron inelastic mean free paths in materials with an accuracy equivalent to those from first-principle calculations in the GW approximation of many-body theory. The present approach is an alternative for calculating the hot-electron lifetime, which is an important quantity in ultrafast electron dynamics. This approach, applied here to solid copper for electron energies below 100 eV, yields results in agreement with experimental data from time-resolved two-photon photoemission, angle-resolved photoelectron spectroscopy, and X-ray absorption fine structure measurements in the energy ranges 2–3.5, 10–15, and 60–100 eV, respectively.

  17. Energy analyzer for Auger electron spectroscopy and low-energy backscattering ion spectroscopy

    International Nuclear Information System (INIS)

    Volkov, S.S.; Gorelik, V.A.; Gutenko, V.T.; Protopopov, O.D.; Trubitsin, A.A.; Shuvalova, Z.A.; Yakushev, G.A.

    1988-01-01

    Energy analyzer for electron Auger spectroscopy and low-energy backscattering ion spectroscopy is described. Analyzer presents one-cascade variant of cylindrical mirror with second-order focusing. Energy relative resolution is continuously adjusted within 0.2-1.2% limits. Signal/noise relation by Cu Auger-line at 1 muA current of exciting beam changes upper limit of range 150-450

  18. Elastic scattering of low-energy electrons from ammonia

    International Nuclear Information System (INIS)

    Alle, D.T.; Gulley, R.J.; Buckman, S.J.; Brunger, M.J.

    1992-01-01

    We report absolute differential cross section measurements for vibrationally elastic electron scattering from NH 3 at incident energies from 2-30 eV. The present results, from a crossed electron-molecular beam apparatus, represent the first comprehensive experimental attempt to quantify the elastic electron-NH 3 scattering process. At each energy studied we have integrated our differential cross section data to generate total elastic and elastic momentum transfer cross sections and a critical comparison of both our differential and integral cross sections against previous experiment and theory is provided. We also report our observation of a strong Feshbach resonance in the elastic channel at an energy of 5.59 ± 0.05 eV. (Author)

  19. Deep-inelastic electron-proton diffraction

    International Nuclear Information System (INIS)

    Dainton, J.B.

    1995-11-01

    Recent measurements by the H1 collaboration at HERA of the cross section for deep-inelastic electron-proton scattering in which the proton interacts with minimal energy transfer and limited 4-momentum transfer squared are presented in the form of the contribution F 2 D(3) to the proton structure function F 2 . By parametrising the cross section phenomenologically in terms of a leading effective Regge pole exchange and comparing the result with a similar parametrisation of hadronic pp physics, the proton interaction is demonstrated to be dominantly of a diffractive nature. The quantitative interpretation of the parametrisation in terms of the properties of an effective leading Regge pole exchange, the pomeron (IP), shows that there is no evidence for a 'harder' BFKL-motivated IP in such deep-inelastic proton diffraction. The total contribution of proton diffraction to deep-inelastic electron-proton scattering is measured to be ∝10% and to be rather insensitive to Bjorken-x and Q 2 . A first measurement of the partonic structure of diffractive exchange is presented. It is shown to be readily interpreted in terms of the exchange of gluons, and to suggest that the bulk of diffractive momentum transfer is carried by a leading gluon. (orig.)

  20. Treatment of surfaces with low-energy electrons

    Science.gov (United States)

    Frank, L.; Mikmeková, E.; Lejeune, M.

    2017-06-01

    Electron-beam-induced deposition of various materials from suitable precursors has represented an established branch of nanotechnology for more than a decade. A specific alternative is carbon deposition on the basis of hydrocarbons as precursors that has been applied to grow various nanostructures including masks for subsequent technological steps. Our area of study was unintentional electron-beam-induced carbon deposition from spontaneously adsorbed hydrocarbon molecules. This process traditionally constitutes a challenge for scanning electron microscopy practice preventing one from performing any true surface studies outside an ultrahigh vacuum and without in-situ cleaning of samples, and also jeopardising other electron-optical devices such as electron beam lithographs. Here we show that when reducing the energy of irradiating electrons sufficiently, the e-beam-induced deposition can be converted to e-beam-induced release causing desorption of hydrocarbons and ultimate cleaning of surfaces in both an ultrahigh and a standard high vacuum. Using series of experiments with graphene samples, we demonstrate fundamental features of e-beam-induced desorption and present results of checks for possible radiation damage using Raman spectroscopy that led to optimisation of the electron energy for damage-free cleaning. The method of preventing carbon contamination described here paves the way for greatly enhanced surface sensitivity of imaging and substantially reduced demands on vacuum systems for nanotechnological applications.

  1. Tomography with energy dispersive diffraction

    Science.gov (United States)

    Stock, S. R.; Okasinski, J. S.; Woods, R.; Baldwin, J.; Madden, T.; Quaranta, O.; Rumaiz, A.; Kuczewski, T.; Mead, J.; Krings, T.; Siddons, P.; Miceli, A.; Almer, J. D.

    2017-09-01

    X-ray diffraction can be used as the signal for tomographic reconstruction and provides a cross-sectional map of the crystallographic phases and related quantities. Diffraction tomography has been developed over the last decade using monochromatic x-radiation and an area detector. This paper reports tomographic reconstruction with polychromatic radiation and an energy sensitive detector array. The energy dispersive diffraction (EDD) geometry, the instrumentation and the reconstruction process are described and related to the expected resolution. Results of EDD tomography are presented for two samples containing hydroxyapatite (hAp). The first is a 3D-printed sample with an elliptical crosssection and contains synthetic hAp. The second is a human second metacarpal bone from the Roman-era cemetery at Ancaster, UK and contains bio-hAp which may have been altered by diagenesis. Reconstructions with different diffraction peaks are compared. Prospects for future EDD tomography are also discussed.

  2. Innovative energy efficient low-voltage electron beam emitters

    International Nuclear Information System (INIS)

    Felis, Kenneth P.; Avnery, Tovi; Berejka, Anthony J.

    2002-01-01

    Advanced electron beams (AEB) has developed a modular, low voltage (80-125 keV), high beam current (up to 40 ma), electron emitter with typically 25 cm of beam width, that is housed in an evacuated, returnable chamber that is easy to plug in and connect. The latest in nanofabrication enables AEB to use an ultra-thin beam window. The power supply for AEB's emitter is based on solid-state electronics. This combination of features results in a remarkable electrical efficiency. AEB's electron emitter relies on a touch screen, computer control system. With 80 μm of unit density beam penetration, AEB's electron emitter has gained market acceptance in the curing of opaque, pigmented inks and coatings used on flexible substrates, metals and fiber composites and in the curing of adhesives in foil based laminates

  3. Innovative energy efficient low-voltage electron beam emitters

    Science.gov (United States)

    Felis, Kenneth P.; Avnery, Tovi; Berejka, Anthony J.

    2002-03-01

    Advanced electron beams (AEB) has developed a modular, low voltage (80-125 keV), high beam current (up to 40 ma), electron emitter with typically 25 cm of beam width, that is housed in an evacuated, returnable chamber that is easy to plug in and connect. The latest in nanofabrication enables AEB to use an ultra-thin beam window. The power supply for AEB's emitter is based on solid-state electronics. This combination of features results in a remarkable electrical efficiency. AEB's electron emitter relies on a touch screen, computer control system. With 80 μm of unit density beam penetration, AEB's electron emitter has gained market acceptance in the curing of opaque, pigmented inks and coatings used on flexible substrates, metals and fiber composites and in the curing of adhesives in foil based laminates.

  4. Low-dose electron energy-loss spectroscopy using electron counting direct detectors.

    Science.gov (United States)

    Maigné, Alan; Wolf, Matthias

    2018-03-01

    Since the development of parallel electron energy loss spectroscopy (EELS), charge-coupled devices (CCDs) have been the default detectors for EELS. With the recent development of electron-counting direct-detection cameras, micrographs can be acquired under very low electron doses at significantly improved signal-to-noise ratio. In spectroscopy, in particular in combination with a monochromator, the signal can be extremely weak and the detection limit is principally defined by noise introduced by the detector. Here we report the use of an electron-counting direct-detection camera for EEL spectroscopy. We studied the oxygen K edge of amorphous ice and obtained a signal noise ratio up to 10 times higher than with a conventional CCD.We report the application of electron counting to record time-resolved EEL spectra of a biological protein embedded in amorphous ice, revealing chemical changes observed in situ while exposed by the electron beam. A change in the fine structure of nitrogen K and the carbon K edges were recorded during irradiation. A concentration of 3 at% nitrogen was detected with a total electron dose of only 1.7 e-/Å2, extending the boundaries of EELS signal detection at low electron doses.

  5. Treatment of surfaces with low-energy electrons

    Energy Technology Data Exchange (ETDEWEB)

    Frank, L., E-mail: ludek@isibrno.cz [Institute of Scientific Instruments of the CAS, v.v.i., Královopolská 147, 61264 Brno (Czech Republic); Mikmeková, E. [Institute of Scientific Instruments of the CAS, v.v.i., Královopolská 147, 61264 Brno (Czech Republic); FEI Company, Achtseweg Noord 5, 5651 GG Eindhoven (Netherlands); Lejeune, M. [LPMC – Faculte des Sciences d’Amiens, Universite de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 2 (France)

    2017-06-15

    Highlights: • Using proper irradiation parameters, adsorbed hydrocarbons are released from surfaces. • Slow electrons remove hydrocarbons instead of depositing carbon. • Prolonged irradiation with very slow electrons does not create defects in graphene. - Abstract: Electron-beam-induced deposition of various materials from suitable precursors has represented an established branch of nanotechnology for more than a decade. A specific alternative is carbon deposition on the basis of hydrocarbons as precursors that has been applied to grow various nanostructures including masks for subsequent technological steps. Our area of study was unintentional electron-beam-induced carbon deposition from spontaneously adsorbed hydrocarbon molecules. This process traditionally constitutes a challenge for scanning electron microscopy practice preventing one from performing any true surface studies outside an ultrahigh vacuum and without in-situ cleaning of samples, and also jeopardising other electron-optical devices such as electron beam lithographs. Here we show that when reducing the energy of irradiating electrons sufficiently, the e-beam-induced deposition can be converted to e-beam-induced release causing desorption of hydrocarbons and ultimate cleaning of surfaces in both an ultrahigh and a standard high vacuum. Using series of experiments with graphene samples, we demonstrate fundamental features of e-beam-induced desorption and present results of checks for possible radiation damage using Raman spectroscopy that led to optimisation of the electron energy for damage-free cleaning. The method of preventing carbon contamination described here paves the way for greatly enhanced surface sensitivity of imaging and substantially reduced demands on vacuum systems for nanotechnological applications.

  6. Atomic excitation and molecular dissociation by low energy electron collisions

    International Nuclear Information System (INIS)

    Weyland, Marvin

    2016-01-01

    In this work, momentum imaging experiments have been conducted for the electron impact excitation of metastable states in noble gases and for dissociative electron attachment (DEA) in polyatomic molecules. For the electron impact excitation study a new experimental technique has been developed which is able to measure the scattering angle distribution of the electrons by detection of the momentum transfer to the atoms. Momentum transfer images have been recorded for helium and neon at fixed electron impact energy close to the excitation threshold and good agreement with current R-matrix theory calculations was found. A new momentum imaging apparatus for negative ions has been built for the purpose of studying DEA in biologically relevant molecules. During this work, DEA was investigated in the molecules ammonia, water, formic acid, furan, pyridine and in two chlorofluorocarbons. Furthermore, the change of DEA resonance energies when molecules form clusters compared to monomers was investigated in ammonia and formic acid. The experimental results of most studied molecules could be compared to recent theoretical calculations and they support further development in the theoretical description of DEA. The new apparatus built in this work also delivered a superior momentum resolution compared to existing setups. This allows the momentum imaging of heavier fragments and fragments with lower kinetic energy.

  7. Atomic excitation and molecular dissociation by low energy electron collisions

    Energy Technology Data Exchange (ETDEWEB)

    Weyland, Marvin

    2016-11-16

    In this work, momentum imaging experiments have been conducted for the electron impact excitation of metastable states in noble gases and for dissociative electron attachment (DEA) in polyatomic molecules. For the electron impact excitation study a new experimental technique has been developed which is able to measure the scattering angle distribution of the electrons by detection of the momentum transfer to the atoms. Momentum transfer images have been recorded for helium and neon at fixed electron impact energy close to the excitation threshold and good agreement with current R-matrix theory calculations was found. A new momentum imaging apparatus for negative ions has been built for the purpose of studying DEA in biologically relevant molecules. During this work, DEA was investigated in the molecules ammonia, water, formic acid, furan, pyridine and in two chlorofluorocarbons. Furthermore, the change of DEA resonance energies when molecules form clusters compared to monomers was investigated in ammonia and formic acid. The experimental results of most studied molecules could be compared to recent theoretical calculations and they support further development in the theoretical description of DEA. The new apparatus built in this work also delivered a superior momentum resolution compared to existing setups. This allows the momentum imaging of heavier fragments and fragments with lower kinetic energy.

  8. Low-energy collisions between electrons and BeD+

    Science.gov (United States)

    Niyonzima, S.; Pop, N.; Iacob, F.; Larson, Å; Orel, A. E.; Mezei, J. Zs; Chakrabarti, K.; Laporta, V.; Hassouni, K.; Benredjem, D.; Bultel, A.; Tennyson, J.; Reiter, D.; Schneider, I. F.

    2018-02-01

    Multichannel quantum defect theory is applied in the treatment of the dissociative recombination and vibrational excitation processes for the BeD+ ion in the 24 vibrational levels of its ground electronic state ({{X}}{}1{{{Σ }}}+,{v}{{i}}+=0\\ldots 23). Three electronic symmetries of BeD** states ({}2{{\\Pi }}, {}2{{{Σ }}}+, and {}2{{Δ }}) are considered in the calculation of cross sections and the corresponding rate coefficients. The incident electron energy range is 10-5-2.7 eV and the electron temperature range is 100-5000 K. The vibrational dependence of these collisional processes is highlighted. The resulting data are useful in magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as ITER and JET, and operating with the deuterium-tritium fuel mix. An extensive rate coefficients database is presented in graphical form and also by analytic fit functions whose parameters are tabulated in the supplementary material.

  9. Application of Electron Backscattered Diffraction (EBSD) and Atomic Force Microscopy (AFM) to Determine Texture, Mesotexture, and Grain Boundary Energies in Ceramics

    International Nuclear Information System (INIS)

    Glass, S.J.; Rohrer, G.S.; Saylor, D.M.; Vedula, V.R.

    1999-01-01

    Crystallographic orientations in alumina (Al 2 0 3 ) and magnesium aluminate spinel (MgAl 2 0 4 ) were obtained using electron backscattered diffraction (EBSD) patterns. The texture and mesotexture (grain boundary mis-orientations) were random and no special boundaries were observed. The relative grain boundary energies were determined by thermal groove geometries using atomic force microscopy (AFM) to identify relationships between the grain boundary energies and mis-orientations

  10. Excitation and dissociation of molecules by low-energy (0-15 eV) electrons

    International Nuclear Information System (INIS)

    Verhaart, G.J.

    1980-01-01

    The author deals with excitation and dissociation processes which result from the interaction between low-energy (0.15 eV) electrons and molecules. Low-energy electron-impact spectroscopy is used to gain a better knowledge of the electronic structure of halomethanes, ethylene and some of its halogen substituted derivatives, and some more complex organic molecules. (Auth.)

  11. PLEASE: The Python Low-energy Electron Analysis SuitE – Enabling Rapid Analysis of LEEM and LEED Data

    Directory of Open Access Journals (Sweden)

    Maxwell Grady

    2018-02-01

    Full Text Available PLEASE, the Python Low-energy Electron Analysis SuitE, provides an open source and cross-platform graphical user interface (GUI for rapid analysis and visualization of low energy electron microscopy (LEEM data sets. LEEM and the associated technique, selected area micro-spot low energy electron diffraction (μ-LEED, are powerful tools for analysis of the surface structure for many novel materials. Specifically, these tools are uniquely suited for the characterization of two-dimensional materials. PLEASE offers a user-friendly point-and-click method for extracting intensity-voltage curves from LEEM and LEED data sets. Analysis of these curves provides insight into the atomic structure of the target material surface with unparalleled resolution.

  12. An electrostatic storage ring for low kinetic energy electron collisions

    Energy Technology Data Exchange (ETDEWEB)

    Reddish, T J; Tessier, D R; Sullivan, M R; Thorn, P A [Department of Physics, University of Windsor, Windsor, N9B 3P4 (Canada); Hammond, P; Alderman, A J [School of Physics, CAMSP, University of Western Australia, Perth WA 6009 (Australia); Read, F H [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

    2009-11-01

    The criteria are presented for stable multiple orbits of charged particles in a race-track shaped storage ring and applied to an electrostatic system consisting of two hemispherical deflector analyzers (HDA) connected by two separate sets of cylindrical lenses. The results of charged particle simulations and the formal matrix theory, including aberrations in the energy-dispersive electrostatic 'prisms', are in good agreement with the observed experimental operating conditions for this Electron Recycling Spectrometer (ERS).

  13. Low-energy electron transmission through high aspect ratio Al O nanocapillaries

    DEFF Research Database (Denmark)

    Milosavljević, A.R.; Jureta, J.; Víkor, G.

    2009-01-01

    Electron transmission through insulating AlO nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2-120 V). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined with resp......Electron transmission through insulating AlO nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2-120 V). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined...

  14. A measurement of electron-wall interactions using transmission diffraction from nanofabricated gratings

    International Nuclear Information System (INIS)

    Barwick, Brett; Gronniger, Glen; Yuan, Lu; Liou, Sy-Hwang; Batelaan, Herman

    2006-01-01

    Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement of the image charge potential between the electron and the grating bars. Image charge potentials that were about 15% of the value for that of a pure electron-metal wall interaction were found. We varied the electron energy from 50 to 900 eV. The interaction time is of the order of typical metal image charge response times and in principle allows the investigation of image charge formation. In addition to the image charge interaction there is a dephasing process reducing the transverse coherence length of the electron wave. The dephasing process causes broadening of the diffraction peaks and is consistent with a model that ascribes the dephasing process to microscopic contact potentials. Surface structures with length scales of about 200 nm observed with a scanning tunneling microscope, and dephasing interaction strength typical of contact potentials of 0.35 eV support this claim. Such a dephasing model motivated the investigation of different metallic coatings, in particular Ni, Ti, Al, and different thickness Au-Pd coatings. Improved quality of diffraction patterns was found for Ni. This coating made electron diffraction possible at energies as low as 50 eV. This energy was limited by our electron gun design. These results are particularly relevant for the

  15. Low energy spread 100 MeV-1 GeV electron bunches from laser wakefield acceleration at LOASIS

    International Nuclear Information System (INIS)

    Geddes, C.G.R.; Esarey, E.; Michel, P.; Nagler, B.; Nakamura, K.; Plateau, G.R.; Schroeder, C.B.; Shadwick, B.A.; Toth, Cs.; Van Tilborg, J.; Leemans, W.P.; Hooker, S.M.; Gonsalves, A.J.; Michel, E.; Cary, J.R.; Bruhwiler, D.

    2006-01-01

    Experiments at the LOASIS laboratory of LBNL recently demonstrated production of 100 MeV electron beams with low energy spread and low divergence from laser wakefield acceleration. The radiation pressure of a 10 TW laser pulse guided over 10 diffraction ranges by a plasma density channel was used to drive an intense plasma wave (wakefield), producing acceleration gradients on the order of 100 GV/m in a mm-scale channel. Beam energy has now been increased from 100 to 1000 MeV by using a cm-scale guiding channel at lower density, driven by a 40TW laser, demonstrating the anticipated scaling to higher beam energies. Particle simulations indicate that the low energy spread beams were produced from self trapped electrons through the interplay of trapping, loading, and dephasing. Other experiments and simulations are also underway to control injection of particles into the wake, and hence improve beam quality and stability further

  16. Low-energy positron and electron scattering from nitrogen dioxide

    International Nuclear Information System (INIS)

    Chiari, Luca; Brunger, M J; Zecca, Antonio; García, Gustavo; Blanco, Francisco

    2013-01-01

    Total cross section (TCS) measurements for positron scattering from nitrogen dioxide (NO 2 ) are presented in the energy range 0.2–40 eV. The TCS, the elastic integral and differential cross sections, and the integral cross section accounting of all the inelastic processes (including positronium formation) have also been computed using the independent atom model with screening corrected additivity rule (IAM-SCAR) for incident energies from 1 to 1000 eV. A qualitative level of agreement is found between the present TCS experiment and theory at the common energies. As no previous measurements or calculations for positron–NO 2  scattering exist in the literature, we also computed the TCS for electron collisions with NO 2  employing the IAM-SCAR method. A comparison of those results to the present positron cross sections and the earlier electron-impact data and calculations is provided. To investigate the role that chemical substitution plays in positron scattering phenomena, we also compare the present positron–NO 2  data with the TCSs measured at the University of Trento for positron scattering from N 2 O and CO 2 . (paper)

  17. Introduction of spectroscopic photoemission and low energy electron microscope in SPring-8

    International Nuclear Information System (INIS)

    Guo, FangZhun; Kobayashi, Keisuke; Kinoshita, Toyohiko

    2005-01-01

    An upright configuration SPELEEM (Spectroscopic PhotoEmission and Low Energy Electron Microscope) has been introduced in SPring-8 in the framework of the nanotechnology support project of Ministry of Education, Culture, Sport, Science and Technology (MEXT), Japan. SPELEEM combines microscopy, spectroscopy and diffraction in one system, which allows a comprehensive characterization of the specimen. The combination of SPELEEM and polarized (circularly or linearly) soft X-rays in SPring-8 is expected to realize the highest performance. The characteristics of SPELEEM and typical results, for example nano-XANES (X-ray absorption near edge structure) of Fe oxide on Fe(100) surface, nano-XPS (X-ray photoemission spectroscopy) of indium (In) on Si(111) and antiferro-magnetic domain structure images of NiO(001) single crystal, are reported. (author)

  18. New insights in low-energy electron-fullerene interactions

    Science.gov (United States)

    Msezane, Alfred Z.; Felfli, Zineb

    2018-03-01

    The robust Regge-pole methodology has been used to probe for long-lived metastable anionic formation in Cn (n = 20, 24, 26, 28, 44, 70, 92 and 112) through the calculated electron elastic scattering total cross sections (TCSs). All the TCSs are found to be characterized by Ramsauer-Townsend minima, shape resonances and dramatically sharp resonances manifesting metastable anionic formation during the collisions. The energy positions of the anionic ground states resonances are found to match the measured electron affinities (EAs). We also investigated the size-effect through the correlation and polarization induced metastable resonances as the fullerene size varied from C20 through C112. The C20 TCSs exhibit atomic behavior while the C112 TCSs demonstrate strong departure from atomic behavior attributed to the size effect. Surprisingly C24 is found to have the largest EA among the investigated fullerenes making it suitable for use in organic solar cells and nanocatalysis.

  19. Solving complex and disordered surface structures with electron diffraction

    International Nuclear Information System (INIS)

    Van Hove, M.A.

    1987-10-01

    The past of surface structure determination with low-energy electron diffraction (LEED) will be briefly reviewed, setting the stage for a discussion of recent and future developments. The aim of these developments is to solve complex and disordered surface structures. Some efficient solutions to the theoretical and experimental problems will be presented. Since the theoretical problems dominate, the emphasis will be on theoretical approaches to the calculation of the multiple scattering of electrons through complex and disordered surfaces. 49 refs., 13 figs., 1 tab

  20. Coherent properties of a tunable low-energy electron-matter-wave source

    Science.gov (United States)

    Pooch, A.; Seidling, M.; Kerker, N.; Röpke, R.; Rembold, A.; Chang, W. T.; Hwang, I. S.; Stibor, A.

    2018-01-01

    A general challenge in various quantum experiments and applications is to develop suitable sources for coherent particles. In particular, recent progress in microscopy, interferometry, metrology, decoherence measurements, and chip-based applications rely on intensive, tunable, coherent sources for free low-energy electron-matter waves. In most cases, the electrons get field emitted from a metal nanotip, where its radius and geometry toward a counter electrode determines the field distribution and the emission voltage. A higher emission is often connected to faster electrons with smaller de Broglie wavelengths, requiring larger pattern magnification after matter-wave diffraction or interferometry. This can be prevented with a well-known setup consisting of two counter electrodes that allow independent setting of the beam intensity and velocity. However, it needs to be tested if the coherent properties of such a source are preserved after the acceleration and deceleration of the electrons. Here, we study the coherence of the beam in a biprism interferometer with a single atom tip electron field emitter if the particle velocity and wavelength varies after emission. With a Wien filter measurement and a contrast correlation analysis we demonstrate that the intensity of the source at a certain particle wavelength can be enhanced up to a factor of 6.4 without changing the transverse and longitudinal coherence of the electron beam. In addition, the energy width of the single atom tip emitter was measured to be 377 meV, corresponding to a longitudinal coherence length of 82 nm. The design has potential applications in interferometry, microscopy, and sensor technology.

  1. Utilization of bio-resources by low energy electron beam

    International Nuclear Information System (INIS)

    Kume, Tamikazu

    2003-01-01

    Utilization of bio-resources by radiation has been investigated for recycling the natural resources and reducing the environmental pollution. Polysaccharides such as chitosan and sodium alginate were easily degraded by irradiation and induced various kinds of biological activities, i.g. anti-microbial activity, promotion of plant growth, suppression of heavy metal stress, phytoalexins induction. Radiation degraded chitosan was effective to enhance the growth of plants in tissue culture. It was demonstrated that the liquid sample irradiation system using low energy EB was effective for the preparation of degraded polysaccharides. Methylcellulose (MC) can be crosslinked under certain radiation condition as same as carboxymethylcellulose (CMC) and produced the biodegradable hydrogel for medical and agricultural use. Treatment of soybean seeds by low energy EB enhanced the growth and the number of rhizobia on the root. (author)

  2. In situ x-ray diffraction investigations during low energy ion nitriding of austenitic stainless steel grade 1.4571

    International Nuclear Information System (INIS)

    Manova, D; Mändl, S; Gerlach, J W; Hirsch, D; Neumann, H; Rauschenbach, B

    2014-01-01

    Insertion of nitrogen into austenitic stainless steel leads to anomalously fast nitrogen diffusion and the formation of an expanded face-centred cubic phase which is known to contain a large amount of mechanical stress. In situ x-ray diffraction (XRD) measurements during low energy nitrogen ion implantation into steel 316Ti at 300–550 °C allow a direct view into diffusion and phase formation. While the layer growth is directly observable from the decreasing substrate reflection intensity, the time evolution of the intensities for the expanded phase reflection is much more complex: several mechanisms including at least formation and annealing of defects, twinning, reduction of the crystal symmetry, or grain rotation may be active inside the expanded phase, besides the thermally activated decay of the metastable expanded phase. This locally varying coherence length or scattering intensity from the expanded phase is furthermore a function of temperature and time, additionally complicating the deconvolution of XRD spectra for stress and concentration gradients. As no concise modelling of this coherence length is possible at present, a simple qualitative model assuming a dependence of the scattering intensity on the depth, influence by stress and plastic flow during the nitriding process is proposed for understanding the underlying processes. (paper)

  3. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gazder, Azdiar A., E-mail: azdiar@uow.edu.au [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Al-Harbi, Fayez; Spanke, Hendrik Th. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Mitchell, David R.G. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Pereloma, Elena V. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia)

    2014-12-15

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. - Highlights: • Multi-condition segmentation of austenite, martensite, polygonal ferrite and ferrite in bainite. • Ferrites in granular bainite and bainitic ferrite segmented by variation in relative carbon counts. • Carbon partitioning during growth explains variation in carbon content of ferrites in bainites. • Developed EBSD image processing tools can be applied to the microstructures of a variety of alloys. • EBSD-based segmentation procedure verified by correlative TEM results.

  4. Electrostatic electron cyclotron waves generated by low-energy electron beams

    Czech Academy of Sciences Publication Activity Database

    Menietti, J. D.; Santolík, Ondřej; Scudder, J. D.; Pickett, J. S.; Gurnett, D. A.

    2002-01-01

    Roč. 107, A10, 1285 (2002), s. SMP 8-1-8-11, doi: 10.1029/2001JA009223 ISSN 0148-0227 R&D Projects: GA ČR GA205/01/1064 Grant - others:NASA(US) NAG5-7943; NASA(US) NAG5-9561; NASA(US) NAG5-8119 Institutional research plan: CEZ:AV0Z3042911; CEZ:MSM 113200004 Keywords : low-energy electron beams * cyclotron frequency Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.245, year: 2002

  5. Future of Electron Scattering and Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Ernest [GE Global Research, Niskayuna, New York (United States); Stemmer, Susanne [Univ. of California, Santa Barbara, CA (United States); Zheng, Haimei [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zhu, Yimei [Brookhaven National Lab. (BNL), Upton, NY (United States); Maracas, George [Dept. of Energy (DOE), Washington DC (United States). Office of Science

    2014-02-25

    The ability to correlate the atomic- and nanoscale-structure of condensed matter with physical properties (e.g., mechanical, electrical, catalytic, and optical) and functionality forms the core of many disciplines. Directing and controlling materials at the quantum-, atomic-, and molecular-levels creates enormous challenges and opportunities across a wide spectrum of critical technologies, including those involving the generation and use of energy. The workshop identified next generation electron scattering and diffraction instruments that are uniquely positioned to address these grand challenges. The workshop participants identified four key areas where the next generation of such instrumentation would have major impact: A – Multidimensional Visualization of Real Materials B – Atomic-scale Molecular Processes C – Photonic Control of Emergence in Quantum Materials D – Evolving Interfaces, Nucleation, and Mass Transport Real materials are comprised of complex three-dimensional arrangements of atoms and defects that directly determine their potential for energy applications. Understanding real materials requires new capabilities for three-dimensional atomic scale tomography and spectroscopy of atomic and electronic structures with unprecedented sensitivity, and with simultaneous spatial and energy resolution. Many molecules are able to selectively and efficiently convert sunlight into other forms of energy, like heat and electric current, or store it in altered chemical bonds. Understanding and controlling such process at the atomic scale require unprecedented time resolution. One of the grand challenges in condensed matter physics is to understand, and ultimately control, emergent phenomena in novel quantum materials that necessitate developing a new generation of instruments that probe the interplay among spin, charge, orbital, and lattice degrees of freedom with intrinsic time- and length-scale resolutions. Molecules and soft matter require imaging and

  6. Three-dimensional characterization of bainitic microstructures in low-carbon high-strength low-alloy steel studied by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Kang, J.S.; Seol, Jae-Bok; Park, C.G.

    2013-01-01

    We investigated the microstructural evolution of high strength low alloy steel, Fe–2.0Mn–0.15Si–0.05C (wt.%), by varying the continuous cooling rates from 1 K/s to 50 K/s using three-dimensional electron backscatter diffraction and transmission electron microscopy. Granular bainitic microstructure was prevalent under a slow cooling rate of 1–10 K/s, while lath-type bainite was dominant at a high cooling rate of 50 K/s. The acicular ferrite that was the major microstructure under the intermediate ranges of cooling rates between 10 K/s and 30 K/s was tangled with each other, leading to a three-dimensional interwoven structure with highly misoriented grains. Because of the formation of three-dimensional structures, we propose that the terms “acicular ferrite” and “bainitic ferrite,” which are currently used in steel, be replaced by the terms “interwoven acicular bainite” and “lath bainite,” respectively. Moreover, we also confirmed that the cooling rate is an important factor in determining whether bainitic microstructures occur in the form of granular bainite, interwoven bainite, or lath bainite. - Highlights: • The morphology of bainitic grains was characterized by 3D-EBSD. • The ‘interwoven bainite’ and ‘lath bainite’ were suggested. • Interwoven bainite consisted of lenticular plates that were interlinked in 3D regime. • The packets of lath bainite were aligned in a specific direction

  7. Three-dimensional characterization of bainitic microstructures in low-carbon high-strength low-alloy steel studied by electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Kang, J.S. [Department of Materials Science and Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Technical Research Laboratories, POSCO, Pohang 790-300 (Korea, Republic of); Seol, Jae-Bok, E-mail: j.seol@mpie.de [Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Park, C.G. [Department of Materials Science and Engineering, POSTECH, Pohang 790-784 (Korea, Republic of)

    2013-05-15

    We investigated the microstructural evolution of high strength low alloy steel, Fe–2.0Mn–0.15Si–0.05C (wt.%), by varying the continuous cooling rates from 1 K/s to 50 K/s using three-dimensional electron backscatter diffraction and transmission electron microscopy. Granular bainitic microstructure was prevalent under a slow cooling rate of 1–10 K/s, while lath-type bainite was dominant at a high cooling rate of 50 K/s. The acicular ferrite that was the major microstructure under the intermediate ranges of cooling rates between 10 K/s and 30 K/s was tangled with each other, leading to a three-dimensional interwoven structure with highly misoriented grains. Because of the formation of three-dimensional structures, we propose that the terms “acicular ferrite” and “bainitic ferrite,” which are currently used in steel, be replaced by the terms “interwoven acicular bainite” and “lath bainite,” respectively. Moreover, we also confirmed that the cooling rate is an important factor in determining whether bainitic microstructures occur in the form of granular bainite, interwoven bainite, or lath bainite. - Highlights: • The morphology of bainitic grains was characterized by 3D-EBSD. • The ‘interwoven bainite’ and ‘lath bainite’ were suggested. • Interwoven bainite consisted of lenticular plates that were interlinked in 3D regime. • The packets of lath bainite were aligned in a specific direction.

  8. RF emittance in a low energy electron linear accelerator

    Science.gov (United States)

    Sanaye Hajari, Sh.; Haghtalab, S.; Shaker, H.; Kelisani, M. Dayyani

    2018-04-01

    Transverse beam dynamics of an 8 MeV low current (10 mA) S-band traveling wave electron linear accelerator has been studied and optimized. The main issue is to limit the beam emittance, mainly induced by the transverse RF forces. The linac is being constructed at Institute for Research in Fundamental Science (IPM), Tehran Iran Labeled as Iran's First Linac, nearly all components of this accelerator are designed and constructed within the country. This paper discusses the RF coupler induced field asymmetry and the corresponding emittance at different focusing levels, introduces a detailed beam dynamics design of a solenoid focusing channel aiming to reduce the emittance growth and studies the solenoid misalignment tolerances. In addition it has been demonstrated that a prebuncher cavity with appropriate parameters can help improving the beam quality in the transverse plane.

  9. Surface modification of TA2 pure titanium by low energy high current pulsed electron beam treatments

    International Nuclear Information System (INIS)

    Gao Yukui

    2011-01-01

    Surface integrity changes of TA2 pure titanium including surface topography, microstructure and nanohardness distribution along surface layer were investigated by different techniques of low energy high current pulsed electron beam treatments (LEHCPEBTs). The surface topography was characterized by SEM. Moreover, the TEM observation and X-ray diffraction analysis were performed to reveal the surface modification mechanism of TA2 pure titanium by LEHCPEBTs. The surface roughness was modified by electron beam treatment and the polishing mechanism was analyzed by studying the cross section microstructure of electron beam treated specimens by SEM and TEM. The results show that the surface finish obtains good polishing quality and there is no phase transformation but the dislocations by LEHCPEBT. Furthermore, the nanohardness in the surface modified layer is improved. The remelt and fine-grain microstructure of surface layer caused by LEHCPEBTs are the main polishing mechanism and the reason of modification of surface topography and the increment in nanohardness is mainly due to the dislocations and fine grains in the modified layer induced by LEHCPEBT.

  10. Atomic effects of electrons and protons at low energies

    International Nuclear Information System (INIS)

    Hippler, R.

    1985-01-01

    Some aspects of electronic and atomic collisions are discussed. Impact ionization by electrons and protons, and electron bremsstrahlung processes are considered in some detail. Emphasis is also given to (uncorrelated and correlated) many-electron processes, which are of particular importance in collisions of highly-charged ions with atoms. 84 refs., 15 figs

  11. Method for controlling low-energy high current density electron beams

    International Nuclear Information System (INIS)

    Lee, J.N.; Oswald, R.B. Jr.

    1977-01-01

    A method and an apparatus for controlling the angle of incidence of low-energy, high current density electron beams are disclosed. The apparatus includes a current generating diode arrangement with a mesh anode for producing a drifting electron beam. An auxiliary grounded screen electrode is placed between the anode and a target for controlling the average angle of incidence of electrons in the drifting electron beam. According to the method of the present invention, movement of the auxiliary screen electrode relative to the target and the anode permits reliable and reproducible adjustment of the average angle of incidence of the electrons in low energy, high current density relativistic electron beams

  12. A permanent magnet electron beam spread system used for a low energy electron irradiation accelerator

    International Nuclear Information System (INIS)

    Huang Jiang; Xiong Yongqian; Chen Dezhi; Liu Kaifeng; Yang Jun; Li Dong; Yu Tiaoqin; Fan Mingwu; Yang Bo

    2014-01-01

    The development of irradiation processing industry brings about various types of irradiation objects and expands the irradiation requirements for better uniformity and larger areas. This paper proposes an innovative design of a permanent magnet electron beam spread system. By clarifying its operation principles, the author verifies the feasibility of its application in irradiation accelerators for industrial use with the examples of its application in electron accelerators with energy ranging from 300 keV to 1 MeV. Based on the finite element analyses of electromagnetic fields and the charged particle dynamics, the author also conducts a simulation of electron dynamics in magnetic field on a computer. The results indicate that compared with the traditional electron beam scanning system, this system boosts the advantages of a larger spread area, non-power supply, simple structure and low cost, etc., which means it is not only suitable for the irradiation of objects with the shape of tubes, strips and panels, but can also achieve a desirable irradiation performance on irregular constructed objects of large size. (authors)

  13. DNA comet assay for rice seeds treated with low energy electrons ('soft-electrons')

    International Nuclear Information System (INIS)

    Todoriki, Setsuko; Hayashi, Toru

    1999-01-01

    As rice seeds are sometimes contaminated with phytopathogenic organisms such as blast disease fungi and nematodes, a novel non-chemical disinfection method for rice seeds is highly required. In order to develop a disinfection method, the effect of low energy electron ('soft-electrons') on seed DNA was examined by using the neutral comet assay. Rice seeds (whole grain) were treated with electrons of different acceleration voltages (180 kV to 1 MV) at a dose of 5 kGy. Nucleus suspensions were prepared from whole brown rice and subjected to electrophoresis. DNA from un-irradiated (control) seeds relaxed and produced comets with a short tail, most of the comets distributed within the range of comet length between 30 μm to 70 μm. In the case of seeds treated with electrons at acceleration voltages up to 190 kV, cells without seed coats were not damaged and the frequency histograms of comet length showed almost the same pattern as that for control. At acceleration voltages higher than 200 kV, the cells were distributed into two categories; DNA comets with a short tail (with little DNA damages, less than 70 μm in the comet length) and DNA comets with long tails (with sever strand breaks, more than 130 μm in the comet length). The ratios of damaged cells increased with increasing acceleration voltage. The growths of rice seedlings were not affected by the treatment with electrons at up to 200 kV. On the contrary, the cells of gamma-irradiated seed showed small variations in the comet length, and which were depending on radiation dose. The individual cells of gamma-irradiated seeds at 1 kGy showed shorter comet than the damaged cells with soft electron, seed treated with gamma rays (1-5 kGy) did not shoot nor root. (author)

  14. Track structure analysis illustrating the prominent role of low-energy electrons in radiobiological effects of low-LET radiations

    International Nuclear Information System (INIS)

    Nikjoo, H.; Goodhead, D.T.

    1991-01-01

    Monte Carlo track structure methods have been used to illustrate the importance of low-energy electrons produced by low-LET radiations. It is shown that these low-energy secondary electrons contribute substantially to the dose in all low-LET irradiations and are particularly efficient at producing highly localized clusters of atomic damage which may be responsible for a major part of the biological effectiveness of low-LET radiations. The data generated by Monte Carlo track structure techniques and by earlier semi-analytical methods based on the LET concept have been compared in terms of cumulative and differential fractions of total dose absorbed as a function of electron energy. The data show that low-energy secondary electrons account for up to nearly 50% of the total dose imparted to a medium when irradiated with electrons or photons. (author)

  15. eV-TEM: Transmission electron microscopy in a low energy cathode lens instrument

    Energy Technology Data Exchange (ETDEWEB)

    Geelen, Daniël, E-mail: geelen@physics.leidenuniv.nl [Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Thete, Aniket [Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Schaff, Oliver; Kaiser, Alexander [SPECS GmbH, Voltastrasse 5, D-13355 Berlin (Germany); Molen, Sense Jan van der [Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Tromp, Rudolf [IBM T.J. Watson Research Center, 1101 Kitchawan Road, P.O. Box 218, Yorktown Heights, NY 10598 (United States)

    2015-12-15

    We are developing a transmission electron microscope that operates at extremely low electron energies, 0–40 eV. We call this technique eV-TEM. Its feasibility is based on the fact that at very low electron energies the number of energy loss pathways decreases. Hence, the electron inelastic mean free path increases dramatically. eV-TEM will enable us to study elastic and inelastic interactions of electrons with thin samples. With the recent development of aberration correction in cathode lens instruments, a spatial resolution of a few nm appears within range, even for these very low electron energies. Such resolution will be highly relevant to study biological samples such as proteins and cell membranes. The low electron energies minimize adverse effects due to radiation damage. - Highlights: • We present a new way of performing low energy transmission electron microscopy in an aberration corrected LEEM/PEEM instrument. • We show a proof of principle where we measure transmitted electrons through a suspended graphene monolayer with a preliminary setup. • We present an improved setup design that provides better control of the incident electron beam.

  16. Treatment of foods with 'soft-electrons' (low-energy electrons)

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Toru [Japan International Research Center for Agricultural Sciences (JIRCAS), Tsukuba, Ibaraki (Japan); Todoriki, Setsuko [National Food Research Institute (NFRI), Tsukuba, Ibaraki (Japan)

    2003-02-01

    Electrons with energies of 300 keV or lower were defined as soft-electrons'. Soft-electrons can eradicate microorganisms residing on the surface of grains, pulses, spices, dehydrated vegetables, tea leaves and seeds, and reduce their microbial loads to levels lower than 10 CFU/g with little quality deterioration. Soft-electrons can inactivate insect pests infesting grains and pulses and inhibit sprouting of potatoes. (author)

  17. Treatment of foods with 'soft-electrons' (low-energy electrons)

    International Nuclear Information System (INIS)

    Hayashi, Toru; Todoriki, Setsuko

    2003-01-01

    Electrons with energies of 300 keV or lower were defined as soft-electrons'. Soft-electrons can eradicate microorganisms residing on the surface of grains, pulses, spices, dehydrated vegetables, tea leaves and seeds, and reduce their microbial loads to levels lower than 10 CFU/g with little quality deterioration. Soft-electrons can inactivate insect pests infesting grains and pulses and inhibit sprouting of potatoes. (author)

  18. Damage of DNA by Low Energy Electrons (< 3 eV)

    International Nuclear Information System (INIS)

    Bald, Ilko; Illenberger, Eugen; Kopyra, Janina

    2012-01-01

    Recent experiments on low energy electron attachment to DNA and its components in the condensed phase and in the gas phase are reviewed and analysed. From different condensed phase experiments the sensitivity of DNA towards low energy electrons is well documented and strand breaks in DNA are observed at subexcitation energies (< 3 eV) and also in ultrafast electron transfer experiments involving electrons in presolvated states. Gas phase experiments indicate that all building blocks of DNA (the nucleobases, the sugar and the phosphate moiety) undergo resonant dissociative electron attachment (DEA) in the subexcitation regime which may ultimately lead to strand breaks. From very recent gas phase experiments on an entire nucleotide it can be concluded that most strand breaks result from direct electron attachment to the DNA backbone, but also initial electron capture by the nucleobase following electron transfer to the backbone contributes.

  19. Surface influence on convoy electron emission at low energies

    International Nuclear Information System (INIS)

    Sanchez, E.A.

    1988-01-01

    It is studied the dependence of the production of convoy electrons induced by H + - 60 KeV with surface conditions of Al targets by in situ deposition of Na and O. The conclusion is that convoy electron production increases with the work function of the surface. (A.C.A.S.) [pt

  20. Monte Carlo simulation of energy deposition by low-energy electrons in molecular hydrogen

    Science.gov (United States)

    Heaps, M. G.; Furman, D. R.; Green, A. E. S.

    1975-01-01

    A set of detailed atomic cross sections has been used to obtain the spatial deposition of energy by 1-20-eV electrons in molecular hydrogen by a Monte Carlo simulation of the actual trajectories. The energy deposition curve (energy per distance traversed) is quite peaked in the forward direction about the entry point for electrons with energies above the threshold of the electronic states, but the peak decreases and broadens noticeably as the electron energy decreases below 10 eV (threshold for the lowest excitable electronic state of H2). The curve also assumes a very symmetrical shape for energies below 10 eV, indicating the increasing importance of elastic collisions in determining the shape of the curve, although not the mode of energy deposition.

  1. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    Energy Technology Data Exchange (ETDEWEB)

    Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie [Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse, France and Fondation STAE, 4 allee Emile Monso, BP 84234-31432, Toulouse Cedex 4 (France); Onera, DESP, 2 Avenue Edouard Belin, 31400 Toulouse (France)

    2010-09-15

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40{+-}1 eV.

  2. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    International Nuclear Information System (INIS)

    Tondu, Thomas; Belhaj, Mohamed; Inguimbert, Virginie

    2010-01-01

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40±1 eV.

  3. Ultrafast electron diffraction using an ultracold source

    Directory of Open Access Journals (Sweden)

    M. W. van Mourik

    2014-05-01

    Full Text Available The study of structural dynamics of complex macromolecular crystals using electrons requires bunches of sufficient coherence and charge. We present diffraction patterns from graphite, obtained with bunches from an ultracold electron source, based on femtosecond near-threshold photoionization of a laser-cooled atomic gas. By varying the photoionization wavelength, we change the effective source temperature from 300 K to 10 K, resulting in a concomitant change in the width of the diffraction peaks, which is consistent with independently measured source parameters. This constitutes a direct measurement of the beam coherence of this ultracold source and confirms its suitability for protein crystal diffraction.

  4. Novel approaches to study low-energy electron-induced damage to DNA oligonucleotides

    International Nuclear Information System (INIS)

    Rackwitz, Jenny; Bald, Ilko; Ranković, Miloš Lj; Milosavljević, Aleksandar R

    2015-01-01

    The novel approach of DNA origami structures as templates for precise quantification of various well- defined oligonucleotides provides the opportunity to determine the sensitivity of complex DNA sequences towards low-energy electrons. (paper)

  5. Precision shape modification of nanodevices with a low-energy electron beam

    Science.gov (United States)

    Zettl, Alex; Yuzvinsky, Thomas David; Fennimore, Adam

    2010-03-09

    Methods of shape modifying a nanodevice by contacting it with a low-energy focused electron beam are disclosed here. In one embodiment, a nanodevice may be permanently reformed to a different geometry through an application of a deforming force and a low-energy focused electron beam. With the addition of an assist gas, material may be removed from the nanodevice through application of the low-energy focused electron beam. The independent methods of shape modification and material removal may be used either individually or simultaneously. Precision cuts with accuracies as high as 10 nm may be achieved through the use of precision low-energy Scanning Electron Microscope scan beams. These methods may be used in an automated system to produce nanodevices of very precise dimensions. These methods may be used to produce nanodevices of carbon-based, silicon-based, or other compositions by varying the assist gas.

  6. Low energy electron beam processing in Europe at the end of the 20th century

    International Nuclear Information System (INIS)

    Lauppi, U.V.

    1999-01-01

    Overview of low energy electron beam processing in Europe was presented. The presentation contained the following topics: the early installations, years of growth, stagnation, status 1999 and the future of this technology

  7. Studies on low energy ion-atom collisions by means of electron-spectroscopy

    International Nuclear Information System (INIS)

    Hirosi Suzuki

    1991-01-01

    The typical results of studies on autoionization processes produced by low energy ion-atom collisions are given by means of the ejected electron spectroscopy, which have been performed by Atomic Physics Group of Sophia University

  8. Beam line design for a low energy electron beam

    International Nuclear Information System (INIS)

    Arvind Kumar; Mahadevan, S.

    2002-01-01

    The design of a beam line for transport of a 70 keV electron beam from a thermionic gun to the Plane Wave Transformer (PWT) linac incorporating two solenoid magnets, a beam profile monitor and drift sections is presented. We used beam dynamics codes EGUN, PARMELA and compare simulated results with analytical calculations. (author)

  9. Examination of Graphene in a Scanning Low Energy Electron Microscope

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Mikmeková, Eliška; Frank, Luděk

    2015-01-01

    Roč. 21, S3 (2015), s. 29-30 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : graphene * LEEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.730, year: 2015

  10. Low-energy electron emitters for targeted radiotherapy of small tumours

    International Nuclear Information System (INIS)

    Bernhardt, Peter; Forssell-Aronsson, Eva; Jacobsson, Lars; Skarnemark, Gunnar

    2001-01-01

    The possibility of using electron emitters to cure a cancer with metastatic spread depends on the energy of the emitted electrons. Electrons with high energy will give a high, absorbed dose to large tumours, but the absorbed dose to small tumours or single tumour cells will be low, because the range of the electrons is too long. The fraction of energy absorbed within the tumour decreases with increasing electron energy and decreasing tumour size. For tumours smaller than 1 g, the tumour-to-normal-tissue mean absorbed dose-rate ratio, TND, will be low, e.g. for 131 I and 90 Y, because of the high energy of the emitted electrons. For radiotherapy of small tumours, radionuclides emitting charged particles with short ranges (a few m u m ) are required. A mathematical model was constructed to evaluate the relation between TND and electron energy, photon-to-electron energy ratio, p/e, and tumour size. Criteria for the selection of suitable radionuclides for the treatment of small tumours were defined based on the results of the TND model. In addition, the possibility of producing such radionuclides and their physical and chemical properties were evaluated. Based on the mathematical model, the energy of the emitted electrons should be = 40 keV for small tumours ( 58m Co, 103m Rh, 119 Sb, 161 Ho, and 189m Os. All of these nuclides by internal transition or electron capture, which yields conversion and Auger electrons, and it should be possible to produce most of them in therapeutic amounts. The five low-energy electron-emitting radionuclides identified may be relevant in the radiation treatment of small tumours, especially if bound to internalizing radiopharmaceuticals

  11. Intensive beam dosimetry of accelerated electrons of low energy

    International Nuclear Information System (INIS)

    Oproiu, C.

    1984-01-01

    Dosimetric control of electron beams ranging between 0.3 MeV and 10 MeV is treated using proper dosimetric methods relying on calorimetry, Tricke chemical solution, dosimetric film of cellulose triacetate. Proper methods are pointed out for measurements in inhomogeneous fields, bringing into evidence the results obtained in deep dose distributions and on the surface of irradiated material. A measuring method of dose distribution in depth by means of an assembly with calorimetric elements, as well as a practical method to pointing out dose distribution and equidose curves along the depth of irradiated electric cable depth are presented. In order to find out the main sizes of accelerated electron beam one uses proper devices relying on Faraday cylinder, total absorption calorimeter, ionization chambers. (author)

  12. Construction of energy loss function for low-energy electrons in helium

    Energy Technology Data Exchange (ETDEWEB)

    Dayashankar, [Bhabha Atomic Research Centre, Bombay (India). Div. of Radiation Protection

    1976-02-01

    The energy loss function for electrons in the energy range from 50 eV to 1 keV in helium gas has been constructed by considering separately the energy loss in overcoming the ionization threshold, the loss manifested as kinetic energy of secondary electrons and the loss in the discrete state excitations. This has been done by utilizing recent measurements of Opal et al. on the energy spectrum of secondary electrons and incorporating the experimental data on cross sections for twenty-four excited states. The present results of the energy loss function are in good agreement with the Bethe formula for energies above 500 eV. For lower energies, where the Bethe formula is not applicable, the present results should be particularly useful.

  13. rf streak camera based ultrafast relativistic electron diffraction.

    Science.gov (United States)

    Musumeci, P; Moody, J T; Scoby, C M; Gutierrez, M S; Tran, T

    2009-01-01

    We theoretically and experimentally investigate the possibility of using a rf streak camera to time resolve in a single shot structural changes at the sub-100 fs time scale via relativistic electron diffraction. We experimentally tested this novel concept at the UCLA Pegasus rf photoinjector. Time-resolved diffraction patterns from thin Al foil are recorded. Averaging over 50 shots is required in order to get statistics sufficient to uncover a variation in time of the diffraction patterns. In the absence of an external pump laser, this is explained as due to the energy chirp on the beam out of the electron gun. With further improvements to the electron source, rf streak camera based ultrafast electron diffraction has the potential to yield truly single shot measurements of ultrafast processes.

  14. Modulation transfer function and detective quantum efficiency of electron bombarded charge coupled device detector for low energy electrons

    International Nuclear Information System (INIS)

    Horacek, Miroslav

    2005-01-01

    The use of a thinned back-side illuminated charge coupled device chip as two-dimensional sensor working in direct electron bombarded mode at optimum energy of the incident signal electrons is demonstrated and the measurements of the modulation transfer function (MTF) and detective quantum efficiency (DQE) are described. The MTF was measured for energy of electrons 4 keV using an edge projection method and a stripe projection method. The decrease of the MTF for a maximum spatial frequency of 20.8 cycles/mm, corresponding to the pixel size 24x24 μm, is 0.75≅-2.5 dB, and it is approximately the same for both horizontal and vertical directions. DQE was measured using an empty image and the mixing factor method. Empty images were acquired for energies of electrons from 2 to 5 keV and for various doses, ranging from nearly dark image to a nearly saturated one. DQE increases with increasing energy of bombarded electrons and reaches 0.92 for electron energy of 5 keV. For this energy the detector will be used for the angle- and energy-selective detection of signal electrons in the scanning low energy electron microscope

  15. Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

    Science.gov (United States)

    Chen, Cheng; Fan, Xue; Diao, Dongfeng

    2016-10-01

    We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp2 nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp2 nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp2 nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

  16. Study of the local structure of binary surfaces by electron diffraction (XPS, LEED)

    OpenAIRE

    Gereová, Katarína

    2006-01-01

    Study of local structure of binary surface with usage of ultra-thin film of cerium deposited on a Pd (111) single-crystal surface is presented. X-ray photoelectron spectroscopy and diffraction (XPS, XPD), angle resolved UV photoemission spectroscopy (ARUPS) and low energy electron diffraction (LEED) was used for our investigations. LEED and X-ray excited photoemission intensities results represent a surface-geometrical structure. As well, mapping of ultra-violet photoelectron intensities as a...

  17. The energy broadening resulting from electron stripping process of a low energy Au- beam

    International Nuclear Information System (INIS)

    Taniike, Akira; Sasao, Mamiko; Hamada, Yasuji; Fujita, Junji; Wada, Motoi.

    1994-12-01

    Energy loss spectra of Au + ions produced from Au - ions by electron stripping in He, Ar, Kr and Xe have been measured in the impact energy range of 24-44 keV. The energy broadening of the Au + beam increases as the beam energy increases, and the spectrum shows a narrower energy width for heavy target atoms. The dependence of the spectrum width upon the beam energy and that upon the target mass are well described by the calculation based on the unified potential and semi-classical internal energy transfer model of Firsov's. (author)

  18. Success and prospects for low energy, self-shielded electron beam accelerators

    International Nuclear Information System (INIS)

    Laeuppi, U.V.

    1988-01-01

    The advantages of self-shielded, low energy, electron beam accelerators for electron beam processing are described. Applications of these accelerators for cross-linking plastic films, drying of coated materials and printing inks and for curing processes are discussed. (U.K.)

  19. A comparison of the microbicidal effectiveness of gamma rays and high and low energy electron radiations

    International Nuclear Information System (INIS)

    Tallentire, Alan; Miller, Arne; Helt-Hansen, Jakob

    2010-01-01

    The radiation response of spores of Bacillus pumilus were examined for irradiation with cobalt 60 photons, 10 MeV electrons and low energy electrons at 100 and 80 keV. The responses were found to be the same for all types of radiation within the measurement uncertainties and were also in agreement with a previously published value.

  20. A method of imaging ultrathin foils with very low energy electrons

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Hovorka, Miloš; Frank, Luděk

    2012-01-01

    Roč. 119, AUG (2012), s. 79-81 ISSN 0304-3991 R&D Projects: GA AV ČR IAA100650902; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : very low energy STEM * penetration of very slow electrons * graphene Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.470, year: 2012

  1. A comparison of the microbicidal effectiveness of gamma rays and high and low energy electron radiations

    DEFF Research Database (Denmark)

    Tallentire, A.; Miller, Arne; Helt-Hansen, Jakob

    2010-01-01

    The radiation response of spores of Bacillus pumilus were examined for irradiation with cobalt 60 photons, 10 MeV electrons and low energy electrons at 100 and 80 keV. The responses were found to be the same for all types of radiation within the measurement uncertainties and were also in agreement...... with a previously published value....

  2. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

    Science.gov (United States)

    Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

    2017-07-21

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  3. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

    KAUST Repository

    Govyadinov, Alexander A.

    2017-07-14

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  4. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

    KAUST Repository

    Govyadinov, Alexander A.; Konečná , Andrea; Chuvilin, Andrey; Vé lez, Saü l; Dolado, Irene; Nikitin, Alexey Y.; Lopatin, Sergei; Casanova, Fè lix; Hueso, Luis E.; Aizpurua, Javier; Hillenbrand, Rainer

    2017-01-01

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  5. Energy-Filtered Tunnel Transistor: A New Device Concept Toward Extremely-Low Energy Consumption Electronics

    Science.gov (United States)

    2015-12-17

    other provision of law , no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a...excellent agreement with experimental findings. The energy filtering has been applied to single-electron transport and clear Coulomb staircases and... Coulomb oscillations have been demonstrated at room temperature. A new architecture of energy-filtered cold electron transistors has been designed and

  6. Generation and transportation of low-energy, high-current electron beams

    International Nuclear Information System (INIS)

    Ozur, G.E.; Proskurovskij, D.I.; Nazarov, D.S.

    1996-01-01

    Experimental data on the production of low-energy, high-current electron beams in a plasma-filled diode are presented. The highest beam energy density achieved is about 40 J/cm 2 , which makes it possible to treat materials in the mode of intense evaporation of the surface layer. It was shown that the use of a hollow cathode improves the beam homogeneity. The feasibility was demonstrated of the production of low-energy high-current electron beams in a gun with plasma anode based on the use of a reflective discharge. (author). 6 figs., 6 refs

  7. Generation and transportation of low-energy, high-current electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Ozur, G E; Proskurovskij, D I; Nazarov, D S [Russian Academy of Sciences, Tomsk (Russian Federation). Institute of High Current Electronics

    1997-12-31

    Experimental data on the production of low-energy, high-current electron beams in a plasma-filled diode are presented. The highest beam energy density achieved is about 40 J/cm{sup 2}, which makes it possible to treat materials in the mode of intense evaporation of the surface layer. It was shown that the use of a hollow cathode improves the beam homogeneity. The feasibility was demonstrated of the production of low-energy high-current electron beams in a gun with plasma anode based on the use of a reflective discharge. (author). 6 figs., 6 refs.

  8. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr_2FeMoO_6 using electron energy-loss magnetic chiral dichroism

    International Nuclear Information System (INIS)

    Wang, Z.C.; Zhong, X.Y.; Jin, L.; Chen, X.F.; Moritomo, Y.; Mayer, J.

    2017-01-01

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr_2FeMoO_6, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. - Highlights: • We demonstrate how to choose the optimal experimental conditions by using dynamical diffraction calculations in Sr_2FeMoO_6. • With optimized diffraction conditions, the signal-to-noise ratio of experimental EMCD spectra has been significantly improved. • We have determined orbital to spin magnetic moment ratio of Sr_2FeMoO_6 quantitatively. • We have discussed the effects of dynamical diffraction conditions on the error bar of quantitative magnetic parameters.

  9. Low-energy electron scattering from pyrimidine: Similarities and differences with benzene

    Science.gov (United States)

    Jones, D. B.; Bellm, S. M.; Limão-Vieira, P.; Brunger, M. J.

    2012-05-01

    Differential cross sections for low-energy electron-impact excitation of the unresolved combinations of 23B2 + 21A1 and 31A1 + 21B2 electronic states of pyrimidine are reported. Comparisons are made with recent differential cross section measurements for the electron-impact excitation of the 1E1u and unresolved 1B1u + 3E2g electronic states of benzene [H. Kato, M. Hoshino, H. Tanaka, P. Limão-Vieira, O. Ingolfsson, L. Campbell, M.J. Brunger, J. Chem. Phys. 134 (2011) 134308.], in order to evaluate the nature of electron impact π-π∗ transitions in aromatic species.

  10. Low-energy particle experiments-electron analyzer (LEPe) onboard the Arase spacecraft

    Science.gov (United States)

    Kazama, Yoichi; Wang, Bo-Jhou; Wang, Shiang-Yu; Ho, Paul T. P.; Tam, Sunny W. Y.; Chang, Tzu-Fang; Chiang, Chih-Yu; Asamura, Kazushi

    2017-12-01

    In this report, we describe the low-energy electron instrument LEPe (low-energy particle experiments-electron analyzer) onboard the Arase (ERG) spacecraft. The instrument measures a three-dimensional distribution function of electrons with energies of ˜ 19 eV-19 keV. Electrons in this energy range dominate in the inner magnetosphere, and measurement of such electrons is important in terms of understanding the magnetospheric dynamics and wave-particle interaction. The instrument employs a toroidal tophat electrostatic energy analyzer with a passive 6-mm aluminum shield. To minimize background radiation effects, the analyzer has a background channel, which monitors counts produced by background radiation. Background counts are then subtracted from measured counts. Electronic components are radiation tolerant, and 5-mm-thick shielding of the electronics housing ensures that the total dose is less than 100 kRad for the one-year nominal mission lifetime. The first in-space measurement test was done on February 12, 2017, showing that the instrument functions well. On February 27, the first all-instrument run test was done, and the LEPe instrument measured an energy dispersion event probably related to a substorm injection occurring immediately before the instrument turn-on. These initial results indicate that the instrument works fine in space, and the measurement performance is good for science purposes.[Figure not available: see fulltext.

  11. A monochromatic, aberration-corrected, dual-beam low energy electron microscope.

    Science.gov (United States)

    Mankos, Marian; Shadman, Khashayar

    2013-07-01

    The monochromatic, aberration-corrected, dual-beam low energy electron microscope (MAD-LEEM) is a novel instrument aimed at imaging of nanostructures and surfaces at sub-nanometer resolution that includes a monochromator, aberration corrector and dual beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector utilizes an electron mirror with negative aberrations that can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies. Dual flood illumination eliminates charging generated when a conventional LEEM is used to image insulating specimens. MAD-LEEM is designed for the purpose of imaging biological and insulating specimens, which are difficult to image with conventional LEEM, Low-Voltage SEM, and TEM instruments. The MAD-LEEM instrument can also be used as a general purpose LEEM with significantly improved resolution. The low impact energy of the electrons is critical for avoiding beam damage, as high energy electrons with keV kinetic energies used in SEMs and TEMs cause irreversible change to many specimens, in particular biological materials. A potential application for MAD-LEEM is in DNA sequencing, which demands imaging techniques that enable DNA sequencing at high resolution and speed, and at low cost. The key advantages of the MAD-LEEM approach for this application are the low electron impact energies, the long read lengths, and the absence of heavy-atom DNA labeling. Image contrast simulations of the detectability of individual nucleotides in a DNA strand have been developed in order to refine the optics blur and DNA base contrast requirements for this application. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. NIST/Sandia/ICDD Electron Diffraction Database: A Database for Phase Identification by Electron Diffraction.

    Science.gov (United States)

    Carr, M J; Chambers, W F; Melgaard, D; Himes, V L; Stalick, J K; Mighell, A D

    1989-01-01

    A new database containing crystallographic and chemical information designed especially for application to electron diffraction search/match and related problems has been developed. The new database was derived from two well-established x-ray diffraction databases, the JCPDS Powder Diffraction File and NBS CRYSTAL DATA, and incorporates 2 years of experience with an earlier version. It contains 71,142 entries, with space group and unit cell data for 59,612 of those. Unit cell and space group information were used, where available, to calculate patterns consisting of all allowed reflections with d -spacings greater than 0.8 A for ~ 59,000 of the entries. Calculated patterns are used in the database in preference to experimental x-ray data when both are available, since experimental x-ray data sometimes omits high d -spacing data which falls at low diffraction angles. Intensity data are not given when calculated spacings are used. A search scheme using chemistry and r -spacing (reciprocal d -spacing) has been developed. Other potentially searchable data in this new database include space group, Pearson symbol, unit cell edge lengths, reduced cell edge length, and reduced cell volume. Compound and/or mineral names, formulas, and journal references are included in the output, as well as pointers to corresponding entries in NBS CRYSTAL DATA and the Powder Diffraction File where more complete information may be obtained. Atom positions are not given. Rudimentary search software has been written to implement a chemistry and r -spacing bit map search. With typical data, a full search through ~ 71,000 compounds takes 10~20 seconds on a PDP 11/23-RL02 system.

  13. Calculation of W for low energy electrons in tissue-equivalent gas. [<10 keV

    Energy Technology Data Exchange (ETDEWEB)

    Dayashankar, [Bhabha Atomic Research Centre, Bombay (India). Div. of Radiation Protection

    1977-11-01

    The mean energy expended per ion pair formed (W-value) in the tissue-equivalent gas for incident electrons of energy up to 10 keV has been calculated in the continuous slowing-down approximation. The effect of secondary and tertiary electrons has been considered by utilizing recent measurements of Opal et al., (1971, J. Chem. Phys., 55,4100) on the energy spectra of low-energy secondary electrons and the Mott formula for the spectra of high-energy secondaries. The results, which are provisional in nature due to the limitations on the accuracy of the input cross-section data and the neglect of the discrete nature of energy loss process, are compared with the available measurements.

  14. Dependence of electron inelastic mean free paths on electron energy and materials at low energy region, 1

    International Nuclear Information System (INIS)

    Tanuma, Shigeo; Powell, C.J.; Penn, D.R.

    1990-01-01

    We have proposed a general formula of electron inelastic mean free path (IMFP) to describe the calculated IMFPs over the 50-2000 eV energy range based on the Inokuti's modified Bethe formula for the inelastic scattering cross section. The IMFPs for 50-2000 eV electrons in 27 elements were calculated using Penn's algorithm. The IMFP dependence on electron energy in the range 50-200 eV varies considerably from material to material. These variations are associated with substantial differences in the electron energy-loss functions amongst the material. We also found that the modified Bethe formula by Inokuti could be fitted to the calculated IMFPs in the range 50-2000 eV within 3% relative error. (author)

  15. A low energy electron microscopy study of the initial growth, structure, and thermal stability of 4,4'-biphenyldicarboxylic acid domains on Cu(001)

    International Nuclear Information System (INIS)

    Khokhar, Fawad S.; Gastel, Raoul van; Schwarz, Daniel; Zandvliet, Harold J. W.; Poelsema, Bene

    2011-01-01

    The growth of 4,4 ' -biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene rings of adsorbed BDA are twisted along the molecular axis. Unconventional growth of the domains, followed by a second nucleation stage, is observed at room temperature. This unanticipated feature is attributed to the accumulation of stress in the islands. Ostwald ripening in the films and the decay of BDA domains at 448 K exhibits features that are consistent with diffusion limited behavior.

  16. A low energy electron microscopy study of the initial growth, structure, and thermal stability of 4,4{sup '}-biphenyldicarboxylic acid domains on Cu(001)

    Energy Technology Data Exchange (ETDEWEB)

    Khokhar, Fawad S.; Gastel, Raoul van; Schwarz, Daniel; Zandvliet, Harold J. W.; Poelsema, Bene [Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, NL-7500AE Enschede (Netherlands)

    2011-09-28

    The growth of 4,4{sup '}-biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene rings of adsorbed BDA are twisted along the molecular axis. Unconventional growth of the domains, followed by a second nucleation stage, is observed at room temperature. This unanticipated feature is attributed to the accumulation of stress in the islands. Ostwald ripening in the films and the decay of BDA domains at 448 K exhibits features that are consistent with diffusion limited behavior.

  17. Ab initio study of low-energy electron collisions with ethylene

    International Nuclear Information System (INIS)

    Trevisan, C.S.; Orel, A.E.; Rescigno, T.N.

    2003-01-01

    We present the results of an investigation of elastic electron scattering by ethylene C 2 H 4 with incident electron energies ranging from 0.5 to 20 eV, using the complex Kohn variational method. These fully ab initio calculations accurately reproduce experimental angular differential cross sections at energies below 3 eV. Low-energy electron scattering by ethylene is sensitive to the inclusion of electronic correlation and target-distortion effects. We therefore report results that describe the dynamic polarization of the target by the incident electron and involve calculations over a range of different geometries, including the effects of nuclear motion in the resonant 2 B 2g symmetry with an adiabatic nuclei treatment of the C-C stretch mode. The inclusion of dynamic polarization and the effect of nuclear motion are equally critical in obtaining accurate results. The calculated cross sections are compared with recent experimental measurements

  18. Positron annihilation induced Auger electron spectroscopy and its implementation at accelerator based low energy positron factories

    International Nuclear Information System (INIS)

    Weiss, A.; Koeymen, A.R.; Mehl, D.; Lee, K.H.; Yang Gimo; Jensen, K.

    1991-01-01

    Positron annihilation induced auger electron spectroscopy (PAES) makes use of a beam of low energy positrons to excite Auger transitions by annihilating core electrons. The large secondary electron background usually present in Auger spectra can be eliminated by setting the positron beam energy well below the Auger electron energy. This allows true Auger lineshapes to be obtained. Further, because the positron is localized just outside the surface before it annihilates, PAES is extremely sensitive to the topmost atomic layer. Recent PAES results obtained at the University of Texas at Arlington will be presented. In addition, the use of high resolution energy analyzers with multichannel particle detection schemes to prevent problems due to the high data rates associated with accelerator based positron beams will be discussed. (orig.)

  19. High-sensitivity visualization of localized electric fields using low-energy electron beam deflection

    Science.gov (United States)

    Jeong, Samuel; Ito, Yoshikazu; Edwards, Gary; Fujita, Jun-ichi

    2018-06-01

    The visualization of localized electronic charges on nanocatalysts is expected to yield fundamental information about catalytic reaction mechanisms. We have developed a high-sensitivity detection technique for the visualization of localized charges on a catalyst and their corresponding electric field distribution, using a low-energy beam of 1 to 5 keV electrons and a high-sensitivity scanning transmission electron microscope (STEM) detector. The highest sensitivity for visualizing a localized electric field was ∼0.08 V/µm at a distance of ∼17 µm from a localized charge at 1 keV of the primary electron energy, and a weak local electric field produced by 200 electrons accumulated on the carbon nanotube (CNT) apex can be visualized. We also observed that Au nanoparticles distributed on a CNT forest tended to accumulate a certain amount of charges, about 150 electrons, at a ‑2 V bias.

  20. The energy-deposition model. Electron loss of heavy ions in collisions with neutral atoms at low and intermediate energies

    International Nuclear Information System (INIS)

    Shevelko, V.P.; Litsarev, M.S.; Kato, D.; Tawara, H.

    2010-09-01

    Single- and multiple-electron loss processes in collisions of heavy many-electron ions (positive and negative) in collisions with neutral atoms at low and intermediate energies are considered using the energy-deposition model. The DEPOSIT computer code, created earlier to calculate electron-loss cross sections at high projectile energies, is extended for low and intermediate energies. A description of a new version of DEPOSIT code is given, and the limits of validity for collision velocity in the model are discussed. Calculated electron-loss cross sections for heavy ions and atoms (N + , Ar + , Xe + , U + , U 28+ , W, W + , Ge - , Au - ), colliding with neutral atoms (He, Ne, Ar, W) are compared with available experimental and theoretical data at energies E > 10 keV/u. It is found that in most cases the agreement between experimental data and the present model is within a factor of 2. Combining results obtained by the DEPOSIT code at low and intermediate energies with those by the LOSS-R code at high energies (relativistic Born approximation), recommended electron-loss cross sections in a wide range of collision energy are presented. (author)

  1. Wavelength dependence of momentum-space images of low-energy electrons generated by short intense laser pulses at high intensities

    International Nuclear Information System (INIS)

    Maharjan, C M; Alnaser, A S; Litvinyuk, I; Ranitovic, P; Cocke, C L

    2006-01-01

    We have measured momentum-space images of low-energy electrons generated by the interaction of short intense laser pulses with argon atoms at high intensities. We have done this over a wavelength range from 400 to 800 nm. The spectra show considerable structure in both the energy and angular distributions of the electrons. Some, but not all, energy features can be identified as multi-photon resonances. The angular structure shows a regularity which transcends the resonant structure and may be due instead to diffraction. The complexity of the results defies easy model-dependent interpretations and invites full solutions to Schroedinger's equation for these systems

  2. Low energy electron attachment to SF6 in N2, Ar, and Xe buffer gases

    International Nuclear Information System (INIS)

    Hunter, S.R.; Carter, J.G.; Christophorou, L.G.

    1989-01-01

    The electron attachment rate constants k/sub a/ for SF 6 have been measured in dilute mixtures of SF 6 in high pressure (>1 atm) N 2 , Ar, and Xe buffer gases at room temperature (T≅300 K) over a wide E/N range (electric field strength to gas number density ratio), corresponding to mean electron energies from near thermal electron energies (≅0.04 eV) to ≅4.3 eV. Particular attention has been paid to the effects of space charge distortion, molecular impurities, and changes in the electron energy distribution function on the measured electron attachment rate constant values at the lower E/N values in these mixtures. The present measured thermal electron attachment rate constants in SF 6 /N 2 and SF 6 /Xe gas mixtures are in excellent agreement with recent accurate measurements of these parameters in several SF 6 /buffer gas mixtures. At higher values, the present SF 6 /N 2 measurements are in fair agreement with previous measurements, while no previous measurements using Ar and Xe buffer gases have been published. These measurements have been used in numerical two term, spherical harmonic Boltzmann equation analyses of the electron motion in these gas mixtures to obtain the low energy ( 6 . The present derived electron attachment cross sections are compared with recently measured and derived nondissociative and dissociative electron attachment cross sections for SF 6

  3. Progress toward an aberration-corrected low energy electron microscope for DNA sequencing and surface analysis.

    Science.gov (United States)

    Mankos, Marian; Shadman, Khashayar; N'diaye, Alpha T; Schmid, Andreas K; Persson, Henrik H J; Davis, Ronald W

    2012-11-01

    Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel imaging technique aimed at high resolution imaging of macromolecules, nanoparticles, and surfaces. MAD-LEEM combines three innovative electron-optical concepts in a single tool: a monochromator, a mirror aberration corrector, and dual electron beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector is needed to achieve subnanometer resolution at landing energies of a few hundred electronvolts. The dual flood illumination approach eliminates charging effects generated when a conventional, single-beam LEEM is used to image insulating specimens. The low landing energy of electrons in the range of 0 to a few hundred electronvolts is also critical for avoiding radiation damage, as high energy electrons with kilo-electron-volt kinetic energies cause irreversible damage to many specimens, in particular biological molecules. The performance of the key electron-optical components of MAD-LEEM, the aberration corrector combined with the objective lens and a magnetic beam separator, was simulated. Initial results indicate that an electrostatic electron mirror has negative spherical and chromatic aberration coefficients that can be tuned over a large parameter range. The negative aberrations generated by the electron mirror can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies and provide a path to achieving subnanometer spatial resolution. First experimental results on characterizing DNA molecules immobilized on Au substrates in a LEEM are presented. Images obtained in a spin-polarized LEEM demonstrate that high contrast is achievable at low electron energies in the range of 1-10 eV and show that small changes in landing energy have a strong impact on the achievable contrast. The MAD-LEEM approach

  4. Role of secondary low energy electrons in radiobiology and chemoradiation therapy of cancer

    Science.gov (United States)

    Sanche, Léon

    2009-05-01

    With the chemotherapeutic agent cisplatin bound to DNA, damage to the molecule by electrons of low and high energies increases by factors varying from 1.3 to 4.4. The enhancement in bond dissociation is triggered by modifications of the interaction of low energy electrons with DNA. From our understanding of the latter, the present Letter attempts to explain the basic radiation-damage mechanism responsible for the efficiency of the concomitant chemoradiation treatment of cancer. Such a basic comprehension of the direct effects of radiation may have implications in the design of new chemotherapeutic and radiosensitizing drugs, as well as in the development of more efficient protocols in chemoradiation therapy.

  5. Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Piot, Philippe [Northern Illinois U.

    2015-12-01

    Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

  6. Ultra-low energy electrons from fast heavy-ion helium collisions: the `target Cusp`

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, W. [Freiburg Univ. (Germany)]|[Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Moshammer, R.; Kollmus, H.; Ullrich, J. [Freiburg Univ. (Germany); O`Rourke, F.S.C. [Queen`s Univ., Belfast, Northern Ireland (United Kingdom); Sarkadi, L. [Magyar Tudomanyos Akademia, Debrecen (Hungary). Atommag Kutato Intezete; Mann, R. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Hagmann, S. [Kansas State Univ., Manhattan, KS (United States). J.R. MacDonald Lab.; Olson, R.E. [Missouri Univ., Rolla, MO (United States). Dept. of Physics

    1998-09-01

    Doubly differential cross sections d{sup 2}{sigma}/dv {sub parallel} dv {sub perpendicular} {sub to} have been obtained by mapping the 3-dimensional velocity space of ultra-low and low-energy electrons (1.5 meV{<=} E{sub e}{<=}100 eV) emitted in singly ionizing 3.6 MeV/u Au{sup 53+} on helium collisions. A sharp ({Delta}E{sub e} {sub perpendicular} {sub to} {sup FWHM} {<=} 22 meV) asymmetric peak centered at vertical stroke anti {nu} vertical stroke =0 is observed to emerge at ultra-low energies from the strongly forward shifted low-energy electron velocity distribution. The shape of this ``target cusp``, which is very sensitive on the details of the two-center potential, is in excellent accord with theoretical CTMC and CDW-EIS predictions. (orig.)

  7. Inelastic scattering of low-energy electrons in metals: the role of kinematics in screening

    International Nuclear Information System (INIS)

    Alducin, M.; Juaristi, J.I.; Nagy, I.; Echenique, P.M.

    2002-01-01

    The inelastic scattering of low-energy electrons with the mobile part of the electron density of free-electron-like materials is investigated. Based on the dielectric theory for the homogeneous electron gas, the concept of Bohm and Pines is adopted in order to separate the single-particle and collective basic channels of the total inelastic rate. An effective screened potential is introduced to describe the separated single-particle part. The role of the relative motion of electrons, a kind of dynamical correlation effect, is modelled in this potential via a physical argument. The results obtained show that the nontrivial correlated motion of electrons may have a measurable influence on the result of dynamical probing of a degenerate electron gas. (author)

  8. Direct Observation of Individual Charges and Their Dynamics on Graphene by Low-Energy Electron Holography.

    Science.gov (United States)

    Latychevskaia, Tatiana; Wicki, Flavio; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2016-09-14

    Visualizing individual charges confined to molecules and observing their dynamics with high spatial resolution is a challenge for advancing various fields in science, ranging from mesoscopic physics to electron transfer events in biological molecules. We show here that the high sensitivity of low-energy electrons to local electric fields can be employed to directly visualize individual charged adsorbates and to study their behavior in a quantitative way. This makes electron holography a unique probing tool for directly visualizing charge distributions with a sensitivity of a fraction of an elementary charge. Moreover, spatial resolution in the nanometer range and fast data acquisition inherent to lens-less low-energy electron holography allows for direct visual inspection of charge transfer processes.

  9. Theory of emission spectra from metal films irradiated by low energy electrons near normal incidence

    International Nuclear Information System (INIS)

    Kretschmann, E.; Callcott, T.A.; Arakawa, E.T.

    1980-01-01

    The emission spectrum produced by low energy electrons incident on a rough metal surface has been calculated for a roughness auto-correlation function containing a prominent peak at a high wave vector. For low energy electrons near normal incidence, the high wavevector peak dominates the roughness coupled surface plasmon radiation (RCSPR) process. The calculation yields estimates of the ratio of RCSPR to transition radiation, the dependence of emission intensity on electron energy and the shape and position of the RCSPR peak. The most interesting result is that the high-wavevector roughness can split the RCSPR radiation into peaks lying above and below the asymptotic surface plasma frequency. The results are compared with data from Ag in the following paper. (orig.)

  10. Low Energy Scanned Electron-Beam Dose Distribution in Thin Layers

    DEFF Research Database (Denmark)

    McLaughlin, W. L.; Hjortenberg, P. E.; Pedersen, Walther Batsberg

    1975-01-01

    Thin radiochromic dye film dosimeters, calibrated by means of calorimetry, make possible the determination of absorbed-dose distributions due to low-energy scanned electron beam penetrations in moderately thin coatings and laminar media. For electrons of a few hundred keV, calibrated dosimeters...... of about 30–60 μm thickness may be used in stacks or interleaved between layers of materials of interest and supply a sufficient number of experimental data points throughout the depth of penetration of electrons to provide a depth-dose curve. Depth doses may be resolved in various polymer layers...... on different backings (wood, aluminum, and iron) for scanned electron beams (Emax = 400 keV) having a broad energy spectrum and diffuse incidence, such as those used in radiation curing of coatings, textiles, plastics, etc. Theoretical calculations of such distributions of energy depositions are relatively...

  11. Development of the techniques for food processing with low-energy electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Todoroki, Setsuko; Hayashi, Toru [National Food Research Inst., Tsukuba, Ibaraki (Japan)

    1999-02-01

    This study aimed to construct a new electron beam irradiation apparatus which allows to perform homogeneous irradiation up to a certain depth of a spherical or granular material through rotating it. And the sterilizing effects of this apparatus on various kinds of spices such as black and white peppers (grains), turmeric (root), coriander (seed), basil (leaves) were investigated to compare with the effects of {gamma}-ray irradiation. Electron beam irradiation was made changing the energy form 200 keV for 15 min to 500 keV for 5 min and a dose-depth curve was drawn for each electron energy. Indicator balls were used to examine the radiation effects. It became possible to make homogeneous irradiation onto a spherical surface of food by using the rotary system of the apparatus. It was demonstrated that satisfactory sterilizing effects as much as those of {gamma}-ray were obtainable by superficial treatments with low-energy electron. (M.N.)

  12. Development of the techniques for food processing with low-energy electron beam

    International Nuclear Information System (INIS)

    Todoroki, Setsuko; Hayashi, Toru

    1999-01-01

    This study aimed to construct a new electron beam irradiation apparatus which allows to perform homogeneous irradiation up to a certain depth of a spherical or granular material through rotating it. And the sterilizing effects of this apparatus on various kinds of spices such as black and white peppers (grains), turmeric (root), coriander (seed), basil (leaves) were investigated to compare with the effects of γ-ray irradiation. Electron beam irradiation was made changing the energy form 200 keV for 15 min to 500 keV for 5 min and a dose-depth curve was drawn for each electron energy. Indicator balls were used to examine the radiation effects. It became possible to make homogeneous irradiation onto a spherical surface of food by using the rotary system of the apparatus. It was demonstrated that satisfactory sterilizing effects as much as those of γ-ray were obtainable by superficial treatments with low-energy electron. (M.N.)

  13. Electrons of high perpendicular energy in the low-density regime of Tokamaks

    International Nuclear Information System (INIS)

    Bornatici, M.; Engelmann, F.

    1978-01-01

    Effects due to instabilities excited in the low-density regime of tokamaks by runaway electrons via the cyclotron resonance ω+Ω=kV along with the formation of a positive slope in the runaway distribution are considered. Conditions for the production of electrons of high perpendicular energy and their trapping in toroidal field ripples, leading to liner damage, are discussed and found to be rather stringent. Fairly good agreement with the experiments is found

  14. Ab initio study of dissociative attachment of low-energy electrons to F2

    International Nuclear Information System (INIS)

    Hazi, A.U.; Orel, A.E.; Rescigno, T.N.

    1981-01-01

    Adiabatic-nuclei resonance theory has been applied to the study of dissociative attachment of low-energy electrons to F 2 . Stieltjes moment theory was used to derive fixed-nuclei electronic resonance parameters from large scale configuration-interaction calculations on F 2 and F 2 - . Dissociative attachment cross sections are reported for the four lowest vibrational levels of F 2 and compared to available experimental data

  15. Direct observations of low-energy solar electrons associated with a type 3 solar radio burst

    Science.gov (United States)

    Frank, L. A.; Gurnett, D. A.

    1972-01-01

    On 6 April 1971 a solar X-ray flare and a type 3 solar radio noise burst were observed with instrumentation on the eccentric-orbiting satellite IMP 6. The type 3 solar radio noise burst was detected down to a frequency of 31 kHz. A highly anisotropic packet of low-energy solar electron intensities arrived at the satellite approximately 6000 seconds after the onset of the solar flare. This packet of solar electron intensities was observed for 4200 seconds. Maximum differential intensities of the solar electrons were in the energy range of one to several keV. The frequency drift rate of the type 3 radio noise at frequencies below 178 kHz also indicated an average particle speed corresponding to that of a 3-keV electron. The simultaneous observations of these solar electron intensities and of the type 3 solar radio burst are presented, and their interrelationships are explored.

  16. Electronic structure of xenon implanted with low energy in amorphous silicon

    International Nuclear Information System (INIS)

    Barbieri, P.F.; Landers, R.; Oliveira, M.H. de; Alvarez, F.; Marques, F.C.

    2007-01-01

    Electronic structure of Xe implanted in amorphous silicon (a-Si) films are investigated. Xe atoms were implanted with low energy by ion beam assisted deposition (IBAD) technique during growth of the a-Si films. The Xe implantation energy varied in the 0-300 eV energy range. X-ray photoelectron spectroscopy (XPS), X-ray Auger excited spectroscopy (XAES) and X-ray absorption spectroscopy (XAS) were used for investigating the Xe electronic structure. The Xe M 4 N 45 N 45 transitions were measured to extract the Auger parameter and to analyze the initial state and relaxation contributions. It was found that the binding energy variation is mainly due to initial state contribution. The relaxation energy variation also shows that the Xe trapped environment depends on the implantation energy. XAS measurements reveals that Xe atoms are dispersed in the a-Si matrix

  17. Electronic diffraction tomography by Green's functions and singular values decompositions

    International Nuclear Information System (INIS)

    Mayer, A.

    2001-01-01

    An inverse scattering technique is developed to enable a three-dimensional sample reconstruction from the diffraction figures obtained for different sample orientations by electronic projection microscopy, thus performing a diffraction tomography. In its Green's-functions formulation, this technique takes account of all orders of diffraction by performing an iterative reconstruction of the wave function on the observation screen and in the sample. In a final step, these quantities enable a reconstruction of the potential-energy distribution, which is assumed real valued. The method relies on the use of singular values decomposition techniques, thus providing the best least-squares solutions and enabling a reduction of noise. The technique is applied to the analysis of a three-dimensional nanometric sample that is observed in Fresnel conditions with an electron energy of 40 eV. The algorithm turns out to provide results with a mean relative error around 3% and to be stable against random noise

  18. An optical study of multiple NEIAL events driven by low energy electron precipitation

    Directory of Open Access Journals (Sweden)

    J. M. Sullivan

    2008-08-01

    Full Text Available Optical data are compared with EISCAT radar observations of multiple Naturally Enhanced Ion-Acoustic Line (NEIAL events in the dayside cusp. This study uses narrow field of view cameras to observe small-scale, short-lived auroral features. Using multiple-wavelength optical observations, a direct link between NEIAL occurrences and low energy (about 100 eV optical emissions is shown. This is consistent with the Langmuir wave decay interpretation of NEIALs being driven by streams of low-energy electrons. Modelling work connected with this study shows that, for the measured ionospheric conditions and precipitation characteristics, growth of unstable Langmuir (electron plasma waves can occur, which decay into ion-acoustic wave modes. The link with low energy optical emissions shown here, will enable future studies of the shape, extent, lifetime, grouping and motions of NEIALs.

  19. Modelling low energy electron and positron tracks in biologically relevant media

    International Nuclear Information System (INIS)

    Blanco, F.; Munoz, A.; Almeida, D.; Ferreira da Silva, F.; Limao-Vieira, P.; Fuss, M.C.; Sanz, A.G.; Garcia, G.

    2013-01-01

    This colloquium describes an approach to incorporate into radiation damage models the effect of low and intermediate energy (0-100 eV) electrons and positrons, slowing down in biologically relevant materials (water and representative biomolecules). The core of the modelling procedure is a C++ computing programme named 'Low Energy Particle Track Simulation (LEPTS)', which is compatible with available general purpose Monte Carlo packages. Input parameters are carefully selected from theoretical and experimental cross section data and energy loss distribution functions. Data sources used for this purpose are reviewed showing examples of electron and positron cross section and energy loss data for interactions with different media of increasing complexity: atoms, molecules, clusters and condense matter. Finally, we show how such a model can be used to develop an effective dosimetric tool at the molecular level (i.e. nanodosimetry). Recent experimental developments to study the fragmentation induced in biologically material by charge transfer from neutrals and negative ions are also included. (authors)

  20. Evaluation and application of the low energy electron emitter 161Tb

    International Nuclear Information System (INIS)

    Lehenberger, Silvia M.

    2010-01-01

    The low energy electron emitter 161 Tb was produced n.c.a. in quantities sufficient for therapeutic applications and successfully used for labeling of peptides and antibodies. Furthermore, these compounds have been compared to n.c.a. 177 Lu labeled mAbs via cell experiments, a radionuclide that is already used in clinical nuclear oncology.

  1. Low-energy electron scattering by C, N, and O atoms

    Energy Technology Data Exchange (ETDEWEB)

    Nesbet, R K [International Business Machines Corp., San Jose, Calif. (USA). Research Lab.

    1977-07-01

    Recent theoretical studies of low-energy electron scattering by C, N, and O atoms are reviewed and results are compared with available experimental data. A critical comparison is made of the two principal methods used in this work-polarized pseudostate expansion with R-matrix computations or direct integration, and Bethe-Goldstone expansion with matrix variational computations. 31 references.

  2. Low energy electronic scattering processes in the topological Weyl semimetal TaAs

    Energy Technology Data Exchange (ETDEWEB)

    Muellner, Silvia; Lemmens, Peter [IPKM, TU-BS, Braunschweig (Germany); Gnezdilov, Vladimir [IPKM, TU-BS, Braunschweig (Germany); ILTPE NAS (Ukraine); Sankar, Raman; Chou, Fangcheng [CCMS, National Taiwan Univ., Taipei (China)

    2016-07-01

    The topological Weyl semimetal TaAs shows Weyl points as well as topological surface states (Fermi arcs) intimately related to symmetry and strong spin orbit interaction. We find evidence for a low energy maximum in the scattering intensity that is compatible with electronic correlations in a collision dominated regime. We compare our observations with topological insulators.

  3. The Generalized Multipole Technique for the Simulation of Low-Loss Electron Energy Loss Spectroscopy

    DEFF Research Database (Denmark)

    Kiewidt, Lars; Karamehmedovic, Mirza

    2018-01-01

    In this study, we demonstrate the use of a Generalized Multipole Technique (GMT) to simulate low-loss Electron Energy Loss Spectroscopy (EELS) spectra of isolated spheriodal nanoparticles. The GMT provides certain properties, such as semi-analytical description of the electromagnetic fields...

  4. Ultra Low Energy Binary Decision Diagram Circuits Using Few Electron Transistors

    Science.gov (United States)

    Saripalli, Vinay; Narayanan, Vijay; Datta, Suman

    Novel medical applications involving embedded sensors, require ultra low energy dissipation with low-to-moderate performance (10kHz-100MHz) driving the conventional MOSFETs into sub-threshold operation regime. In this paper, we present an alternate ultra-low power computing architecture using Binary Decision Diagram based logic circuits implemented using Single Electron Transistors (SETs) operating in the Coulomb blockade regime with very low supply voltages. We evaluate the energy - performance tradeoff metrics of such BDD circuits using time domain Monte Carlo simulations and compare them with the energy-optimized CMOS logic circuits. Simulation results show that the proposed approach achieves better energy-delay characteristics than CMOS realizations.

  5. Improved age-diffusion model for low-energy electron transport in solids. I. Theory

    International Nuclear Information System (INIS)

    Devooght, J.; Dubus, A.; Dehaes, J.C.

    1987-01-01

    We have developed in this paper a semianalytical electron transport model designed for parametric studies of secondary-electron emission induced by low-energy electrons (keV range) and by fast light ions (100 keV range). The primary-particle transport is assumed to be known and to give rise to an internal electron source. The importance of the nearly isotropic elastic scattering in the secondary-electron energy range (50 eV) and the slowing-down process strongly reduce the influence of the anisotropy of the internal electron source, and the internal electron flux is nearly isotropic as is evidenced by the experimental results. The differential energy behavior of the inelastic scattering kernel is very complicated and the real kernel is replaced by a synthetic scattering kernel of which parameters are obtained by energy and angle moments conservation. Through a P 1 approximation and the use of the synthetic scattering kernel, the Boltzmann equation is approximated by a diffusion--slowing-down equation for the isotropic part of the internal electron flux. The energy-dependent partial reflection boundary condition reduces to a Neumann-Dirichlet boundary condition. An analytical expression for the Green's function of the diffusion--slowing-down equation with the surface boundary condition is obtained by means of approximations close to the age-diffusion theory and the model allows for transient conditions. Independently from the ''improved age-diffusion'' model, a correction formula is developed in order to take into account the backscattering of primary electrons for an incident-electron problem

  6. Bragg's Law diffraction simulations for electron backscatter diffraction analysis

    International Nuclear Information System (INIS)

    Kacher, Josh; Landon, Colin; Adams, Brent L.; Fullwood, David

    2009-01-01

    In 2006, Angus Wilkinson introduced a cross-correlation-based electron backscatter diffraction (EBSD) texture analysis system capable of measuring lattice rotations and elastic strains to high resolution. A variation of the cross-correlation method is introduced using Bragg's Law-based simulated EBSD patterns as strain free reference patterns that facilitates the use of the cross-correlation method with polycrystalline materials. The lattice state is found by comparing simulated patterns to collected patterns at a number of regions on the pattern using the cross-correlation function and calculating the deformation from the measured shifts of each region. A new pattern can be simulated at the deformed state, and the process can be iterated a number of times to converge on the absolute lattice state. By analyzing an iteratively rotated single crystal silicon sample and recovering the rotation, this method is shown to have an angular resolution of ∼0.04 o and an elastic strain resolution of ∼7e-4. As an example of applications, elastic strain and curvature measurements are used to estimate the dislocation density in a single grain of a compressed polycrystalline Mg-based AZ91 alloy.

  7. The Role of Low-Energy Electrons in Astrochemistry: A Tale of Two Molecules

    Science.gov (United States)

    Arumainayagam, Chris; Cambell, Jyoti; Leon Sanche, Michael Boyer, and Petra Swiderek.

    2016-06-01

    In the interstellar medium, UV photolysis of ice mantles encasing dust grains is thought to be the mechanism that drives the synthesis of “complex” molecules. The source of this reaction-initiating UV light is assumed to be local because externally-sourced UV radiation cannot pass through the ice-containing dark, dense molecular clouds. Externally sourced cosmic rays (Emax ~ 1020 eV), in addition to producing UV light within these clouds, also produce large numbers of low-energy (≤ 20 eV) secondary electrons. 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. Using electron stimulated desorption (ESD), post-irradiation temperature-programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS), we have investigated the radiolysis initiated by electrons in condensed methanol and ammonia at ~ 90 K under ultrahigh vacuum (1×10-9 Torr) conditions. We have identified fifteen low-energy (≤ 20 eV) electron-induced methanol radiolysis products, many of which have been previously identified as being formed by methanol UV photolysis in the interstellar medium. We have also found evidence for the electron-induced formation from ammonia of hydrazine (N2H4), diazene (N2H2), cyclotriazane/triazene (N3H3) and triazane (N3H5). We have investigated the reaction yields’ dependence on film thickness, irradiation time, incident current, electron energy, and metal substrate. These results provide a basis from which we can begin to understand the mechanisms by which methanol and ammonia can form more complex species in cosmic ices. Studies such as ours may ultimately help us better understand the initial stages of the genesis of life.

  8. Radiation induced low-energy electron transport in a tissue environment

    International Nuclear Information System (INIS)

    Toburen, L.H.; Dingfelder, M.; Ozturk, N.; Christou, C.; Shinpaugh, J.L.; Friedland, W.; Wilson, W.E.; Paretzke, H.G.

    2003-01-01

    Monte Carlo (MC) track simulation codes are used extensively in radiobiology to quantify the spatial distributions of interactions initiated by the absorption of ionizing radiation. The spatial patterns of ionization and excitation are instrumental for assessing the formation of damage clusters in DNA and chromosomes leading to such biologic endpoints as cellular transformation and mutation. The MC codes rely on an extensive database of elastic and inelastic scattering cross sections to follow the production and slowing of secondary electrons. Because of inherent uncertainties in this database we are exploring the sensitivity of MC results to the details of the cross sections used with emphasis on low-energy electrons, i.e., track ends, that are anticipated to play a dominant role in damage cluster formation. Simulations of electron transport using gas or liquid based interaction cross sections illustrate substantial difference in the spectra of electrons with energies less than about 50 eV. In addition, the electron yields from MC simulations appear to be nearly a factor of five larger than our recent measurements of electron transport spectra in water (ice) at electron energies of about 10 eV. Examples of the changes in electron transport spectra for variations in the electron scattering cross sections used for the MC calculations will be illustrated and compared with an evolving database of measured spectra of electrons from ion induced secondary electron transport in thin foils. These measurements provide guidance for assessment of elastic and elastic cross sections appropriate to condensed phase transport. This work is supported in part by the U.S. Department of Energy, Grant No. DE-FG02-01ER-63233; the National Cancer Institute, Grant No. 1R01CA93351-01A1; and the European Community under Contract No. FIGH-CT-1999-00005

  9. A Novel Low Energy Electron Microscope for DNA Sequencing and Surface Analysis

    Science.gov (United States)

    Mankos, M.; Shadman, K.; Persson, H.H.J.; N’Diaye, A.T.; Schmid, A.K.; Davis, R.W.

    2014-01-01

    Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel technique that is directed towards imaging nanostructures and surfaces with sub-nanometer resolution. The technique combines a monochromator, a mirror aberration corrector, an energy filter, and dual beam illumination in a single instrument. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. Simulation results predict that the novel aberration corrector design will eliminate the second rank chromatic and third and fifth order spherical aberrations, thereby improving the resolution into the sub-nanometer regime at landing energies as low as one hundred electron-Volts. The energy filter produces a beam that can extract detailed information about the chemical composition and local electronic states of non-periodic objects such as nanoparticles, interfaces, defects, and macromolecules. The dual flood illumination eliminates charging effects that are generated when a conventional LEEM is used to image insulating specimens. A potential application for MAD-LEEM is in DNA sequencing, which requires high resolution to distinguish the individual bases and high speed to reduce the cost. The MAD-LEEM approach images the DNA with low electron impact energies, which provides nucleobase contrast mechanisms without organometallic labels. Furthermore, the micron-size field of view when combined with imaging on the fly provides long read lengths, thereby reducing the demand on assembling the sequence. Experimental results from bulk specimens with immobilized single-base oligonucleotides demonstrate that base specific contrast is available with reflected, photo-emitted, and Auger electrons. Image contrast simulations of model rectangular features mimicking the individual nucleotides in a DNA strand have been developed to translate measurements of contrast on bulk DNA to the detectability of

  10. A novel low energy electron microscope for DNA sequencing and surface analysis.

    Science.gov (United States)

    Mankos, M; Shadman, K; Persson, H H J; N'Diaye, A T; Schmid, A K; Davis, R W

    2014-10-01

    Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel technique that is directed towards imaging nanostructures and surfaces with sub-nanometer resolution. The technique combines a monochromator, a mirror aberration corrector, an energy filter, and dual beam illumination in a single instrument. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. Simulation results predict that the novel aberration corrector design will eliminate the second rank chromatic and third and fifth order spherical aberrations, thereby improving the resolution into the sub-nanometer regime at landing energies as low as one hundred electron-Volts. The energy filter produces a beam that can extract detailed information about the chemical composition and local electronic states of non-periodic objects such as nanoparticles, interfaces, defects, and macromolecules. The dual flood illumination eliminates charging effects that are generated when a conventional LEEM is used to image insulating specimens. A potential application for MAD-LEEM is in DNA sequencing, which requires high resolution to distinguish the individual bases and high speed to reduce the cost. The MAD-LEEM approach images the DNA with low electron impact energies, which provides nucleobase contrast mechanisms without organometallic labels. Furthermore, the micron-size field of view when combined with imaging on the fly provides long read lengths, thereby reducing the demand on assembling the sequence. Experimental results from bulk specimens with immobilized single-base oligonucleotides demonstrate that base specific contrast is available with reflected, photo-emitted, and Auger electrons. Image contrast simulations of model rectangular features mimicking the individual nucleotides in a DNA strand have been developed to translate measurements of contrast on bulk DNA to the detectability of

  11. Precession electron diffraction – a topical review

    Directory of Open Access Journals (Sweden)

    Paul A. Midgley

    2015-01-01

    Full Text Available In the 20 years since precession electron diffraction (PED was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis.

  12. Phase inversion and frequency doubling of reflection high-energy electron diffraction intensity oscillations in the layer-by-layer growth of complex oxides

    Science.gov (United States)

    Mao, Zhangwen; Guo, Wei; Ji, Dianxiang; Zhang, Tianwei; Gu, Chenyi; Tang, Chao; Gu, Zhengbin; Nie*, Yuefeng; Pan, Xiaoqing

    In situ reflection high-energy electron diffraction (RHEED) and its intensity oscillations are extremely important for the growth of epitaxial thin films with atomic precision. The RHEED intensity oscillations of complex oxides are, however, rather complicated and a general model is still lacking. Here, we report the unusual phase inversion and frequency doubling of RHEED intensity oscillations observed in the layer-by-layer growth of SrTiO3 using oxide molecular beam epitaxy. In contacts to the common understanding that the maximum(minimum) intensity occurs at SrO(TiO2) termination, respectively, we found that both maximum or minimum intensities can occur at SrO, TiO2, or even incomplete terminations depending on the incident angle of the electron beam, which raises a fundamental question if one can rely on the RHEED intensity oscillations to precisely control the growth of thin films. A general model including surface roughness and termination dependent mean inner potential qualitatively explains the observed phenomena, and provides the answer to the question how to prepare atomically and chemically precise surface/interfaces using RHEED oscillations for complex oxides. We thank National Basic Research Program of China (No. 11574135, 2015CB654901) and the National Thousand-Young-Talents Program.

  13. The use of low energy electron accelerator for processing of liquid matter in Indonesia

    International Nuclear Information System (INIS)

    Danu, Sugiarto

    2003-01-01

    Activities of radiation processing in Indonesia covering various fields are reviewed. The low and medium energy electron accelerator specially designed for radiation processing of liquid materials is introduced. P3TIR-BATAN is mostly engaged in radiation processing in general with Co-60 source and electron accelerators (300 keV, 50 mA and 2 MeV, 10 mA). A private company, Gajah Tunggal, has an accelerator of 500 keV, 20 mA. The use of low energy electron accelerator to irradiate liquid matter matter such as natural rubber latex, polysaccharides, starch, chitosan and other natural polymers in Indonesia are reported and future program of national research cooperation between government institutions and private companies are described. (S. Ohno)

  14. Dμ-A new concept in industrial low-energy electron dosimetry

    International Nuclear Information System (INIS)

    Helt-Hansen, Jakob; Miller, Arne; Sharpe, Peter; Laurell, Bengt; Weiss, Doug; Pageau, Gary

    2010-01-01

    Irradiation with low-energy electrons (100-300 keV) results in dose gradients across the thickness of the dosimeters that are typically used for dose measurement at these energies. This leads to different doses being measured with different thickness dosimeters irradiated at the same electron beam, resulting in difficulties in providing traceable dose measurements using reference dosimeters. In order to overcome these problems a new concept is introduced of correcting all measured doses to the average dose in the first micrometer-D μ . We have applied this concept to dose measurements with dosimeters of different thickness at two electron accelerators operating over a range of energies. The uncertainties of the dose measurements were evaluated, and it was shown that the dose in terms of D μ was the same at each energy for all dosimeters within the measurement uncertainty. Using the concept of D μ it is therefore possible to calibrate and measure doses from low-energy electron irradiations with measurement traceability to national standards.

  15. A novel low energy electron microscope for DNA sequencing and surface analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, M., E-mail: marian@electronoptica.com [Electron Optica Inc., 1000 Elwell Court #110, Palo Alto, CA 94303 (United States); Shadman, K. [Electron Optica Inc., 1000 Elwell Court #110, Palo Alto, CA 94303 (United States); Persson, H.H.J. [Stanford Genome Technology Center, Stanford University School of Medicine, 855 California Avenue, Palo Alto, CA 94304 (United States); N’Diaye, A.T. [Electron Optica Inc., 1000 Elwell Court #110, Palo Alto, CA 94303 (United States); NCEM, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Schmid, A.K. [NCEM, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Davis, R.W. [Stanford Genome Technology Center, Stanford University School of Medicine, 855 California Avenue, Palo Alto, CA 94304 (United States)

    2014-10-15

    Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel technique that is directed towards imaging nanostructures and surfaces with sub-nanometer resolution. The technique combines a monochromator, a mirror aberration corrector, an energy filter, and dual beam illumination in a single instrument. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. Simulation results predict that the novel aberration corrector design will eliminate the second rank chromatic and third and fifth order spherical aberrations, thereby improving the resolution into the sub-nanometer regime at landing energies as low as one hundred electron-Volts. The energy filter produces a beam that can extract detailed information about the chemical composition and local electronic states of non-periodic objects such as nanoparticles, interfaces, defects, and macromolecules. The dual flood illumination eliminates charging effects that are generated when a conventional LEEM is used to image insulating specimens. A potential application for MAD-LEEM is in DNA sequencing, which requires high resolution to distinguish the individual bases and high speed to reduce the cost. The MAD-LEEM approach images the DNA with low electron impact energies, which provides nucleobase contrast mechanisms without organometallic labels. Furthermore, the micron-size field of view when combined with imaging on the fly provides long read lengths, thereby reducing the demand on assembling the sequence. Experimental results from bulk specimens with immobilized single-base oligonucleotides demonstrate that base specific contrast is available with reflected, photo-emitted, and Auger electrons. Image contrast simulations of model rectangular features mimicking the individual nucleotides in a DNA strand have been developed to translate measurements of contrast on bulk DNA to the detectability of

  16. Low-energy electron energy losses and inelastic mean free paths in zinc, selenium, and zinc selenide

    Energy Technology Data Exchange (ETDEWEB)

    Bourke, J.D.; Chantler, C.T., E-mail: chantler@unimelb.edu.au

    2014-10-15

    We compute low-energy optical energy loss spectra for the elemental solids zinc and selenium, and for the binary compound zinc selenide. The optical data are transformed via a constrained partial-pole algorithm to produce momentum-dependent electron energy loss spectra and electron inelastic mean free paths. This enables a comparison between the electron scattering behaviour in a compound solid and its constituent elements. Results cannot be explained by aggregation methods or commonly used universal curves, and prove that new approaches are required. Our work demonstrates new capabilities for the determination of fundamental material properties for a range of structures previously inaccessible to established theoretical models, and at energy levels inaccessible to most experimental techniques.

  17. Low-energy electron energy losses and inelastic mean free paths in zinc, selenium, and zinc selenide

    International Nuclear Information System (INIS)

    Bourke, J.D.; Chantler, C.T.

    2014-01-01

    We compute low-energy optical energy loss spectra for the elemental solids zinc and selenium, and for the binary compound zinc selenide. The optical data are transformed via a constrained partial-pole algorithm to produce momentum-dependent electron energy loss spectra and electron inelastic mean free paths. This enables a comparison between the electron scattering behaviour in a compound solid and its constituent elements. Results cannot be explained by aggregation methods or commonly used universal curves, and prove that new approaches are required. Our work demonstrates new capabilities for the determination of fundamental material properties for a range of structures previously inaccessible to established theoretical models, and at energy levels inaccessible to most experimental techniques

  18. Origin of the Differential Fluxes of Low-energy Electrons in the Inner Heliosheath

    Energy Technology Data Exchange (ETDEWEB)

    Fahr, H. J. [Argelander Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn (Germany); Krimigis, S. M. [Office of Space Research and Technology, Academy of Athens, 10679 Athens (Greece); Fichtner, H.; Scherer, K.; Sylla, A. [Institut für Theoretische Physik IV, Ruhr-Universität Bochum, 44780 Bochum (Germany); Ferreira, S. E. S.; Potgieter, M. S., E-mail: hf@tp4.rub.de [Centre for Space Research, North-West University, 2520 Potchefstroom (South Africa)

    2017-10-10

    The study addresses the question of the origin of low-energy electrons measured by Voyager 1 in the multi-keV range in the inner heliosheath. It intends to demonstrate that the observed keV-fluxes of electrons are consistent with their transmission through the termination shock under the influence of the associated electrostatic field. A power-law representation of the electron velocity distribution just downstream of the solar wind termination shock is motivated and formulated in terms of a so-called κ -distribution function. From this initial function spectral electron fluxes in the range 40–70 keV are derived and compared to the data. It is shown that with κ -values between 7 and 8 the data can be satisfactorily explained. Given these comparatively high κ -values, it is concluded that the electron distribution just downstream of the termination shock relaxes toward but does not reach a Maxwellian shape in the inner heliosheath.

  19. Micro-channel plate detector for ultra-fast relativistic electron diffraction

    International Nuclear Information System (INIS)

    Musumeci, P.; Moody, J.T.; Scoby, C.M.; Gutierrez, M.S.; Bender, H.A.; Hilko, B.; Kruschwitz, C.A.; Wilcox, N.S.

    2011-01-01

    Using relativistic ultra-short electron beams to obtain single-shot diffraction patterns holds the promise to yield real-time resolution of atomic motion in an easily accessible environment, such as a university laboratory, at a fraction of the cost of fourth-generation X-ray sources. One of the main issues in bringing this technique to full maturity is the development of efficient detector systems to record the diffraction pattern using a few MeV electron beams. Low noise, high spatial resolution, and single-electron detection capability are all characteristics of an ideal detector. In this paper, we compare the performances of a traditional fluorescent phosphor screen with a detection system based on the micro-channel plate (MCP). Since MCPs are typically used with lower energy electron beams, these tests constitute one of the few experimental data points available on the use of these devices with MeV energy beams.

  20. Micro-channel plate detector for ultra-fast relativistic electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Musumeci, P., E-mail: musumeci@physics.ucla.edu [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA, 90095-1547 (United States); Moody, J.T.; Scoby, C.M.; Gutierrez, M.S. [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA, 90095-1547 (United States); Bender, H.A.; Hilko, B.; Kruschwitz, C.A.; Wilcox, N.S. [National Security Technologies, LLC, Los Alamos Operations, Los Alamos, NM (United States)

    2011-05-01

    Using relativistic ultra-short electron beams to obtain single-shot diffraction patterns holds the promise to yield real-time resolution of atomic motion in an easily accessible environment, such as a university laboratory, at a fraction of the cost of fourth-generation X-ray sources. One of the main issues in bringing this technique to full maturity is the development of efficient detector systems to record the diffraction pattern using a few MeV electron beams. Low noise, high spatial resolution, and single-electron detection capability are all characteristics of an ideal detector. In this paper, we compare the performances of a traditional fluorescent phosphor screen with a detection system based on the micro-channel plate (MCP). Since MCPs are typically used with lower energy electron beams, these tests constitute one of the few experimental data points available on the use of these devices with MeV energy beams.

  1. Low-energy electron transmission and secondary-electron emission experiments on crystalline and molten long-chain alkanes

    International Nuclear Information System (INIS)

    Ueno, N.; Sugita, K.; Seki, K.; Inokuchi, H.

    1986-01-01

    This paper describes the results of low-energy electron transmission and secondary-electron emission experiments on thin films of long-chain alkanes deposited on metal substrates. The spectral changes due to crystal-melt phase transition were measured in situ in both experiments. The ground-state energy V 0 of the quasifree electron in crystalline state was determined to be 0.5 +- 0.1 eV. The value of V 0 for the molten state was found to be negative. Further, in the crystalline state evidence is found for a direct correspondence between the transmission maxima and the high value of the density of states in the conduction bands

  2. Determining the sputter yields of molybdenum in low-index crystal planes via electron backscattered diffraction, focused ion beam and atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.S., E-mail: 160184@mail.csc.com.tw [New Materials Research and Development Department, China Steel Corporation, 1 Chung Kang Road, Hsiao Kang, Kaohsiung 812, Taiwan, ROC (China); Chiu, C.H.; Hong, I.T.; Tung, H.C. [New Materials Research and Development Department, China Steel Corporation, 1 Chung Kang Road, Hsiao Kang, Kaohsiung 812, Taiwan, ROC (China); Chien, F.S.-S. [Department of Physics, Tunghai University, 1727, Sec. 4, Xitun Dist., Taiwan Boulevard, Taichung 407, Taiwan, ROC (China)

    2013-09-15

    Previous literature has used several monocrystalline sputtering targets with various crystalline planes, respectively, to investigate the variations of the sputter yield of materials in different crystalline orientations. This study presents a method to measure the sputtered yields of Mo for the three low-index planes (100), (110), and (111), through using an easily made polycrystalline target. The procedure was firstly to use electron backscattered diffraction to identify the grain positions of the three crystalline planes, and then use a focused ion beam to perform the micro-milling of each identified grain, and finally the sputter yields were calculated from the removed volumes, which were measured by atomic force microscope. Experimental results showed that the sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}, coincidental with the ranking of their planar atomic packing densities. The concept of transparency of ion in the crystalline substance was applied to elucidate these results. In addition, the result of (110) orientation exhibiting higher sputter yield is helpful for us to develop a Mo target with a higher deposition rate for use in industry. By changing the deformation process from straight rolling to cross rolling, the (110) texture intensity of the Mo target was significantly improved, and thus enhanced the deposition rate. - Highlights: • We used EBSD, FIB and AFM to measure the sputter yields of Mo in low-index planes. • The sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}. • The transparency of ion was used to elucidate the differences in the sputter yield. • We improved the sputter rate of polycrystalline Mo target by adjusting its texture.

  3. A design for a subminiature, low energy scanning electron microscope with atomic resolution

    International Nuclear Information System (INIS)

    Eastham, D. A.; Edmondson, P.; Greene, S.; Donnelly, S.; Olsson, E.; Svensson, K.; Bleloch, A.

    2009-01-01

    We describe a type of scanning electron microscope that works by directly imaging the electron field-emission sites on a nanotip. Electrons are extracted from the nanotip through a nanoscale aperture, accelerated in a high electric field, and focused to a spot using a microscale Einzel lens. If the whole microscope (accelerating section and lens) and the focal length are both restricted in size to below 10 μm, then computer simulations show that the effects of aberration are extremely small and it is possible to have a system with approximately unit magnification at electron energies as low as 300 eV. Thus a typical emission site of 1 nm diameter will produce an image of the same size, and an atomic emission site will give a resolution of 0.1-0.2 nm (1-2 A). Also, because the beam is not allowed to expand beyond 100 nm in diameter, the depth of field is large and the contribution to the beam spot size from chromatic aberrations is less than 0.02 nm (0.2 A) for 500 eV electrons. Since it is now entirely possible to make stable atomic sized emitters (nanopyramids), it is expected that this instrument will have atomic resolution. Furthermore the brightness of the beam is determined only by the field emission and can be up to 1x10 6 times larger than in a typical (high energy) electron microscope. The advantages of this low energy, bright-beam electron microscope with atomic resolution are described and include the possibility of it being used to rapidly sequence the human genome from a single strand of DNA as well as being able to identify atomic species directly from the elastic scattering of electrons

  4. Simple polynomial approximation to modified Bethe formula low-energy electron stopping powers data

    Energy Technology Data Exchange (ETDEWEB)

    Taborda, A., E-mail: ana.taborda@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-HOM/SDI/LEDI, BP-17, 92262 Fontenay-aux-Roses (France); Desbrée, A. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-HOM/SDI/LEDI, BP-17, 92262 Fontenay-aux-Roses (France); Reis, M.A. [C" 2TN, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, EN10 km139.7, 2685-066 Bobadela LRS (Portugal)

    2015-08-01

    A recently published detailed and exhaustive paper on cross-sections for ionisation induced by keV electrons clearly shows that electron phenomena occurring in parallel with X-ray processes may have been dramatically overlooked for many years, mainly when low atomic number species are involved since, in these cases, the fluorescence coefficient is smaller than the Auger yield. An immediate problem is encountered while attempting to tackle the issue. Accounting for electron phenomena requires the knowledge of the stopping power of electrons within, at least, a reasonably small error. Still, the Bethe formula for stopping powers is known to not be valid for electron energies below 30 keV, and its use leads to values far off experimental ones. Recently, a few authors have addressed this problem and both detailed tables of electron stopping powers for various atomic species and attempts to simplify the calculations, have emerged. Nevertheless, its implementation in software routines to efficiently calculate keV electron effects in materials quickly becomes a bit cumbersome. Following a procedure already used to establish efficient methods to calculate ionisation cross-sections by protons and alpha particles, it became clear that a simple polynomial approximation could be set, which allows retrieving the electronic stopping powers with errors of less than 20% for energies above 500 eV and less than 50% for energies between 50 eV and 500 eV. In this work, we present this approximation which, based on just six parameters, allows to recover electron stopping power values that are less than 20% different from recently published experimentally validated tabulated data.

  5. Electron back scattered diffraction study of SmCo magnets

    International Nuclear Information System (INIS)

    Yonamine, T.; Fukuhara, M.; Machado, R.; Missell, F.P.

    2008-01-01

    The remanence and energy product of permanent magnets is a strong function of their crystallographic texture. Electron back scattered diffraction (EBSD) is a tool for texture analysis providing information about the atomic layers up to 50 nm below the surface of the material. This paper discusses experimental requirements for performing EBSD measurements on rare-earth permanent magnets and presents results on commercial SmCo magnet material. EBSD measurements proved to be very sensitive to misaligned grains and were sensitive to texture in good agreement with information provided by X-ray diffraction scans. Results for nanostructured Sm(CoFeCuZr) z magnets are also discussed

  6. Radiation vulcanization of natural rubber latex (NRL) using low energy electron beam accelerator

    International Nuclear Information System (INIS)

    Feroza Akhtar; Keizo Makuuchi; Fumio Yoshii

    1996-01-01

    The electron beam induced vulcanization of natural rubber latex has been studied using low energy Electron Beam (EB) accelerators of 300, 250 and 175 keV ne latex was irradiated in a special type stainless steel reaction reactor with a stirrer at the bottom of the reactor. From the results it was found that 300 and 250 keV accelerators could effectively vulcanize NRL. But accelerator of 175 keV is too low energy to vulcanize the latex. At the same time a drum type irradiator where thin layer of NRL was irradiated by accelerator, was used for vulcanization of NRL. This type of irradiator also showed good physical properties of vulcanized latex. The effects of beam current and stirrer speed on vulcanization were studied

  7. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    International Nuclear Information System (INIS)

    Figuera, Juan de la; Vergara, Lucía; N'Diaye, Alpha T.; Quesada, Adrian; Schmid, Andreas K.

    2013-01-01

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along directions. ► Magnetic domain wall structures include wide Néel-caps

  8. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-07-15

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

  9. Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study

    International Nuclear Information System (INIS)

    Song, H. Z.; Usuki, T.; Nakata, Y.; Yokoyama, N.; Sasakura, H.; Muto, S.

    2006-01-01

    InAs/GaAs quantum dots (QD's) are formed by postgrowth annealing of an InAs wetting layer thinner than the critical thickness for the transition from two- (2D) to three-dimensional (3D) growth mode. Reflection high energy electron diffraction is used to monitor the QD formation. Based on a mean-field theory [Phys. Rev. Lett. 79, 897 (1997)], the time evolution of total QD's volume, first increasing and finally saturating, is well explained by precursors forming during wetting layer growth and converting into nucleated QD's after growth stop. Both the saturation QD's volume and the QD nucleation rate depend exponentially on the InAs coverage. These behaviors and their temperature and InAs growth rate dependences are essentially understandable in the frame of the mean-field theory. Similar analysis to conventional QD growth suggests that the often observed significant mass transport from wetting layer to QD's can be ascribed to the precursors existing before 2D-3D growth mode transition

  10. Guiding of low-energy electrons by highly ordered Al2 O3 nanocapillaries

    DEFF Research Database (Denmark)

    Milosavljević, A.R.; Víkor, G.; Pešić, Z.D.

    2007-01-01

    We report an experimental study of guided transmission of low-energy (200-350 eV) electrons through highly ordered Al2 O3 nanocapillaries with large aspect ratio (140 nm diameter and 15 μm length). The nanochannel array was prepared using self-ordering phenomena during a two-step anodization...... process of a high-purity aluminum foil. The experimental results clearly show the existence of the guiding effect, as found for highly charged ions. The guiding of the electron beam was observed for tilt angles up to 12°. As seen for highly charged ions, the guiding efficiency increases with decreasing...

  11. Ab initio calculations on collisions of low energy electrons with polyatomic molecules

    International Nuclear Information System (INIS)

    Rescigno, T.N.

    1991-01-01

    The Kohn variational method is one of simplest, and oldest, techniques for performing scattering calculations. Nevertheless, a number of formal problems, as well as practical difficulties associated with the computation of certain required matrix elements, delayed its application to electron--molecule scattering problems for many years. This paper will describe the recent theoretical and computational developments that have made the ''complex'' Kohn variational method a practical tool for carrying out calculations of low energy electron--molecule scattering. Recent calculations on a number of target molecules will also be summarized. 41 refs., 7 figs

  12. Initial state dependence of low-energy electron emission in fast ion atom collisions

    International Nuclear Information System (INIS)

    Moshammer, R.; Schmitt, W.; Kollmus, H.; Ullrich, J.; Fainstein, P.D.; Hagmann, S.

    1999-06-01

    Single and multiple ionization of Neon and Argon atoms by 3.6 MeV/u Au 53+ impact has been explored in kinematically complete experiments. Doubly differential cross sections for low-energy electron emission have been obtained for defined charge state of the recoiling target ion and the receding projectile. Observed target specific structures in the electron continuum are attributable to the nodal structure of the initial bound state momentum distribution. The experimental data are in excellent accord with CDW-EIS single ionization calculations if multiple ionization is considered appropriately. (orig.)

  13. Molecular beam epitaxial growth mechanism of ZnSe epilayers on (100) GaAs as determined by reflection high-energy electron diffraction, transmission electron microscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ruppert, P.; Hommel, D.; Behr, T.; Heinke, H.; Waag, A.; Landwehr, G. (Physikalisches Inst., Univ. Wuerzburg (Germany))

    1994-04-14

    The properties of molecular beam epitaxial growth of ZnSe epilayers deposited directly on a GaAs substrate are compared to those grown on a GaAs buffer layer. The superior quality of the latter is confirmed by RHEED, TEM and X-ray diffraction. Based on RHEED oscillation studies, a model explaining the dependence of the ZnSe growth rate on Zn and Se fluxes and the substrate temperature is developed taking into account physisorbed and chemisorbed states. For partially relaxed epilayers, the correlation between the relaxation state and the crystalline mosaicity, as found by high resolution X-ray diffraction, is discussed

  14. Direct nanopatterning of polymer/silver nanoblocks under low energy electron beam irradiation.

    Science.gov (United States)

    El Mel, Abdel-Aziz; Stephant, Nicolas; Gautier, Romain

    2016-10-06

    In this communication, we report on the growth, direct writing and nanopatterning of polymer/silver nanoblocks under low energy electron beam irradiation using a scanning electron microscope. The nanoblocks are produced by placing a droplet of an ethylene glycol solution containing silver nitrate and polyvinylpyrrolidone diluted in ethanol directly on a hot substrate heated up to 150 °C. Upon complete evaporation of the droplet, nanospheres, nano- and micro-triangles and nanoblocks made of silver-containing polymers, form over the substrate surface. Considering the nanoblocks as a model system, we demonstrate that such nanostructures are extremely sensitive to the e-beam extracted from the source of a scanning electron microscope operating at low acceleration voltages (between 5 and 7 kV). This sensitivity allows us to efficiently create various nanopatterns (e.g. arrays of holes, oblique slits and nanotrenches) in the material under e-beam irradiation. In addition to the possibility of writing, the nanoblocks revealed a self-healing ability allowing them to recover a relatively smooth surface after etching. Thanks to these properties, such nanomaterials can be used as a support for data writing and erasing on the nanoscale under low energy electron beam irradiation.

  15. Calculation on spectrum of direct DNA damage induced by low-energy electrons including dissociative electron attachment.

    Science.gov (United States)

    Liu, Wei; Tan, Zhenyu; Zhang, Liming; Champion, Christophe

    2017-03-01

    In this work, direct DNA damage induced by low-energy electrons (sub-keV) is simulated using a Monte Carlo method. The characteristics of the present simulation are to consider the new mechanism of DNA damage due to dissociative electron attachment (DEA) and to allow determining damage to specific bases (i.e., adenine, thymine, guanine, or cytosine). The electron track structure in liquid water is generated, based on the dielectric response model for describing electron inelastic scattering and on a free-parameter theoretical model and the NIST database for calculating electron elastic scattering. Ionization cross sections of DNA bases are used to generate base radicals, and available DEA cross sections of DNA components are applied for determining DNA-strand breaks and base damage induced by sub-ionization electrons. The electron elastic scattering from DNA components is simulated using cross sections from different theoretical calculations. The resulting yields of various strand breaks and base damage in cellular environment are given. Especially, the contributions of sub-ionization electrons to various strand breaks and base damage are quantitatively presented, and the correlation between complex clustered DNA damage and the corresponding damaged bases is explored. This work shows that the contribution of sub-ionization electrons to strand breaks is substantial, up to about 40-70%, and this contribution is mainly focused on single-strand break. In addition, the base damage induced by sub-ionization electrons contributes to about 20-40% of the total base damage, and there is an evident correlation between single-strand break and damaged base pair A-T.

  16. Structure determination of modulated structures by powder X-ray diffraction and electron diffraction

    Czech Academy of Sciences Publication Activity Database

    Zhou, Z.Y.; Palatinus, Lukáš; Sun, J.L.

    2016-01-01

    Roč. 3, č. 11 (2016), s. 1351-1362 ISSN 2052-1553 Institutional support: RVO:68378271 Keywords : electron diffraction * incommensurate structure * powder diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.036, year: 2016

  17. The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors

    Directory of Open Access Journals (Sweden)

    Rachel M. Thorman

    2015-09-01

    Full Text Available Focused electron beam induced deposition (FEBID is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (3, Pt(PF34, Co(CO3NO, and W(CO6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors.

  18. Low-energy electron-helium scattering in a Nd–YAG laser field

    International Nuclear Information System (INIS)

    Ajana, I.; Makhoute, A.; Khalil, D.

    2014-01-01

    Highlights: • Laser assisted electron helium excitation is studied at low incident energies. • The inclusion of the second-order Born contributions is significant at low incident energies. • The target distortion induced by the laser field should be taken into account. • The effect of the second term of the Born series is reduced as the energy increases. - Abstract: We study the electron-impact excitation of atomic helium, in the presence of a linearly polarized Nd–YAG laser field, accompanied by the transfer of ℓ photons, for low collision energy of 25 eV and laser intensity of 5.3 × 10 11 W cm −2 . The second-order Born approximation has been used to calculate the differential cross sections. Detailed calculations of the scattering amplitudes are performed by using the Sturmian basis expansion. A detailed analysis is made of the excitation of the 1 1 S → 2 1 S and 1 1 S → 2 1 P transitions. We discuss the behavior and the variation of the cross sections corresponding to the excitation process for various geometrical configurations

  19. Mineralogical applications of electron diffraction. 1. Theory and techniques

    Science.gov (United States)

    Ross, Malcolm; Christ, C.L.

    1958-01-01

    The small wavelengths used in electron-diffraction experiments and the thinness of the crystals necessary for the transmission of the electron beam combine to require a somewhat different diffraction geometry for the interpretation of electron-diffraction patterns than is used in the interpretation of X-ray diffraction patterns. This geometry, based on the reciprocal lattice concept and geometrical construction of Ewald, needed for the interpretation.

  20. Low-Energy Electrons Emitted in Ion Collisions with Thin Foils

    Science.gov (United States)

    Kraemer, Michael; Kozhuharov, Christophor; Durante, Marco; Hagmann, Siegbert; Kraft, Gerhard; Lineva, Natallia

    The realistic description of radiation damage after charged particle passage is an ongoing issue for both radiotherapy as well as space applications. In both areas of applied radiological science, living as well as nonliving matter is exposed to ionizing radiation, and it is of vital interest to predict the responses of structures like cells, detectors or electronic devices. In ion beam radiotherapy, for example, the Local Effect Model (LEM) is being used to calculate radiobiological effects with so far unprecedented versatility. This has been shown in the GSI radiotherapy pilot project and consequently this model has become the "industry standard" for treatment planning in subsequent commercial ion radiotherapy sites. The model has also been extended to nonliving matter, i.e. to describe the response of solid state detectors such as TLDs and films. A prerequisite for this model (and possibly similar ones) is the proper description of microscopic track structure and energy deposition. In particular, the area at a very low distance (¡20 nm) from the ion path needs special attention due to the locally very high dose and the rather limited experimental evidence for the shape of the dose distribution. The dose distribution at low distances is inevitably associated with the creation and transport of low-energy (sub-keV) electrons. While some data, elementary cross sections as well as dose distributions, exist for gaseous media, i.e. under single collision conditions, experimental data for the condensed phase are scarce. We have, therefore, launched a project aimed at systematic research of the energy and angular distributions of low-energy (sub-keV) electrons emitted from solids. These investigations com-prise creation as well as transport of low-energy electrons under multiple collision conditions and hence require accounting for the properties of the target, both bulk and surface, i.e. for the inherent inhomogeneity of the thickness and for the surface roughness. To

  1. Design and commissioning of an aberration-corrected ultrafast spin-polarized low energy electron microscope with multiple electron sources.

    Science.gov (United States)

    Wan, Weishi; Yu, Lei; Zhu, Lin; Yang, Xiaodong; Wei, Zheng; Liu, Jefferson Zhe; Feng, Jun; Kunze, Kai; Schaff, Oliver; Tromp, Ruud; Tang, Wen-Xin

    2017-03-01

    We describe the design and commissioning of a novel aberration-corrected low energy electron microscope (AC-LEEM). A third magnetic prism array (MPA) is added to the standard AC-LEEM with two prism arrays, allowing the incorporation of an ultrafast spin-polarized electron source alongside the standard cold field emission electron source, without degrading spatial resolution. The high degree of symmetries of the AC-LEEM are utilized while we design the electron optics of the ultrafast spin-polarized electron source, so as to minimize the deleterious effect of time broadening, while maintaining full control of electron spin. A spatial resolution of 2nm and temporal resolution of 10ps (ps) are expected in the future time resolved aberration-corrected spin-polarized LEEM (TR-AC-SPLEEM). The commissioning of the three-prism AC-LEEM has been successfully finished with the cold field emission source, with a spatial resolution below 2nm. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Effect of tissue inhomogeneity on dose distribution of point sources of low-energy electrons

    International Nuclear Information System (INIS)

    Kwok, C.S.; Bialobzyski, P.J.; Yu, S.K.; Prestwich, W.V.

    1990-01-01

    Perturbation in dose distributions of point sources of low-energy electrons at planar interfaces of cortical bone (CB) and red marrow (RM) was investigated experimentally and by Monte Carlo codes EGS and the TIGER series. Ultrathin LiF thermoluminescent dosimeters were used to measure the dose distributions of point sources of 204 Tl and 147 Pm in RM. When the point sources were at 12 mg/cm 2 from a planar interface of CB and RM equivalent plastics, dose enhancement ratios in RM averaged over the region 0--12 mg/cm 2 from the interface were measured to be 1.08±0.03 (SE) and 1.03±0.03 (SE) for 204 Tl and 147 Pm, respectively. The Monte Carlo codes predicted 1.05±0.02 and 1.01±0.02 for the two nuclides, respectively. However, EGS gave consistently 3% higher dose in the dose scoring region than the TIGER series when point sources of monoenergetic electrons up to 0.75 MeV energy were considered in the homogeneous RM situation or in the CB and RM heterogeneous situation. By means of the TIGER series, it was demonstrated that aluminum, which is normally assumed to be equivalent to CB in radiation dosimetry, leads to an overestimation of backscattering of low-energy electrons in soft tissue at a CB--soft-tissue interface by as much as a factor of 2

  3. Simulations and measurements in scanning electron microscopes at low electron energy

    Czech Academy of Sciences Publication Activity Database

    Walker, C.; Frank, Luděk; Müllerová, Ilona

    2016-01-01

    Roč. 38, č. 6 (2016), s. 802-818 ISSN 0161-0457 R&D Projects: GA TA ČR(CZ) TE01020118; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 EU Projects: European Commission(XE) 606988 - SIMDALEE2 Institutional support: RVO:68081731 Keywords : Monte Carlo modeling * scanned probe * computer simulation * electron-solid interactions * surface analysis Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.345, year: 2016

  4. Determination of the electron energy distribution function of a low temperature plasma from optical emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dodt, Dirk Hilar

    2009-01-05

    The experimental determination of the electron energy distribution of a low pressure glow discharge in neon from emission spectroscopic data has been demonstrated. The spectral data were obtained with a simple overview spectrometer and analyzed using a strict probabilistic, Bayesian data analysis. It is this Integrated Data Analysis (IDA) approach, which allows the significant extraction of non-thermal properties of the electron energy distribution function (EEDF). The results bear potential as a non-invasive alternative to probe measurements. This allows the investigation of spatially inhomogeneous plasmas (gradient length smaller than typical probe sheath dimensions) and plasmas with reactive constituents. The diagnostic of reactive plasmas is an important practical application, needed e.g. for the monitoring and control of process plasmas. Moreover, the experimental validation of probe theories for magnetized plasmas as a long-standing topic in plasma diagnostics could be addressed by the spectroscopic method. (orig.)

  5. Determination of the electron energy distribution function of a low temperature plasma from optical emission spectroscopy

    International Nuclear Information System (INIS)

    Dodt, Dirk Hilar

    2009-01-01

    The experimental determination of the electron energy distribution of a low pressure glow discharge in neon from emission spectroscopic data has been demonstrated. The spectral data were obtained with a simple overview spectrometer and analyzed using a strict probabilistic, Bayesian data analysis. It is this Integrated Data Analysis (IDA) approach, which allows the significant extraction of non-thermal properties of the electron energy distribution function (EEDF). The results bear potential as a non-invasive alternative to probe measurements. This allows the investigation of spatially inhomogeneous plasmas (gradient length smaller than typical probe sheath dimensions) and plasmas with reactive constituents. The diagnostic of reactive plasmas is an important practical application, needed e.g. for the monitoring and control of process plasmas. Moreover, the experimental validation of probe theories for magnetized plasmas as a long-standing topic in plasma diagnostics could be addressed by the spectroscopic method. (orig.)

  6. A theoretical approach to low multiplicity diffractive dissociation

    International Nuclear Information System (INIS)

    Bishari, M.

    1977-01-01

    The dynamics of low mass inelastic diffractive production in the framework of the ''1/N dual unitarization'' scheme are investigated. The smallness of inelastic diffractive dissociation is explicitly demonstrated by incorporating a Deck type mechanism with the crucial planar bootstrap equation. Although both inelastic and elastic pomeron couplings are of the same order in 1/N, the origin for their smallness is not identical. The work further confirms the validity of the iterative procedure, where the elastic amplitude is first generated from only non-diffractive intermediate states (except possibly for central collisions). Using a previous study of the ''Cylinder'' strength, a semi-quantitative results for the integrated cross-section for low multiplicity diffractive production is also presented, and is compared with the elastic cross-section at very high energies. (author)

  7. Observation of strong reflection of electron waves exiting a ballistic channel at low energy

    Energy Technology Data Exchange (ETDEWEB)

    Vaz, Canute I.; Campbell, Jason P.; Ryan, Jason T.; Gundlach, David; Cheung, Kin. P., E-mail: Kin.Cheung@NIST.gov [National Institute of Standards and Technology, Gaithersburg, MD 20899-8120 (United States); Liu, Changze [National Institute of Standards and Technology, Gaithersburg, MD 20899-8120 (United States); Institute of Microelectronics, Peking University, Beijing 100871 (China); Southwick, Richard G. [National Institute of Standards and Technology, Gaithersburg, MD 20899-8120 (United States); IBM Research, Albany, NY 12205 (United States); Oates, Anthony S. [Taiwan Semiconductor Manufacturing Corporation, Hsinchu 30844, Taiwan (China); Huang, Ru [Institute of Microelectronics, Peking University, Beijing 100871 (China)

    2016-06-15

    Wave scattering by a potential step is a ubiquitous concept. Thus, it is surprising that theoretical treatments of ballistic transport in nanoscale devices, from quantum point contacts to ballistic transistors, assume no reflection even when the potential step is encountered upon exiting the device. Experiments so far seem to support this even if it is not clear why. Here we report clear evidence of coherent reflection when electron wave exits the channel of a nanoscale transistor and when the electron energy is low. The observed behavior is well described by a simple rectangular potential barrier model which the Schrodinger’s equation can be solved exactly. We can explain why reflection is not observed in most situations but cannot be ignored in some important situations. Our experiment also represents a direct measurement of electron injection velocity - a critical quantity in nanoscale transistors that is widely considered not measurable.

  8. Material dependence of electron inelastic mean free paths at low energies

    International Nuclear Information System (INIS)

    Tanuma, S.; Powell, C.J.; Penn, D.R.

    1990-01-01

    We present and discuss electron inelastic mean free path (IMFP) data for aluminum and gold in the 50--200 eV range. These elements serve as examples of IMFP calculations that have been made for 50--2000 eV electrons in 31 materials (27 elements and 4 compounds). Substantial differences are found in the shapes of the IMFP versus energy curves for Al and Au and these can be understood in terms of the different inelastic scattering mechanisms in the two metals. The minimum IMFP value occurs at 40 eV in aluminum and at 120 eV in gold, a result which is consistent with the trends expected from free-electron IMFP calculations. This result differs, however, from that expected from the Seah and Dench attenuation length formula which shows essentially no material dependence at low energies. We have extended a general formula derived earlier to describe the calculated IMFPs over the 200--2000 eV energy range to give the IMFP dependences on material and energy from 50 to 2000 eV

  9. Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

    Energy Technology Data Exchange (ETDEWEB)

    Byrd, John; De Santis, Stefano; Sonnad, Kiran; Caspers, Fritz; Kroyer, Tom; Krasnykh, Anatoly; Pivi, Mauro

    2008-06-01

    Clouds of low energy electronsin the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energyelectron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.

  10. Monte Carlo dose calculation improvements for low energy electron beams using eMC

    International Nuclear Information System (INIS)

    Fix, Michael K; Frei, Daniel; Volken, Werner; Born, Ernst J; Manser, Peter; Neuenschwander, Hans

    2010-01-01

    The electron Monte Carlo (eMC) dose calculation algorithm in Eclipse (Varian Medical Systems) is based on the macro MC method and is able to predict dose distributions for high energy electron beams with high accuracy. However, there are limitations for low energy electron beams. This work aims to improve the accuracy of the dose calculation using eMC for 4 and 6 MeV electron beams of Varian linear accelerators. Improvements implemented into the eMC include (1) improved determination of the initial electron energy spectrum by increased resolution of mono-energetic depth dose curves used during beam configuration; (2) inclusion of all the scrapers of the applicator in the beam model; (3) reduction of the maximum size of the sphere to be selected within the macro MC transport when the energy of the incident electron is below certain thresholds. The impact of these changes in eMC is investigated by comparing calculated dose distributions for 4 and 6 MeV electron beams at source to surface distance (SSD) of 100 and 110 cm with applicators ranging from 6 x 6 to 25 x 25 cm 2 of a Varian Clinac 2300C/D with the corresponding measurements. Dose differences between calculated and measured absolute depth dose curves are reduced from 6% to less than 1.5% for both energies and all applicators considered at SSD of 100 cm. Using the original eMC implementation, absolute dose profiles at depths of 1 cm, d max and R50 in water lead to dose differences of up to 8% for applicators larger than 15 x 15 cm 2 at SSD 100 cm. Those differences are now reduced to less than 2% for all dose profiles investigated when the improved version of eMC is used. At SSD of 110 cm the dose difference for the original eMC version is even more pronounced and can be larger than 10%. Those differences are reduced to within 2% or 2 mm with the improved version of eMC. In this work several enhancements were made in the eMC algorithm leading to significant improvements in the accuracy of the dose calculation

  11. Monte Carlo dose calculation improvements for low energy electron beams using eMC.

    Science.gov (United States)

    Fix, Michael K; Frei, Daniel; Volken, Werner; Neuenschwander, Hans; Born, Ernst J; Manser, Peter

    2010-08-21

    The electron Monte Carlo (eMC) dose calculation algorithm in Eclipse (Varian Medical Systems) is based on the macro MC method and is able to predict dose distributions for high energy electron beams with high accuracy. However, there are limitations for low energy electron beams. This work aims to improve the accuracy of the dose calculation using eMC for 4 and 6 MeV electron beams of Varian linear accelerators. Improvements implemented into the eMC include (1) improved determination of the initial electron energy spectrum by increased resolution of mono-energetic depth dose curves used during beam configuration; (2) inclusion of all the scrapers of the applicator in the beam model; (3) reduction of the maximum size of the sphere to be selected within the macro MC transport when the energy of the incident electron is below certain thresholds. The impact of these changes in eMC is investigated by comparing calculated dose distributions for 4 and 6 MeV electron beams at source to surface distance (SSD) of 100 and 110 cm with applicators ranging from 6 x 6 to 25 x 25 cm(2) of a Varian Clinac 2300C/D with the corresponding measurements. Dose differences between calculated and measured absolute depth dose curves are reduced from 6% to less than 1.5% for both energies and all applicators considered at SSD of 100 cm. Using the original eMC implementation, absolute dose profiles at depths of 1 cm, d(max) and R50 in water lead to dose differences of up to 8% for applicators larger than 15 x 15 cm(2) at SSD 100 cm. Those differences are now reduced to less than 2% for all dose profiles investigated when the improved version of eMC is used. At SSD of 110 cm the dose difference for the original eMC version is even more pronounced and can be larger than 10%. Those differences are reduced to within 2% or 2 mm with the improved version of eMC. In this work several enhancements were made in the eMC algorithm leading to significant improvements in the accuracy of the dose

  12. Polymeric reaction of polymer-monomer system for pressure sensitive adhesives by low energy electron beam

    International Nuclear Information System (INIS)

    Takiguchi, R.; Uryu, T.

    1985-01-01

    Application of low-energy electron beam to non-solvent type pressure sensitive adhesives is investigated. The adhesive properties such as peel strength and holding time (dead-load strength) were closely related to the reaction of acrylate polymer-monomer systems. The reaction behavior is elucidated by combining the measurement of gel fraction, infrared spectrum of gel, and the molecular weight distribution detected by gel permeation chromatography. It was important for the production of pressure sensitive adhesives by electron beam that the adhesive with high peel strength and long holding time is composed of a proper combination of three factors, that is, about 35% gel fraction, 25% monomer units in gel, and 15% graft efficiency by irradiating the polymer-monomer system containing low molecular weight poly (butyl acrylate). (author)

  13. X-Ray diffraction and scanning electron microscopy-energy dispersive spectroscopic analysis of ceramõmetal interface at different firing temperatures

    Directory of Open Access Journals (Sweden)

    Monika Saini

    2010-01-01

    Full Text Available Objective: Porcelain chipping from porcelain fused to metal restoration has been Achilles heel till date. There has been advent of newer ceramics in past but but none of them has been a panacea for Porcelain fracture. An optimal firing is thus essential for the clinical success of the porcelain-fused to metal restoration. The aim of the present study was to evaluate ceramo-metal interface at different firing temperature using XRD and SEM-EDS analysis. Clinical implication of the study was to predict the optimal firing temperature at which porcelain should be fused with metal in order to possibly prevent the occasional failure of the porcelain fused to metal restorations. Materials and Methods: To meet the above-mentioned goal, porcelain was fused to metal at different firing temperatures (930-990°C in vacuum. The microstructural observations of interface between porcelain and metal were evaluated using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. Results: Based on the experimental investigation of the interaction zone of porcelain fused to metal samples, it was observed that as the firing temperature was increased, the pores became less in number as well as the size of the pores decreased at the porcelain/metal interface upto 975°C but increased in size at 990°C. The least number of pores with least diameter were found in samples fired at 975°C. Several oxides like Cr 2 O 3 , NiO, and Al 2 O 3 and intermetallic compounds (CrSi 2 , AlNi 3 were also formed in the interaction zone. Conclusions : It is suggested that the presence of pores may trigger the crack propagation along the interface, causing the failure of the porcelain fused to metal restoration during masticatory action.

  14. Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5–18 eV) electron interactions with DNA

    Energy Technology Data Exchange (ETDEWEB)

    Rezaee, Mohammad, E-mail: Mohammad.Rezaee@USherbrooke.ca; Hunting, Darel J.; Sanche, Léon [Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4 (Canada)

    2014-07-15

    Purpose: The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Methods: Absorbed dose and stopping cross section for the Auger electrons of 5–18 eV emitted by{sup 125}I within DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure–response curves for induction of DNA strand breaks. Results: For a single decay of{sup 125}I within DNA, the Auger electrons of 5–18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm{sup 3} volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Conclusions: Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should

  15. Ab initio study of low-energy electrons interacting with HCN molecules

    International Nuclear Information System (INIS)

    Jain, A.; Norcross, D.W.

    1984-01-01

    Our earlier study of low-energy electron scattering with HCN molecules is further improved by treating exchange exactly (in a separable exchange approximation 2 ) in Σ, π and Δ symmetries: the 3.8 eV π resonance is shifted towards lower energy (2.56 eV, the experimental position is around 2.26 eV 3 ), while in Σ and the Δ symmetries the difference is within 15%. We also study possible negative ion states of HCN by calculating potential energy curves with respect to C-H and C-N stretches. For example, there is evidence of an avoiding crossing between a 1Σ + and a 2Σ + state (C-H stretch) of HCN -

  16. Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

    Science.gov (United States)

    Bhatia, A. K.; Sinha, Chandana

    2010-01-01

    We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very loud incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering weave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts the exchange approximation has only been considered. We calculate the laser assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

  17. Laboratory Measurements of Charging of Apollo 17 Lunar Dust Grains by Low Energy Electrons

    Science.gov (United States)

    Abbas, Mian M.; Tankosic, Dragana; Spann, James F.; Dube, Michael J.; Gaskin, Jessica

    2007-01-01

    It is well recognized that the charging properties of individual micron/sub-micron size dust grains by various processes are expected to be substantially different from the currently available measurements made on bulk materials. Solar UV radiation and the solar wind plasma charge micron size dust grains on the lunar surface with virtually no atmosphere. The electrostatically charged dust grains are believed to be levitated and transported long distances over the lunar terminator from the day to the night side. The current models do not fully explain the lunar dust phenomena and laboratory measurements are needed to experimentally determine the charging properties of lunar dust grains. An experimental facility has been developed in the Dusty Plasma Laboratory at NASA Marshall Space Flight Center MSFC for investigating the charging properties of individual micron/sub-micron size positively or negatively charged dust grains by levitating them in an electrodynamic balance in simulated space environments. In this paper, we present laboratory measurements on charging of Apollo 17 individual lunar dust grains by low energy electron beams in the 5-100 eV energy range. The measurements are made by levitating Apollo 17 dust grains of 0.2 to 10 micrometer diameters, in an electrodynamic balance and exposing them to mono-energetic electron beams. The charging rates and the equilibrium potentials produced by direct electron impact and by secondary electron emission processes are discussed.

  18. Selected Energy Epitaxial Deposition and Low Energy Electron Microscopy of AlN, GaN and SiC Thin Films

    National Research Council Canada - National Science Library

    Davis, R

    1999-01-01

    The homoepitaxial growth of GaN(0001) layers was studied in situ and in real time using the low-energy electron microscope and ex situ using atomic force microscopy and transmission electron microscopy...

  19. Low-Energy Electron Scattering Data for Chemical Plasma Treatment of Biomass

    International Nuclear Information System (INIS)

    Lima, Marco A.P.

    2014-01-01

    Full text: Replacing fossil fuels with biofuels from renewable sources is an important goal for reducing greenhouse gas emissions. Many countries are already using few percent of ethanol in the gasoline and few of them, with more aggressive programs, have developed flex fuel engines that can run with any mixture of gasoline and ethanol. An important point is how to produce ethanol in a sustainable way and with which technology? Biomass is a good candidate since it has cellulose and hemicellulose as source of sugars. In order to liberate these sugars for fermentation, it is important to learn how to separate the main components. Chemical routes (acid treatment) and biological routes (enzymatic hydrolysis) are combined and used for these purposes. Atmospheric plasmas can be useful for attacking the biomass in a controlled manner and low-energy electrons may have an important role in the process. Recently we have been studying the interaction of electrons with lignin subunits (phenol, guaiacol, p-coumaryl alcohol), cellulose components, β-D-glucose and cellobiose (β(1 - 4) linked glucose dimer) and hemicellulose components (β-D-xylose). We also obtained results for the amylose subunits α-D-glucose and maltose (α(1 - 4) linked glucose dimer). Altogether, the resonance spectra of lignin, cellulose and hemicellulose components establish a physical–chemical basis for electron-induced biomass pretreatment that could be applied to biofuel production. In my talk I will give a progress report on this matter. We will also discuss microsolvation effects on the electron-phenol scattering process and present our strategy to study molecular dissociation through electronic excitation of low energy triplet states. (author)

  20. Projectile Coulomb center effects on low-energy electron emission from H[sup +][yields]Ne collisions

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, S. (Centro Atomico Bariloche e Inst. Balseiro, Comision Nacional de Energia Atomica, S.C. de Bariloche, Rio Negro (Argentina)); Garibotti, C. (Centro Atomico Bariloche e Inst. Balseiro, Comision Nacional de Energia Atomica, S.C. de Bariloche, Rio Negro (Argentina) Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)); Bernardi, G. (Centro Atomico Bariloche e Inst. Balseiro, Comision Nacional de Energia Atomica, S.C. de Bariloche, Rio Negro (Argentina) Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)); Focke, P. (Centro Atomico Bariloche e Inst. Balseiro, Comision Nacional de Energia Atomica, S.C. de Bariloche, Rio Negro (Argentina)); Meckbach, W. (Centro Atomico Bariloche e Inst. Balseiro, Comision Nacional de Energia Atomica, S.C. de Bariloche, Rio Negro (Argentina) Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina))

    1994-03-01

    We present doubly differential energy distributions of low-energy electrons emitted in collisions of 106 keV H[sup +] on Ne atoms. We find a relevant dependence of the measured distribution of low-energy electrons on the physical extension of the gas target and discuss a correction procedure. Our measurements enable a quantitative analysis of the shape of the soft electron peak, which is clearly evidenced by measured contour lines. Present results indicate that ''two center effects'' must be considered in order to account for the strong asymmetry of the soft electron peak observed experimentaly. (orig.)

  1. An electron cyclotron resonance ion source based low energy ion beam platform

    International Nuclear Information System (INIS)

    Sun, L. T.; Shang, Y.; Ma, B. H.; Zhang, X. Z.; Feng, Y. C.; Li, X. X.; Wang, H.; Guo, X. H.; Song, M. T.; Zhao, H. Y.; Zhang, Z. M.; Zhao, H. W.; Xie, D. Z.

    2008-01-01

    To satisfy the requirements of surface and atomic physics study in the field of low energy multiple charge state ion incident experiments, a low energy (10 eV/q-20 keV/q) ion beam platform is under design at IMP. A simple test bench has been set up to test the ion beam deceleration systems. Considering virtues such as structure simplicity, easy handling, compactness, cost saving, etc., an all-permanent magnet ECRIS LAPECR1 [Lanzhou all-permanent magnet electron cyclotron resonance (ECR) ion source No. 1] working at 14.5 GHz has been adopted to produce intense medium and low charge state ion beams. LAPECR1 source has already been ignited. Some intense low charge state ion beams have been produced on it, but the first test also reveals that many problems are existing on the ion beam transmission line. The ion beam transmission mismatches result in the depressed performance of LAPECR1, which will be discussed in this paper. To obtain ultralow energy ion beam, after being analyzed by a double-focusing analyzer magnet, the selected ion beam will be further decelerated by two afocal deceleration lens systems, which is still under design. This design has taken into consideration both ions slowing down and also ion beam focusing. In this paper, the conceptual design of deceleration system will be discussed

  2. An electron cyclotron resonance ion source based low energy ion beam platform.

    Science.gov (United States)

    Sun, L T; Shang, Y; Ma, B H; Zhang, X Z; Feng, Y C; Li, X X; Wang, H; Guo, X H; Song, M T; Zhao, H Y; Zhang, Z M; Zhao, H W; Xie, D Z

    2008-02-01

    To satisfy the requirements of surface and atomic physics study in the field of low energy multiple charge state ion incident experiments, a low energy (10 eV/q-20 keV/q) ion beam platform is under design at IMP. A simple test bench has been set up to test the ion beam deceleration systems. Considering virtues such as structure simplicity, easy handling, compactness, cost saving, etc., an all-permanent magnet ECRIS LAPECR1 [Lanzhou all-permanent magnet electron cyclotron resonance (ECR) ion source No. 1] working at 14.5 GHz has been adopted to produce intense medium and low charge state ion beams. LAPECR1 source has already been ignited. Some intense low charge state ion beams have been produced on it, but the first test also reveals that many problems are existing on the ion beam transmission line. The ion beam transmission mismatches result in the depressed performance of LAPECR1, which will be discussed in this paper. To obtain ultralow energy ion beam, after being analyzed by a double-focusing analyzer magnet, the selected ion beam will be further decelerated by two afocal deceleration lens systems, which is still under design. This design has taken into consideration both ions slowing down and also ion beam focusing. In this paper, the conceptual design of deceleration system will be discussed.

  3. Radiobiological application of simulation of low-energy electron transport in liquid water

    International Nuclear Information System (INIS)

    Eudaldo Puell, Teresa.

    1979-01-01

    A Monte-Carlo transport simulation method, so-called event-after-event method provide results about trajectories of low-energy electrons, slowing-down in liquid water. A radiosensitive target model constituted by water cylindrical volumes, like the ones which surround the DNA molecule, is taken into consideration. The results characterizing the primary physical stage of radiation action, such as, space ionization distributions, interionization distance distributions ..., are obtained in some configurations constituted by single or several targets, in order to approach the biological reality [fr

  4. Immobilization of enzyme and antibody by low energy electron beam polymerization

    International Nuclear Information System (INIS)

    Kaetsu, Isao; Kumakura, Minoru

    1987-01-01

    Immobilization of glucoamylase and AFP-antibody was studied using an electron beam of relatively low energy. A thin polymer membrane formed by irradiation of monomer enzyme mixture in a buffer, which had a considerable enzymatic activity. A membrane of almost the same thickness and activity was obtained by repeated irradiation. The effect of irradiation conditions on the immobilization and the variations of irradiation method for immobilization were investigated. The immobilization of antibody was carried out in similar ways as for enzyme, and the product also showed a considerable activity. (author)

  5. Improved age-diffusion model for low-energy electron transport in solids. II. Application to secondary emission from aluminum

    International Nuclear Information System (INIS)

    Dubus, A.; Devooght, J.; Dehaes, J.C.

    1987-01-01

    The ''improved age-diffusion'' model for secondary-electron transport is applied to aluminum. Electron cross sections for inelastic collisions with the free-electron gas using the Lindhard dielectric function and for elastic collisions with the randomly distributed ionic cores are used in the calculations. The most important characteristics of backward secondary-electron emission induced by low-energy electrons on polycrystalline Al targets are calculated and compared to experimental results and to Monte Carlo calculations. The model appears to predict the electronic yield, the energy spectra, and the spatial dependence of secondary emission with reasonable accuracy

  6. Low-energy magnetic dipole response in 56Fe from high-resolution electron scattering

    International Nuclear Information System (INIS)

    Fearick, R.W.; Hartung, G.; Langanke, K.; Martinez-Pinedo, G.; Neumann-Cosel, P. von; Richter, A.

    2003-01-01

    The 56 Fe(e, e') reaction has been studied for excitation energies up to about 8 MeV and momentum transfers q≅0.4-0.55 fm -1 at the Darmstadt electron linear accelerator (DALINAC) with kinematics emphasizing M1 transitions. Additional data have been taken for q≅0.8-1.7 fm -1 at the electron accelerator NIKHEF, Amsterdam. A PWBA analysis allows spin and parity determination of the excited states. For M1 excitations, transition strengths are derived with a DWBA analysis using shell-model form factors. The resulting B(M1) strength distribution is compared to shell-model calculations employing different effective interactions. The form factor of the prominent low-lying M1 transition at 3.449 MeV demonstrates its dominant orbital nature. It represents a major part of the scissors mode in 56 Fe

  7. Acceleration of Electrons in a Diffraction Dominated IFEL

    CERN Document Server

    Musumeci, Pietro; Pellegrini, Claudio; Ralph, J; Rosenzweig, J B; Sung, C; Tochitsky, Sergei Ya; Travish, Gil

    2004-01-01

    We report on the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected ina 50 cm long undulator strongly tapered both in period and field amplitude. A CO2 10 μ m laser with power >300 GW is used as the IFEL driver. The Rayleigh range of the laser (1.8cm) is shorter than the undulator length so that the interaction is diffraction dominated. Few per cent of the injected particles are trapped in stable accelerating buckets and electrons with energies up to 35 MeV are detected on the magnetic spectrometers. Experimental results on the scaling of the accelerator characteristics versus input parameters like injection energy, laser focus position and laser power are discussed. Three dimensional simulations are in good agreement with the electron energy spectrums observed in the experiment and indicate that substantial energy exchange between laser and electron beam only occurs in the firs...

  8. Generation of a pulsed low-energy electron beam using the channel spark device

    Energy Technology Data Exchange (ETDEWEB)

    Elgarhy, M. A. I., E-mail: elgarhy@azhar.edu.eg; Hassaballa, S. E.; Rashed, U. M.; ElSabbagh, M. M.; Saudy, A. H. [Physics Department, Faculty of Science, Al-Azhar University, Cairo (Egypt); Soliman, H. M. [Plasma and Nuclear Fusion Department, Atomic Energy Authority, Enshas (Egypt)

    2015-12-15

    For the generation of low-energy electron beam, the design and characteristics of channel spark discharge (CSD) operating at a low voltage are presented in this paper. The discharge voltage, discharge current, X-ray emissions, and electron beam current were experimentally determined. The effects of the applied voltage, working gas pressure, and external capacitance on the CSD and beam parameters were measured. At an applied voltage of 11 kV, an oxygen gas pressure of 25 mTorr, and an external capacitance of 16.45 nF, the maximum measured current was 900 A. The discharge current increased with the increase in the pressure and capacitance, while its periodic time decreased with the increase in the pressure. Two types of the discharge were identified and recorded: the hollow cathode discharge and the conduction discharge. A Faraday cup was used to measure the beam current. The maximum measured beam current was 120 A, and the beam signal exhibited two peaks. The increase in both the external capacitance and the applied discharge voltage increased the maximum electron beam current. The electron-beam pulse time decreased with the increase in the gas pressure at a constant voltage and increased with the decrease in the applied discharge voltage. At an applied voltage of 11 kV and an oxygen gas pressure of 15 mTorr, the maximum beam energy was 2.8 keV. The X-ray signal intensity decreased with the increase in the gas pressure and increased with the increase in the capacitance.

  9. Low energy electron-initiated ion-molecule reactions of ribose analogues

    International Nuclear Information System (INIS)

    Mozejko, P.

    2003-01-01

    Recent experiments in which plasmid DNA samples were bombarded with low energy ( 2 O, DNA bases, and sugar-phosphate backbone analogues. To this end, the cyclic molecule tetrahydrofuran, and its derivatives, provide useful models for the sugar-like molecules contained in the backbone of DNA. In addition to LEE induced dissociation by processes such as dissociative electron attachment (DEA), molecules may be damaged by ions and neutral species of non-thermal energies created by LEE in the surrounding environment. In this contribution, we investigate with electron stimulated desorption techniques, LEE damage to films of desoxy-ribose analogues in the presence of various molecular coadsorbates, that simulate changes in local molecular environment. In one type of experiments tetrahydrofuran is deposited onto multilayer O2. A desorbed signal of OH - indicates ion-molecule reactions of the type O - + C 4 H 8 O -> OH - + C 4 H 7 O, where the O - was formed initially by DEA to O 2 . Further electron stimulated desorption measurements for tetrahydrofuran and derivatives adsorbed on H 2 O, Kr, N 2 O and CH 3 OH will be presented and discussed

  10. Low Energy Electron Cooling and Accelerator Physics for the Heidelberg CSR

    International Nuclear Information System (INIS)

    Fadil, H.; Grieser, M.; Hahn, R. von; Orlov, D.; Schwalm, D.; Wolf, A.; Zajfman, D.

    2006-01-01

    The Cryogenic Storage Ring (CSR) is currently under construction at MPI-K in Heidelberg. The CSR is an electrostatic ring with a total circumference of about 34 m, straight section length of 2.5 m and will store ions in the 20 ∼ 300 keV energy range (E/Q). The cryogenic system in the CSR is expected to cool the inner vacuum chamber down to 2 K. The CSR will be equipped with an electron cooler which has also to serve as an electron target for high resolution recombination experiments. In this paper we present the results of numerical investigations of the CSR lattice with finite element calculations of the deflection and focusing elements of the ring. We also present a layout of the CSR electron cooler which will have to operate in low energy mode to cool 20 keV protons in the CSR, as well as numerical estimations of the cooling times to be expected with this device

  11. Low-energy-electron interactions with DNA: approaching cellular conditions with atmospheric experiments

    International Nuclear Information System (INIS)

    Alizadeh, E.; Sanche, L.

    2014-01-01

    A novel technique has been developed to investigate low energy electron (LEE)-DNA interactions in the presence of small biomolecules (e.g., N 2 , O 2 , H 2 O) found near DNA in the cell nucleus, in order to simulate cellular conditions. In this technique, LEEs are emitted from a metallic surface exposed by soft X-rays and interact with DNA thin films at standard ambient temperature and pressure (SATP). Whereas atmospheric N 2 had little effect on the yields of LEE-induced single and double strand breaks, both O 2 and H 2 O considerably modified and increased such damage. The highest yields were obtained when DNA is embedded in a combined O 2 and H 2 O atmosphere. In this case, the amount of additional double strand breaks was supper-additive. The effect of modifying the chemical and physical stability of DNA by platinum-based chemotherapeutic agents (Pt-drugs) including cisplatin, carboplatin and oxaliplatin was also investigated with this technique. The results obtained provide information on the role played by subexcitation-energy electrons and dissociative electron attachment in the radiosensitization of DNA by Pt-drugs, which is an important step to unravel the mechanisms of radiosensitization of these agents in chemo-radiation cancer therapy. (authors)

  12. Role of Electronic Structure In Ion Band State Theory of Low Energy Nuclear Reactions

    Science.gov (United States)

    Chubb, Scott

    2004-03-01

    The Nuts and Bolts of our Ion Band State (IBS) theory of low energy nuclear reactions (LENR's) in palladium-deuteride (PdD) and palladium-hydride (PdH) are the electrons that hold together or tear apart the bonds (or lack of bonds) between deuterons (d's) or protons (p's) and the host material. In PdDx and PdH_x, this bonding is strongly correlated with loading: in ambient loading conditions (x< 0. 6), the bonding in hibits IBS occupation. As x arrow 1, slight increases and decreases in loading can lead to vibrations (which have conventionally been thought to occur from phonons) that can induce potential losses or increases of p/d. Naive assumptions about phonons fail to include these losses and increases. These effects can occur because neither H or D has core electrons and because in either PdD or PdH, the electrons near the Fermi Energy have negligible overlap with the nucleus of either D or H. I use these ideas to develop a formal justification, based on a generalization of conventional band theory (Scott Chubb, "Semi-Classical Conduction of Charged and Neutral Particles in Finite Lattices," 2004 March Meeting."), for the idea that occupation of IBS's can occur and that this can lead to nuclear reactions.

  13. Low-energy-electron interactions with DNA: approaching cellular conditions with atmospheric experiments

    Science.gov (United States)

    Alizadeh, Elahe; Sanche, Léon

    2014-04-01

    A novel technique has been developed to investigate low energy electron (LEE)-DNA interactions in the presence of small biomolecules (e.g., N2, O2, H2O) found near DNA in the cell nucleus, in order to simulate cellular conditions. In this technique, LEEs are emitted from a metallic surface exposed by soft X-rays and interact with DNA thin films at standard ambient temperature and pressure (SATP). Whereas atmospheric N2 had little effect on the yields of LEE-induced single and double strand breaks, both O2 and H2O considerably modified and increased such damage. The highest yields were obtained when DNA is embedded in a combined O2 and H2O atmosphere. In this case, the amount of additional double strand breaks was supper-additive. The effect of modifying the chemical and physical stability of DNA by platinum-based chemotherapeutic agents (Pt-drugs) including cisplatin, carboplatin and oxaliplatin was also investigated with this technique. The results obtained provide information on the role played by subexcitation-energy electrons and dissociative electron attachment in the radiosensitization of DNA by Pt-drugs, which is an important step to unravel the mechanisms of radiosensitisation of these agents in chemoradiation cancer therapy.

  14. Electro-optic sampling for time resolving relativistic ultrafast electron diffraction

    International Nuclear Information System (INIS)

    Scoby, C. M.; Musumeci, P.; Moody, J.; Gutierrez, M.; Tran, T.

    2009-01-01

    The Pegasus laboratory at UCLA features a state-of-the-art electron photoinjector capable of producing ultrashort (<100 fs) high-brightness electron bunches at energies of 3.75 MeV. These beams recently have been used to produce static diffraction patterns from scattering off thin metal foils, and it is foreseen to take advantage of the ultrashort nature of these bunches in future pump-probe time-resolved diffraction studies. In this paper, single shot 2-d electro-optic sampling is presented as a potential technique for time of arrival stamping of electron bunches used for diffraction. Effects of relatively low bunch charge (a few 10's of pC) and modestly relativistic beams are discussed and background compensation techniques to obtain high signal-to-noise ratio are explored. From these preliminary tests, electro-optic sampling is suitable to be a reliable nondestructive time stamping method for relativistic ultrafast electron diffraction at the Pegasus lab.

  15. Electron response of some low-Z scintillators in wide energy range

    International Nuclear Information System (INIS)

    Swiderski, L; Marcinkowski, R; Moszynski, M; Czarnacki, W; Szawlowski, M; Szczesniak, T; Pausch, G; Plettner, C; Roemer, K

    2012-01-01

    Light yield nonproportionality and the intrinsic resolution of some low atomic number scintillators were studied by means of the Wide Angle Compton Coincidence (WACC) technique. The plastic and liquid scintillator response to Compton electrons was measured in the energy range of 10 keV up to 4 MeV, whereas a CaF 2 :Eu sample was scanned from 3 keV up to 1 MeV. The nonproportionality of the CaF 2 :Eu light yield has characteristics typical for inorganic scintillators of the multivalent halides group, whereas tested organic scintillators show steeply increasing nonproportionality without saturation point. This is in contrast to the behavior of all known inorganic scintillators having their nonproportionality curves at saturation above energies between tens and several hundred keV.

  16. Electron response of some low-Z scintillators in wide energy range

    Science.gov (United States)

    Swiderski, L.; Marcinkowski, R.; Moszynski, M.; Czarnacki, W.; Szawlowski, M.; Szczesniak, T.; Pausch, G.; Plettner, C.; Roemer, K.

    2012-06-01

    Light yield nonproportionality and the intrinsic resolution of some low atomic number scintillators were studied by means of the Wide Angle Compton Coincidence (WACC) technique. The plastic and liquid scintillator response to Compton electrons was measured in the energy range of 10 keV up to 4 MeV, whereas a CaF2:Eu sample was scanned from 3 keV up to 1 MeV. The nonproportionality of the CaF2:Eu light yield has characteristics typical for inorganic scintillators of the multivalent halides group, whereas tested organic scintillators show steeply increasing nonproportionality without saturation point. This is in contrast to the behavior of all known inorganic scintillators having their nonproportionality curves at saturation above energies between tens and several hundred keV.

  17. Performance studies of the vibration wire monitor on the test stand with low energy electron beam

    International Nuclear Information System (INIS)

    Okabe, Kota; Yoshimoto, Masahiro; Kinsho, Michikazu

    2015-01-01

    In the high intensity proton accelerator as the Japan Proton Accelerator Research Complex (J-PARC) accelerators, serious radiation and residual dose is induced by a small beam loss such a beam halo. Therefore, diagnostics of the beam halo formation is one of the most important issues to control the beam loss. For the beam halo monitor, the vibration wire monitor (VWM) has a potential for investigating the beam halo and weak beam scanning. The VWM has a wide dynamic range, high resolution and the VWM is not susceptible to secondary electrons and electric noises. We have studied the VWM features as a new beam-halo monitor on the test stand with low energy electron gun. The frequency shift of the irradiated vibration wire was confirmed about wire material and the electron beam profile measured by using the VWM was consistent with the results of the Faraday cup measurement. Also we calculated a temperature distribution on the vibration wire which is irradiated by the electron beam with the numerical simulation. The simulations have been fairly successful in reproducing the transient of the irradiated vibration wire frequency measured by test stand experiments. In this paper, we will report a result of performance evaluation for the VWM on the test stands and discuss the VWM for beam halo diagnostic. (author)

  18. Methods for functionality improvement of digital electronics with low switching energy

    International Nuclear Information System (INIS)

    Wetzstein, Olaf

    2010-01-01

    This thesis is a contribution to automate electronic circuit design for technologies dealing with low switching energy.The intention is to increase the stability of Rapid Single Flux Quantum (RSFQ) circuits. In order to achieve this goal, new design tools are introduced and innovative circuit topologies are implemented.The concepts that have been elaborated are demonstrated using RSFQ circuits, but they are valid for any other digital electronics.Future developments with main focus on power efficiency will take advantage of these new concepts and design tools.The aim of this work is to analyze the influences of thermal noise on the reliability of sensitive electronics.By means of an analytic description, the influence of thermal noise is classified. Based on this estimation the stability of circuits is evaluated. This approach of correlating the topology of a circuit with its immunity to thermal noise is unique so far.The results of the analysis demonstrate that using a symmetric circuit topology significantly improves the circuit's robustness against both the influence of thermal noise and parameter spread caused by the fabrication process. In order to realize symmetric circuits, phase-shifting-elements such as pi-junctions become important.The technology that permits the fabrication of phase-shifting-elements has been developed during the recent years.The essential work flow which is necessary to implement these elements into RSFQ electronics is presented in detail in this work. The predicted improvements are experimentally proved.

  19. Electron cooling of PB$^{54+}$ ions in the low energy ion ring (LEIR)

    CERN Document Server

    Bosser, Jacques; Chanel, M; MacCaferri, R; Maury, S; Möhl, D; Molinari, G; Tranquille, G

    1998-01-01

    For the preparation of dense bunches of lead ions for the LHC, electron cooling will be essential for accumula tion in a storage ring at 4.2 MeV/u. Tests have been carried out on the LEAR ring (renamed LEIR for Low Energy Ion Ring) in order to determine the optimum parameters for a future state-of-the-art electron cooling device which would be able to cool linac pulses of lead ions in less than 100 ms. The experiments focused on the generation of a stable high intensity electron beam that is needed to free space in both longitudinal and transverse phase space for incoming pulses. Investigations on the ion beam lifetime in the presence of the electron beam and on the dependency of the cooling times on the optical settings of the storage ring will also be discussed. This paper concentrates on the cooling aspects with the multiturn injection, vacuum, and high intensity aspects discussed in a companion paper at this conference.

  20. Determining neutrino mass hierarchy from electron disappearance at a low energy neutrino factory

    International Nuclear Information System (INIS)

    Raut, Sushant K.

    2013-01-01

    Reactor neutrino experiments have recently measured the value of θ 13 , to be non-zero and moderately large. This makes the determination of the neutrino mass hierarchy possible. However, our lack of knowledge of δ CP results in a parameter degeneracy, which makes this task difficult. The electron neutrino disappearance probability does not depend on δ CP . Therefore, in principle, it is possible to determine the hierarchy independently of δ CP using this channel. Previous studies of neutrino factories have not considered this channel, because the effect of systematics in electron disappearance is substantial. However, we show that for the moderately large value of θ 13 measured, hierarchy determination is possible in spite of systematic effects. We consider a low energy neutrino factory (LENF) setup with a totally active scintillator detector (TASD) with charge-identification. We optimize the setup in muon energy and baseline, for different allowed values of θ 13 and runtime. We find that a LENF with baseline of around 1300 km and muon energy around 3-4 GeV is well suited for hierarchy determination. For the RENO best-fit value of θ 13 , this setup can determine the hierarchy at 5ω, for all values of δ CP and for both hierarchies. (author)

  1. Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas

    Science.gov (United States)

    Li, Jun; Zhang, Song Bin; Ye, Bang Jiao; Wang, Jian Guo; Janev, R. K.

    2017-09-01

    Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas have been investigated by employing the exterior complex scaling method. The interactions between charged particles in the plasmas have been represented by Debye-Hückel potentials. The 1 s -1 s elastic collision strengths below the n =2 excitation threshold of He+ dominated by resonance structures are calculated for different screening lengths. As the screening strength increases, the resonance peaks studied [2(1,0) 2 +1Se,3Po,1De , and 2(0,1) 2 +1Po] exhibit blueshifts and then redshifts with a further increase of the screening strength, which results in dramatic changes of the collision strengths. It is found that these dynamic variation features of the resonances are related to the changes of energy levels of He+ in the screened potential and geometric configurations of resonances. Triple-differential-ionization cross sections in coplanar geometries at 6-Ry incident electron energy are also reported, significant changes are observed with varying screening length.

  2. A Low-Energy-Spread Rf Accelerator for a Far-Infrared Free-Electron Laser

    NARCIS (Netherlands)

    van der Geer, C. A. J.; Bakker, R. J.; van der Meer, A. F. G.; van Amersfoort, P. W.; Gillespie, W. A.; Saxon, G.; Poole, M. W.

    1993-01-01

    A high electron current and a small energy spread are essential for the operation of a free electron laser (FEL). In this paper we discuss the design and performance of the accelerator for FELIX, the free electron laser for infrared experiments. The system consists of a thermionic gun, a prebuncher,

  3. Calculations on Electron Capture in Low Energy Ion-Molecule Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Stancil, P.C. [Oak Ridge National Lab., TN (United States); Zygelman, B. [W.M. Keck Lab. for Computational Physics, Univ. of Nevada, Las Vegas, NV (United States); Kirby, K. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

    1997-12-31

    Recent progress on the application of a quantal, molecular-orbital, close-coupling approach to the calculation of electron capture in collisions of multiply charged ions with molecules is discussed. Preliminary results for single electron capture by N{sup 2+} with H{sub 2} are presented. Electron capture by multiply charged ions colliding with H{sub 2} is an important process in laboratory and astrophysical plasmas. It provides a recombination mechanism for multiply charged ions in x-ray ionized astronomical environments which may have sparse electron and atomic hydrogen abundances. In the divertor region of a tokamak fusion device, charge exchange of impurity ions with H{sub 2} plays a role in the ionization balance and the production of radiative energy loss leading to cooling, X-ray and ultraviolet auroral emission from Jupiter is believed to be due to charge exchange of O and S ions with H{sub 2} in the Jovian atmosphere. Solar wind ions interacting with cometary molecules may have produced the x-rays observed from Comet Hyakutake. In order to model and understand the behavior of these environments, it is necessary to obtain total, electronic state-selective (ESS), and vibrational (or rotational) state-selective (VSS) capture cross sections for collision energies as low as 10 meV/amu to as high as 100 keV/amu in some instances. Fortunately, charge transfer with molecular targets has received considerable experimental attention. Numerous measurements have been made with flow tubes, ion traps, and ion beams. Flow tube and ion trap studies generally provide information on rate coefficients for temperatures between 800 K and 20,000 K. In this article, we report on the progress of our group in implementing a quantum-mechanical Molecular Orbital Close Coupling (MOCC) approach to the study of electron capture by multiply charged ions in collisions with molecules. We illustrate this with a preliminary investigation of Single Electron Capture (SEC) by N{sup 2+} with H

  4. Investigation on the correlation between energy deposition and clustered DNA damage induced by low-energy electrons.

    Science.gov (United States)

    Liu, Wei; Tan, Zhenyu; Zhang, Liming; Champion, Christophe

    2018-05-01

    This study presents the correlation between energy deposition and clustered DNA damage, based on a Monte Carlo simulation of the spectrum of direct DNA damage induced by low-energy electrons including the dissociative electron attachment. Clustered DNA damage is classified as simple and complex in terms of the combination of single-strand breaks (SSBs) or double-strand breaks (DSBs) and adjacent base damage (BD). The results show that the energy depositions associated with about 90% of total clustered DNA damage are below 150 eV. The simple clustered DNA damage, which is constituted of the combination of SSBs and adjacent BD, is dominant, accounting for 90% of all clustered DNA damage, and the spectra of the energy depositions correlating with them are similar for different primary energies. One type of simple clustered DNA damage is the combination of a SSB and 1-5 BD, which is denoted as SSB + BD. The average contribution of SSB + BD to total simple clustered DNA damage reaches up to about 84% for the considered primary energies. In all forms of SSB + BD, the SSB + BD including only one base damage is dominant (above 80%). In addition, for the considered primary energies, there is no obvious difference between the average energy depositions for a fixed complexity of SSB + BD determined by the number of base damage, but average energy depositions increase with the complexity of SSB + BD. In the complex clustered DNA damage constituted by the combination of DSBs and BD around them, a relatively simple type is a DSB combining adjacent BD, marked as DSB + BD, and it is of substantial contribution (on average up to about 82%). The spectrum of DSB + BD is given mainly by the DSB in combination with different numbers of base damage, from 1 to 5. For the considered primary energies, the DSB combined with only one base damage contributes about 83% of total DSB + BD, and the average energy deposition is about 106 eV. However, the

  5. Quantitative convergent beam electron diffraction measurements of bonding in alumina

    International Nuclear Information System (INIS)

    Johnson, A.W.S.

    2002-01-01

    Full text: The QCBED technique of measuring accurate structure factors has been made practical by advances in energy filtering, computing and in the accurate measurement of intensity. Originally attempted in 1965 by the late Peter Goodman (CSIRO, Melbourne) while working with Gunter Lehmpfuhl (Fritz Haber Institut, Berlin), QCBED has been successfully developed and tested in the last decade on simple structures such as Si and MgO. Our work on Alumina is a step up in complexity and has shown that extinction in X-ray diffraction is not correctable to the precision required. In combination with accurate X-ray diffraction, QCBED promises to revolutionize the accuracy of bonding charge density measurements, experimental results which are of significance in the development of Density Functional Theory used in predictive chemistry. Copyright (2002) Australian Society for Electron Microscopy Inc

  6. Single Hit Energy-resolved Laue Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Shamim; Suggit, Matthew J.; Stubley, Paul G.; Ciricosta, Orlando; Wark, Justin S.; Higginbotham, Andrew [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Hawreliak, James A.; Collins, Gilbert W.; Eggert, Jon H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Comley, Andrew J.; Foster, John M. [Atomic Weapons Establishment, Aldermaston, Reading RG7 4PR (United Kingdom)

    2015-05-15

    In situ white light Laue diffraction has been successfully used to interrogate the structure of single crystal materials undergoing rapid (nanosecond) dynamic compression up to megabar pressures. However, information on strain state accessible via this technique is limited, reducing its applicability for a range of applications. We present an extension to the existing Laue diffraction platform in which we record the photon energy of a subset of diffraction peaks. This allows for a measurement of the longitudinal and transverse strains in situ during compression. Consequently, we demonstrate measurement of volumetric compression of the unit cell, in addition to the limited aspect ratio information accessible in conventional white light Laue. We present preliminary results for silicon, where only an elastic strain is observed. VISAR measurements show the presence of a two wave structure and measurements show that material downstream of the second wave does not contribute to the observed diffraction peaks, supporting the idea that this material may be highly disordered, or has undergone large scale rotation.

  7. Single Hit Energy-resolved Laue Diffraction

    International Nuclear Information System (INIS)

    Patel, Shamim; Suggit, Matthew J.; Stubley, Paul G.; Ciricosta, Orlando; Wark, Justin S.; Higginbotham, Andrew; Hawreliak, James A.; Collins, Gilbert W.; Eggert, Jon H.; Comley, Andrew J.; Foster, John M.

    2015-01-01

    In situ white light Laue diffraction has been successfully used to interrogate the structure of single crystal materials undergoing rapid (nanosecond) dynamic compression up to megabar pressures. However, information on strain state accessible via this technique is limited, reducing its applicability for a range of applications. We present an extension to the existing Laue diffraction platform in which we record the photon energy of a subset of diffraction peaks. This allows for a measurement of the longitudinal and transverse strains in situ during compression. Consequently, we demonstrate measurement of volumetric compression of the unit cell, in addition to the limited aspect ratio information accessible in conventional white light Laue. We present preliminary results for silicon, where only an elastic strain is observed. VISAR measurements show the presence of a two wave structure and measurements show that material downstream of the second wave does not contribute to the observed diffraction peaks, supporting the idea that this material may be highly disordered, or has undergone large scale rotation

  8. Pathogens Inactivated by Low-Energy-Electron Irradiation Maintain Antigenic Properties and Induce Protective Immune Responses

    Science.gov (United States)

    Fertey, Jasmin; Bayer, Lea; Grunwald, Thomas; Pohl, Alexandra; Beckmann, Jana; Gotzmann, Gaby; Casado, Javier Portillo; Schönfelder, Jessy; Rögner, Frank-Holm; Wetzel, Christiane; Thoma, Martin; Bailer, Susanne M.; Hiller, Ekkehard; Rupp, Steffen; Ulbert, Sebastian

    2016-01-01

    Inactivated vaccines are commonly produced by incubating pathogens with chemicals such as formaldehyde or β-propiolactone. This is a time-consuming process, the inactivation efficiency displays high variability and extensive downstream procedures are often required. Moreover, application of chemicals alters the antigenic components of the viruses or bacteria, resulting in reduced antibody specificity and therefore stimulation of a less effective immune response. An alternative method for inactivation of pathogens is ionizing radiation. It acts very fast and predominantly damages nucleic acids, conserving most of the antigenic structures. However, currently used irradiation technologies (mostly gamma-rays and high energy electrons) require large and complex shielding constructions to protect the environment from radioactivity or X-rays generated during the process. This excludes them from direct integration into biological production facilities. Here, low-energy electron irradiation (LEEI) is presented as an alternative inactivation method for pathogens in liquid solutions. LEEI can be used in normal laboratories, including good manufacturing practice (GMP)- or high biosafety level (BSL)-environments, as only minor shielding is necessary. We show that LEEI efficiently inactivates different viruses (influenza A (H3N8), porcine reproductive and respiratory syndrome virus (PRRSV), equine herpesvirus 1 (EHV-1)) and bacteria (Escherichia coli) and maintains their antigenicity. Moreover, LEEI-inactivated influenza A viruses elicit protective immune responses in animals, as analyzed by virus neutralization assays and viral load determination upon challenge. These results have implications for novel ways of developing and manufacturing inactivated vaccines with improved efficacy. PMID:27886076

  9. Model of convection mass transfer in titanium alloy at low energy high current electron beam action

    Science.gov (United States)

    Sarychev, V. D.; Granovskii, A. Yu; Nevskii, S. A.; Konovalov, S. V.; Gromov, V. E.

    2017-01-01

    The convection mixing model is proposed for low-energy high-current electron beam treatment of titanium alloys, pre-processed by heterogeneous plasma flows generated via explosion of carbon tape and powder TiB2. The model is based on the assumption vortices in the molten layer are formed due to the treatment by concentrated energy flows. These vortices evolve as the result of thermocapillary convection, arising because of the temperature gradient. The calculation of temperature gradient and penetration depth required solution of the heat problem with taking into account the surface evaporation. However, instead of the direct heat source the boundary conditions in phase transitions were changed in the thermal conductivity equation, assuming the evaporated material takes part in the heat exchange. The data on the penetration depth and temperature distribution are used for the thermocapillary model. The thermocapillary model embraces Navier-Stocks and convection heat transfer equations, as well as the boundary conditions with the outflow of evaporated material included. The solution of these equations by finite elements methods pointed at formation of a multi-vortices structure when electron-beam treatment and its expansion over new zones of material. As the result, strengthening particles are found at the depth exceeding manifold their penetration depth in terms of the diffusion mechanism.

  10. Validities of three multislice algorithms for quantitative low-energy transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ming, W.Q.; Chen, J.H., E-mail: jhchen123@hnu.edu.cn

    2013-11-15

    Three different types of multislice algorithms, namely the conventional multislice (CMS) algorithm, the propagator-corrected multislice (PCMS) algorithm and the fully-corrected multislice (FCMS) algorithm, have been evaluated in comparison with respect to the accelerating voltages in transmission electron microscopy. Detailed numerical calculations have been performed to test their validities. The results show that the three algorithms are equivalent for accelerating voltage above 100 kV. However, below 100 kV, the CMS algorithm will introduce significant errors, not only for higher-order Laue zone (HOLZ) reflections but also for zero-order Laue zone (ZOLZ) reflections. The differences between the PCMS and FCMS algorithms are negligible and mainly appear in HOLZ reflections. Nonetheless, when the accelerating voltage is further lowered to 20 kV or below, the PCMS algorithm will also yield results deviating from the FCMS results. The present study demonstrates that the propagation of the electron wave from one slice to the next slice is actually cross-correlated with the crystal potential in a complex manner, such that when the accelerating voltage is lowered to 10 kV, the accuracy of the algorithms is dependent of the scattering power of the specimen. - Highlights: • Three multislice algorithms for low-energy transmission electron microscopy are evaluated. • The propagator-corrected algorithm is a good alternative for voltages down to 20 kV. • Below 20 kV, a fully-corrected algorithm has to be employed for quantitative simulations.

  11. Effect of low energy electron irradiation on DNA damage by Cu{sup 2+} ion

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Hyung Ah; Cho, Hyuck [Dept. of Physics, Chungnam National University, Daejeon (Korea, Republic of); Park, Yeun Soo [Plasma Technology Research Center, National Fusion Research Institute, Gunsan (Korea, Republic of)

    2017-03-15

    The combined effect of the low energy electron (LEE) irradiation and Cu{sup 2+} ion on DNA damage was investigated. Lyophilized pBR322 plasmid DNA films with various concentrations (1–15 mM) of Cu{sup 2+} ion were independently irradiated by monochromatic LEEs with 5 eV. The types of DNA damage, single strand break (SSB) and double strand break (DSB), were separated and quantified by gel electrophoresis. Without electron irradiation, DNA damage was slightly increased with increasing Cu ion concentration via Fenton reaction. LEE-induced DNA damage, with no Cu ion, was only 6.6% via dissociative electron attachment (DEA) process. However, DNA damage was significantly increased through the combined effect of LEE-irradiation and Cu ion, except around 9 mM Cu ion. The possible pathways of DNA damage for each of these different cases were suggested. The combined effect of LEE-irradiation and Cu ion is likely to cause increasing dissociation after elevated transient negative ion state, resulting in the enhanced DNA damage. For the decrease of DNA damage at around 9-mM Cu ion, it is assumed to be related to the structural stabilization due to DNA inter- and intra-crosslinks via Cu ion.

  12. Validities of three multislice algorithms for quantitative low-energy transmission electron microscopy

    International Nuclear Information System (INIS)

    Ming, W.Q.; Chen, J.H.

    2013-01-01

    Three different types of multislice algorithms, namely the conventional multislice (CMS) algorithm, the propagator-corrected multislice (PCMS) algorithm and the fully-corrected multislice (FCMS) algorithm, have been evaluated in comparison with respect to the accelerating voltages in transmission electron microscopy. Detailed numerical calculations have been performed to test their validities. The results show that the three algorithms are equivalent for accelerating voltage above 100 kV. However, below 100 kV, the CMS algorithm will introduce significant errors, not only for higher-order Laue zone (HOLZ) reflections but also for zero-order Laue zone (ZOLZ) reflections. The differences between the PCMS and FCMS algorithms are negligible and mainly appear in HOLZ reflections. Nonetheless, when the accelerating voltage is further lowered to 20 kV or below, the PCMS algorithm will also yield results deviating from the FCMS results. The present study demonstrates that the propagation of the electron wave from one slice to the next slice is actually cross-correlated with the crystal potential in a complex manner, such that when the accelerating voltage is lowered to 10 kV, the accuracy of the algorithms is dependent of the scattering power of the specimen. - Highlights: • Three multislice algorithms for low-energy transmission electron microscopy are evaluated. • The propagator-corrected algorithm is a good alternative for voltages down to 20 kV. • Below 20 kV, a fully-corrected algorithm has to be employed for quantitative simulations

  13. Determination of low-energy ion-induced electron yields from thin carbon foils

    International Nuclear Information System (INIS)

    Allegrini, Frederic; Wimmer-Schweingruber, Robert F.; Wurz, Peter; Bochsler, Peter

    2003-01-01

    Ion beams crossing thin carbon foils can cause electron emission from the entrance and exit surface. Thin carbon foils are used in various types of time-of-flight (TOF) mass spectrometers to produce start pulses for TOF measurements. The yield of emitted electrons depends, among other parameters, on the energy of the incoming ion and its mass, and it has been experimentally determined for a few projectile elements. The electron emission yield is of great importance for deriving abundance ratios of elements and isotopes in space plasmas using TOF mass spectrometers. We have developed a detector for measuring ion-induced electron yields, and we have extended the electron yield measurements for oxygen to energies relevant for solar wind research. We also present first measurements of the carbon foil electron emission yield for argon and iron in the solar wind energy range

  14. The Heisenberg Uncertainty Principle Demonstrated with An Electron Diffraction Experiment

    Science.gov (United States)

    Matteucci, Giorgio; Ferrari, Loris; Migliori, Andrea

    2010-01-01

    An experiment analogous to the classical diffraction of light from a circular aperture has been realized with electrons. The results are used to introduce undergraduate students to the wave behaviour of electrons. The diffraction fringes produced by the circular aperture are compared to those predicted by quantum mechanics and are exploited to…

  15. Models for the transport of low energy electrons in water and the yield of hydrated electrons at early times

    International Nuclear Information System (INIS)

    Brenner, D.J.; Miller, J.H.; Ritchie, R.H.; Bichsel, H.

    1985-01-01

    An insulator model with four experimental energy bands was used to fit the optical properties of liquid water and to extend these data to non-zero momentum transfer. Inelastic mean free paths derived from this dielectric response function provided the basic information necessary to degrade high energy electrons to the subexcitation energy domain. Two approaches for the transport of subexcitation electrons were investigated. (i) Gas phase cross sections were used to degrade subexcitation electrons to thermal energy and the thermalization lengths were scaled to unit density. (ii) Thermalization lengths were estimated by age-diffusion theory with a stopping power deduced from the data on liquid water and transport cross sections derived from elastic scattering in water vapor. Theoretical ranges were compared to recent experimental results. A stochastic model was used to calculate the rapid diffusion and reaction of hydrated electrons with other radiolysis products. The sensitivity of the calculated yields to the model assumptions and comparison with experimental data are discussed

  16. Dynamical electron diffraction simulation for non-orthogonal crystal system by a revised real space method.

    Science.gov (United States)

    Lv, C L; Liu, Q B; Cai, C Y; Huang, J; Zhou, G W; Wang, Y G

    2015-01-01

    In the transmission electron microscopy, a revised real space (RRS) method has been confirmed to be a more accurate dynamical electron diffraction simulation method for low-energy electron diffraction than the conventional multislice method (CMS). However, the RRS method can be only used to calculate the dynamical electron diffraction of orthogonal crystal system. In this work, the expression of the RRS method for non-orthogonal crystal system is derived. By taking Na2 Ti3 O7 and Si as examples, the correctness of the derived RRS formula for non-orthogonal crystal system is confirmed by testing the coincidence of numerical results of both sides of Schrödinger equation; moreover, the difference between the RRS method and the CMS for non-orthogonal crystal system is compared at the accelerating voltage range from 40 to 10 kV. Our results show that the CMS method is almost the same as the RRS method for the accelerating voltage above 40 kV. However, when the accelerating voltage is further lowered to 20 kV or below, the CMS method introduces significant errors, not only for the higher-order Laue zone diffractions, but also for zero-order Laue zone. These indicate that the RRS method for non-orthogonal crystal system is necessary to be used for more accurate dynamical simulation when the accelerating voltage is low. Furthermore, the reason for the increase of differences between those diffraction patterns calculated by the RRS method and the CMS method with the decrease of the accelerating voltage is discussed. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  17. Properties of a new magnetic dipole mode discovered in low energy electron scattering

    International Nuclear Information System (INIS)

    Bohle, D.; Guhr, T.; Hartmann, U.; Hummel, K.D.; Kilgus, G.; Milkau, U.; Richter, A.

    1986-01-01

    In a large range of nuclei low lying J π =1 + states have been found that are excited predominantly by a new M1 mode. Four properties of the new mode will be discussed in detail. Firstly, from the excitation energy systematics observed the strength of the Majorana force of the interacting boson model (IBA) is deduced. Secondly, through the comparison of electron scattering and proton scattering experiments it is shown that the new mode is largely due to the orbital motion of protons with respect to neutrons. Thirdly, taking the nucleus 164 Dy as an example, g-factors and effective boson charges of the M1-, E2- and M3 IBA transition operators, respectively, are studied. The F-scalar magnetic octupol g-factor Ω S is derived for the first time. Finally, the distribution of M1 strength in 156 Gd will be discussed in the light of recent theoretical calculations. (orig.)

  18. Electronic energy states of HfSe/sub 2/ and NbSe/sub 2/ by low energy electron loss spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Ito, T; Iwami, M; Hiraki, A [Osaka Univ., Suita (Japan). Faculty of Engineering

    1981-06-01

    Low energy electron loss spectroscopy (ELS) study was performed on 1T-HfSe/sub 2/ (group IVB metal compound) and 2H-NbSe/sub 2/ (group VB metal compound) by using incident electron energies of 30-250 eV. From the loss data in the second derivative form, maxima in density-of-states in the conduction band of the compounds were deduced through the information on the filled core states by X-ray photoelectron spectroscopy. The conduction band of the transition-metal dichalcogenides could be divided into two parts. The results are discussed in relation to the previous work on WS/sub 2/ (group VIB metal compound), and also to proposals based on band calculations and experimental studies on the transition-metal dichalcogenides with constituent metals of group IVB, VB and VIB.

  19. A method for extraction of crystallography-related information from a data cube of very-low-energy electron micrographs

    Czech Academy of Sciences Publication Activity Database

    Knápek, Alexandr; Pokorná, Zuzana

    2015-01-01

    Roč. 148, JAN 2015 (2015), s. 52-56 ISSN 0304-3991 R&D Projects: GA MŠk(CZ) LO1212 Keywords : Very low energy * Scanning electron microscopy * SLEEM * Data cube * Image processing Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.874, year: 2015

  20. Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions.

    Science.gov (United States)

    Krafft, C; Volokitin, A

    2013-05-01

    Horseshoe distributions are shell-like particle distributions that can arise in space and laboratory plasmas when particle beams propagate into increasing magnetic fields. The present paper studies the stability and the dynamics of wave packets interacting resonantly with electrons presenting low-energy horseshoe or shell-type velocity distributions in a magnetized plasma. The linear instability growth rates are determined as a function of the ratio of the plasma to the cyclotron frequencies, of the velocity and the opening angle of the horseshoe, and of the relative thickness of the shell. The nonlinear stage of the instability is investigated numerically using a symplectic code based on a three-dimensional Hamiltonian model. Simulation results show that the dynamics of the system is mainly governed by wave-particle interactions at Landau and normal cyclotron resonances and that the high-order normal cyclotron resonances play an essential role. Specific features of the dynamics of particles interacting simultaneously with two or more waves at resonances of different natures and orders are discussed, showing that such complex processes determine the main characteristics of the wave spectrum's evolution. Simulations with wave packets presenting quasicontinuous spectra provide a full picture of the relaxation of the horseshoe distribution, revealing two main phases of the evolution: an initial stage of wave energy growth, characterized by a fast filling of the shell, and a second phase of slow damping of the wave energy, accompanied by final adjustments of the electron distribution. The influence of the density inhomogeneity along the horseshoe on the wave-particle dynamics is also discussed.

  1. Design aspects of an electrostatic electron cooler for low-energy RHIC operation

    International Nuclear Information System (INIS)

    Fedotov, A.; Ben-Zvi, I.; Brodowski, J.; Chang, X.Y.; Gassner, D.; Hoff, L.; Kayran, D.; Kewisch, J.; Oerter, B.; Pendzick, A.; Tepikian, S.; Thieberger, P.; Prost, L.; Shemyakin, A.

    2011-01-01

    Electron cooling was proposed to increase the luminosity of the Relativistic Heavy Ion Collider (RHIC) operation for heavy ion beam energies below 10 GeV/nucleon. The electron cooling system needed should be able to deliver an electron beam of adequate quality in a wide range of electron beam energies (0.9-5 MeV). An option of using an electrostatic accelerator to produce electrons for cooling heavy ions in RHIC was evaluated in detail. In this paper, we describe the requirements and options which were considered in the design of such a cooler for RHIC, as well as the associated challenges. The expected luminosity improvement and limitations with such an electron cooling system are also discussed.

  2. Modeling and Simulation of Longitudinal Dynamics for Low Energy Ring-High Energy Ring at the Positron-Electron Project

    International Nuclear Information System (INIS)

    Rivetta, Claudio; Mastorides, T.; Fox, J.D.; Teytelman, D.; Van Winkle, D.

    2007-01-01

    A time domain dynamic modeling and simulation tool for beam-cavity interactions in the Low Energy Ring (LER) and High Energy Ring (HER) at the Positron-Electron Project (PEP-II) is presented. Dynamic simulation results for PEP-II are compared to measurements of the actual machine. The motivation for this tool is to explore the stability margins and performance limits of PEP-II radio-frequency (RF) systems at future higher currents and upgraded RF configurations. It also serves as a test bed for new control algorithms and can define the ultimate limits of the low-level RF (LLRF) architecture. The time domain program captures the dynamic behavior of the beam-cavity-LLRF interaction based on a reduced model. The ring current is represented by macrobunches. Multiple RF stations in the ring are represented via one or two macrocavities. Each macrocavity captures the overall behavior of all the 2 or 4 cavity RF stations. Station models include nonlinear elements in the klystron and signal processing. This enables modeling the principal longitudinal impedance control loops interacting via the longitudinal beam model. The dynamics of the simulation model are validated by comparing the measured growth rates for the LER with simulation results. The simulated behavior of the LER at increased operation currents is presented via low-mode instability growth rates. Different control strategies are compared and the effects of both the imperfections in the LLRF signal processing and the nonlinear drivers and klystrons are explored

  3. Two types of charge transfer excitations in low dimensional cuprates: an electron energy-loss study

    Czech Academy of Sciences Publication Activity Database

    Knupfer, M.; Fink, J.; Drechsler, S.-L.; Hayn, R.; Málek, Jiří; Moskvin, A.S.

    137-140, - (2004), s. 469-473 ISSN 0368-2048 Institutional research plan: CEZ:AV0Z1010914 Keywords : cuprates * electronic excitations * electron energy-loss spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.069, year: 2004

  4. Interactions between low energy electrons and DNA: a perspective from first-principles simulations

    Science.gov (United States)

    Kohanoff, Jorge; McAllister, Maeve; Tribello, Gareth A.; Gu, Bin

    2017-09-01

    DNA damage caused by irradiation has been studied for many decades. Such studies allow us to better assess the dangers posed by radiation, and to increase the efficiency of the radiotherapies that are used to combat cancer. A full description of the irradiation process involves multiple size and time scales. It starts with the interaction of radiation—either photons or swift ions—and the biological medium, which causes electronic excitation and ionisation. The two main products of ionising radiation are thus electrons and radicals. Both of these species can cause damage to biological molecules, in particular DNA. In the long run, this molecular level damage can prevent cells from replicating and can hence lead to cell death. For a long time it was assumed that the main actors in the damage process were the radicals. However, experiments in a seminal paper by the group of Leon Sanche in 2000 showed that low-energy electrons (LEE), such as those generated when ionising biological targets, can also cause bond breaks in biomolecules, and strand breaks in plasmid DNA in particular (Boudaiffa et al 2000 Science 287 1658-60). These results prompted a significant amount of experimental and theoretical work aimed at elucidating the role played by LEE in DNA damage. In this Topical Review we provide a general overview of the problem. We discuss experimental findings and theoretical results hand in hand with the aim of describing the physics and chemistry that occurs during the process of radiation damage, from the initial stages of electronic excitation, through the inelastic propagation of electrons in the medium, the interaction of electrons with DNA, and the chemical end-point effects on DNA. A very important aspect of this discussion is the consideration of a realistic, physiological environment. The role played by the aqueous solution and the amino acids from the histones in chromatin must be considered. Moreover, thermal fluctuations must be incorporated when

  5. Coincident Auger electron and recoil ion momentum spectroscopy for low-energy ion-atom collisions

    International Nuclear Information System (INIS)

    Laurent, G.; Tarisien, M.; Flechard, X.; Jardin, P.; Guillaume, L.; Sobocinski, P.; Adoui, L.; Bordenave-Montesquieu, A.; Bordenave-Montesquieu, D.; Chesnel, J.-Y.; Fremont, F.; Hennecart, D.; Lienard, E.; Maunoury, L.; Moretto-Capelle, P.; Cassimi, A.

    2003-01-01

    The recoil ion momentum spectroscopy (RIMS) method combined with the detection of Auger electrons has been used successfully to analyse double electron capture following O 6+ + He collisions at low impact velocities. Although RIMS and Auger spectroscopies are known to be efficient tools to obtain details on the primary processes occurring during the collision, the conjunction of both techniques provides new insights on the electron capture process. In the present experiment, triple coincidence detection of the scattered projectile, the target recoil ion and the Auger electron allows for a precise identification of the doubly excited states O 4+ (1s 2 nln ' l ' ) populated after double electron-capture events

  6. Atomic resolution three-dimensional electron diffraction microscopy

    International Nuclear Information System (INIS)

    Miao Jianwei; Ohsuna, Tetsu; Terasaki, Osamu; Hodgson, Keith O.; O'Keefe, Michael A.

    2002-01-01

    We report the development of a novel form of diffraction-based 3D microscopy to overcome resolution barriers inherent in high-resolution electron microscopy and tomography. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a nanocrystal can be determined ab initio at a resolution of 1 Angstrom from 29 simulated noisy diffraction patterns. This new form of microscopy can be used to image the 3D structures of nanocrystals and noncrystalline samples, with resolution limited only by the quality of sample diffraction

  7. Experimental investigation of electron cooling and stacking of lead ions in a low energy accumulation ring

    CERN Document Server

    Bosser, Jacques; Chanel, M; Hill, C; Lombardi, A M; MacCaferri, R; Maury, S; Möhl, D; Molinari, G; Rossi, S; Tanke, E; Tranquille, G; Vretenar, Maurizio

    1999-01-01

    This report gives the results of a programme of experimental investigations, which were carried out to test stacking of lead ions in a storage ring (the former Low Energy Antiproton Ring, LEAR) at 4.2 MeV per nucleon. The motivation was to demonstrate the feasibility of gaining the large factor in the phase-space density required for injection into the LHC. In the first part of the report, the layout of the experiments is described, the choice of the parameters of the electron cooling system used for stacking is reported and the multi-turn injection using horizontal- and longitudinal- (and in the final project also vertical-) phase space is discussed. In the second part the experimental results are presented. Factors of vital importance are the stacking efficiency, the beam life-time and the cooling time of the ions. The beam decay owing to charge exchange with the residual gas and to recombination by the capture of cooling electrons was intensively studied. Beam instabilities and space-charge effects in the ...

  8. On the idea of low-energy nuclear reactions in metallic lattices by producing neutrons from protons capturing "heavy" electrons

    Science.gov (United States)

    Tennfors, Einar

    2013-02-01

    The present article is a critical comment on Widom and Larsens speculations concerning low-energy nuclear reactions (LENR) based on spontaneous collective motion of protons in a room temperature metallic hydride lattice producing oscillating electric fields that renormalize the electron self-energy, adding significantly to the effective electron mass and enabling production of low-energy neutrons. The frequency and mean proton displacement estimated on the basis of neutron scattering from protons in palladium and applied to the Widom and Larsens model of the proton oscillations yield an electron mass enhancement less than one percent, far below the threshold for the proposed neutron production and even farther below the mass enhancement obtained by Widom and Larsen assuming a high charge density. Neutrons are not stopped by the Coulomb barrier, but the energy required for the neutron production is not low.

  9. Advances in imaging and electron physics time resolved electron diffraction for chemistry, biology and material science

    CERN Document Server

    Hawkes, Peter W

    2014-01-01

    Advances in Imaging & Electron Physics merges two long-running serials-Advances in Electronics & Electron Physics and Advances in Optical & Electron Microscopy. The series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. Contributions from leading authorities Informs and updates on all the latest developments in the field.

  10. First Detection of Low Energy Electron Neutrinos in Liquid Argon Time Projection Chambers

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Corey James [Yale U.

    2016-01-01

    Electron neutrino appearance is the signature channel to address the most pressing questions in neutrino oscillations physics, at both long and short baselines. This includes the search for CP violation in the neutrino sector, which the U.S. flagship neutrino experiment DUNE will address. In addition, the Short Baseline Neutrino Program at Fermilab (MicroBooNE, SBND, ICARUS-T600) searches for new physics, such as sterile neutrinos, through electron neutrino appearance. Liquid argon time projection chambers are the forefront of neutrino detection technology, and the detector of choice for both short and long baseline neutrino oscillation experiments. This work presents the first experimental observation and study of electron neutrinos in the 1-10 GeV range, the essential oscillation energy regime for the above experiments. The systematic uncertainties for an electron neutrino appearance search for the Fermilab Short Baseline Neutrino Program are carefully quantified, and the characterization of separation between electrons and high energy photons is examined.

  11. On artefact-free reconstruction of low-energy (30–250 eV) electron holograms

    Energy Technology Data Exchange (ETDEWEB)

    Latychevskaia, Tatiana, E-mail: tatiana@physik.uzh.ch; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2014-10-15

    Low-energy electrons (30–250 eV) have been successfully employed for imaging individual biomolecules. The most simple and elegant design of a low-energy electron microscope for imaging biomolecules is a lensless setup that operates in the holographic mode. In this work we address the problem associated with the reconstruction from the recorded holograms. We discuss the twin image problem intrinsic to inline holography and the problem of the so-called biprism-like effect specific to low-energy electrons. We demonstrate how the presence of the biprism-like effect can be efficiently identified and circumvented. The presented sideband filtering reconstruction method eliminates the twin image and allows for reconstruction despite the biprism-like effect, which we demonstrate on both, simulated and experimental examples. - Highlights: • Radiation damage-free imaging of individual biomolecules. • Elimination of the twin image in inline holograms. • Circumventing biprism-like effect in low-energy electron holograms. • Artefact-free reconstructions of low-energy electron holograms.

  12. On artefact-free reconstruction of low-energy (30–250 eV) electron holograms

    International Nuclear Information System (INIS)

    Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2014-01-01

    Low-energy electrons (30–250 eV) have been successfully employed for imaging individual biomolecules. The most simple and elegant design of a low-energy electron microscope for imaging biomolecules is a lensless setup that operates in the holographic mode. In this work we address the problem associated with the reconstruction from the recorded holograms. We discuss the twin image problem intrinsic to inline holography and the problem of the so-called biprism-like effect specific to low-energy electrons. We demonstrate how the presence of the biprism-like effect can be efficiently identified and circumvented. The presented sideband filtering reconstruction method eliminates the twin image and allows for reconstruction despite the biprism-like effect, which we demonstrate on both, simulated and experimental examples. - Highlights: • Radiation damage-free imaging of individual biomolecules. • Elimination of the twin image in inline holograms. • Circumventing biprism-like effect in low-energy electron holograms. • Artefact-free reconstructions of low-energy electron holograms

  13. electron energy-loss spectroscopy

    International Nuclear Information System (INIS)

    Egerton, R.

    1997-01-01

    As part of a commemorative series of articles to mark the hundredth anniversary of the discovery of the electron, this article describes the use of electron energy-loss spectroscopy. The physical and chemical properties of materials can be studied by considering the energy that electrons use as they travel through a solid, often in conjunction with other analytical techniques. The technique is often combined with electron diffraction and high-resolution imaging and can be used to provide elemental identification down to the atomic scale. 6 figs

  14. Electron energy-loss spectroscopy

    International Nuclear Information System (INIS)

    Egerton, R.

    1997-01-01

    As part of the commemorative series of articles to mark the hundredth anniversary of the discovery of the electron, this article discusses electron energy-loss spectroscopy. The physical and chemical properties of materials can be studied by considering the energy that electrons use as they travel through a solid, often in conjunction with other analytical techniques. The technique is often combined with electron diffraction and high-resolution imaging and can be used to provide elemental identification down to the atomic scale. (UK)

  15. Energy deposition model for low-energy electrons (10-10 000 eV) in air

    International Nuclear Information System (INIS)

    Roldan, A.; Perez, J.M.; Williart, A.; Blanco, F.; Garcia, G.

    2004-01-01

    An energy deposition model for electrons in air that can be useful in microdosimetric applications is presented in this study. The model is based on a Monte Carlo simulation of the single electron scattering processes that can take place with the molecular constituents of the air in the energy range 10-10 000 eV. The input parameters for this procedure have been the electron scattering cross sections, both differential and integral. These parameters were calculated using a model potential method which describes the electron scattering with the molecular constituent of air. The reliability of the calculated integral cross section values has been evaluated by comparison with direct total electron scattering cross-section measurements performed by us in a transmission beam experiment. Experimental energy loss spectra for electrons in air have been used as probability distribution functions to define the electron energy loss in single collision events. The resulting model has been applied to simulate the electron transport through a gas cell containing air at different pressures and the results have been compared with those observed in the experiments. Finally, as an example of its applicability to dosimetric issues, the energy deposition of 10 000 eV by means of successive collisions in a free air chamber has been simulated

  16. Calculation and construction of electron-diffraction photographs using computer

    International Nuclear Information System (INIS)

    Khayurov, S.S.; Notkin, A.B.

    1981-01-01

    A method of computer construction and indexing of theoretical electronograms for monophase structures with arbitrary type of crystal lattice and for polyphase ones with known orientational coorrelations between phases is presented. Electron-diffraction photograph is presented, obtained from the foil area of two-phase VT22 alloy at β phase orientation in comparison with theoretical electron-diffraction photographs, built ap by computer, with the [100] β phase zone axis and with three variants of α phase orientation relatively to β phase. It is shown that on the experimental electron-diffraction photograph simultaneously presents α-phase three orientations, which reflexes can be indexing correctly [ru

  17. Calculated and experimental low-loss electron energy loss spectra of dislocations in diamond and GaN

    CERN Document Server

    Jones, R; Gutiérrez-Sosa, A; Bangert, U; Heggie, M I; Blumenau, A T; Frauenheim, T; Briddon, P R

    2002-01-01

    First-principles calculations of electron energy loss (EEL) spectra for bulk GaN and diamond are compared with experimental spectra acquired with a scanning tunnelling electron microscope offering ultra-high-energy resolution in low-loss energy spectroscopy. The theoretical bulk low-loss EEL spectra, in the E sub g to 10 eV range, are in good agreement with experimental data. Spatially resolved spectra from dislocated regions in both materials are distinct from bulk spectra. The main effects are, however, confined to energy losses lying above the band edge. The calculated spectra for low-energy dislocations in diamond are consistent with the experimental observations, but difficulties remain in understanding the spectra of threading dislocations in GaN.

  18. Before the Ring: synthesis of linear organic molecules in astrophysical ices by low energy electron impact

    Science.gov (United States)

    Huels, Michael A.; Bass Andrew, D.; Mirsaleh-Kohan, Nasrin; Sanche, Leon

    The question of the origin for the building blocks of life, either synthesized here on earth, or in space [1], has been the subject of much debate, experimental investigation, or astronomical observation, much of it stimulated by the early experiments of Miller [2], and subsequent space radiation related variations thereof [3-5]. And while the precise details of the formation of even the simplest biomolecules that make up life on earth still remain shrouded inmystery, one of the notions that persist throughout the debate is that the building blocks of life, such as amino-acids, or even the cyclic components of RNA and DNA, or other cyclic hydrocarbons (e.g. PHAs), where synthesized via radiolysis [6] either in the earths proto-atmosphere, its early oceans, or in the near interstellar space surrounding the early earth. Here we provide experimental evidence for the hypothesis that interactions of low energy secondary electrons and ions, formed during the radiolysis of matter, with atoms and molecules in the medium, may have played, and may still play an important role in the chemical transformation of astrophysical or planetary surface ices [7], where they lead to the synthesis of more complex chemical species from less complex, naturally occurring components. We report the synthesis and desorption of new chemical species from simple molecular surface ices, containing CH4 / CD4 , C2 D2 , O2 , CO, CO2 , or N2 in various combination mixtures, irradiated by low energy (CO+ (n = 1-3), among others. The formation of all these linear, pre-biotic molecular species, produced here by electron initiated cation-reactions in simple molecular films, suggests that similar mechanisms likely precede the synthesis of life's most basic cyclic molecular components in planetary, or astrophysical surface ices that are continuously subjected to the types of space radiations (UV, X-or -ray, or heavy ions) that can generate such low energy secondary electrons. [Funded by NSERC and Canadian

  19. The low energy (140 MeV) chemistry facility at the 500 MeV electron accelerator MEA at Amsterdam

    International Nuclear Information System (INIS)

    Brinkman, G.A.; Kapteyn, J.C.; Louwrier, P.W.F.; Lindner, L.; Peelen, B.; Polak, P.; Schimmel, A.; Stock, F.R.; Veenboer, J.T.; Visser, J.

    1980-01-01

    The facility includes the Low Energy Chemistry (LECH) hall equipped with a beam-line for pulse-radiolysis and a second one for the production of radioisotopes and for experiments with electron-free photon beams. It also includes the Low Energy Laboratory (LELAB) containing two chemistry laboratories and a control room. These facilities are also available to outside research groups. (orig./HP)

  20. Trial production of low protein irradiated natural rubber latex by low energy electron beam in pilot scale

    International Nuclear Information System (INIS)

    Utama, Marga; Yoshii, F.; Kume, T.

    2006-01-01

    Three importance factors for producing low protein by low energy electron beam (250 keV/10 mA) irradiation in pilot scale (20 liters per bath) with 1,9-nonediol diacrylate (NDA) namely: maturation time of natural rubber latex before irradiation, treatment of irradiated natural rubber latex (INRL) before and after centrifugation, and standard irradiation method has been carried out. The results showed that the optimum irradiation time for producing INRL with 5 phr (part hundred ratio of rubber) of NDA as sensitize agent, and with the rotation speed of agitation 210 rpm (rotation per minutes) was between 20-30 minutes. By using this condition tensile strength of the INRL film was 26 MPa. The maturation of natural rubber latex before irradiation is the key for driving the quality of INRL. Water extractable protein content of INRL after leaching in 1% ammonia solution for 30 minutes at room temperature was around 47 μ/g, and after adding with 1 phr of PVA (poly vinyl alcohol) or 0.1 phr CMC (carboxy methyl cellulose) the water extractable protein content decrease less than 6 μ/g. (author)

  1. Time-resolved measurements with streaked diffraction patterns from electrons generated in laser plasma wakefield

    Science.gov (United States)

    He, Zhaohan; Nees, John; Hou, Bixue; Krushelnick, Karl; Thomas, Alec; Beaurepaire, Benoît; Malka, Victor; Faure, Jérôme

    2013-10-01

    Femtosecond bunches of electrons with relativistic to ultra-relativistic energies can be robustly produced in laser plasma wakefield accelerators (LWFA). Scaling the electron energy down to sub-relativistic and MeV level using a millijoule laser system will make such electron source a promising candidate for ultrafast electron diffraction (UED) applications due to the intrinsic short bunch duration and perfect synchronization with the optical pump. Recent results of electron diffraction from a single crystal gold foil, using LWFA electrons driven by 8-mJ, 35-fs laser pulses at 500 Hz, will be presented. The accelerated electrons were collimated with a solenoid magnetic lens. By applying a small-angle tilt to the magnetic lens, the diffraction pattern can be streaked such that the temporal evolution is separated spatially on the detector screen after propagation. The observable time window and achievable temporal resolution are studied in pump-probe measurements of photo-induced heating on the gold foil.

  2. Dose estimation in low-energy electron beam irradiation for industrial purposes

    International Nuclear Information System (INIS)

    Kijima, Toshiyuki; Nakase, Yoshiaki.

    1997-03-01

    A Monte Carlo method for the passage of electrons based on a single scattering model is developed, in which the relativistic correction has been taken into accounted. A code based on this method is operable on personal computers, and has been applied to analyze electron behavior in a layered system consisting Ti as an accelerator window, air, cellulose triacetate (CTA) and backing material irradiated by mainly 300 keV electrons. The energy spectra and the angular distributions of electrons on CTA surface as well as depth-dose distributions of energy deposition in the CTA for various backing materials have been obtained. Some of these results are compared with experimentals, and showed fairly good agreement. (author). 322 refs

  3. Study of copper pre-oxydation structures by electron diffraction at high energy in relation with (410) and (530) facet formation

    International Nuclear Information System (INIS)

    Ponslet, A.; Legrand-Bonnyns, E.

    1975-01-01

    When a copper sample heated at 900 deg C in presence of 10 -6 torr oxygen for a couple of hours is cooled the surface between the (111) or (100) facets breaks up into a very fine structure consisting of facets having their pole almost in coincidence either with a (410) or (530) pole of copper crystal. This occurs at a critical temperature T(c) laying between 620 deg C and 700 deg C depending on type of facets and on surface orientation. The facets will disappear from the surface almost instantaneously by elevating the temperature of the crystal by 25 deg C and they will reappear by cooling down again to T(c) in a very reproducible way: when the copper crystal is cooled oxygen in excess in the bulk will segregate at the surface giving rise to the adsorption structures. The modification of the surface topography was studied by microscopy. The optical microscope and the diffraction apparatus are mounted on the vacuum vessel. The orientation of the facets and their size have been studied by electron microscopy. The crystal surface breaks up into (410) or (530) facets when a bidimensional stable Cu(x)O(y) structure has been formed on the surface was established [fr

  4. The low-energy electron accelerator LEA for pilot scale operations

    International Nuclear Information System (INIS)

    Mehnert, R.; Klenert, P.

    1990-01-01

    An electron processor equipped with a linear cathode has been developed for use in pilot scale radiation processing. It can provide electron beam powers up to 6 kW at energies between 150 and 200 keV. The design of some components of the processor system and first results of its operation as part of a pilot unit for curing of furniture elements will be discussed. (author)

  5. Spatial distribution of fluorescent light emitted from neon and nitrogen excited by low energy electron beams

    International Nuclear Information System (INIS)

    Morozov, A.; Kruecken, R.; Ulrich, A.; Wieser, J.

    2006-01-01

    Side-view intensity profiles of fluorescent light were measured for neon and nitrogen excited with 12 keV electron beams at gas pressures from 250 to 1400 hPa. The intensity profiles were compared with theoretical profiles calculated using the CASINO program which performs Monte Carlo simulations of electron scattering. It was assumed that the spatial distribution of fluorescent intensity is directly proportional to the spatial distribution of energy loss by primary electrons. The comparison shows good correlation of experimental data and the results of numeric simulations

  6. Shifts in electron capture to the continuum at low collision energies: Enhanced role of target postcollision interactions

    International Nuclear Information System (INIS)

    Shah, M. B.; McGrath, C.; Luna, H.; Crothers, D.S.F.; O'Rourke, S.F.C.; Gilbody, H.B.; Illescas, Clara; Riera, A.; Pons, B.

    2003-01-01

    Measurements of electron velocity distributions emitted at 0 deg. for collisions of 10- and 20-keV H + incident ions on H 2 and He show that the electron capture to the continuum cusp formation, which is still possible at these low impact energies, is shifted to lower momenta than its standard position (centered on the projectile velocity), as recently predicted. Classical trajectory Monte Carlo calculations reproduce the observations remarkably well, and indicate that a long-range residual interaction of the electron with the target ion after ionization is responsible for the shifts, which is a general effect that is enhanced at low nuclear velocities

  7. Electron-induced desorption of europium atoms from oxidized tungsten surface: concentration dependence of low-energy peak

    CERN Document Server

    Davydov, S Y

    2002-01-01

    One discusses nature of electron induced desorption of Eu sup 0 europium atoms under E sub e irradiating electron low-energies (approx 30 eV) and peculiarities of yield dependence of Eu sup 0 atoms on their concentration at oxidized tungsten surface. Primary act of vacancy origination in europium adatom inner 5p-shell turned to be the determining stage. Evaluations have shown that just the first of two possible scenarios of ionization (electron intra-atomic to Eu adatom external quasi-level or realise of knocked out electron into vacuum) leads to Eu sup 0 desorption. One determined concentration threshold for yield of Eu sup 0 atoms

  8. Low-Energy Electron Potentiometry: Contactless Imaging of Charge Transport on the Nanoscale.

    Science.gov (United States)

    Kautz, J; Jobst, J; Sorger, C; Tromp, R M; Weber, H B; van der Molen, S J

    2015-09-04

    Charge transport measurements form an essential tool in condensed matter physics. The usual approach is to contact a sample by two or four probes, measure the resistance and derive the resistivity, assuming homogeneity within the sample. A more thorough understanding, however, requires knowledge of local resistivity variations. Spatially resolved information is particularly important when studying novel materials like topological insulators, where the current is localized at the edges, or quasi-two-dimensional (2D) systems, where small-scale variations can determine global properties. Here, we demonstrate a new method to determine spatially-resolved voltage maps of current-carrying samples. This technique is based on low-energy electron microscopy (LEEM) and is therefore quick and non-invasive. It makes use of resonance-induced contrast, which strongly depends on the local potential. We demonstrate our method using single to triple layer graphene. However, it is straightforwardly extendable to other quasi-2D systems, most prominently to the upcoming class of layered van der Waals materials.

  9. Chemical effects of low-energy electron impact on hydrocarbons in the gas phase. II. Propene

    International Nuclear Information System (INIS)

    Derai, R.; Danon, J.

    1977-01-01

    The chemical effects of low-energy (3.5 to 15.0 eV) electron impact on propene were investigated. The setup used for the irradiations has previously been described. Appearance curves for stable products were determined, from which correlations between products and precursors were deduced. In the excitation range, the main precursors are the triplet state at 4.4 eV and various singlet states around 7.0 and 9.0 eV. Above the ionization potential, contribution from superexcited molecules and ions was noted. Superexcited molecules are formed with a much higher cross section than excited molecules. A reaction scheme was proposed to account for the chemical effects associated with excited states and the yields of excited molecules in dissociating states were derived from experimental data. Results concerning the fragmentation of propene excited in singlet states conform to photolysis data. The following new results were obtained: the decomposition of propene excited in the triplet state at 4.4 eV involves mainly C--C bond rupture; the decomposition processes of superexcited and excited molecules are similar. A higher degree of fragmentation is observed in the case of superexcited molecules

  10. Coincident Auger electron and recoil ion momentum spectroscopy for low-energy ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, G. E-mail: glaurent@ganil.fr; Tarisien, M.; Flechard, X.; Jardin, P.; Guillaume, L.; Sobocinski, P.; Adoui, L.; Bordenave-Montesquieu, A.; Bordenave-Montesquieu, D.; Chesnel, J.-Y.; Fremont, F.; Hennecart, D.; Lienard, E.; Maunoury, L.; Moretto-Capelle, P.; Cassimi, A

    2003-05-01

    The recoil ion momentum spectroscopy (RIMS) method combined with the detection of Auger electrons has been used successfully to analyse double electron capture following O{sup 6+} + He collisions at low impact velocities. Although RIMS and Auger spectroscopies are known to be efficient tools to obtain details on the primary processes occurring during the collision, the conjunction of both techniques provides new insights on the electron capture process. In the present experiment, triple coincidence detection of the scattered projectile, the target recoil ion and the Auger electron allows for a precise identification of the doubly excited states O{sup 4+} (1s{sup 2}nln{sup '}l{sup '}) populated after double electron-capture events.

  11. Electronic energy loss of low velocity H+ beams in Al, Ag, Sb, Au and Bi

    International Nuclear Information System (INIS)

    Valdes, J.E.; Martinez Tamayo, G.; Lantschner, G.H.; Eckardt, J.C.; Arista, N.R.

    1993-01-01

    The energy loss of H + ions in thin polycrystalline Al, Sb, Ag, Au and Bi films has been determined in the energy range below 10 keV. This low-energy range is of special interest to fill a lack of low-energy experimental data and test various theoretical predictions and semiempirical formulas. We find that the general theoretical prediction of a velocity-proportional dependence of energy loss does not hold for all targets studied in this work. The velocity-proportionality is better satisfied for Al, Sb and Bi, whereas a departure from such dependence is observed at lower energies for Ag and Au targets. The results obtained here are in good general agreement with nonlinear stopping power calculations based on density functional theory. Comparison with semiempirical predictions, and other experimental results are also done. (orig.)

  12. Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

    International Nuclear Information System (INIS)

    Huh, Sung-Ryul; Kim, Nam-Kyun; Jung, Bong-Ki; Chung, Kyoung-Jae; Hwang, Yong-Seok; Kim, Gon-Ho

    2015-01-01

    A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the bi-Maxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies

  13. AREAL low energy electron beam applications in life and materials sciences

    Energy Technology Data Exchange (ETDEWEB)

    Tsakanov, V.M., E-mail: tsakanov@asls.candle.am [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Yerevan State University, 0025 Yerevan (Armenia); Aroutiounian, R.M. [Yerevan State University, 0025 Yerevan (Armenia); Amatuni, G.A. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Aloyan, L.R.; Aslanyan, L.G. [Yerevan State University, 0025 Yerevan (Armenia); Avagyan, V.Sh. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Babayan, N.S. [Yerevan State University, 0025 Yerevan (Armenia); Institute of Molecular Biology NAS, 0014 Yerevan (Armenia); Buniatyan, V.V. [State Engineering University of Armenia, 0009 Yerevan (Armenia); Dalyan, Y.B.; Davtyan, H.D. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Derdzyan, M.V. [Institute for Physical Research NAS, 0203 Ashtarak (Armenia); Grigoryan, B.A. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Grigoryan, N.E. [A.I. Alikhanyan National Science Laboratory (YerPhi), 0036 Yerevan (Armenia); Hakobyan, L.S. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Haroutyunian, S.G. [Yerevan State University, 0025 Yerevan (Armenia); Harutiunyan, V.V. [A.I. Alikhanyan National Science Laboratory (YerPhi), 0036 Yerevan (Armenia); Hovhannesyan, K.L. [Institute for Physical Research NAS, 0203 Ashtarak (Armenia); Khachatryan, V.G. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Martirosyan, N.W. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); State Engineering University of Armenia, 0009 Yerevan (Armenia); Melikyan, G.S. [State Engineering University of Armenia, 0009 Yerevan (Armenia); and others

    2016-09-01

    The AREAL laser-driven RF gun provides 2–5 MeV energy ultrashort electron pulses for experimental study in life and materials sciences. We report the first experimental results of the AREAL beam application in the study of molecular-genetic effects, silicon-dielectric structures, ferroelectric nanofilms, and single crystals for scintillators.

  14. Influence of the excited states on the electron-energy distribution function in low-pressure microwave argon plasmas

    International Nuclear Information System (INIS)

    Yanguas-Gil, A.; Cotrino, J.; Gonzalez-Elipe, A.R.

    2005-01-01

    In this work the influence of the excited states on the electron-energy distribution function has been determined for an argon microwave discharge at low pressure. A collisional-radiative model of argon has been developed taking into account the most recent experimental and theoretical values of argon-electron-impact excitation cross sections. The model has been solved along with the electron Boltzmann equation in order to study the influence of the inelastic collisions from the argon excited states on the electron-energy distribution function. Results show that under certain conditions the excited states can play an important role in determining the shape of the distribution function and the mean kinetic energy of the electrons, deplecting the high-energy tail due to inelastic processes from the excited states, especially from the 4s excited configuration. It has been found that from the populations of the excited states an excitation temperature can be defined. This excitation temperature, which can be experimentally determined by optical emission spectroscopy, is lower than the electron kinetic temperature obtained from the electron-energy distribution function

  15. Vertical Silicon Nanowire Platform for Low Power Electronics and Clean Energy Applications

    Directory of Open Access Journals (Sweden)

    D.-L. Kwong

    2012-01-01

    Full Text Available This paper reviews the progress of the vertical top-down nanowire technology platform developed to explore novel device architectures and integration schemes for green electronics and clean energy applications. Under electronics domain, besides having ultimate scaling potential, the vertical wire offers (1 CMOS circuits with much smaller foot print as compared to planar transistor at the same technology node, (2 a natural platform for tunneling FETs, and (3 a route to fabricate stacked nonvolatile memory cells. Under clean energy harvesting area, vertical wires could provide (1 cost reduction in photovoltaic energy conversion through enhanced light trapping and (2 a fully CMOS compatible thermoelectric engine converting waste-heat into electricity. In addition to progress review, we discuss the challenges and future prospects with vertical nanowires platform.

  16. Reassessment of the electron density in Cu2O using γ-ray diffraction.

    Science.gov (United States)

    Jauch, Wolfgang; Reehuis, Manfred

    2014-12-01

    The electron-density distribution in Cu2O has been critically reexamined to test controversial conclusions from earlier experimental and theoretical studies. The electron density is derived via multipole refinement of high-quality single-crystal diffraction data, collected at room temperature with 316.5 keV gamma radiation. Four γ-lines in the energy range 200-600 keV have been used to extrapolate extinction-free low-order structure factors. The remaining extinction corrections refine to a crystal mosaicity identical to the observed one. There is no support for anharmonic contributions to the thermal parameters. Important features of the derived electron density are (i) a partially filled d_{z^2} orbital, (ii) an incomplete ionization of Cu and O, and (iii) no interstitial Cu-Cu charge pileup, thereby refuting the covalent bonding hypothesis.

  17. Doubly differential cross sections of low-energy electrons emitted in the ionization of molecular hydrogen by bare carbon ions

    International Nuclear Information System (INIS)

    Tribedi, L.C.; Richard, P.; Ling, D.; Wang, Y.D.; Lin, C.D.; Moshammer, R.; Kerby, G.W. III; Gealy, M.W.; Rudd, M.E.

    1996-01-01

    We have measured the double differential cross sections (DDCS) (d 2 σ/d var-epsilon ed Ω e ) of low-energy electron emission in the ionization of H 2 bombarded by bare carbon ions of energy 30 MeV. The energy and angular distributions of the electron DDCS have been obtained for 12 different emission angles and for electron energies varying between 0.1 and 300 eV. We have also deduced the single differential and total ionization cross section from the measured DDCS. The data have been compared with the predictions of first Born approximations and the CDW-EIS (continuum distorted wave endash eikonal initial state) model. The CDW-EIS model provides an excellent agreement with the data. copyright 1996 The American Physical Society

  18. Track reconstruction method in a small volume self-shunted streamer chamber - analysis of the errors for low energy electrons

    International Nuclear Information System (INIS)

    Parizet, M.J.; Augerat, J.; Avan, M.; Ballet, M.; Vialle, M.

    1977-01-01

    A programme has been worked out to reconstruct electron tracks of low energy (from 100 keV to 2 MeV) curved by a magnetic field in a small streamer chamber (size 10x11x51 cm 3 ). Before a study of the problems involved in the experimental set-up, the geometrical programme is described and the different errors are evaluated. Finally the accuracies on kinetic energies and angles which can be obtained for low energy elctron tracks are given. (Auth.)

  19. Low energy electron attachment to cyanamide (NH{sub 2}CN)

    Energy Technology Data Exchange (ETDEWEB)

    Tanzer, Katrin; Denifl, Stephan, E-mail: Andrzej.Pelc@poczta.umcs.lublin.pl, E-mail: Stephan.Denifl@uibk.ac.at [Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck (Austria); Pelc, Andrzej, E-mail: Andrzej.Pelc@poczta.umcs.lublin.pl, E-mail: Stephan.Denifl@uibk.ac.at [Mass Spectrometry Department, Institute of Physics, Marie Curie-Sklodowska University, Pl. M. C.-Sklodowskiej 1, 20-031 Lublin (Poland); Huber, Stefan E. [Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck (Austria); Lehrstuhl für Theoretische Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany); Czupyt, Z. [Ion Microprobe Facility Micro-area Analysis Laboratory, Polish Geological Institute–National Research Institute, Rakowiecka 4, 00-975 Warszawa (Poland)

    2015-01-21

    Cyanamide (NH{sub 2}CN) is a molecule relevant for interstellar chemistry and the chemical evolution of life. In the present investigation, dissociative electron attachment to NH{sub 2}CN has been studied in a crossed electron–molecular beams experiment in the electron energy range from about 0 eV to 14 eV. The following anionic species were detected: NHCN{sup −}, NCN{sup −}, CN{sup −}, NH{sub 2}{sup −}, NH{sup −}, and CH{sub 2}{sup −}. The anion formation proceeds within two broad electron energy regions, one between about 0.5 and 4.5 eV and a second between 4.5 and 12 eV. A discussion of possible reaction channels for all measured negative ions is provided. The experimental results are compared with calculations of the thermochemical thresholds of the anions observed. For the dehydrogenated parent anion, we explain the deviation between the experimental appearance energy of the anion with the calculated corresponding reaction threshold by electron attachment to the isomeric form of NH{sub 2}CN—carbodiimide.

  20. Preparation of {sup 114m}In low energy conversion electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Wrede, C., E-mail: wrede@uw.ed [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Filippone, B.W. [Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Garcia, A.; Harper, G.C. [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Lassell, S. [Department of Nuclear Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Liu, J. [Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Mendenhall, M.P. [Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Palmer, A.S.C. [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Pattie, R.W. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Will, D.I. [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Young, A.R. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2011-05-15

    Highlights: {yields} Controlled ion implantation of In-113 into thin Al substrate. {yields} Production of In-114m (half life = 50 days) by neutron irradiation. {yields} Use of In-114m as a source of electron lines and continuum for calibrations. {yields} Source reactivation by short neutron irradiation. -- Abstract: The preparation of {sup 114m}In sources of conversion electrons in the energy range 162-190 keV and {beta} continuum with a 1989 keV endpoint via ion implantation of {sup 113}In into Al substrates and subsequent irradiation by thermal and epi-thermal neutrons in a nuclear reactor is described.

  1. Electron spectra resulting from autoionization in low-energy Li+ + He collisions

    International Nuclear Information System (INIS)

    Yagishita, A.; Wakiya, K.; Takayanagi, T.; Suzuki, H.; Koike, F.

    1979-09-01

    Spectra of electrons ejected from doubly excited states of helium have been extensively measured at several observation angles fro impact with lithium ions at energies lower than 5 KeV. ''Molecular-autoionization'' spectra have been found at forward observation angles, and analyzed in terms of the Gerber-Niehaus theory with modification. The spectral shapes of atomic-autoionization peaks have been discussed in relation to both the Barker-Berry effect and the Doppler effect. Excitation cross sections of autoionizing states have been determined by a new method that uses simultaneous impact of ions and electrons. (author)

  2. Preparation of 114mIn low energy conversion electron sources

    International Nuclear Information System (INIS)

    Wrede, C.; Filippone, B.W.; Garcia, A.; Harper, G.C.; Lassell, S.; Liu, J.; Mendenhall, M.P.; Palmer, A.S.C.; Pattie, R.W.; Will, D.I.; Young, A.R.

    2011-01-01

    Highlights: → Controlled ion implantation of In-113 into thin Al substrate. → Production of In-114m (half life = 50 days) by neutron irradiation. → Use of In-114m as a source of electron lines and continuum for calibrations. → Source reactivation by short neutron irradiation. -- Abstract: The preparation of 114m In sources of conversion electrons in the energy range 162-190 keV and β continuum with a 1989 keV endpoint via ion implantation of 113 In into Al substrates and subsequent irradiation by thermal and epi-thermal neutrons in a nuclear reactor is described.

  3. Extraction of topographic and material contrasts on surfaces from SEM images obtained by energy filtering detection with low-energy primary electrons.

    Science.gov (United States)

    Nagoshi, Masayasu; Aoyama, Tomohiro; Sato, Kaoru

    2013-01-01

    Secondary electron microscope (SEM) images have been obtained for practical materials using low primary electron energies and an in-lens type annular detector with changing negative bias voltage supplied to a grid placed in front of the detector. The kinetic-energy distribution of the detected electrons was evaluated by the gradient of the bias-energy dependence of the brightness of the images. This is divided into mainly two parts at about 500 V, high and low brightness in the low- and high-energy regions, respectively and shows difference among the surface regions having different composition and topography. The combination of the negative grid bias and the pixel-by-pixel image subtraction provides the band-pass filtered images and extracts the material and topographic information of the specimen surfaces. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Evidence for CO formation in irradiated methanol and acetone: contribution of low-energy electron-energy-loss spectroscopy to γ-radiolysis

    International Nuclear Information System (INIS)

    Jay-Gerin, J.-P.; Fraser, M.-J.; Michaud, M.; Sanche, L.; Swiderek, P.; Ferradini, C.

    1997-01-01

    Energy-loss spectra for low-energy electrons incident on acetone condensed on a multilayer film of argon, and on a methanol film deposited on a metallic substrate, are reported. In both cases, the formation of carbon monoxide has been detected. These results are directly related to those obtained in the liquid-phase γ-radiolysis of the two compounds. (author)

  5. The Role of Low-Energy (less than 20 eV) Electrons in Astrochemistry: A Tale of Two Molecules

    Science.gov (United States)

    Arumainayagam, Chris

    2016-07-01

    In the interstellar medium, UV photolysis of ice mantles encasing dust grains is thought to be the mechanism that drives the synthesis of "complex" molecules. The source of this reaction-initiating UV light is assumed to be local because externally-sourced UV radiation cannot pass through the ice-containing dark, dense molecular clouds. Externally sourced cosmic rays (E_{max} ˜10^{20} eV), in addition to producing UV light within these clouds, also produce large numbers of low-energy (≤ 20 eV) secondary electrons. 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. Using electron stimulated desorption (ESD), post-irradiation temperature-programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS), we have investigated the radiolysis initiated by electrons in condensed methanol and ammonia at ˜90K under ultrahigh vacuum (1 × 10^{-9} Torr) conditions. We have identified fifteen low-energy electron-induced methanol radiolysis products, many of which have been previously identified as being formed by methanol UV photolysis in the interstellar medium. We have also found evidence for the electron-induced formation from ammonia of hydrazine (N_2 H_4), diazene (N_2 H_2), cyclotriazane/triazene (N_3 H_3) and triazane (N_3 H_5). We have investigated the reaction yields' dependence on film thickness, irradiation time, incident current, electron energy, and metal substrate. These results provide a basis from which we can begin to understand the mechanisms by which methanol and ammonia can form more complex species in cosmic ices. Studies such as ours may ultimately help us better understand the initial stages of the genesis of life.

  6. A coincidence-type ion-electron converter detector for low-energy protons

    International Nuclear Information System (INIS)

    Benka, O.; Weinzierl, P.; Dobrozemsky, R.; Stratowa, C.

    1981-04-01

    A coincidence type ion-electron converter detector has been developed and used - together with an electrostatic energy-analyser - for precision measurements of the energy distribution of recoil protons from free-neutron decay. The most important aspect of the development was, besides keeping the background below 0,2 counts/sec in the presence of a certain radiation background, to achieve a high and energy-independent counting probability for protons with energies between 100 and 1000 eV. With an acceleration voltage of about 25 kV and Al-foils (20 to 35 ug/cmsup2) as converter, we obtained counting efficiences of 70 to 85 percent. The design and performance of the detector system, employing six foils with different sensitive areas, are described and discussed in detail. (author)

  7. Electrical performance of the InGaP solar cell irradiated with low energy electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Okuno, Yasuki; Okuda, Shuichi; Kojima, Takeo; Oka, Takashi [Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai City, Osaka (Japan); Kawakita, Shirou; Imaizumi, Mitsuru; Kusawake, Hiroaki [Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Ibaraki (Japan)

    2015-06-15

    The investigation of the radiation degradation characteristics of InGaP space solar cells is important. In order to understand the mechanism of the degradation by radiation the samples of the InGaP solar cell were irradiated in vacuum and at ambient temperature with electron beams from a Cockcroft-Walton type accelerator at Osaka Prefecture University. The threshold energies for recoil were obtained by theoretical calculation. The energies and the fluences of the electron beams were from 60 to 400 keV and from 3 x 10{sup 14} to 3 x 10{sup 16} cm{sup -2}, respectively. The light-current-voltage measurements were performed. The degradation of Isc caused by the defects related to the phosphorus atoms was observed and the degradation was suppressed by irradiation at an energy higher than the threshold energy for recoiling Indium atoms. At an energy of 60 keV, where the recoil does not occur, the V{sub oc} was degraded. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. D-mu-A new concept in industrial low-energy electron dosimetry

    DEFF Research Database (Denmark)

    Helt-Hansen, Jakob; Miller, Arne; Sharpe, Peter

    2010-01-01

    , resulting in difficulties in providing traceable dose measurements using reference dosimeters. In order to overcome these problems a new concept is introduced of correcting all measured doses to the average dose in the first micrometer—Dμ. We have applied this concept to dose measurements with dosimeters...... of different thickness at two electron accelerators operating over a range of energies. The uncertainties of the dose measurements were evaluated, and it was shown that the dose in terms of Dμ was the same at each energy for all dosimeters within the measurement uncertainty. Using the concept of Dμ...

  9. Interaction of low energy electrons with surface lattice vibrations. Final report

    International Nuclear Information System (INIS)

    Tong, S.Y.

    1984-01-01

    In carrying out the DOE contract, we have succeeded in constructing a new microscopic theory, with multiple scattering, for the inelastic scattering of electrons by surface vibrations. We have applied the theory to detailed studies of angle and energy variations of the inelastic cross-section for two important systems in surface physics: carbon monoxide molecules adsorbed on the (100) surface of a nickel crystal, and hydrogen atoms adsorbed on a reconstructed tungsten (100) surface. These calculations have outlined general trends that we expect to apply to a wide variety of systems. Also, we have discovered a series of new selection rules that apply to off-specular scattering. Particularly interesting are pseudo-selection rules which are not group theoretical in origin, but approximate statements that hold well when the electron scattering amplitude exhibits a slow energy variation. We have found and defined conditions for which these selection rules would hold and break down

  10. Inelastic nucleon diffraction at high energy

    International Nuclear Information System (INIS)

    Goggi, G.

    1975-01-01

    Experiments carried out at ISR and at FNAL which have yielded a substantial amount of data on double diffraction processes, which were unambiguously indentified and measured and which provide new tools to study the dynamical properties shared by different classes of diffractive reactions are identified. In this review interest is focused on the experimental aspects of inclusive and exclusive results both on single and double diffraction and on the problems arising from their comparison. Problems covered include; inclusive and semi-inclusive diffraction, multiparticle inclusive studies, single-particle inclusive studies, resonance region, high mass region, exclusive single diffractive reactions, mass spectra, cross sections, t-dependence, decay angular properties, and double diffraction. (U.K.)

  11. Ultrafast electron diffraction studies of optically excited thin bismuth films

    International Nuclear Information System (INIS)

    Rajkovic, Ivan

    2008-01-01

    This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)

  12. Ultrafast electron diffraction studies of optically excited thin bismuth films

    Energy Technology Data Exchange (ETDEWEB)

    Rajkovic, Ivan

    2008-10-21

    This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)

  13. Electron capture in collisions of Si3+ ions with atomic hydrogen from low to intermediate energies

    Science.gov (United States)

    Liu, C. H.; Liu, L.; Wang, J. G.

    2014-07-01

    The electron capture process for the Si3+(3s) + H(1s) collisions is investigated by the quantum-mechanical molecular orbital close-coupling (MOCC) method and by the two-center atomic orbital close-coupling (AOCC) method in the energy range of 10-5-10 keV/u and 0.8-200 keV/u, respectively. Total and state-selective cross sections are presented and compared with the available theoretical and experimental results. The present MOCC and AOCC results agree well with the experimental measurements, but show some discrepancy with the calculations of Wang et al. [Phys. Rev. A 74, 052709 (2006), 10.1103/PhysRevA.74.052709] at E > 40 eV/u because of the inclusion of rotational couplings, which play important roles in the electron capture process. At lower energies, the present results are about three to five times smaller than those of Wang et al. due to the difference in the molecular data at large internuclear distances. The energy behaviors of the electron capture cross sections are discussed on the basis of identified reaction mechanisms.

  14. Diffractive interactions of hadrons at high energies

    International Nuclear Information System (INIS)

    Goulianos, K.

    1982-01-01

    Elastic scattering, inclusive single diffraction dissociation and total cross section results are reviewed, with emphasis on the inter-relationship among the parameters that characterize these processes

  15. Monte Carlo calculation of scattered radiation from applicators in low energy clinical electron beams

    International Nuclear Information System (INIS)

    Jabbari, N.; Hashemi-Malayeri, B.; Farajollahi, A. R.; Kazemnejad, A.

    2007-01-01

    In radiotherapy with electron beams, scattered radiation from an electron applicator influences the dose distribution in the patient. The contribution of this radiation to the patient dose is significant, even in modern accelerators. In most of radiotherapy treatment planning systems, this component is not explicitly included. In addition, the scattered radiation produced by applicators varies based on the applicator design as well as the field size and distance from the applicators. The aim of this study was to calculate the amount of scattered dose contribution from applicators. We also tried to provide an extensive set of calculated data that could be used as input or benchmark data for advanced treatment planning systems that use Monte Carlo algorithms for dose distribution calculations. Electron beams produced by a NEPTUN 10PC medical linac were modeled using the BEAMnrc system. Central axis depth dose curves of the electron beams were measured and calculated, with and without the applicators in place, for different field sizes and energies. The scattered radiation from the applicators was determined by subtracting the central axis depth dose curves obtained without the applicators from that with the applicator. The results of this study indicated that the scattered radiation from the electron applicators of the NEPTUN 10PC is significant and cannot be neglected in advanced treatment planning systems. Furthermore, our results showed that the scattered radiation depends on the field size and decreases almost linearly with depth. (author)

  16. Comparative study of macrotexture analysis using X-ray diffraction and electron backscattered diffraction techniques

    International Nuclear Information System (INIS)

    Serna, Marilene Morelli

    2002-01-01

    The macrotexture is one of the main characteristics in metallic materials, which the physical properties depend on the crystallographic direction. The analysis of the macrotexture to middles of the decade of 80 was just accomplished by the techniques of Xray diffraction and neutrons diffraction. The possibility of the analysis of the macrotexture using, the technique of electron backscattering diffraction in the scanning electronic microscope, that allowed to correlate the measure of the orientation with its location in the micro structure, was a very welcome tool in the area of engineering of materials. In this work it was studied the theoretical aspects of the two techniques and it was used of both techniques for the analysis of the macrotexture of aluminum sheets 1050 and 3003 with intensity, measured through the texture index 'J', from 2.00 to 5.00. The results obtained by the two techniques were shown reasonably similar, being considered that the statistics of the data obtained by the technique of electron backscatter diffraction is much inferior to the obtained by the X-ray diffraction. (author)

  17. Low energy electron irradiation induced carbon etching: Triggering carbon film reacting with oxygen from SiO{sub 2} substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Cheng [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Wang, Chao, E-mail: cwang367@szu.edu.cn, E-mail: dfdiao@szu.edu.cn; Diao, Dongfeng, E-mail: cwang367@szu.edu.cn, E-mail: dfdiao@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China)

    2016-08-01

    We report low-energy (50–200 eV) electron irradiation induced etching of thin carbon films on a SiO{sub 2} substrate. The etching mechanism was interpreted that electron irradiation stimulated the dissociation of the carbon film and SiO{sub 2}, and then triggered the carbon film reacting with oxygen from the SiO{sub 2} substrate. A requirement for triggering the etching of the carbon film is that the incident electron penetrates through the whole carbon film, which is related to both irradiation energy and film thickness. This study provides a convenient electron-assisted etching with the precursor substrate, which sheds light on an efficient pathway to the fabrication of nanodevices and nanosurfaces.

  18. A research of possibility for negative muon production by a low energy electron beam accompanying ion beam

    International Nuclear Information System (INIS)

    Uramoto, Joshin.

    1993-12-01

    A low energy electron beam (≤ 2000 eV) is injected perpendicularly to a uniform magnetic field, together with a low energy positive ion beam. On this magnetic mass analysis (using the uniform magnetic field), a peak of secondary electron current to the beam collector (arranging as a mass analyzer of 90deg type), appears at an analyzing magnetic field which corresponds exactly to a relation of negative muon μ - (the mass m=207 m e and the charge q=e, where m e and e are mass and charge of electron). The ion beam is essential for the peak appearance, which is produced by decelerating electrically the electron beam in front of the entrance slit of the mass analyzer, and by introducing a neutral gas into the electron beam region and producing a plasma through the ionization. We consider that a very small amount of negative muons may be produced through local cyclotron motions of the injected beam electrons in the ion beam or by an interaction between the bunched beam electrons and beam ions. (author)

  19. A method of combining STEM image with parallel beam diffraction and electron-optical conditions for diffractive imaging

    International Nuclear Information System (INIS)

    He Haifeng; Nelson, Chris

    2007-01-01

    We describe a method of combining STEM imaging functionalities with nanoarea parallel beam electron diffraction on a modern TEM. This facilitates the search for individual particles whose diffraction patterns are needed for diffractive imaging or structural studies of nanoparticles. This also lays out a base for 3D diffraction data collection

  20. Single-electron capture in low-energy Ar6+-He collisions

    International Nuclear Information System (INIS)

    Akguengoer, K.; Kamber, E.Y.; Ferguson, S.M.

    1997-01-01

    Double differential cross sections for state-selective single-electron capture processes in Ar 6+ -He collisions have been measured at laboratory energies between 75 and 900 eV and scattering angles between 0 and 8 . At the lowest energy, the zero-angle spectrum shows capture into Ar 5+ (4p) to be the most important channel. However, as the scattering angle is increased, a second peak appears at angles ≥2 and becomes more pronounced relative to the 4p capture channel. The energy spectra are interpreted qualitatively in terms of the reaction windows, which are calculated using the single-crossing Landau-Zener model. Total and differential cross sections are also measured and compared with available measurements and calculations. (orig.)

  1. Femtosecond electron diffraction. Next generation electron sources for atomically resolved dynamics

    International Nuclear Information System (INIS)

    Hirscht, Julian

    2015-08-01

    Three instruments for femtosecond electron diffraction (FED) experiments were erected, partially commissioned and used for first diffraction experiments. The Relativistic Electron Gun for Atomic Exploration (REGAE) was completed by beamline elements including supports, a specimen chamber and dark current or electron beam collimating elements such that the commissioning process, including first diffraction experiments in this context, could be started. The temporal resolution of this machine is simulated to be 25 fs (fwhm) short, while a transverse coherence length of 30 nm (fwhm) is feasible to resolve proteins on this scale. Whether this machine is capable of meeting these predictions or whether the dynamics of the electron beam will stay limited by accelerator components, is not finally determined by the end of this work, because commissioning and improvement of accelerator components is ongoing. Simultaneously, a compact DC electron diffraction apparatus, the E-Gun 300, designed for solid and liquid specimens and a target electron energy of 300 keV, was built. Fundamental design issues of the high potential carrying and beam generating components occurred and are limiting the maximum potential and electron energy to 120 keV. Furthermore, this is limiting the range of possible applications and consequently the design and construction of a brand new instrument began. The Femtosecond Electron Diffraction CAmera for Molecular Movies (FED-CAMM) bridges the performance problems of very high electric potentials and provides optimal operational conditions for all applied electron energies up to 300 keV. The variability of gap spacings and optimized manufacturing of the high voltage electrodes lead to the best possible electron pulse durations obtainable with a compact DC setup, that does not comprise of rf-structures. This third apparatus possesses pulse durations just a few tenth femtoseconds apart from the design limit of the highly relativistic REGAE and combines the

  2. Femtosecond electron diffraction. Next generation electron sources for atomically resolved dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hirscht, Julian

    2015-08-15

    Three instruments for femtosecond electron diffraction (FED) experiments were erected, partially commissioned and used for first diffraction experiments. The Relativistic Electron Gun for Atomic Exploration (REGAE) was completed by beamline elements including supports, a specimen chamber and dark current or electron beam collimating elements such that the commissioning process, including first diffraction experiments in this context, could be started. The temporal resolution of this machine is simulated to be 25 fs (fwhm) short, while a transverse coherence length of 30 nm (fwhm) is feasible to resolve proteins on this scale. Whether this machine is capable of meeting these predictions or whether the dynamics of the electron beam will stay limited by accelerator components, is not finally determined by the end of this work, because commissioning and improvement of accelerator components is ongoing. Simultaneously, a compact DC electron diffraction apparatus, the E-Gun 300, designed for solid and liquid specimens and a target electron energy of 300 keV, was built. Fundamental design issues of the high potential carrying and beam generating components occurred and are limiting the maximum potential and electron energy to 120 keV. Furthermore, this is limiting the range of possible applications and consequently the design and construction of a brand new instrument began. The Femtosecond Electron Diffraction CAmera for Molecular Movies (FED-CAMM) bridges the performance problems of very high electric potentials and provides optimal operational conditions for all applied electron energies up to 300 keV. The variability of gap spacings and optimized manufacturing of the high voltage electrodes lead to the best possible electron pulse durations obtainable with a compact DC setup, that does not comprise of rf-structures. This third apparatus possesses pulse durations just a few tenth femtoseconds apart from the design limit of the highly relativistic REGAE and combines the

  3. Electron energy distribution function in a low-power Hall thruster discharge and near-field plume

    Science.gov (United States)

    Tichý, M.; Pétin, A.; Kudrna, P.; Horký, M.; Mazouffre, S.

    2018-06-01

    Electron temperature and plasma density, as well as the electron energy distribution function (EEDF), have been obtained inside and outside the dielectric channel of a 200 W permanent magnet Hall thruster. Measurements were carried out by means of a cylindrical Langmuir probe mounted onto a compact fast moving translation stage. The 3D particle-in cell numerical simulations complement experiments. The model accounts for the crossed electric and magnetic field configuration in a weakly collisional regime where only electrons are magnetized. Since only the electron dynamics is of interest in this study, an artificial mass of ions corresponding to mi = 30 000me was used to ensure ions could be assumed at rest. The simulation domain is located at the thruster exit plane and does not include the cathode. The measured EEDF evidences a high-energy electron population that is superimposed onto the low energy bulk population outside the channel. Inside the channel, the EEDF is close to Maxwellian. Both the experimental and numerical EEDF depart from an equilibrium distribution at the channel exit plane, a region of high magnetic field. We therefore conclude that the fast electron group found in the experiment corresponds to the electrons emitted by the external cathode that reach the thruster discharge without experiencing collision events.

  4. Charge Exchange in Low-Energy H, D + C4+ Collisions with Full Account of Electron Translation

    Directory of Open Access Journals (Sweden)

    N. Vaeck

    2002-03-01

    Full Text Available We report the application of the quantum approach, which takes full account of electron translation at low collisional energies, to the charge exchange process H, D + C4+ → H+, D+ + C3+(3s; 3p; 3d. The partial and the total integral cross sections of the process are calculated in the energy range from 1 till 60 eV/amu. It is shown that the present results are independent from the upper integration limit for numerical solution of the coupled channel equations although nonadiabatic couplings remain nonzero up to infinity. The calculated partial and total cross sections are in agreement with the previous low-energy calculations and the available experimental data. It is shown that for low collisional energies the isotopic effect takes place. The observed effect is explained in terms of the nonadiabatic dynamics.

  5. Transport of low energy electrons in water and some physico-chemical implications

    International Nuclear Information System (INIS)

    Brenner, D.J.; Zaider, M.

    1983-01-01

    Considerable effort by numerous groups is currently being devoted to measuring or calculating cross-sections for use as input to Monte-Carlo studies of radiation effects. We address the question of how well do low-energy cross-sections need to be known in order to calculate adequately quantities of interest in the radiobiological domain. 11 references, 4 figures

  6. Theoretical treatment of electron capture and excitation in two-electron system ion-atom, atom-atom collisions at low to intermediate energy

    International Nuclear Information System (INIS)

    Kimura, M.

    1986-01-01

    A review of various theoretical treatments which have been used to study electron-capture and excitation processes in two-electron-system ion-atom, atom-atom collisions at low to intermediate energy is presented. Advantages as well as limitations associated with these theoretical models in application to practical many-electron ion-atom, atom-atom collisions are specifically pointed out. Although a rigorous theoretical study of many-electron systems has just begun so that reports of theoretical calculations are scarce to date in comparison to flourishing experimental activities, some theoretical results are of great interest and provide important information for understanding collision dynamics of the system which contains many electrons. Selected examples are given for electron capture in a multiply charged ion-He collision, ion-pair formation in an atom-atom collision and alignment and orientation in a Li + + He collision. (Auth.)

  7. Free-Free Transitions in the Presence of Laser Fields and Debye Potential at Very Low Incident Electron Energies

    Science.gov (United States)

    Bhatia, Anand

    2012-01-01

    We study the free-free transition in electron-helium ion in the ground state and embedded in a Debye potential in the presence of an external laser field at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen as monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function for it. The scattering wave function for the incident electron on the target embedded in a Debye potential is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transition for absorption/emission of a single photon or no photon exchange. The results will be presented at the conference.

  8. Development of methodology for assessment of absorbed dose and stopping power for low energy conversion electrons

    International Nuclear Information System (INIS)

    Almeida, Ivan Pedro Salati de

    1995-08-01

    The evaluation of absorbed dose in the case of external and internal contamination due to radionuclides is sometimes hard, because of the difficulties in the assessment of the absorbed dose caused by electrons with energy less than 100 KeV in mucous membrane. In this work, a methodology for assessment of absorbed dose and stopping power in VYNS (co-polymer of polivinyl chloride - acetate) absorbers, for the 62.5 KeV and 84-88 KeV energy 109 Cd conversion electrons, working with a 4 π proportional pressurized detector, is presented. In order to assure the reproducibility of measurement conditions, one of the detector halves has been used to obtain a spectrum of a thin 109 Cd source, without absorber. The other half of the detector was used in concomitance to obtain spectra with different thicknesses if absorber. The absorbed energy was obtained subtracting each spectrum with absorber from the spectrum without absorber, which were stored in a microcomputer connected to signal processing systems by ACE type interface. The VYNS weight and thickness were evaluated using common radionuclide metrology procedures. As VYNS has characteristics similar to a tissue equivalent material, the results obtained are consistent with dosimetric concepts and have a good agreement with those of the literature. (author)

  9. Significance of Space Charge and the Earth Magnetic Field on the Dispersive Characteristics of a Low Energy Electron Beam

    CERN Document Server

    Kishek, Rami A; Bernal, Santiago; Godlove, Terry; Haber, Irving; Quinn, Bryan; Reiser, Martin; Tobin, C; Walter, Mark

    2005-01-01

    The combination of energy spread and space charge provides a rich domain for interesting beam dynamics that are currently not well understood. The University of Maryland Electron Ring (UMER) [1] is a small scaled ring designed to probe the little-known regions of higher beam intensities using low-energy electrons. As such, design, commissioning and operation of UMER present many challenges, some quite novel. For example the UMER beam energy of 10 keV makes the beam very sensitive to the Earth magnetic field, which we can fortunately use to assist in bending the beam. This paper presents a systematic simulation study of the interaction of space charge and energy spread, with and without the earth magnetic field.

  10. On the extension of the Fermi-Watson Theorem to high energy diffraction

    International Nuclear Information System (INIS)

    Malecki, A.; Istituto Nazionale di Fisica Nucleare, Frascati

    1995-12-01

    The Fermi-Watson theorem, established for low energy reactions and then applied to high energy collision, is revisited. Its use for the processes of inelastic diffraction is discussed. The theorem turns out to be valid in the case inclusive cross-section of diffractive transition

  11. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr{sub 2}FeMoO{sub 6} using electron energy-loss magnetic chiral dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.C. [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhong, X.Y., E-mail: xyzhong@mail.tsinghua.edu.cn [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Jin, L. [Peter Grünberg Institute and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich (Germany); Chen, X.F. [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Moritomo, Y. [Graduate School of Pure & Applied Science and Faculty of Pure & Applied Science, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-7571 (Japan); Mayer, J. [Peter Grünberg Institute and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich (Germany); Central Facility for Electron Microscopy, RWTH Aachen University, 52074 Aachen (Germany)

    2017-05-15

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr{sub 2}FeMoO{sub 6}, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. - Highlights: • We demonstrate how to choose the optimal experimental conditions by using dynamical diffraction calculations in Sr{sub 2}FeMoO{sub 6}. • With optimized diffraction conditions, the signal-to-noise ratio of experimental EMCD spectra has been significantly improved. • We have determined orbital to spin magnetic moment ratio of Sr{sub 2}FeMoO{sub 6} quantitatively. • We have discussed the effects of dynamical diffraction conditions on the error bar of quantitative magnetic parameters.

  12. Energy deposition evaluation for ultra-low energy electron beam irradiation systems using calibrated thin radiochromic film and Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, S., E-mail: smatsui@gpi.ac.jp; Mori, Y. [The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsucho, Nishiku, Hamamatsu, Shizuoka 431-1202 (Japan); Nonaka, T.; Hattori, T.; Kasamatsu, Y.; Haraguchi, D.; Watanabe, Y.; Uchiyama, K.; Ishikawa, M. [Hamamatsu Photonics K.K. Electron Tube Division, 314-5 Shimokanzo, Iwata, Shizuoka 438-0193 (Japan)

    2016-05-15

    For evaluation of on-site dosimetry and process design in industrial use of ultra-low energy electron beam (ULEB) processes, we evaluate the energy deposition using a thin radiochromic film and a Monte Carlo simulation. The response of film dosimeter was calibrated using a high energy electron beam with an acceleration voltage of 2 MV and alanine dosimeters with uncertainty of 11% at coverage factor 2. Using this response function, the results of absorbed dose measurements for ULEB were evaluated from 10 kGy to 100 kGy as a relative dose. The deviation between the responses of deposit energy on the films and Monte Carlo simulations was within 15%. As far as this limitation, relative dose estimation using thin film dosimeters with response function obtained by high energy electron irradiation and simulation results is effective for ULEB irradiation processes management.

  13. Low-energy rate enhancement in recombination processes of electrons into bare uranium ions

    International Nuclear Information System (INIS)

    Wu Yong; Zeng Siliang; Duan Bin; Yan Jun; Wang Jianguo; Chinese Academy of Sciences, Lanzhou; Dong Chenzhong; Ma Xinwen

    2007-01-01

    Based on the Dirac-Fork-Slater method combined with the multichannel quantum defect theory, the recombination processes of electrons into bare uranium ions (U 92+ ) are investigated in the relative energy range close to zero, and the x-ray spectrum emitted in the direct radiative recombination and cascades processes are simulated. Compared with the recent measurement, it is found that the rate enhancement comes from the additional populations on high Rydberg states. These additional populations may be produced by other recombination mechanisms, such as the external electric-magnetic effects and the many-body correlation effects, which still remains an open problem. (authors)

  14. Inclusion of electron correlation for the target wave function in low- to intermediate-energy e-N2 scattering

    Science.gov (United States)

    Weatherford, C. A.; Brown, F. B.; Temkin, A.

    1987-01-01

    In a recent calculation, an exact exchange method was developed for use in the partial-differential-equation approach to electron-molecule scattering and was applied to e-N2 scattering in the fixed-nuclei approximation with an adiabatic polarization potential at low energies (0-10 eV). Integrated elastic cross sections were calculated and found to be lower than experiment at energies both below and above the Pi(g) resonance. It was speculated at that time that improved experimental agreement could be obtained if a correlated target representation were used in place of the uncorrelated one. The present paper implements this suggestion and demonstrates the improved agreement. These calculations are also extended to higher energies (0-30 eV) so asd to include the Sigma(u) resonance. Some discrepancies among the experiments and between experiment and the various calculations at very low energy are noted.

  15. Limitations of the condensed history method for low-energy electrons

    International Nuclear Information System (INIS)

    Martin, W.R.; Ballinger, C.T.; Rathkopf, J.A.

    1991-01-01

    A systematic evaluation of the conventional, condensed history electron transport methodology has been performed through comparisons with more accurate single-scatter Monte Carlo calculations. These comparisons highlight the inaccuracies associated with the condensed history method and indicate its range of validity. The condensed history method is used in codes such as MCNP4, SANDYL, ETRAN, ITS, and EGS and requires a number of restrictive assumptions about the scattering characteristics to make tractable the analytical solution to the infinite-medium transport equation. Distributions describing electron characteristics after multiple collisions (multiscatter distributions) are constructed from such solutions and serve as the heart of the condensed history codes. A two-level approach is taken to quantify the errors inherent in condensed history. First, conventional condensed history multiscattering distributions in energy and angle are compared directly with analogous distributions generated with a single-scatter Monte Carlo code. This recently developed code directly simulates individual electron interactions. Second, the conventional distributions are replaced in the condensed history code by distributions constructed via a single-scatter Monte Carlo simulation

  16. Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

    Energy Technology Data Exchange (ETDEWEB)

    Pekin, Thomas C. [Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, USA 94720 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States); Gammer, Christoph [Erich Schmid Institute of Materials Science, Jahnstrasse 12, Leoben, Austria 8700 (Austria); Ciston, Jim [National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States); Minor, Andrew M. [Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, USA 94720 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States); Ophus, Colin, E-mail: cophus@gmail.com [National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States)

    2017-05-15

    Scanning nanobeam electron diffraction strain mapping is a technique by which the positions of diffracted disks sampled at the nanoscale over a crystalline sample can be used to reconstruct a strain map over a large area. However, it is important that the disk positions are measured accurately, as their positions relative to a reference are directly used to calculate strain. In this study, we compare several correlation methods using both simulated and experimental data in order to directly probe susceptibility to measurement error due to non-uniform diffracted disk illumination structure. We found that prefiltering the diffraction patterns with a Sobel filter before performing cross correlation or performing a square-root magnitude weighted phase correlation returned the best results when inner disk structure was present. We have tested these methods both on simulated datasets, and experimental data from unstrained silicon as well as a twin grain boundary in 304 stainless steel.

  17. Development of positron diffraction and holography at LLNL

    International Nuclear Information System (INIS)

    Hamza, A.; Asoka-Kumar, P.; Stoeffl, W.; Howell, R.; Miller, D.; Denison, A.

    2003-01-01

    A low-energy positron diffraction and holography spectrometer is currently being constructed at the Lawrence Livermore National Laboratory (LLNL) to study surfaces and adsorbed structures. This instrument will operate in conjunction with the LLNL intense positron beam produced by the 100 MeV LINAC allowing data to be acquired in minutes rather than days. Positron diffraction possesses certain advantages over electron diffraction which are discussed. Details of the instrument based on that of low-energy electron diffraction are described

  18. 15.0 MeV/u He2+ ion-induced low energy electrons from water vapor

    International Nuclear Information System (INIS)

    Okada, Y.; Sato, Y.; Soga, F.; Ohsawa, D.

    2005-01-01

    We present the absolute doubly differential cross sections (DDCS) of low-energy electrons and their angular distributions (20deg - 160deg ) produced in the collisions of 15.0 MeV/u He 2+ ions with water vapor. Details of the experiments by 6.0 and 10.0 MeV/u He 2+ ions were already reported in our previous paper, in which the total uncertainty (±13%) was discussed. This paper shows the absolute DDCS data (1 - 100 eV) by 15.0 MeV/u He 2+ ions, in which the cover surrounding the interaction region was changed to μ-metal from Cu, in order to suppress the residual magnetic field for measuring the low-energy electrons effectively. (author)

  19. An experimental investigation of the reflection of low energy electrons from surfaces of 2H-MoS2

    International Nuclear Information System (INIS)

    Komolov, S.A.; Chadderton, L.T.

    1978-01-01

    Experiments are described in which a new technique - total current spectroscopy (TCS) - has been used to investigate the energy dependence of the reflection of low energy electrons from clean surfaces of the naturally occuring mineral molybdenite (2H-MoS 2 ). A theory involving both elastic and inelastic scattering of electrons is applied to a band structure calculated for molybdenite by Mattheiss. With relatively few approximations the results of numerical calculations for a TCS spectrum from molybdenite agree surprisingly well with experiment. It is suggested that TCS will prove to be a convenient and sensitive tool for the probing of energy structures in other solid surfaces. For the transition metal dichalcogenide series it should be possible to observe systematic changes in TCS spectra associated with changes in band structure, and subsequently to predict details in the density of states distributions using iterative computer procedures. (Auth.)

  20. Very low-energy conversion electron detection (VLECED) system at the isocele on-line isotope separator, Orsay

    International Nuclear Information System (INIS)

    Kilcher, P.; Sauvage, J.; Munsch, J.; Obert, J.; Caruette, A.; Ferro, A.; Boissier, G.; Fournet-Fayas, J.; Ducourtieux, M.; Landois, G.

    1988-01-01

    A system designed and installed at the on-line isotope separator ISOCELE II allows the high resolution detection of low-energy conversion electrons (down to 1 keV) emitted by mass separated radioactive sources: the use of a special tape transport permits both the slowing down of the incoming beam of radioactive ions up to a collection point and the acceleration of the electrons emitted by the collected sources brought to a flat magnetic spectrograph. Typical spectra so obtained are presented

  1. A low-cost approach to electronic excitation energies based on the driven similarity renormalization group

    Science.gov (United States)

    Li, Chenyang; Verma, Prakash; Hannon, Kevin P.; Evangelista, Francesco A.

    2017-08-01

    We propose an economical state-specific approach to evaluate electronic excitation energies based on the driven similarity renormalization group truncated to second order (DSRG-PT2). Starting from a closed-shell Hartree-Fock wave function, a model space is constructed that includes all single or single and double excitations within a given set of active orbitals. The resulting VCIS-DSRG-PT2 and VCISD-DSRG-PT2 methods are introduced and benchmarked on a set of 28 organic molecules [M. Schreiber et al., J. Chem. Phys. 128, 134110 (2008)]. Taking CC3 results as reference values, mean absolute deviations of 0.32 and 0.22 eV are observed for VCIS-DSRG-PT2 and VCISD-DSRG-PT2 excitation energies, respectively. Overall, VCIS-DSRG-PT2 yields results with accuracy comparable to those from time-dependent density functional theory using the B3LYP functional, while VCISD-DSRG-PT2 gives excitation energies comparable to those from equation-of-motion coupled cluster with singles and doubles.

  2. In situ observation of electron beam-induced phase transformation of CaCO3 to CaO via ELNES at low electron beam energies.

    Science.gov (United States)

    Golla-Schindler, Ute; Benner, Gerd; Orchowski, Alexander; Kaiser, Ute

    2014-06-01

    It is demonstrated that energy-filtered transmission electron microscope enables following of in situ changes of the Ca-L2,3 edge which can originate from variations in both local symmetry and bond lengths. Low accelerating voltages of 20 and 40 kV slow down radiation damage effects and enable study of the start and finish of phase transformations. We observed electron beam-induced phase transformation of single crystalline calcite (CaCO3) to polycrystalline calcium oxide (CaO) which occurs in different stages. The coordination of Ca in calcite is close to an octahedral one streched along the direction. Changes during phase transformation to an octahedral coordination of Ca in CaO go along with a bond length increase by 5 pm, where oxygen is preserved as a binding partner. Electron loss near-edge structure of the Ca-L2,3 edge show four separated peaks, which all shift toward lower energies during phase transformation at the same time the energy level splitting increases. We suggest that these changes can be mainly addressed to the change of the bond length on the order of picometers. An important pre-condition for such studies is stability of the energy drift in the range of meV over at least 1 h, which is achieved with the sub-Ångström low-voltage transmission electron microscope I prototype microscope.

  3. Development of a SEM-based low-energy in-line electron holography microscope for individual particle imaging.

    Science.gov (United States)

    Adaniya, Hidehito; Cheung, Martin; Cassidy, Cathal; Yamashita, Masao; Shintake, Tsumoru

    2018-05-01

    A new SEM-based in-line electron holography microscope has been under development. The microscope utilizes conventional SEM and BF-STEM functionality to allow for rapid searching of the specimen of interest, seamless interchange between SEM, BF-STEM and holographic imaging modes, and makes use of coherent low-energy in-line electron holography to obtain low-dose, high-contrast images of light element materials. We report here an overview of the instrumentation and first experimental results on gold nano-particles and carbon nano-fibers for system performance tests. Reconstructed images obtained from the holographic imaging mode of the new microscope show substantial image contrast and resolution compared to those acquired by SEM and BF-STEM modes, demonstrating the feasibility of high-contrast imaging via low-energy in-line electron holography. The prospect of utilizing the new microscope to image purified biological specimens at the individual particle level is discussed and electron optical issues and challenges to further improve resolution and contrast are considered. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Highlighting material structure with transmission electron diffraction correlation coefficient maps.

    Science.gov (United States)

    Kiss, Ákos K; Rauch, Edgar F; Lábár, János L

    2016-04-01

    Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Extraction of topographic and material contrasts on surfaces from SEM images obtained by energy filtering detection with low-energy primary electrons

    International Nuclear Information System (INIS)

    Nagoshi, Masayasu; Aoyama, Tomohiro; Sato, Kaoru

    2013-01-01

    Secondary electron microscope (SEM) images have been obtained for practical materials using low primary electron energies and an in-lens type annular detector with changing negative bias voltage supplied to a grid placed in front of the detector. The kinetic-energy distribution of the detected electrons was evaluated by the gradient of the bias-energy dependence of the brightness of the images. This is divided into mainly two parts at about 500 V, high and low brightness in the low- and high-energy regions, respectively and shows difference among the surface regions having different composition and topography. The combination of the negative grid bias and the pixel-by-pixel image subtraction provides the band-pass filtered images and extracts the material and topographic information of the specimen surfaces. -- Highlights: ► Scanning electron (SE) images contain many kind of information on material surfaces. ► We investigate energy-filtered SE images for practical materials. ► The brightness of the images is divided into two parts by the bias voltage. ► Topographic and material contrasts are extracted by subtracting the filtered images.

  6. Studying the molecular mechanisms of radiation damage : low-energy electron interactions with biomolecules and medically relevant molecules

    International Nuclear Information System (INIS)

    Tanzer, K.

    2015-01-01

    Since it was discovered in the year 2000 that secondary electrons with energies below 20 eV, which are the most abundant secondary species produced upon the interaction of ionizing radiation with biological tissue, can induce severe damages in the DNA such as single and double strand breaks, the interest for the study of the interaction of electrons with essential molecules of the human body has grown immensely. Double strand breaks can lead to cancer and are therefore a substantial threat to human health, however, the radiation research community is not sure how these strand breaks are formed upon interaction with ionizing radiation. The fact that even electrons with energies well below the ionization threshold can induce great damage in biological molecules via a resonant process called dissociative electron attachment (DEA), has even furthered the interest in these electron interactions, as it was shown to be a very efficient decomposition mechanism. A variety of studies, such as DEA studies to components of the DNA, for example, have been undertaken so far to shed more light on the role electrons play in the radiation damage of biomolecules. In this thesis two nucleobases, adenine and hypoxanthine, have been studied by observing their response towards low-energy electrons. It has been found that these nucleobases behave in a similar manner upon low-energy electron interaction, as do other nucleobases, that have been studied previously. The loss of hydrogen is suspected to act as a precursor for the decomposition of the DNA and the nucleobases can also undergo ring cleavage, which will induce substantial damage in the DNA. Furthermore, the search for improved and more efficient methods for the treatment of cancer is as important as ever, considering the ever-rising number of cancer deaths. Radiotherapy has proven to be one of the best treatments for tumors, but was found to be ineffective in hypoxic - oxygen deprived - tumors. Compounds called radiosensitizers

  7. Low energy electron capture in collisions of C3+ with He

    International Nuclear Information System (INIS)

    Wu, Y.; Qi, Y.Y.; Yan, J.; Wang, J.G.; Li, Y.; Buenker, R.J.; Kato, D.

    2009-06-01

    Charge transfer processes due to collisions of ground state C 3+ (1s 2 2s 2 S) ions with He atom are investigated using the quantum-mechanical molecular-orbital close-coupling (QMOCC) method for energies between 10 -4 eV/u and 10 3 eV/u. The ab initio adiabatic potential and radial coupling utilized in the QMOCC calculations are obtained from the multi-reference single- and double-excitation configuration interaction (MRD-CI) approach. Total and state-selective single electron capture (SEC) cross sections and rate coefficients are obtained and compared with the available experimental and theoretical data. Good agreement between the measured SEC cross sections and the present calculation is found, but the previous calculation of total rate coefficient using the Landau-Zener model is one or two orders of magnitude smaller than the present result. (author)

  8. Ultrashort and coherent single-electron pulses for diffraction at ultimate resolutions

    International Nuclear Information System (INIS)

    Kirchner, Friedrich Oscar

    2013-01-01

    Ultrafast electron diffraction is a powerful tool for studying structural dynamics with femtosecond temporal and sub-aangstroem spatial resolutions. It benefits from the high scattering cross-sections of electrons compared X-rays and allows the examination of thin samples, surfaces and gases. One of the main challenges in ultrafast electron diffraction is the generation of electron pulses with a short duration and a large transverse coherence. The former limits the temporal resolution of the experiment while the latter determines the maximum size of the scattering structures that can be studied. In this work, we strive to push the limits of electron diffraction towards higher temporal and spatial resolutions. The decisive step in our approach is to eliminate all detrimental effects caused by Coulomb repulsion between the electrons by reducing the number of electrons per pulse to one. In this situation, the electrons' longitudinal and transverse velocity distributions are determined solely by the photoemission process. By reducing the electron source size on the photocathode, we make use of the small transverse velocity spread to produce electron pulses with a transverse coherence length of 20 nm, which is about an order of magnitude larger than the reported values for comparable experiments. The energy distribution of an ensemble of single-electron pulses from a photoemission source is directly linked to the mismatch between the photon energy and the cathode's work function. This excess energy can be reduced by using a photon energy close to the material's work function. Using a tunable source of ultraviolet pulses, we demonstrate the reduction of the velocity spread of the electrons, resulting in a shorter duration of the electron pulses. The reduced electron pulse durations achieved by a tunable excitation or by other approaches require new characterization techniques for electron pulses. We developed a novel method for the characterization of electron pulses at

  9. Colour centres induced in LiF by low-energy electrons

    CERN Document Server

    Baldacchini, G; Montereali, R M; Scacco, A

    1998-01-01

    A detailed study has been carried out on the optical properties of intrinsic colour centres, created in LiF crystals under irradiation with low-penetration 3 keV electrons. The kinetics of the production of F and M centres, determined from optical absorption measurements, exhibits a typical three-stage structure and an evident saturation at high doses. The quantitative evaluation of the kinetic parameters is in excellent agreement with the predictions of the most comprehensive theoretical model. A comparison of the effects of irradiation at different temperatures, determined from absorption and photoluminescence spectra, allows one to deduce the conditions for preferential formation of F sub 2 or F sub 3 sup + defects in LiF crystals. (author)

  10. Flow direction variations of low energy ions as measured by the ion electron sensor (IES) flying on board of Rosetta

    Science.gov (United States)

    Szegö, Karoly; Nemeth, Zoltan; Foldy, Lajos; Burch, James L.; Goldstein, Raymond; Mandt, Kathleen; Mokashi, Prachet; Broiles, Tom

    2015-04-01

    The Ion Electron Sensor (IES) simultaneously measures ions and electrons with two separate electrostatic plasma analyzers in the energy range of 4 eV- 22 keV for ions. The field of view is 90ox360o, with angular resolution 5ox45o for ions, with a sector containing the solar wind being further segmented to 5o × 5o. IES has operated continuously since early 2014. In the ion data a low energy (energy ions. Here we analyze the arrival direction of this low energy component. The origin of these low energy ions is certainly the ionized component of the neutral gas emitted due to solar activity from comet 67P/Churiumov-Gerasimenko. The low energy component in general shows a 6h periodicity due to cometary rotation. The data show, however, that the arrival direction of the low energy ions is smeared both in azimuth and elevation, due possibly to the diverse mechanisms affecting these ions. One of these effects is the spacecraft potential (~-10V), which accelerates the ions towards the spacecraft omnidirectionally. To characterize the flow direction in azimuth-elevation, we have integrated over the lowest 8 energy channels using weighted energy: sum(counts * energy)/sum(counts); and considered only cases when the counts are above 30. When we apply higher cut for counts, the flow direction became more definite. For this analysis we use data files where the two neighbouring energy values and elevation values are collapsed; and the azimuthal resolution is 45o, that is the solar wind azimuthal segmentation is also collapsed. Here we use day 2014.09.11. as illustration. On that day a solar wind shock reached the spacecraft at about ~10 UT. After the shock transition the energy of the solar wind became higher, and after ~12 UT the flow direction of the solar wind fluctuated, sometimes by 35o. On this day Rosetta flew at about 29.3-29.6 km from the nucleus. In the azimuth-elevation plots summed over "weighted energy" (as defined above) we were able to identify two flow directions

  11. Serial single molecule electron diffraction imaging: diffraction background of superfluid helium droplets

    Science.gov (United States)

    Zhang, Jie; He, Yunteng; Lei, Lei; Alghamdi, Maha; Oswalt, Andrew; Kong, Wei

    2017-08-01

    In an effort to solve the crystallization problem in crystallography, we have been engaged in developing a method termed "serial single molecule electron diffraction imaging" (SS-EDI). The unique features of SS-EDI are superfluid helium droplet cooling and field-induced orientation: together the two features constitute a molecular goniometer. Unfortunately, the helium atoms surrounding the sample molecule also contribute to a diffraction background. In this report, we analyze the properties of a superfluid helium droplet beam and its doping statistics, and demonstrate the feasibility of overcoming the background issue by using the velocity slip phenomenon of a pulsed droplet beam. Electron diffraction profiles and pair correlation functions of ferrocene-monomer-doped droplets and iodine-nanocluster-doped droplets are presented. The timing of the pulsed electron gun and the effective doping efficiency under different dopant pressures can both be controlled for size selection. This work clears any doubt of the effectiveness of superfluid helium droplets in SS-EDI, thereby advancing the effort in demonstrating the "proof-of-concept" one step further.

  12. Ultrafast molecular imaging by laser-induced electron diffraction

    International Nuclear Information System (INIS)

    Peters, M.; Nguyen-Dang, T. T.; Cornaggia, C.; Saugout, S.; Charron, E.; Keller, A.; Atabek, O.

    2011-01-01

    We address the feasibility of imaging geometric and orbital structures of a polyatomic molecule on an attosecond time scale using the laser-induced electron diffraction (LIED) technique. We present numerical results for the highest molecular orbitals of the CO 2 molecule excited by a near-infrared few-cycle laser pulse. The molecular geometry (bond lengths) is determined within 3% of accuracy from a diffraction pattern which also reflects the nodal properties of the initial molecular orbital. Robustness of the structure determination is discussed with respect to vibrational and rotational motions with a complete interpretation of the laser-induced mechanisms.

  13. Highlighting material structure with transmission electron diffraction correlation coefficient maps

    International Nuclear Information System (INIS)

    Kiss, Ákos K.; Rauch, Edgar F.; Lábár, János L.

    2016-01-01

    Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. - Highlights: • We propose a novel technique to image the structure of polycrystalline TEM-samples. • Correlation coefficients maps highlights the evolution of the diffracting signal. • 3D views of grain boundaries are provided for nano-particles or polycrystals.

  14. Changes of electronic properties of p-GaN(0 0 0 1) surface after low-energy N+-ion bombardment

    Science.gov (United States)

    Grodzicki, M.; Mazur, P.; Ciszewski, A.

    2018-05-01

    The p-GaN(0 0 0 1) crystal with a relatively low acceptor concentration of 5 × 1016 cm-3 is used in these studies, which are carried out in situ under ultrahigh vacuum (UHV) by ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED). The p-GaN(0 0 0 1)-(1 × 1) surface is achieved by thermal cleaning. N+-ion bombardment by a 200 eV ion beam changes the surface stoichiometry, enriches it with nitrogen, and disorders it. Such modified surface layer inverts its semiconducting character from p- into n-type. The electron affinity for the already cleaned p-GaN surface and that just after bombardment shows a shift from 2.2 eV to 3.2 eV, as well as an increase of band bending at the vacuum/surface interface from 1.4 eV to 2.5 eV. Proper post-bombardment heating of the sample restores the initial atomic order of the modified layer, leaving its n-type semiconducting character unchanged. The results of the measurements are discussed based on two types of surface states concepts.

  15. Ab initio calculation of scattering length and cross sections at very low energies for electron-helium scattering

    International Nuclear Information System (INIS)

    Saha, H.P.

    1993-01-01

    The multiconfiguration Hartree-Fock method for continuum wave functions has been used to calculate the scattering length and phase shifts over extremely low energies ranging from 0 to 1 eV very accurately for electron-helium scattering. The scattering length is calculated very accurately with wave functions computed exactly at zero energy, resulting in an upper bound of 1.1784. The electron correlation and polarization of the target by the scattering electron, which are very important in these calculations, have been taken into account in an accurate ab initio manner through the configuration-interaction procedure by optimizing both bound and continuum orbitals simultaneously at each kinetic energy of the scattered electron. Detailed results for scattering length, differential, total, and momentum-transfer cross sections obtained from the phase shifts are presented. The present scattering length is found to be in excellent agreement with the experimental result of Andrick and Bitsch [J. Phys. B 8, 402 (1975)] and the theoretical result of O'Malley, Burke, and Berrington [J. Phys. B 12, 953 (1979)]. There is excellent agreement between the present total cross sections and the corresponding experimental measurements of Buckman and Lohmann [J. Phys. B 19, 2547 (1986)]. The present momentum-transfer cross sections also show remarkable agreement with the experimental results of Crompton, Elford, and Robertson [Aust. J. Phys. 23, 667 (1970)

  16. An investigation of the reflection of low energy electrons from the surfaces of layered transition metal dichalcogenides

    International Nuclear Information System (INIS)

    Smith, A.E.; Mohamed, M.H.; Wohlenberg, T.; Johnson, E.; Chadderton, L.T.; Moeller, P.J.

    1980-01-01

    Experimental measurements, using the total current spectroscopy (TCS) technique, on the energy dependence of the reflection of low energy electrons from clean surfaces of layered transition metal dichalcogenides are reported for the molybdenum semiconductor compounds 2H-MoS 2 and 2H-MoSe 2 . A simple model calculation involving both elastic and inelastic scattering is presented and correspondence established with the experimental spectra. In this picture information on the electronic band structure of the materials can then be extracted from the single particle component of the inelastic scattering. The model is extended to show that a feature in the 2H-MoS 2 experimental spectrum may be attributed to the excitation of an intermediate plasmon. (Auth.)

  17. A Dictionary Approach to Electron Backscatter Diffraction Indexing.

    Science.gov (United States)

    Chen, Yu H; Park, Se Un; Wei, Dennis; Newstadt, Greg; Jackson, Michael A; Simmons, Jeff P; De Graef, Marc; Hero, Alfred O

    2015-06-01

    We propose a framework for indexing of grain and subgrain structures in electron backscatter diffraction patterns of polycrystalline materials. We discretize the domain of a dynamical forward model onto a dense grid of orientations, producing a dictionary of patterns. For each measured pattern, we identify the most similar patterns in the dictionary, and identify boundaries, detect anomalies, and index crystal orientations. The statistical distribution of these closest matches is used in an unsupervised binary decision tree (DT) classifier to identify grain boundaries and anomalous regions. The DT classifies a pattern as an anomaly if it has an abnormally low similarity to any pattern in the dictionary. It classifies a pixel as being near a grain boundary if the highly ranked patterns in the dictionary differ significantly over the pixel's neighborhood. Indexing is accomplished by computing the mean orientation of the closest matches to each pattern. The mean orientation is estimated using a maximum likelihood approach that models the orientation distribution as a mixture of Von Mises-Fisher distributions over the quaternionic three sphere. The proposed dictionary matching approach permits segmentation, anomaly detection, and indexing to be performed in a unified manner with the additional benefit of uncertainty quantification.

  18. Analysis of low energy neutral hydrogen fluxes using an electron cyclotron resonance heated discharge

    International Nuclear Information System (INIS)

    Cain, B.L.

    1989-01-01

    This dissertation describes the design, construction, and proof-of-principle verification of a neutral hydrogen flux detection system, based on an ECRH discharge as the neutral flux ionizer. The significant features of the ionizer are its small size and simultaneous excitation of the ECRH mode using a 30 MHz RF driver and relatively small static magnetic fields. Demonstrated is the ability of the ECRH ionizer to ionize ∼ 900 eV neutral hydrogen fluxes with subsequent detection in a high resolution energy analyzer. A versatile calibration technique is applied to determine the ionizer efficiency, which additionally gives a variety of elastic scattering and charge exchange cross section results. Also described are the details of a new low energy beam-target interaction research facility, along with the basic techniques required to calibrate many of the system components. The facility has potential applications in areas such as fundamental cross section measurement, plasma diagnostics, beam-plasma interactions, and further beam-target research. 111 refs., 82 figs

  19. A new calculation on the stopping power and mean free path for low energy electrons in toluene over energy range of 20-10 000 eV

    International Nuclear Information System (INIS)

    Tan Zhenyu; Xia Yueyuan; Liu Xiangdong; Zhao Mingwen; Zhang Liming

    2009-01-01

    A new calculation of the stopping powers (SP) and inelastic mean free paths (IMFP) for electrons in toluene at energies below 10 keV has been presented. The calculation is based on the dielectric model and on an empirical evaluation approach of optical energy loss function (OELF). The reliability for the evaluated OELFs of several hydrocarbons with available experimental optical data has been systematically checked. For toluene, using the empirical OELF, the evaluated mean ionization potential, is compared with that given by Bragg's rule, and the calculated SP at 10 keV is also compared with the Bethe-Bloch prediction. The present results for SP and IMFP provide an alternative basic data for the study on the energy deposition of low-energy electrons transport through toluene, and also show that the method used in this work may be a good one for evaluating the SP and IMFP for hydrocarbons

  20. Low-energy electron dose-point kernel simulations using new physics models implemented in Geant4-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Bordes, Julien, E-mail: julien.bordes@inserm.fr [CRCT, UMR 1037 INSERM, Université Paul Sabatier, F-31037 Toulouse (France); UMR 1037, CRCT, Université Toulouse III-Paul Sabatier, F-31037 (France); Incerti, Sébastien, E-mail: incerti@cenbg.in2p3.fr [Université de Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Lampe, Nathanael, E-mail: nathanael.lampe@gmail.com [Université de Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Bardiès, Manuel, E-mail: manuel.bardies@inserm.fr [CRCT, UMR 1037 INSERM, Université Paul Sabatier, F-31037 Toulouse (France); UMR 1037, CRCT, Université Toulouse III-Paul Sabatier, F-31037 (France); Bordage, Marie-Claude, E-mail: marie-claude.bordage@inserm.fr [CRCT, UMR 1037 INSERM, Université Paul Sabatier, F-31037 Toulouse (France); UMR 1037, CRCT, Université Toulouse III-Paul Sabatier, F-31037 (France)

    2017-05-01

    When low-energy electrons, such as Auger electrons, interact with liquid water, they induce highly localized ionizing energy depositions over ranges comparable to cell diameters. Monte Carlo track structure (MCTS) codes are suitable tools for performing dosimetry at this level. One of the main MCTS codes, Geant4-DNA, is equipped with only two sets of cross section models for low-energy electron interactions in liquid water (“option 2” and its improved version, “option 4”). To provide Geant4-DNA users with new alternative physics models, a set of cross sections, extracted from CPA100 MCTS code, have been added to Geant4-DNA. This new version is hereafter referred to as “Geant4-DNA-CPA100”. In this study, “Geant4-DNA-CPA100” was used to calculate low-energy electron dose-point kernels (DPKs) between 1 keV and 200 keV. Such kernels represent the radial energy deposited by an isotropic point source, a parameter that is useful for dosimetry calculations in nuclear medicine. In order to assess the influence of different physics models on DPK calculations, DPKs were calculated using the existing Geant4-DNA models (“option 2” and “option 4”), newly integrated CPA100 models, and the PENELOPE Monte Carlo code used in step-by-step mode for monoenergetic electrons. Additionally, a comparison was performed of two sets of DPKs that were simulated with “Geant4-DNA-CPA100” – the first set using Geant4′s default settings, and the second using CPA100′s original code default settings. A maximum difference of 9.4% was found between the Geant4-DNA-CPA100 and PENELOPE DPKs. Between the two Geant4-DNA existing models, slight differences, between 1 keV and 10 keV were observed. It was highlighted that the DPKs simulated with the two Geant4-DNA’s existing models were always broader than those generated with “Geant4-DNA-CPA100”. The discrepancies observed between the DPKs generated using Geant4-DNA’s existing models and “Geant4-DNA-CPA100” were

  1. Development of splitting convergent beam electron diffraction (SCBED)

    Energy Technology Data Exchange (ETDEWEB)

    Houdellier, Florent, E-mail: Florent.Houdellier@cemes.fr [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse (France); Röder, Falk [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse (France); Triebenberg Lab, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Snoeck, Etienne [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse (France)

    2015-12-15

    Using a combination of condenser electrostatic biprism with dedicated electron optic conditions for sample illumination, we were able to split a convergent beam electron probe focused on the sample in two half focused probes without introducing any tilt between them. As a consequence, a combined convergent beam electron diffraction pattern is obtained in the back focal plane of the objective lens arising from two different sample areas, which could be analyzed in a single pattern. This splitting convergent beam electron diffraction (SCBED) pattern has been tested first on a well-characterized test sample of Si/SiGe multilayers epitaxially grown on a Si substrate. The SCBED pattern contains information from the strained area, which exhibits HOLZ lines broadening induced by surface relaxation, with fine HOLZ lines observed in the unstrained reference part of the sample. These patterns have been analyzed quantitatively using both parts of the SCBED transmitted disk. The fine HOLZ line positions are used to determine the precise acceleration voltage of the microscope while the perturbed HOLZ rocking curves in the stained area are compared to dynamical simulated ones. The combination of these two information leads to a precise evaluation of the sample strain state. Finally, several SCBED setups are proposed to tackle fundamental physics questions as well as applied materials science ones and demonstrate how SCBED has the potential to greatly expand the range of applications of electron diffraction and electron holography. - Highlights: • Using a condenser biprism, we split the CBED pattern in two half-CBED disks. • We have determined the electron optical conditions used to perform various SCBED. • We propose new applications possible for this new SCBED configuration.

  2. Modulation transfer function and detective quantum efficiency of electron bombarded charge coupled device detector for low energy electrons

    Czech Academy of Sciences Publication Activity Database

    Horáček, Miroslav

    2005-01-01

    Roč. 76, č. 9 (2005), 093704:1-6 ISSN 0034-6748 R&D Projects: GA ČR(CZ) GA202/03/1575 Keywords : electron bombarded CCD * modulation transfer function * detective quantum efficiency Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.235, year: 2005

  3. Relativistic electron planar channeling and diffraction in thin monocrystals

    International Nuclear Information System (INIS)

    Vorob'ev, S.A.; Nurmagambetov, S.B.; Kaplin, V.V.; Rozum, E.I.

    1985-01-01

    The interaction of relativistic electrons with thin monocrystals was investigated in approximation of continuous potential of crystal plane system. Numerical technique for solution of one-dimensional Schroedinger equation with a periodic potential was developed. Numerical solutions conducted according to the technique were used to determine the forms of ngular distributions of electrons located in various zones of lteral motion. Calculation results were applied for analyzing experimentally obtained data on agular distribution of 5.1 MeV electrons projected at small angles onto the (110) planar system of a Si monocrystal. The conducted complex experimental and theoretical: investigations demonstrated the possibility of prevalen occupation of certain states of lateral motion and enabled to determine angular reg in directions of the electron beam projection on a crystal where either channeling effects or those of electron diffraction are important

  4. Low-energy plasma-cathode electron gun with a perforated emission electrode

    Science.gov (United States)

    Burdovitsin, Victor; Kazakov, Andrey; Medovnik, Alexander; Oks, Efim; Tyunkov, Andrey

    2017-11-01

    We describe research of influence of the geometric parameters of perforated electrode on emission parameters of a plasma cathode electron gun generating continuous electron beams at gas pressure 5-6 Pa. It is shown, that the emission current increases with increasing the hole diameters and decreasing the thickness of the perforated emission electrode. Plasma-cathode gun with perforated electron can provide electron extraction with an efficiency of up to 72 %. It is shown, that the current-voltage characteristic of the electron gun with a perforated emission electrode differs from that of similar guns with fine mesh grid electrode. The plasma-cathode electron gun with perforated emission electrode is used for electron beam welding and sintering.

  5. Usability of a soft-electron (low-energy electron) machine for disinfestation of grains contaminated with insect pests

    International Nuclear Information System (INIS)

    Imamura, Taro; Miyanoshita, Akihiro; Todoriki, Setsuko; Hayashi, Toru

    2004-01-01

    Efficacy of soft-electron treatment for disinfestations of grains was investigated by treating pre-infested brown rice and adzuki bean with a commercial-scale soft-electron machine (soft-electron processor). Soft-electrons at 150 kV efficiently disinfested brown rice grains pre-infested with maize weevil (Stiophilus zeamais Motchulsky) and Indian meal moth (Plodia interpunctella (Huebner)) and adzuki beans with adzuki bean weevil (Callosobruchus chinensis (Linne)), although small numbers of the internal feeders such as C. chinensis in adzuki bean and S. zeamais in brown rice survived. The results indicate that the commercial-scale soft-electron machine can disinfest grains and beans, especially those contaminated with external feeders

  6. Usability of a soft-electron (low-energy electron) machine for disinfestation of grains contaminated with insect pests

    Science.gov (United States)

    Imamura, Taro; Miyanoshita, Akihiro; Todoriki, Setsuko; Hayashi, Toru

    2004-09-01

    Efficacy of soft-electron treatment for disinfestations of grains was investigated by treating pre-infested brown rice and adzuki bean with a commercial-scale soft-electron machine (soft-electron processor). Soft-electrons at 150 kV efficiently disinfested brown rice grains pre-infested with maize weevil ( Stiophilus zeamais Motchulsky) and Indian meal moth ( Plodia interpunctella (Hübner)) and adzuki beans with adzuki bean weevil ( Callosobruchus chinensis (Linne)), although small numbers of the internal feeders such as C. chinensis in adzuki bean and S. zeamais in brown rice survived. The results indicate that the commercial-scale soft-electron machine can disinfest grains and beans, especially those contaminated with external feeders.

  7. Diffraction and microscopy with attosecond electron pulse trains

    Science.gov (United States)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Attosecond spectroscopy1-7 can resolve electronic processes directly in time, but a movie-like space-time recording is impeded by the too long wavelength ( 100 times larger than atomic distances) or the source-sample entanglement in re-collision techniques8-11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons1-7 or re-colliding wavepackets8-11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space-time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

  8. UV photon and low-energy (5--150 eV) electron-stimulated processes at environmental interfaces

    International Nuclear Information System (INIS)

    Orlando, T.M.

    1997-01-01

    Irradiation of surfaces and interfaces with low-energy (5--150 eV) electrons and ultraviolet photons occurs during the storage of ''mixed'' (chemical/radioactive) waste forms and during processing steps which involve the use of low temperature plasmas. It is well known that electron- and photon-stimulated desorption (ESD and PSD) from wide band-gap materials and interfaces can be initiated by Auger decay of deep valence and shallow core holes. This process consists of hole production, Auger decay, reversal of the Madelung potential, and ion expulsion due to the Coulomb repulsion. ESD and PSD of neutrals also occurs and involves production of electron-hole pairs and excitons. Generally, neutral yields dominate ESD and PSD cross sections, which typically vary between ∼10 -16 and 10 -22 cm 2 . The authors present results on the ESD and PSD of environmentally relevant substrates such as ZrO 2 (100), soda-glass, and NaNO 3 . The major cation thresholds and yields indicate that ESD and PSD from these complex materials involves Auger stimulated events. In particular, desorption thresholds correlate with ionization of the O(2s), Zr(4p), Si(2p) and Na(2s) levels. The near band-gap threshold energy (∼5--7 eV) for the desorption of neutrals (i.e., atomic oxygen, NO, etc) demonstrate the overall importance of self-trapped and localized excitons in both ESD and PSD of typical ceramics and oxides

  9. Low-energy electron-induced dissociation in gas-phase nicotine, pyridine, and methyl-pyrrolidine

    Science.gov (United States)

    Ryszka, Michal; Alizadeh, Elahe; Li, Zhou; Ptasińska, Sylwia

    2017-09-01

    Dissociative electron attachment to nicotine, pyridine, and N-methyl-pyrrolidine was studied in the gas phase in order to assess their stability with respect to low-energy electron interactions. Anion yield curves for different products at electron energies ranging from zero to 15 eV were measured, and the molecular fragmentation pathways were proposed. Nicotine does not form a stable parent anion or a dehydrogenated anion, contrary to other biological systems. However, we have observed complex dissociation pathways involving fragmentation at the pyrrolidine side accompanied by isomerization mechanisms. Combining structure optimization and enthalpy calculations, performed with the Gaussian09 package, with the comparison with a deuterium-labeled N-methyl-d3-pyrrolidine allowed for the determination of the fragmentation pathways. In contrast to nicotine and N-methylpyrrolidine, the dominant pathway in dissociative electron attachment to pyridine is the loss of hydrogen, leading to the formation of an [M—H]- anion. The presented results provide important new information about the stability of nicotine and its constituent parts and contribute to a better understanding of the fragmentation mechanisms and their effects on the biological environment.

  10. Electron diffraction, elemental and image analysis of nanocrystals

    Czech Academy of Sciences Publication Activity Database

    Šlouf, Miroslav; Pavlova, Ewa; Hromádková, Jiřina; Králová, Daniela; Tyrpekl, Václav

    2009-01-01

    Roč. 16, 2a (2009), s. 33-34 ISSN 1211-5894. [Struktura - Colloquium of Czech and Slovak Crystallographic Association. Hluboká nad Vltavou, 22.06.2009-25.06.2009] R&D Projects: GA AV ČR KAN200520704; GA ČR GA203/07/0717 Institutional research plan: CEZ:AV0Z40500505 Keywords : TEM * electron diffraction * nanocrystals Subject RIV: CD - Macromolecular Chemistry

  11. The energy distribution function of excess electrons trapped in the pulse irradiated low density polyethylene (LDPE)

    International Nuclear Information System (INIS)

    Wysocki, S.; Mazurek, L.; Karolczak, S.; Kroh, J.

    1995-01-01

    Distribution function D (E) of electrons trapped in irradiated LDPE was calculated on the basis of time resolved absorption spectra recorded at temperatures of 20-250 K. Variation of absorption spectra with time and temperature were observed and discussed in terms of simultaneous decay and relocation of electrons from shallow to deeper traps. Results obtained imply domination of trap limited transport for shallowly trapped electrons. For deeper traps, hopping mechanism is prevailing. (author)

  12. Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

    Energy Technology Data Exchange (ETDEWEB)

    Wuestling, Sascha, E-mail: sascha.wuestling@kit.ed [Forschungszentrum Karlsruhe, Institut fuer Prozessdatenverarbeitung und Elektronik, Postfach 3640, 76021 Karlsruhe (Germany); Fraenkle, F.; Habermehl, F.; Renschler, P. [Universitaet Karlsruhe - TH, Institut fuer Experimentelle Kernphysik, Postfach 6980, 76128 Karlsruhe (Germany); Steidl, M [Forschungszentrum Karlsruhe, Institut fuer Kernphysik, Postfach 3640, 76021 Karlsruhe (Germany)

    2010-12-11

    The KATRIN neutrino mass experiment is based on a precise energy measurement ({Delta}E/E=5x10{sup -5}) of electrons emerging from tritium beta decay (E{sub max}=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area ({approx}80 cm{sup 2}), a certain energy resolution ({Delta}E=600 eV - 18.6 keV) but also a certain spatial resolution ({approx}3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm{sup 2}) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. , this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement . The detector allows for background searches with a sensitivity as low as 1.3x10{sup -3} cps/cm{sup 2} in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10{sup 5} and the search for ultra low Penning discharge emissions.

  13. Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

    Science.gov (United States)

    Wuestling, Sascha; Fraenkle, F.; Habermehl, F.; Renschler, P.; Steidl, M.

    2010-12-01

    The KATRIN neutrino mass experiment is based on a precise energy measurement (Δ E/ E=5×10 -5) of electrons emerging from tritium beta decay ( Emax=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area (˜80 cm 2), a certain energy resolution (Δ E=600 eV @ 18.6 keV) but also a certain spatial resolution (˜3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm 2) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. [6], this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement [7]. The detector allows for background searches with a sensitivity as low as 1.3×10 -3 cps/cm 2 in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10 5 and the search for ultra low Penning discharge emissions.

  14. 2-D Low Energy Electron Beam Profile Measurement Based on Computer Tomography Algorithm with Multi-Wire Scanner

    CERN Document Server

    Yu, Nengjie; Li Qing Feng; Tang, Chuan-Xiang; Zheng, Shuxin

    2005-01-01

    A new method for low energy electron beam profile measurement is advanced, which presents a full 2-D beam profile distribution other than the traditional 2-D beam profile distribution given by 1-D vertical and horizontal beam profiles. The method is based on the CT (Computer Tomography) algorithm. Multi-sets of data about the 1-D beam profile projections are attained by rotating the multi-wire scanner. Then a 2-D beam profile is reconstructed from these projections with CT algorithm. The principle of this method is presented. The simulation and the experiment results are compared and analyzed in detail.

  15. Development and characterization of electron sources for diffraction applications

    Energy Technology Data Exchange (ETDEWEB)

    Casandruc, Albert

    2015-12-15

    The dream to control chemical reactions that are essential to life is now closer than ever to gratify. Recent scientific progress has made it possible to investigate phenomena and processes which deploy at the angstroms scale and at rates on the order femtoseconds. Techniques such as Ultrafast Electron Diffraction (UED) are currently able to reveal the spatial atomic configuration of systems with unit cell sizes on the order of a few nanometers with about 100 femtosecond temporal resolution. Still, major advances are needed for structural interrogation of biological systems like protein crystals, which have unit cell sizes of 10 nanometers or larger, and sample sizes of less than one micrometer. For such samples, the performance of these electron-based techniques is now limited by the quality, in particular the brightness, of the electron source. The current Ph.D. work represents a contribution towards the development and the characterization of electron sources which are essential to static and time-resolved electron diffraction techniques. The focus was on electron source fabrication and electron beam characterization measurements, using the solenoid and the aperture scan techniques, but also on the development and maintenance of the relevant experimental setups. As a result, new experimental facilities are now available in the group and, at the same time, novel concepts for generating electron beams for electron diffraction applications have been developed. In terms of existing electron sources, the capability to trigger and detect field emission from single double-gated field emitter Mo tips was successfully proven. These sharp emitter tips promise high brightness electron beams, but for investigating individual such structures, new engineering was needed. Secondly, the influence of the surface electric field on electron beam properties has been systematically performed for flat Mo photocathodes. This study is very valuable especially for state

  16. Development and characterization of electron sources for diffraction applications

    International Nuclear Information System (INIS)

    Casandruc, Albert

    2015-12-01

    The dream to control chemical reactions that are essential to life is now closer than ever to gratify. Recent scientific progress has made it possible to investigate phenomena and processes which deploy at the angstroms scale and at rates on the order femtoseconds. Techniques such as Ultrafast Electron Diffraction (UED) are currently able to reveal the spatial atomic configuration of systems with unit cell sizes on the order of a few nanometers with about 100 femtosecond temporal resolution. Still, major advances are needed for structural interrogation of biological systems like protein crystals, which have unit cell sizes of 10 nanometers or larger, and sample sizes of less than one micrometer. For such samples, the performance of these electron-based techniques is now limited by the quality, in particular the brightness, of the electron source. The current Ph.D. work represents a contribution towards the development and the characterization of electron sources which are essential to static and time-resolved electron diffraction techniques. The focus was on electron source fabrication and electron beam characterization measurements, using the solenoid and the aperture scan techniques, but also on the development and maintenance of the relevant experimental setups. As a result, new experimental facilities are now available in the group and, at the same time, novel concepts for generating electron beams for electron diffraction applications have been developed. In terms of existing electron sources, the capability to trigger and detect field emission from single double-gated field emitter Mo tips was successfully proven. These sharp emitter tips promise high brightness electron beams, but for investigating individual such structures, new engineering was needed. Secondly, the influence of the surface electric field on electron beam properties has been systematically performed for flat Mo photocathodes. This study is very valuable especially for state

  17. Wave Optical Calculation of Probe Size in Low Energy Scanning Electron Microscope

    Czech Academy of Sciences Publication Activity Database

    Radlička, Tomáš

    2015-01-01

    Roč. 21, S4 (2015), s. 212-217 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : scanning electron microscope * optical calculation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.730, year: 2015

  18. Characterization of calcium crystals in Abelia using x-ray diffraction and electron microscopes

    Science.gov (United States)

    Localization, chemical composition, and morphology of calcium crystals in leaves and stems of Abelia mosanensis and A. ×grandiflora were analyzed with a variable pressure scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, low temperature SEM (LT-SEM) and a transmission ...

  19. FPGA-based upgrade of the read-out electronics for the low energy polarimeter at the cooler synchrotron

    Energy Technology Data Exchange (ETDEWEB)

    Hempelmann, Nils [Institut fuer Kernphysik, Forschungszentrum Juelich (Germany); Collaboration: JEDI-Collaboration

    2015-07-01

    The Cooler Synchrotron (COSY) is a storage ring used for experiments with polarized proton and deuteron beams. The low energy polarimeter is used to determine the vector and tensor polarization of the beam before injection at kinetic energies up to 45 MeV for protons and 75 MeV for deuterons. The polarimeter uses scintillators to measure the energy of both outgoing particles of a scattering reaction and the time between their detection. The present read-out electronics consists of analog NIM modules and is limited in terms of time resolution and the capability for online data analysis. The read-out electronics will be replaced with a a new system based on analog pulse sampling and an FPGA chip for logic operations. The new system will be able to measure the time at which particles arrive to a precision better than 50 ps, facilitating better background reduction using coincidence measurement. In addition to measuring the beam polarization, the system will be used to precisely determine the vector and tensor analyzing powers for deuteron scattering off carbon at a kinetic energy of 75 MeV.

  20. Structure refinement using precession electron diffraction tomography and dynamical diffraction: tests on experimental data

    Czech Academy of Sciences Publication Activity Database

    Palatinus, Lukáš; Correa, Cinthia Antunes; Steciuk, G.; Jacob, D.; Roussel, P.; Boullay, P.; Klementová, Mariana; Gemmi, M.; Kopeček, Jaromír; Domeneghetti, C.; Cámara, F.; Petříček, Václav

    2015-01-01

    Roč. 71, č. 6 (2015), 740-751 ISSN 2052-5206 R&D Projects: GA MŠk(CZ) LM2011029; GA ČR GA13-25747S; GA MŠk LO1409 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132; FUNBIO(XE) CZ.2.16/3.1.00/21568 Keywords : XRD * structure refinement * precession electron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.892, year: 2015

  1. Rate coefficients for low-energy electron dissociative attachment to molecular hydrogen

    International Nuclear Information System (INIS)

    Horacek, J.; Houfek, K.; Cizek, M.; Murakami, I.; Kato, T.

    2003-02-01

    Calculation of rate constants for dissociative electron attachment to molecular hydrogen is reported. The calculation is based on an improved nonlocal resonance model of Cizek, Horacek and Domcke which takes fully into account the nonlocality of the resonance dynamics and uses potentials with correct asymptotic forms. The rate constants are calculated for all quantum numbers v and J of the target molecules and for electron temperature in the range 0-30000 K. (author)

  2. Magnetic energy analyser for slow electrons

    International Nuclear Information System (INIS)

    Limberg, W.

    1974-08-01

    A differential spectrometer with high time and energy resolution has been developed using the principle of energy analysis with a longitudinal homogeneous magnetic field. This way it is possible to measure the energy distribution of low energy electrons (eV-range) in the presence of high energy electrons without distortions by secondary electrons. The functioning and application of the analyzer is demonstrated by measuring the energy distributions of slow electrons emitted by a filament. (orig.) [de

  3. Identification of phases in zinc alloy powders using electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Martin G. [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States); Kenik, Edward A. [Oak Ridge National Laboratory, 100 Bethel Valley Rd., Bldg. 4515, MS-6064, P.O. Box 2008, Oak Ridge, TN 37831 (United States); O' Keefe, Matthew J. [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States)]. E-mail: mjokeefe@umr.edu; Miller, F. Scott [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States); Johnson, Benedict [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States)

    2006-05-25

    Scanning electron microscopy and electron backscatter diffraction (EBSD) were used for the structural characterization of phases in Zn alloy powders. Commercial Zn alloy powders contained additions of <1000 ppm of Bi, In, Al or Mg. Bismuth and In have extremely low solubility in Zn and form intermetallic Bi-In compounds which segregate to the Zn grain boundaries. The Bi-In phases were <0.3 {mu}m in size, had low melting points, and were not abundant enough for EBSD analysis. Increasing the alloying additions 20-40-fold resulted in Bi-In phases >1 {mu}m that could be used for EBSD analysis for phase characterization. Deformation-free microstructures were obtained by mechanical polishing and ion milling. The Zn matrix was characterized as Zn via EBSD. A BiIn{sub 2} phase was identified in the powder microstructures via EBSD. An In phase with 8-9 wt.% Bi was identified using low voltage energy dispersive spectroscopy and closely matched the composition predicted by the Bi-In phase diagram.

  4. Electronic diffraction study of the chlorination of nickel; Etude par diffraction electronique de la chloruration du nickel

    Energy Technology Data Exchange (ETDEWEB)

    Vigner, D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    A study has been made of the chlorination of the (100), (110) and (111) crystal faces of nickel using high energy electron diffraction and electron microscopy. Two methods have been used: bombardment with chlorine ions having an energy of between 10 and 30 keV, and direct chlorination in a diffractor at pressures of about 10{sup -4} torr. It has thus been possible to show the very special properties of nickel chloride (CdBr{sub 2} type, space group R 3-bar m) which is always formed along the (0001) plane, whatever the orientation of the substrate. It has also been possible to attain the metal-halide interface and to show the existence of two-dimensional chemisorbed films which are ordered or disordered according to the crystal orientation. (author) [French] La chloruration des faces (100) (110) et (111) du nickel a ete etudiee par diffraction des electrons de haute energie et par microscopie electronique. Deux methodes ont ete utilisees: le bombardement avec des ions chlore ayant une energie comprise entre 10 et 30 keV, et la chloruration directe dans un diffracteur pour des pressions de l'ordre de 10{sup -4} torr. Ainsi ont ete mises en evidence les proprietes tres particulieres du chlorure de nickel (type CdBr{sub 2}, groupe spatial R 3-bar m) qui s'accole toujours suivant le plan (0001), quelle que soit l'orientation du substrat. Il a ete egalement possible d'atteindre l'interface metal-halogenure et de montrer l'existence de couches chimisorbees bidimensionnelles, ordonnees ou desordonnees suivant l'orientation cristalline etudiee. (auteur)

  5. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions

    Science.gov (United States)

    Ren, Xueguang; Pflüger, Thomas; Weyland, Marvin; Baek, Woon Yoon; Rabus, Hans; Ullrich, Joachim; Dorn, Alexander

    2014-10-01

    We study the low-energy (E0 = 26 eV) electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 eV has been achieved using the recently developed photoemission electron source. Here, we will discuss the fragmentation reactions for the cations C4H8O+, C4H7O+, C2H3O+, C3H_6^+, C3H_5^+, C3H_3^+, CH3O+, CHO+, and C2H_3^+.

  6. Approximations to the electron energy distribution and positive column models for low-pressure discharge light sources

    International Nuclear Information System (INIS)

    Lister, G G; Sheverev, V A; Uhrlandt, D

    2002-01-01

    The applicability of 'fluid' models based on analytic approximations of the electron energy distribution function (EEDF) and of kinetic models for low-pressure discharge light sources is discussed. Traditionally, 'fluid' models of fluorescent lamps assume that the EEDF is Maxwellian up to the energy of the first excited state. It is shown that such an approach is sufficiently accurate in most cases of conventional as well as of 'highly loaded' fluorescent lamps. However, this assumption is strongly violated for many rare gas glow discharges for mercury free light sources. As an example, a neon dc discharge is studied. The densities of the four lowest excited states and the electric field have been measured. The experimental results can be fairly well reproduced by a kinetic positive column model. This article was scheduled to appear in issue 14 of J. Phys. D: Appl. Phys. To access this special issue please follow this link: http://stacks.iop.org/0022-3727/35/i=14/

  7. Research of transportation efficiency of low-energy high- current electron beam in plasma channel in external magnetic field

    International Nuclear Information System (INIS)

    Vagin, E S; Grigoriev, V P

    2015-01-01

    Effective high current (5-20 kA) and low energy (tens of keV) electrons beam transportation is possible only with almost complete charging neutralization. It is also necessary to use quite high current neutralization for elimination beam self-pinching effect. The research is based on the self-consistent mathematical model that takes into account beam and plasma particles dynamic, current and charge neutralization of electron beam and examines the transportation of electron beam into a chamber with low-pressure plasma in magnetic field. A numerical study was conducted using particle in cell (PIC) method. The study was performed with various system parameters: rise time and magnitude of the beam current, gas pressure and plasma density and geometry of the system. Regularities of local virtual cathode field generated by the beam in the plasma channel, as well as ranges of parameters that let transportation beam with minimal losses, depending on the external magnetic field were determined through a series of numerical studies. In addition, the assessment of the impact of the plasma ion mobility during the transition period and during steady beam was performed. (paper)

  8. Spectroscopic studies of organic-inorganic composite film cured by low energy electron beam

    International Nuclear Information System (INIS)

    Mahathir Mohamed; Dahlan Mohd; Ibrahim Abdullah; Eda Yuhana Ariffin

    2009-01-01

    Liquid epoxidized natural rubber acrylate (LENRA) film was reinforced with silica particles formed in-situ via sol gel process. Combination of these two components produces organic-inorganic composites. Tetraethyl orthosilicate (TEOS) was used as precursor material for silica generation. Sol gel reactions was carried out at different concentrations of TEOS i.e. between 10 and 50 phr. The compounds that contain silica were crosslinked by electron beam. Structural properties studies were carried out by Fourier Transform Infrared Spectrometer (FTIR). It was found that miscibility between organic and inorganic components improved with the presence of silanol groups (Si-OH) and polar solvent i.e. THF, via hydrogen bonding formation between siloxane and LENRA. Morphology study by the transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed in-situ generated silica particles were homogenous and well dispersed at any concentrations of TEOS. (author)

  9. Optical radiation emitted by a silver surface bombarded by low-energy electrons

    International Nuclear Information System (INIS)

    Miserey, F.; Lebon, P.; Septier, A.; Trehin, F.; Beaugrand, C.

    1975-01-01

    Thick silver targets are obtained on flat glass discs by evaporation in a UHV cell (p -10 torr) and their optical coefficients measured by ellipsometry. A field-emission electron gun bombards a limited region of the target, corresponding to the entry pupil of a light spectrometer. Radiation emitted in the domain 250-600nm is analyzed for both normal and parallel polarizations. Spectral distributions of photons are obtained by using a very sensitive counting device including a multi channel analyzer. First experimental results concerning optical radiation generated by 6keV electrons are reported and compared to Transition Radiation and Bremsstrahlung theoretical spectra [fr

  10. Attenuation of 10 MeV electron beam energy to achieve low doses does not affect Salmonella spp. inactivation kinetics

    International Nuclear Information System (INIS)

    Hieke, Anne-Sophie Charlotte; Pillai, Suresh D.

    2015-01-01

    The effect of attenuating the energy of a 10 MeV electron beam on Salmonella inactivation kinetics was investigated. No statistically significant differences were observed between the D 10 values of either Salmonella 4,[5],12:i:- or a Salmonella cocktail (S. 4,[5],12:i:-, Salmonella Heidelberg, Salmonella Newport, Salmonella Typhimurium, Salmonella) when irradiated with either a non-attenuated 10 MeV eBeam or an attenuated 10 MeV eBeam (~2.9±0.22 MeV). The results show that attenuating the energy of a 10 MeV eBeam to achieve low doses does not affect the inactivation kinetics of Salmonella spp. when compared to direct 10 MeV eBeam irradiation. - Highlights: • 10 MeV eBeam energy was attenuated to 2.9±0.22 MeV using HDPE sheets. • Attenuation of eBeam energy does not affect the inactivation kinetics of Salmonella. • Microbial inactivation is independent of eBeam energy in the range of 3–10 MeV

  11. Interaction of low-energy electrons and positrons with condensed matter: Stopping powers and inelastic mean free paths from optical data

    International Nuclear Information System (INIS)

    Ashley, J.C.

    1989-01-01

    An ''optical-data model'' is described for evaluating energy loss per unit pathlength and inelastic mean free path for low-energy electrons and positrons (approx lt 10 keV) from optical data on the medium of interest. Exchange between the incident electron and electrons in the medium is included. Results from the optical-data model are compared with previous theoretical calculations. 15 refs., 6 figs., 2 tabs

  12. Electron--noble-gas spin-flip scattering at low energy

    International Nuclear Information System (INIS)

    Walker, T.G.; Bonin, K.; Happer, W.

    1987-01-01

    The spin-exchange rates and spin-relaxation rates for thermal electrons colliding with noble-gas atoms are calculated using the orthogonalized-plane-wave approximation and via partial-wave analysis. The two techniques give similar results and are in order-of-magnitude agreement with the experimental rate in Ar

  13. UKRmol: a low-energy electron- and positron-molecule scattering suite

    Science.gov (United States)

    Carr, J. M.; Galiatsatos, P. G.; Gorfinkiel, J. D.; Harvey, A. G.; Lysaght, M. A.; Madden, D.; Mašín, Z.; Plummer, M.; Tennyson, J.; Varambhia, H. N.

    2012-03-01

    We describe the UK computational implementation of the R-matrix method for the treatment of electron and positron scattering from molecules. Recent developments in the UKRmol suite are detailed together with the collision processes it is enabling us to treat.

  14. First observation of low energy electron neutrinos in a liquid argon time projection chamber

    Energy Technology Data Exchange (ETDEWEB)

    Acciarri, R.; Adams, C.; Asaadi, J.; Baller, B.; Bolton, T.; Bromberg, C.; Cavanna, F.; Church, E.; Edmunds, D.; Ereditato, A.; Farooq, S.; Fitzpatrick, R. S.; Fleming, B.; Hackenburg, A.; Horton-Smith, G.; James, C.; Lang, K.; Luo, X.; Mehdiyev, R.; Page, B.; Palamara, O.; Rebel, B.; Schukraft, A.; Scanavini, G.; Soderberg, M.; Spitz, J.; Szelc, A. M.; Weber, M.; Yang, T.; Zeller, G. P.

    2017-04-06

    Liquid argon time projection chambers (LArTPCs) produce remarkable fidelity in the observation of neutrino interactions. The superior capabilities of such detectors to reconstruct the spatial and calorimetric information of neutrino events have made them the detectors of choice in a number of experiments, specifically those looking to observe electron neutrino ($\

  15. Instrumental development of a quasi-relativistic ultrashort electron beam source for electron diffractions and spectroscopies.

    Science.gov (United States)

    Shin, Young-Min; Figora, Michael

    2017-10-01

    A stable femtosecond electron beam system has been configured for time-resolved pump-probe experiments. The ultrafast electron diffraction (UED) system is designed with a sub-MeV photoelectron beam source pulsed by a femtosecond UV laser and nondispersive beamline components, including a bunch compressor-a pulsed S-band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 μs pulse length. A single-cell RF photo-gun is designed to produce 1.6-16 pC electron bunches in a photoemission mode with 150 fs pulse duration at 0.5-1 MeV. The measured RF system jitters are within 1% in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of ΔE, corresponding to 80 fs and 5 fs of Δt, respectively. Our particle-in-cell simulations indicate that the designed bunch compressor reduces the time-of-arrival jitter by about an order of magnitude. The transport and focusing optics of the designed beamline with the bunch compressor enables an energy spread within 10 -4 and a bunch length (electron probe) within quasi-relativistic UED system.

  16. Quantitative nanoscale water mapping in frozen-hydrated skin by low-loss electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yakovlev, Sergey [Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Misra, Manoj; Shi, Shanling [Unilever Research and Development, Trumbull, CT 06611 (United States); Firlar, Emre [Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Libera, Matthew, E-mail: mlibera@stevens.edu [Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

    2010-06-15

    Spatially resolved low-loss electron energy-loss spectroscopy (EELS) is a powerful method to quantitatively determine the water distribution in frozen-hydrated biological materials at high spatial resolution. However, hydrated tissue, particularly its hydrophilic protein-rich component, is very sensitive to electron radiation. This sensitivity has traditionally limited the achievable spatial resolution because of the relatively high noise associated with low-dose data acquisition. We show that the damage caused by high-dose data acquisition affects the accuracy of a multiple-least-squares (MLS) compositional analysis because of inaccuracies in the reference spectrum used to represent the protein. Higher spatial resolution combined with more accurate compositional analysis can be achieved if a reference spectrum is used that better represents the electron-beam-damaged protein component under frozen-hydrated conditions rather than one separately collected from dry protein under low-dose conditions. We thus introduce a method to extract the best-fitting protein reference spectrum from an experimental spectrum dataset. This method can be used when the MLS-fitting problem is sufficiently constrained so that the only unknown is the reference spectrum for the protein component. We apply this approach to map the distribution of water in cryo-sections obtained from frozen-hydrated tissue of porcine skin. The raw spectral data were collected at doses up to 10{sup 5} e/nm{sup 2} despite the fact that observable damage begins at doses as low as 10{sup 3} e/nm{sup 2}. The resulting spatial resolution of 10 nm is 5-10 times better than that in previous studies of frozen-hydrated tissue and is sufficient to resolve sub-cellular water fluctuations as well as the inter-cellular lipid-rich regions of skin where water-mediated processes are believed to play a significant role in the phenotype of keratinocytes in the stratum corneum.

  17. Quantitative nanoscale water mapping in frozen-hydrated skin by low-loss electron energy-loss spectroscopy

    International Nuclear Information System (INIS)

    Yakovlev, Sergey; Misra, Manoj; Shi, Shanling; Firlar, Emre; Libera, Matthew

    2010-01-01

    Spatially resolved low-loss electron energy-loss spectroscopy (EELS) is a powerful method to quantitatively determine the water distribution in frozen-hydrated biological materials at high spatial resolution. However, hydrated tissue, particularly its hydrophilic protein-rich component, is very sensitive to electron radiation. This sensitivity has traditionally limited the achievable spatial resolution because of the relatively high noise associated with low-dose data acquisition. We show that the damage caused by high-dose data acquisition affects the accuracy of a multiple-least-squares (MLS) compositional analysis because of inaccuracies in the reference spectrum used to represent the protein. Higher spatial resolution combined with more accurate compositional analysis can be achieved if a reference spectrum is used that better represents the electron-beam-damaged protein component under frozen-hydrated conditions rather than one separately collected from dry protein under low-dose conditions. We thus introduce a method to extract the best-fitting protein reference spectrum from an experimental spectrum dataset. This method can be used when the MLS-fitting problem is sufficiently constrained so that the only unknown is the reference spectrum for the protein component. We apply this approach to map the distribution of water in cryo-sections obtained from frozen-hydrated tissue of porcine skin. The raw spectral data were collected at doses up to 10 5 e/nm 2 despite the fact that observable damage begins at doses as low as 10 3 e/nm 2 . The resulting spatial resolution of 10 nm is 5-10 times better than that in previous studies of frozen-hydrated tissue and is sufficient to resolve sub-cellular water fluctuations as well as the inter-cellular lipid-rich regions of skin where water-mediated processes are believed to play a significant role in the phenotype of keratinocytes in the stratum corneum.

  18. Direct Detection and Imaging of Low-Energy Electrons with Delta-Doped Charge-Coupled Devices

    Science.gov (United States)

    Nikzad, S.; Yu, Q.; Smith, A. L.; Jones, T. J.; Tombrello, T. A.; Elliott, S. T.

    1998-01-01

    We report the use fo delta-doped charge-coupled devices (CCDs) for direct detection of electrons in the 50-1500 eV energy range. These are the first measurements with a solid state device to detect electrons in this energy range.

  19. A comparison of the relative biological effectiveness of low energy electronic brachytherapy sources in breast tissue: a Monte Carlo study.

    Science.gov (United States)

    White, Shane A; Reniers, Brigitte; de Jong, Evelyn E C; Rusch, Thomas; Verhaegen, Frank

    2016-01-07

    Electronic brachytherapy sources use low energy photons to treat the tumor bed during or after breast-conserving surgery. The relative biological effectiveness of two electronic brachytherapy sources was explored to determine if spectral differences due to source design influenced radiation quality and if radiation quality decreased with distance in the breast. The RBE was calculated through the number of DNA double strand breaks (RBEDSB) using the Monte Carlo damage simulator (MCDS) in combination with other Monte Carlo electron/photon spectrum calculations. 50kVp photons from the Intrabeam (Carl Zeiss Surgical) and Axxent (Xoft) through 40-mm spherical applicators were simulated to account for applicator and tissue attenuation in a variety of breast tissue compositions. 40kVp Axxent photons were also simulated. Secondary electrons (known to be responsible for most DNA damage) spectra at different distance were inputted into MCDS to calculate the RBEDSB. All RBEDSB used a cobalt-60 reference. RBEDSB data was combined with corresponding average photon spectrum energy for the Axxent and applied to model-based average photon energy distributions to produce an RBEDSB map of an accelerated partial breast irradiation (APBI) patient. Both Axxent and Intrabeam 50kVp spectra were shown to have a comparable RBEDSB of between 1.4 and 1.6 at all distances in spite of progressive beam hardening. The Axxent 40kVp also demonstrated a similar RBEDSB at distances. Most RBEDSB variability was dependent on the tissue type as was seen in rib (RBEDSB  ≈  1.4), gland (≈1.55), adipose (≈1.59), skin (≈1.52) and lung (≈1.50). RBEDSB variability between both sources was within 2%. A correlation was shown between RBEDSB and average photon energy and used to produce an RBEDSB map of a dose distribution in an APBI patient dataset. Radiation quality is very similar between electronic brachytherapy sources studied. No significant reductions in RBEDSB were observed with

  20. Diffraction and absorption of inelastically scattered electrons for K-shell ionization

    International Nuclear Information System (INIS)

    Josefsson, T.W.; Allen, L.J.

    1995-01-01

    An expression for the nonlocal inelastic scattering cross section for fast electrons in a crystalline environment, which explicitly includes diffraction as well as absorption for the inelastically scattered electrons, is used to carry out realistic calculations of K-shell electron energy loss spectroscopy (EELS) and energy dispersive x-ray (EDX) analysis cross sections. The calculations demonstrate quantitatively why, in EDX spectroscopy, integration over the dynamical states of the inelastically scattered electron averages in such a way that an effective plane wave representation of the scattered electrons is a good approximation. This is only the case for large enough acceptance angles of the detector in an EELS experiment. For EELS with smaller detector apertures, explicit integration over the dynamical final states is necessary and inclusion of absorption for the scattered electrons is important, particularly for thicker crystals. 50 refs., 7 figs