WorldWideScience

Sample records for graphite crystal monochromator

  1. A pseudo-curved oriented pyrolytic graphite neutron monochromator

    International Nuclear Information System (INIS)

    Ettedgui, H.; Gurewitz, E.; Pinto, H.

    1979-03-01

    A pseudo-curved neutron monochromator with a continuously variable curvature was constructed with four flat pieces of oriented pyrolytic graphite (OPG). Curvatures which yield maximum diffracted intensities were determined for neutrons of wavelengths 1 A and 2.4 A. The increase of the intensity relatively to that of a flat monochromator is by a factor of 2 and 1.5, for 1 A and 2.4 A, respectively. The neutron flux at three positions along the neutron path was determined by gold foils activation and compared with the flux from flat monochromators of OPG and copper

  2. Characteristics of Pyrolytic Graphite as a Neutron Monochromator

    International Nuclear Information System (INIS)

    Adib, M.; Habib, N.; El-Mesiry, M.S.; Fathallah, M.

    2011-01-01

    Pyrolytic graphite (PG) has become nearly indispensable in neutron spectroscopy. Since the integrated reflectivity of the monochromatic neutrons from PG crystals cut along its c-axis is high within a wavelength band from 0.1 nm up to .65 nm. The monochromatic features of PG crystal is detailed in terms of the optimum mosaic spread, crystal thickness and reactor moderating temperature for efficient integrated neutron reflectivity within the wavelength band. A computer code Mono-PG has been developed to carry out the required calculations for the PG hexagonal close-packed structure. Calculation shows that, 2 mm thick of PG crystal having 0.30 FWHM on mosaic spread are the optimum parameters of PG crystal as a monochromator at selected neutron wavelength shorter than 2 nm. However, the integrated neutron intensity of 2nd and 3rd orders from thermal reactor flux is even higher than that of the 1st order one at neutron wavelengths longer than 2 nm. While, from cold reactor flux, integrated neutron intensity of the 1st order within the wavelength band from 0.25 up to 0.5 nm is higher than the 2nd and 3rd ones

  3. Monolithic I-Beam Crystal Monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Bagnasco, John

    2001-10-16

    Curved crystal, focusing monochromators featuring cubed-root thickness profiles typically employ side-clamped cooling to reduce thermally induced overall bend deformation of the crystal. While performance is improved, residual bend deformation is often an important limiting factor in the monochromator performance. A slightly asymmetric ``I-beam'' crystal cross section with cubed-root flange profiles has been developed to further reduce this effect. Physical motivation, finite-element modeling evaluation and performance characteristics of this design are discussed. Reduction of high mounting stress at the fixed end of the crystal required the soldering of an Invar support fixture to the crystal. Detailed descriptions of this process along with its performance characteristics are also presented.

  4. Second crystal cooling on cryogenically cooled undulator and wiggler double crystal monochromators

    International Nuclear Information System (INIS)

    Knapp, G. S.

    1998-01-01

    Simple methods for the cooling of the second crystals of cryogenically cooled undulator and wiggler double crystal monochromators are described. Copper braids between the first and second crystals are used to cool the second crystals of the double crystal monochromators. The method has proved successful for an undulator monochromator and we describe a design for a wiggler monochromator

  5. Multiple order reflections in crystal neutron monochromators

    International Nuclear Information System (INIS)

    Fulfaro, R.

    1976-01-01

    A study of the higher order reflections in neutron crystal monochromators was made in order to obtain, for the IEA single crystal spectrometer, the operation range of 1,0eV to 0,01eV. Two crystals were studied, an Al(III) near 1,0eV and a Ge(III) in lower energies. For the Ge(III) case the higher order contaminations in the reflected beam were determined using as standard the gold total neutron cross section and performing the crystal reflectivity calculation for several orders of reflection. The knowledge of the contamination for each order as a function of neutron wavelength allows the optimization of the filter thickness in order to avoid higher order neutrons. The Ge(III) crystal was used because its second order reflections are theoretically forbidden, giving an advantage on other crystals, since measurements can be made until 0.02eV directly without filters. In the energy range 0.02 to 0.01eV, order contaminations higher than the second are present, therefore, either quartz filters are employed or calculated corrections are applied to the experimental data. The Al(III) crystal was used in order to estimate the second order contamination effect, in the iridium resonance measurements, at E 0 = 0.654eV. In that region, approximations can be made and it was not necessary to make the crystal reflectivity calculation for the filters thickness optimization. Since only the second order affects the results in that region, tellurium was used for the filtration, because this element has a resonance in the range of neutrons with energy 4E [pt

  6. Realisation of a novel crystal bender for a fast double crystal monochromator

    CERN Document Server

    Zaeper, R; Wollmann, R; Luetzenkirchen-Hecht, D; Frahm, R

    2001-01-01

    A novel crystal bender for an X-ray undulator beamline as part of a fast double crystal monochromator development for full EXAFS energy range was characterized. Rocking curves of the monochromator crystal system were recorded under different heat loads and bending forces of the indirectly cooled first Si(1 1 1) crystal. The monochromator development implements new piezo-driven tilt tables with wide angular range to adjust the crystals' Bragg angles and a high pressure actuated bender mechanism for the first crystal.

  7. A Double-Crystal Monochromator for Neutron Stress Diffractometry

    Czech Academy of Sciences Publication Activity Database

    Em, V.; Balagurov, A. M.; Glazkov, V. P.; Karpov, I. D.; Mikula, Pavol; Miron, N. F.; Somenkov, V. A.; Sumin, V. V.; Šaroun, Jan; Shushunov, M. N.

    2017-01-01

    Roč. 60, č. 4 (2017), s. 526-532 ISSN 0020-4412 Institutional support: RVO:61389005 Keywords : neutron diffraction * double-crystal * monochromator Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.437, year: 2016

  8. Vibrating crystals as possible neutron monochromators

    International Nuclear Information System (INIS)

    Stoica, A.D.; Popovici, M.

    1983-09-01

    The Bragg reflection of neutrons of vibratinq perfect crystals is considered. The additional possibilities offered by the Doppler effect for shaping neutron beams in the k-space are discussed. A simple model for computing the vibrating crystal reflectivity is proposed. (author)

  9. A compact double crystal monochromator for electrochemistry beamline at PLS

    CERN Document Server

    Rah, S; Kim, G H

    2001-01-01

    A compact double crystal monochromator based on 16.5'' CF flange has been designed, fabricated and installed for electrochemistry beamline at Pohang light source. The Bragg angle range of the monochromator is 7-75 deg. The mechanical design is modified from typical Boomerang design [J.A. Golovchenko et al., Rev. Sci. Instrum. 52 (1981) 509; J.P. Kirkland, Nucl. Instr. and Meth. A291 (1990) 185] to have fixed beam offset and single driving axis for spectroscopy experiments. The parallelism error of the crystals is minimized to less than 6 mu rad for the range, by using a precision single axis linear guide, Also, the number of mechanical parts in the vacuum is minimized and 1.8x10 sup - sup 9 Torr of vacuum is achieved without baking.

  10. Design and performance of the ALS double-crystal monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G.; Ryce, S.; Perera, R.C.C. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    A new {open_quotes}Cowan type{close_quotes} double-crystal monochromator, based on the boomerang design used at NSLS beamline X-24A, has been developed for beamline 9.3.1 at the ALS, a windowless UHV beamline covering the 1-6 keV photon-energy range. Beamline 9.3.1 is designed to simultaneously achieve the goals of high energy resolution, high flux, and high brightness at the sample. The mechanical design has been simplified, and recent developments in technology have been included. Measured mechanical precision of the monochromator shows significant improvement over existing designs. In tests with x-rays at NSLS beamline X-23 A2, maximum deviations in the intensity of monochromatic light were just 7% during scans of several hundred eV in the vicinity of the Cr K edge (6 keV) with the monochromator operating without intensity feedback. Such precision is essential because of the high brightness of the ALS radiation and the overall length of beamline 9.3.1 (26 m).

  11. Design and performance of the ALS double-crystal monochromator

    International Nuclear Information System (INIS)

    Jones, G.; Ryce, S.; Perera, R.C.C.

    1997-01-01

    A new open-quotes Cowan typeclose quotes double-crystal monochromator, based on the boomerang design used at NSLS beamline X-24A, has been developed for beamline 9.3.1 at the ALS, a windowless UHV beamline covering the 1-6 keV photon-energy range. Beamline 9.3.1 is designed to simultaneously achieve the goals of high energy resolution, high flux, and high brightness at the sample. The mechanical design has been simplified, and recent developments in technology have been included. Measured mechanical precision of the monochromator shows significant improvement over existing designs. In tests with x-rays at NSLS beamline X-23 A2, maximum deviations in the intensity of monochromatic light were just 7% during scans of several hundred eV in the vicinity of the Cr K edge (6 keV) with the monochromator operating without intensity feedback. Such precision is essential because of the high brightness of the ALS radiation and the overall length of beamline 9.3.1 (26 m)

  12. Development of Bent Perfect Crystal Monochromator (II): Experiments for the evaluation of BPC for a monochromator of neutron diffractometers

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong Nam; Kim, Shin Ae; Lee, Chang Hee [KAERI, Taejon (Korea, Republic of); Kim, Sung Kyu [Pusan National Univ., Pusan (Korea, Republic of); Kim, Seong Baek [Kookmin Univ., Seoul (Korea, Republic of); Mikula, P. [NPI, Prague (Czech Republic)

    2004-11-01

    Various experimental properties of BPC monochromator at the FCD mode of the ST1 test station have been investigated. To test and verify the performance of the Si-BPC monochromator for the substitutional monochromator, diffraction measurements using copper single crystal and polycrystalline copper rod at various diffraction geometries were carried out. Considering the situation of FCD instrument which is used for both single crystal and texture measurement, a special cut silicon BPC slab which contains (331), (311) and (220) diffraction planes would be a best candidate. Diffraction measurements at the monochromatic focusing is the first experimental demonstration of the theoretical properties and give us a suggestion that the simultaneous measurement at both parallel and anti-parallel diffraction positions could be achievable with a reasonal resolution property as well as the intensity gain.

  13. Measurement & Minimization of Mount Induced Strain on Double Crystal Monochromator Crystals

    Science.gov (United States)

    Kelly, J.; Alcock, S. G.

    2013-03-01

    Opto-mechanical mounts can cause significant distortions to monochromator crystals and mirrors if not designed or implemented carefully. A slope measuring profiler, the Diamond-NOM [1], was used to measure the change in tangential slope as a function of crystal clamping configuration and load. A three point mount was found to exhibit the lowest surface distortion (Diamond Light Source.

  14. Performance of a beam-multiplexing diamond crystal monochromator at the Linac Coherent Light Source

    DEFF Research Database (Denmark)

    Zhu, Diling; Feng, Yiping; Stoupin, Stanislav

    2014-01-01

    A double-crystal diamond monochromator was recently implemented at the Linac Coherent Light Source. It enables splitting pulses generated by the free electron laser in the hard x-ray regime and thus allows the simultaneous operations of two instruments. Both monochromator crystals are High-Pressu...

  15. Microcontroller-based servo for two-crystal X-ray monochromators.

    Science.gov (United States)

    Siddons, D P

    1998-05-01

    Microcontrollers have become increasingly easy to incorporate into instruments as the architectures and support tools have developed. The PIC series is particularly easy to use, and this paper describes a controller used to stabilize the output of a two-crystal X-ray monochromator at a given offset from its peak intensity position, as such monochromators are generally used.

  16. Performance of a beam-multiplexing diamond crystal monochromator at the Linac Coherent Light Source

    International Nuclear Information System (INIS)

    Zhu, Diling; Feng, Yiping; Lemke, Henrik T.; Fritz, David M.; Chollet, Matthieu; Glownia, J. M.; Alonso-Mori, Roberto; Sikorski, Marcin; Song, Sanghoon; Williams, Garth J.; Messerschmidt, Marc; Boutet, Sébastien; Robert, Aymeric; Stoupin, Stanislav; Shvyd'ko, Yuri V.; Terentyev, Sergey A.; Blank, Vladimir D.; Driel, Tim B. van

    2014-01-01

    A double-crystal diamond monochromator was recently implemented at the Linac Coherent Light Source. It enables splitting pulses generated by the free electron laser in the hard x-ray regime and thus allows the simultaneous operations of two instruments. Both monochromator crystals are High-Pressure High-Temperature grown type-IIa diamond crystal plates with the (111) orientation. The first crystal has a thickness of ∼100 μm to allow high reflectivity within the Bragg bandwidth and good transmission for the other wavelengths for downstream use. The second crystal is about 300 μm thick and makes the exit beam of the monochromator parallel to the incoming beam with an offset of 600 mm. Here we present details on the monochromator design and its performance

  17. Test results of a diamond double-crystal monochromator at the advanced photon source

    International Nuclear Information System (INIS)

    Fernandez, P.B.; Graber, T.; Krasnicki, S.; Lee, W.; Mills, D.M.; Rogers, C.S.; Assoufid, L.

    1997-01-01

    We have tested the first diamond double-crystal monochromator at the Advanced Photon Source (APS). The monochromator consisted of two synthetic type 1b (111) diamond plates in symmetric Bragg geometry. We tested two pairs of single-crystal plates: the first pair was 6 mm by 5 mm by 0.25 mm and 6 mm by 5 mm by 0.37 mm; the second set was 7 mm by 5.5 mm by 0.44 mm. The monochromator first crystal was indirectly cooled by edge contact with a water-cooled copper holder. We studied the performance of the monochromator under the high-power x-ray beam delivered by the APS undulator A. We found no indication of thermal distortions or strains even at the highest incident power (280 watts) and power density (123W/mm 2 at normal incidence). The calculated maximum power and power density absorbed by the first crystal were 37 watts and 4.3W/mm 2 , respectively. We also compared the maximum intensity delivered by the diamond monochromator and by a silicon (111) cryogenically cooled monochromator. For energies in the range of 6 to 10 keV, the flux through the diamond monochromator was about a factor of two less than through the silicon monochromator, in good agreement with calculations. We conclude that water-cooled diamond monochromators can handle the high-power beams from the undulator beamlines at the APS. As single-crystal diamond plates of larger size and better quality become available, the use of diamond monochromators will become a very attractive option. copyright 1997 American Institute of Physics

  18. Diffractive-refractive optics: (+,-,-,+) X-ray crystal monochromator with harmonics separation

    Czech Academy of Sciences Publication Activity Database

    Hrdý, Jaromír; Mikulík, P.; Oberta, Peter

    2011-01-01

    Roč. 18, č. 2 (2011), s. 299-301 ISSN 0909-0495 R&D Projects: GA MPO FR-TI1/412 Institutional research plan: CEZ:AV0Z10100522 Keywords : diffractive-refractive optics * x-ray synchrotron radiation monochromator * x-ray crystal monochromator * harmonics separation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.726, year: 2011

  19. Monochromator for synchrotron light with temperature controlled by electrical current on silicon crystal

    Energy Technology Data Exchange (ETDEWEB)

    Cusatis, Cesar; Souza, Paulo E.N. [Universidade Federal do Parana (LORXI/UFPR), Curitiba, PR (Brazil). Dept. de Fisica. Lab. de Optica de Raios X e Instrumentacao; Franco, Margareth Kobayaski; Kakuno, Edson [Laboratorio Nacional de Luz Sincroton (LNLS), Campinas, SP (Brazil); Gobbi, Angelo; Carvalho Junior, Wilson de [Centro de Pesquisa e Desenvolvimento em Telecomunicacoes (CPqD), Campinas, SP (Brazil)

    2011-07-01

    Full text. doped silicon crystal was used simultaneously as a monochromator, sensor and actuator in such way that its temperature could be controlled. Ohmic contacts allowed resistance measurements on a perfect silicon crystal, which were correlated to its temperature. Using the ohmic contacts, an electrical current caused Joule heating on the monochromator that was used to control its temperature. A simple stand-alone electronic box controlled the system. The device was built and tested with white beam synchrotron light on the double crystal monochromator of the XRD line of LNLS, Laboratorio Nacional de Luz Sincrotron, Campinas. The first crystal of a double crystal monochromator determines the energy that is delivered to a synchrotron experimental station and its temperature instability is a major source of energy and intensity instability. If the (333) silicon monochromator is at theta Bragg near 45 degree the variation of the diffraction angle is around one second of arc per degree Kelvin. It may take several minutes for the first crystal temperature to stabilize at the beginning of the station operation when the crystal and its environment are cold. With water refrigeration, the average overall temperature of the crystal may be constant, but the temperature of the surface changes with and without the white beam. The time used to wait for stabilization of the beam energy/intensity is lost unless the temperature of the crystal surface is kept constant. One solution for keeping the temperature of the monochromator and its environment constant or nearly constant is Joule heating it with a controlled small electrical current flowing on the surface of a doped perfect crystal. When the white beam is on, this small amount of extra power will be more concentrated at the beam footpath because the resistance is lower in this region due to the higher temperature. In addition, if the crystal itself is used to detect the temperature variation by measuring the electrical

  20. Active phase double crystal monochromator for JET (diagnostic system KS1)

    International Nuclear Information System (INIS)

    Andelfinger, C.; Fink, J.; Fussmann, G.; Krause, H.; Roehr, H.; Schilling, H.B.; Schumacher, U.; Becker, P.; Siegert, H.; Abel, P.; Keul, J.

    1984-03-01

    The determination of the impurity concentrations in JET plasmas by absolute radiation measurements in a wide spectral range can be done with a double crystal monochromator device in parallel mode, which is able to operate during all experimental phases of JET. The report describes the engineering design and tests for a double crystal monochromator that fulfills the conditions of parallel orientation of the two crystals during fast wavelength scan, of shielding against neutrons and gamma rays by its folded optical pathway and of sufficient spectral resolution for line profile measurements. (orig.)

  1. Design of a cryo-cooled artificial channel-cut crystal monochromator for the European XFEL

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xiaohao, E-mail: xiaohao.dong@xfel.eu; Sinn, Harald, E-mail: harald.sinn@xfel.eu [European XFEL GmbH, Hamburg, D-22761 (Germany); Shu, Deming, E-mail: shu@aps.anl.gov [Argonne National Laboratory, Argonne, IL 60439, U.S.A (United States)

    2016-07-27

    An artificial channel-cut crystal monochromator for the hard X-Ray beamlines of SASE 1&2, cryogenically cooled by the so-called pulse tube cooler (cryorefrigerator), is currently under development at the European XFEL ( http://www.xfel.eu/ ). The fabrication is on-going. We present here the crystal optical consideration and the novel cooling configuration, according to the X-Ray FEL pulses proprieties. The mechanical design improvements are pointed out as well to implement such kind of monochromator based on the previous similar design.

  2. Thermal bump removal of a crystal monochromator by designing an optimal shape

    Energy Technology Data Exchange (ETDEWEB)

    Micha, Jean-Sébastien, E-mail: micha@esrf.fr [CRG-IF BM32 Beamline, ESRF, 6 rue J. Horowitz, BP 220, 38043 Grenoble (France); UMR SPrAM 5819, CEA-Grenoble/INAC/SPrAM, 17 avenue des Martyrs, 38054 Grenoble Cedex 9 (France); Geaymond, Olivier [CRG-IF BM32 Beamline, ESRF, 6 rue J. Horowitz, BP 220, 38043 Grenoble (France); Institut Néel, CNRS, 25 avenue des Martyrs, 38054 Grenoble Cedex 9 (France); Rieutord, Francois [CRG-IF BM32 Beamline, ESRF, 6 rue J. Horowitz, BP 220, 38043 Grenoble (France); CEA-Grenoble/INAC/NRS, 17 avenue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2013-05-11

    Thermal bump arising at illuminated area of a water cooled monochromator crystal can be considerably reduced by designing an appropriate shape. Temperature and deformation have been simulated by finite element analysis (FEA) computations as a function of few geometrical parameters describing the shape of the crystal. As a result, a new crystal shape has been found which optimizes the throughput of a double crystals monochromator (DCM). Performances of the initial rectangular crystal and the new designed crystal predicted by FEA-based calculations and measured during experimental tests on a synchrotron beamline are reported. General design principles to overcome heat load issues and the objective function using the slope errors derived from FEA results are detailed. Current and foreseen performances at higher load are presented. Finally, advantages and limits of this simple-to-design and cheap solution are discussed.

  3. A fine adjustment mechanism of the second crystal in a double-crystal monochromator with a 3-PS parallel manipulator

    International Nuclear Information System (INIS)

    Cao Chongzhen; Gao, X.; Ma, P.; Yu, H.; Wang, F.; Huang, Y.; Liu, P.

    2005-01-01

    A novel fine adjustment mechanism of the second crystal in a double-crystal monochromator is put forward, which is based on a 3-PS parallel manipulator and the magnetic force. Not only is the principle of fine adjusting the pitch angle and the roll angle analyzed, but also optimization of the structure parameters of the permanent magnet, a key part of the fine adjustment mechanism. The fine adjustment mechanism with the 3-PS parallel manipulator has been applied successfully in the double-crystal monochromator of 4W1B beam line in the Beijing Synchrotron Radiation Facility (BSRF)

  4. Diamond double-crystal monochromator in Bragg geometry installed on BL-11XU at SPring-8

    CERN Document Server

    Marushita, M; Fukuda, T; Takahasi, M; Inami, T; Katayama, Y; Shiwaku, H; Mizuki, J

    2001-01-01

    We present here the feature of the diamond double-crystal monochromator in Bragg geometry installed on a standard undulator beamline at SPring-8. The crystal was manufactured by Sumitomo Electric Industries, Ltd., whose size was 8.6 mm (w) x3.5 mm (l) x0.35 mm (t) for the first crystal and 10 mm (w) x4.7 mm (l) x0.39 mm (t) for the second. The feature of the monochromator was tested by rocking curve measurements as a function of the total power and of the energy that impinged on the crystal. As a result, no significant increase of the full-width at half-maximum was observed up to a total power of 330 W on the first crystal. We discuss the experimental results with the comparison to the calculated FWHM with use of the beamline parameters.

  5. Calculation of thermal deformations in water-cooled monochromator crystals

    International Nuclear Information System (INIS)

    Nakamura, Ario; Hashimoto, Shinya; Motohashi, Haruhiko

    1994-11-01

    Through calculation of temperature distribution and thermal deformation of monochromators, optical degradation by the heat loads in SPring-8 have been discussed. Cooling experiments were made on three models of copper structures with the JAERI Electron Beam Irradiation Stand (JEBIS) and the results were used to estimate heat transfer coefficients in the models. The heat transfer coefficients have been adopted to simulate heating processes on silicon models of the same structures as the copper models, for which radiations from the SPring-8 bending magnet and the JAERI prototype undulator (WPH-33J) were considered. It has been concluded that, in the case of bending magnet (with power density of 0.27[MW/m 2 ] on monochromator surface), the temperature at the surface center reaches about 30[degC] from the initial temperature of 27[degC] in all the models. In the case of WPH-33J (with power density of 8.2[MW/m 2 ]), the temperature reaches about 200 to 280[degC] depending on the models. The radiation from WPH-33J yields slope errors bigger than the Darwin's width(23[μrad]). (author)

  6. Double crystal monochromator controlled by integrated computing on BL07A in New SUBARU, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Okui, Masato, E-mail: okui@kohzu.co.jp [Kohzu Precision Co., Ltd., 2-6-15, Kurigi, Asao-ku, Kawasaki-shi, Kanagawa 215-8521 (Japan); Laboratory of Advanced Science and Technology for Industry, University of Hyogo (Japan); Yato, Naoki; Watanabe, Akinobu; Lin, Baiming; Murayama, Norio [Kohzu Precision Co., Ltd., 2-6-15, Kurigi, Asao-ku, Kawasaki-shi, Kanagawa 215-8521 (Japan); Fukushima, Sei, E-mail: FUKUSHIMA.Sei@nims.go.jp [Laboratory of Advanced Science and Technology for Industry, University of Hyogo (Japan); National Institute for Material Sciences (Japan); Kanda, Kazuhiro [Laboratory of Advanced Science and Technology for Industry, University of Hyogo (Japan)

    2016-07-27

    The BL07A beamline in New SUBARU, University of Hyogo, has been used for many studies of new materials. A new double crystal monochromator controlled by integrated computing was designed and installed in the beamline in 2014. In this report we will discuss the unique features of this new monochromator, MKZ-7NS. This monochromator was not designed exclusively for use in BL07A; on the contrary, it was designed to be installed at low cost in various beamlines to facilitate the industrial applications of medium-scale synchrotron radiation facilities. Thus, the design of the monochromator utilized common packages that can satisfy the wide variety of specifications required at different synchrotron radiation facilities. This monochromator can be easily optimized for any beamline due to the fact that a few control parameters can be suitably customized. The beam offset can be fixed precisely even if one of the two slave axes is omitted. This design reduces the convolution of mechanical errors. Moreover, the monochromator’s control mechanism is very compact, making it possible to reduce the size of the vacuum chamber can be made smaller.

  7. Design of an adaptive cooled first crystal for an X-ray monochromator

    International Nuclear Information System (INIS)

    Dezoret, D.; Marmoret, R.; Freund, A.K.; Kvick, AA.; Ravelet, R.

    1994-01-01

    We report here on the design of the first crystal in an x-ray monochromator for E.S.R.F. beam lines. This crystal is a thin silicon foil bonded to a cooled beryllium support. A system of piezoelectric actuators is used to counterbalance the deformations induced by synchrotron beams. This work was carried out by the C.E.A. in collaboration with the E.S.R.F. and the LASERDOT Company (Aerospatiale Group). (orig.)

  8. Test of a high-heat-load double-crystal diamond monochromator at the advanced photon source

    International Nuclear Information System (INIS)

    Fernandez, P.B.; Graber, T.; Lee, W.-K.; Mills, D.M.; Rogers, C.S.; Assoufid, L.

    1997-01-01

    We have tested the first diamond double-crystal monochromator at the advanced photon source (APS). The monochromator consisted of two synthetic type 1b (111) diamond plates in symmetric Bragg geometry. The single-crystal plates were 6 mm x 5 mm x 0.25 mm and 6 mm x 5 mm x 0.37 mm and showed a combination of mosaic spread/strain of the order of 2-4 arcsec over a central 1.4 mm-wide strip. The monochromator first crystal was indirectly cooled by edge contact with a water-cooled copper holder. We studied the performance of the monochromator under the high-power X-ray beam delivered by the APS undulator A. By changing the undulator gap, we varied the power incident on the first crystal and found no indication of thermal distortions or strains even at the highest incident power (200 W) and power density (108 W/mm 2 in normal incidence). The calculated maximum power and power density absorbed by the first crystal were 14.5 W and 2.4 W/mm 2 , respectively. We also compared the maximum intensity delivered by this monochromator and by a silicon (111) cryogenically cooled monochromator. For energies in the range 6-10 keV, the flux through the diamond monochromator was about a factor of two less than through the silicon monochromator, in good agreement with calculations. We conclude that water-cooled diamond monochromators can handle the high-power beams from the undulator beamlines at the APS. As single-crystal diamond plates of larger size and better quality become available, the use of diamond monochromators will become a very attractive option. (orig.)

  9. Radiation-shielded double crystal X-ray monochromator for JET

    International Nuclear Information System (INIS)

    Barnsley, R.; Morsi, H.W.; Rupprecht, G.; Kaellne, E.

    1989-01-01

    A double crystal X-ray monochromator for absolute wavelength and intensity measurements with very effective shielding of its detector against neutrons and hard X-rays was brought into operation at JET. Fast wavelength scans were taken of impurity line radiation in the wavelength region from about 0.1 nm to 2.3 nm, and monochromatic as well as spectral line scans, for different operational modes of JET. (author) 5 refs., 4 figs

  10. Diffractive-refractive optics: (+,-,-,+) X-ray crystal monochromator with harmonics separation.

    Science.gov (United States)

    Hrdý, Jaromír; Mikulík, Petr; Oberta, Peter

    2011-03-01

    A new kind of two channel-cut crystals X-ray monochromator in dispersive (+,-,-,+) position which spatially separates harmonics is proposed. The diffracting surfaces are oriented so that the diffraction is inclined. Owing to refraction the diffracted beam is sagittally deviated. The deviation depends on wavelength and is much higher for the first harmonics than for higher harmonics. This leads to spatial harmonics separation. The idea is supported by ray-tracing simulation.

  11. Selection method and characterization of neutron monochromator natural crystals

    International Nuclear Information System (INIS)

    Stasiulevicius, R.; Kastner, G.F.

    2000-01-01

    Thermal neutrons are important analytical tools for microscopic material probe. These neutrons can be selected by diffraction technique using monocrystal, usually artificial. A crystal selection process was implemented and the characteristics of natural specimens were studied by activation analysis-k 0 method. The representative 120 samples, of which 21 best types, were irradiated in IPR-R1 and measured with a neutron diffractometer at IEA-R1m Brazilian reactors. These results are useful for database build up and ease the choice of appropriate natural crystal, with some advantage options: highest intensity diffracted, enlarging the energy operational interval and optimal performance in special applications. (author)

  12. Strain-free polished channel-cut crystal monochromators: a new approach and results

    Science.gov (United States)

    Kasman, Elina; Montgomery, Jonathan; Huang, XianRong; Lerch, Jason; Assoufid, Lahsen

    2017-08-01

    The use of channel-cut crystal monochromators has been traditionally limited to applications that can tolerate the rough surface quality from wet etching without polishing. We have previously presented and discussed the motivation for producing channel cut crystals with strain-free polished surfaces [1]. Afterwards, we have undertaken an effort to design and implement an automated machine for polishing channel-cut crystals. The initial effort led to inefficient results. Since then, we conceptualized, designed, and implemented a new version of the channel-cut polishing machine, now called C-CHiRP (Channel-Cut High Resolution Polisher), also known as CCPM V2.0. The new machine design no longer utilizes Figure-8 motion that mimics manual polishing. Instead, the polishing is achieved by a combination of rotary and linear functions of two coordinated motion systems. Here we present the new design of C-CHiRP, its capabilities and features. Multiple channel-cut crystals polished using the C-CHiRP have been deployed into several beamlines at the Advanced Photon Source (APS). We present the measurements of surface finish, flatness, as well as topography results obtained at 1-BM of APS, as compared with results typically achieved when polishing flat-surface monochromator crystals using conventional polishing processes. Limitations of the current machine design, capabilities and considerations for strain-free polishing of highly complex crystals are also discussed, together with an outlook for future developments and improvements.

  13. Hard x-ray monochromator with milli-electron volt bandwidth for high-resolution diffraction studies of diamond crystals

    Energy Technology Data Exchange (ETDEWEB)

    Stoupin, Stanislav; Shvyd' ko, Yuri; Shu Deming; Khachatryan, Ruben; Xiao, Xianghui; DeCarlo, Francesco; Goetze, Kurt; Roberts, Timothy; Roehrig, Christian; Deriy, Alexey [Advanced Photon Source, Argonne National Laboratory, Illinois 60439 (United States)

    2012-02-15

    We report on design and performance of a high-resolution x-ray monochromator with a spectral bandwidth of {Delta}E{sub X}{approx_equal} 1.5 meV, which operates at x-ray energies in the vicinity of the backscattering (Bragg) energy E{sub H} = 13.903 keV of the (008) reflection in diamond. The monochromator is utilized for high-energy-resolution diffraction characterization of diamond crystals as elements of advanced x-ray crystal optics for synchrotrons and x-ray free-electron lasers. The monochromator and the related controls are made portable such that they can be installed and operated at any appropriate synchrotron beamline equipped with a pre-monochromator.

  14. Accuracy synthesis of T-shaped exit fixed mechanism in a double-crystal monochromator

    International Nuclear Information System (INIS)

    Wang Fengqin; Cao Chongzhen; Wang Jidai; Li Yushan; Gao Xueguan

    2007-01-01

    It is a key performance requirement for a double-crystal monochromator that the exit is fixed, and in order to improve the height accuracy of the exit in T-shaped exit fixed mechanism, the expression between the height of the exit and various original errors was put forward using geometrical analysis method. According to the independent action principle of original errors, accuracy synthesis of T-shaped exit fixed mechanism was studied by using the equal accuracy method, and the tolerance ranges of original errors were obtained. How to calculate the tolerance ranges of original errors was explained by giving an example. (authors)

  15. Rotation of X-ray polarization in the glitches of a silicon crystal monochromator.

    Science.gov (United States)

    Sutter, John P; Boada, Roberto; Bowron, Daniel T; Stepanov, Sergey A; Díaz-Moreno, Sofía

    2016-08-01

    EXAFS studies on dilute samples are usually carried out by collecting the fluorescence yield using a large-area multi-element detector. This method is susceptible to the 'glitches' produced by all single-crystal monochromators. Glitches are sharp dips or spikes in the diffracted intensity at specific crystal orientations. If incorrectly compensated, they degrade the spectroscopic data. Normalization of the fluorescence signal by the incident flux alone is sometimes insufficient to compensate for the glitches. Measurements performed at the state-of-the-art wiggler beamline I20-scanning at Diamond Light Source have shown that the glitches alter the spatial distribution of the sample's quasi-elastic X-ray scattering. Because glitches result from additional Bragg reflections, multiple-beam dynamical diffraction theory is necessary to understand their effects. Here, the glitches of the Si(111) four-bounce monochromator of I20-scanning just above the Ni  K edge are associated with their Bragg reflections. A fitting procedure that treats coherent and Compton scattering is developed and applied to a sample of an extremely dilute (100 micromolal) aqueous solution of Ni(NO 3 ) 2 . The depolarization of the wiggler X-ray beam out of the electron orbit is modeled. The fits achieve good agreement with the sample's quasi-elastic scattering with just a few parameters. The X-ray polarization is rotated up to ±4.3° within the glitches, as predicted by dynamical diffraction. These results will help users normalize EXAFS data at glitches.

  16. Rotation of X-ray polarization in the glitches of a silicon crystal monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Sutter, John P.; Boada, Roberto; Bowron, Daniel T.; Stepanov, Sergey A.; Díaz-Moreno, Sofía

    2016-07-06

    EXAFS studies on dilute samples are usually carried out by collecting the fluorescence yield using a large-area multi-element detector. This method is susceptible to the `glitches' produced by all single-crystal monochromators. Glitches are sharp dips or spikes in the diffracted intensity at specific crystal orientations. If incorrectly compensated, they degrade the spectroscopic data. Normalization of the fluorescence signal by the incident flux alone is sometimes insufficient to compensate for the glitches. Measurements performed at the state-of-the-art wiggler beamline I20-scanning at Diamond Light Source have shown that the glitches alter the spatial distribution of the sample's quasi-elastic X-ray scattering. Because glitches result from additional Bragg reflections, multiple-beam dynamical diffraction theory is necessary to understand their effects. Here, the glitches of the Si(111) four-bounce monochromator of I20-scanning just above the Ni Kedge are associated with their Bragg reflections. A fitting procedure that treats coherent and Compton scattering is developed and applied to a sample of an extremely dilute (100 micromolal) aqueous solution of Ni(NO3)2. The depolarization of the wiggler X-ray beam out of the electron orbit is modeled. The fits achieve good agreement with the sample's quasi-elastic scattering with just a few parameters. The X-ray polarization is rotated up to ±4.3° within the glitches, as predicted by dynamical diffraction. These results will help users normalize EXAFS data at glitches.

  17. Neutron monochromators of BeO, MgO and ZnO single crystals

    Science.gov (United States)

    Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.; Mansy, M. S.

    2014-05-01

    The monochromatic features of BeO, MgO and ZnO single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.05 up to 0.5 nm. A computer program MONO, written in “FORTRAN”, has been developed to carry out the required calculations. Calculation shows that a 5 mm thick MgO single crystal cut along its (2 0 0) plane having mosaic spread of 0.5° FWHM has the optimum parameters when it is used as a neutron monochromator. Moreover, at wavelengths shorter than 0.24 nm the reflected monochromatic neutrons are almost free from the higher order ones. The same features are seen with BeO (0 0 2) with less reflectivity than that of the former. Also, ZnO cut along its (0 0 2) plane is preferred over the others only at wavelengths longer than 0.20 nm. When the selected monochromatic wavelength is longer than 0.24 nm, the neutron intensities of higher orders from a thermal reactor flux are higher than those of the first-order one. For a cold reactor flux, the first order of BeO and MgO single crystals is free from the higher orders up to 0.4 nm, and ZnO at wavelengths up to 0.5 nm.

  18. Beryllium, zinc and lead single crystals as a thermal neutron monochromators

    Science.gov (United States)

    Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.; Mansy, M. S.

    2015-03-01

    The monochromatic features of Be, Zn and Pb single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.04 up to 0.5 nm. A computer program MONO written in "FORTRAN-77", has been adapted to carry out the required calculations. Calculations show that a 5 mm thick of beryllium (HCP structure) single crystal cut along its (0 0 2) plane having 0.6° FWHM are the optimum parameters when it is used as a monochromator with high reflected neutron intensity from a thermal neutron flux. Furthermore, at wavelengths shorter than 0.16 nm it is free from the accompanying higher order ones. Zinc (HCP structure) has the same parameters, with intensity much less than the latter. The same features are seen with lead (FCC structure) cut along its (3 1 1) plane with less reflectivity than the former. However, Pb (3 1 1) is more preferable than others at neutron wavelengths ⩽ 0.1 nm, since the glancing angle (θ ∼ 20°) is more suitable to carry out diffraction experiments. For a cold neutron flux, the first-order neutrons reflected from beryllium is free from the higher orders up to 0.36 nm. While for Zn single crystal is up to 0.5 nm.

  19. Neutron transmission through pyrolytic graphite crystals

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M. [Reactor Physics Department NRC, Reactor Physics Division, Nuclear Research Center, Egyptian Atomic Energy Authority, Cairo 13759 (Egypt); Habib, N. [Reactor Physics Department NRC, Reactor Physics Division, Nuclear Research Center, Egyptian Atomic Energy Authority, Cairo 13759 (Egypt)]. E-mail: nadiahabib15@yahoo.com; Fathaalla, M. [Reactor Physics Department NRC, Reactor Physics Division, Nuclear Research Center, Egyptian Atomic Energy Authority, Cairo 13759 (Egypt)

    2006-05-15

    Calculation of the total cross-section, neutron transmission and removal coefficient of pyrolytic graphite (PG) for thermal neutron energies were carried out using an additive formula. The formula takes into account the variation of thermal diffuse and Bragg scattering cross-sections in terms of PG temperature and mosaic spread for neutron energies in the range 1 meV to 1 eV. A computer code PG has been developed which allow calculations for the graphite in its hexagonal close-packed structure, when its c-direction is parallel with incident neutron beam (parallel orientation). The calculated total neutron cross-sections for PG in parallel orientation at different mosaic spreads were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data at room and liquid nitrogen temperatures. A feasibility study for use of PG crystals as second-order neutron filter is detailed in terms of mosaic spread, optimum thickness and temperature. The calculated removal coefficients of PG crystals show that such crystals are high efficiency second-order filter within neutron energy intervals (4-7 meV) and (10-15 meV)

  20. Neutron monochromators of BeO, MgO and ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M.; Habib, N. [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Bashter, I.I. [Physics Department, Faculty of Science, Zagazig University (Egypt); Morcos, H.N.; El-Mesiry, M.S. [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Mansy, M.S., E-mail: mohamedmansy_np@yahoo.com [Physics Department, Faculty of Science, Zagazig University (Egypt)

    2014-05-21

    The monochromatic features of BeO, MgO and ZnO single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.05 up to 0.5 nm. A computer program MONO, written in “FORTRAN”, has been developed to carry out the required calculations. Calculation shows that a 5 mm thick MgO single crystal cut along its (2 0 0) plane having mosaic spread of 0.5° FWHM has the optimum parameters when it is used as a neutron monochromator. Moreover, at wavelengths shorter than 0.24 nm the reflected monochromatic neutrons are almost free from the higher order ones. The same features are seen with BeO (0 0 2) with less reflectivity than that of the former. Also, ZnO cut along its (0 0 2) plane is preferred over the others only at wavelengths longer than 0.20 nm. When the selected monochromatic wavelength is longer than 0.24 nm, the neutron intensities of higher orders from a thermal reactor flux are higher than those of the first-order one. For a cold reactor flux, the first order of BeO and MgO single crystals is free from the higher orders up to 0.4 nm, and ZnO at wavelengths up to 0.5 nm. - Highlights: • Monochromatic features of BeO, MgO and ZnO single crystals. • Calculations of neutron reflectivity using a computer program MONO. • Optimum mosaic spread, thickness and cutting plane of single crystals.

  1. Beryllium, zinc and lead single crystals as a thermal neutron monochromators

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M.; Habib, N. [Reactor Physics Department, NRC, Atomic Energy Authority, Cairo (Egypt); Bashter, I.I. [Physics Department, Faculty of Science, Zagazig University (Egypt); Morcos, H.N.; El-Mesiry, M.S. [Reactor Physics Department, NRC, Atomic Energy Authority, Cairo (Egypt); Mansy, M.S., E-mail: drmohamedmansy88@hotmail.com [Physics Department, Faculty of Science, Zagazig University (Egypt)

    2015-03-15

    Highlights: •Monochromatic features of Be, Zn and Pb single crystals. •Calculations of neutron reflectivity using a computer program MONO. •Optimum mosaic spread, thickness and cutting plane of single crystals. -- Abstract: The monochromatic features of Be, Zn and Pb single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.04 up to 0.5 nm. A computer program MONO written in “FORTRAN-77”, has been adapted to carry out the required calculations. Calculations show that a 5 mm thick of beryllium (HCP structure) single crystal cut along its (0 0 2) plane having 0.6° FWHM are the optimum parameters when it is used as a monochromator with high reflected neutron intensity from a thermal neutron flux. Furthermore, at wavelengths shorter than 0.16 nm it is free from the accompanying higher order ones. Zinc (HCP structure) has the same parameters, with intensity much less than the latter. The same features are seen with lead (FCC structure) cut along its (3 1 1) plane with less reflectivity than the former. However, Pb (3 1 1) is more preferable than others at neutron wavelengths ⩽ 0.1 nm, since the glancing angle (θ ∼ 20°) is more suitable to carry out diffraction experiments. For a cold neutron flux, the first-order neutrons reflected from beryllium is free from the higher orders up to 0.36 nm. While for Zn single crystal is up to 0.5 nm.

  2. Neutron transmission through pyrolytic graphite crystal II

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M., E-mail: mamdouhshihata@yahoo.com [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Habib, N. [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Bashter, I.; Saleh, A. [Faculty of Science, Zagazig University (Egypt)

    2011-04-15

    The measured neutron transmissions through 6.7 mm thick pyroletic graphite (PG) crystal set at different take-off-angles with respect to the beam, as a function of wavelength, were compared with the calculated values using a general formula. An adapted version of the computer package graphite was developed in order to provide the required calculations in the neutron energy range from 0.1 MeV to 10 eV. An overall agreement was obtained between the formula fits and the measured data at different take-off-angles. The major dips in transmission caused by various reflections were identified. From the shape of the dips due to 0 0 l reflections, the mosaic spread of the used PG crystal has been determined within an accuracy of 0.12{sup o}. A feasibility study is carried out on using two PG crystals to select from the reactor spectrum a neutron monochromatic beam with wavelengths longer than 0.3 nm and almost free from accompanying higher-order reflections. Calculation shows that 2 mm thick highly oriented PG (0.5{sup o} FWHM on mosaic spread) crystal set at glancing angle 20.0{sup o} reflects first-order monochromatic neutrons with 0.3 nm wavelengths. When 6.0 cm thick PG crystal (2{sup o} FWHM on mosaic spread) set at 60.63{sup o} take-off-angle is inserted on the way of the reflected neutrons, it transmits more than 70% of the first-order neutrons while attenuating the high- order ones by more than 20 times. Similar results were obtained when the selected monochromatic neutrons had wavelengths longer than 0.3 nm.

  3. Design, Build & Test of a Double Crystal Monochromator for Beamlines I09 & I23 at the Diamond Light Source

    Science.gov (United States)

    Kelly, J.; Lee, T.; Alcock, S.; Patel, H.

    2013-03-01

    A high stability Double Crystal Monochromator has been developed at The Diamond Light Source for beamlines I09 and I23. The design specification was a cryogenic, fixed exit, energy scanning monochromator, operating over an energy range of 2.1 - 25 keV using a Si(111) crystal set. The novel design concepts are the direct drive, air bearing Bragg axis, low strain crystal mounts and the cooling scheme. The instrument exhibited superb stability and repeatability on the B16 Test Beamline. A 20 keV Si(555), 1.4 μrad rocking curve was demonstrated. The DCM showed good stability without any evidence of vibration or Bragg angle nonlinearity.

  4. Crystallization degree change of expanded graphite by milling and annealing

    International Nuclear Information System (INIS)

    Tang Qunwei; Wu Jihuai; Sun Hui; Fang Shijun

    2009-01-01

    Expanded graphite was ball milled with a planetary mill in air atmosphere, and subsequently thermal annealed. The samples were characterized by using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was found that in the milling initial stage (less than 12 h), the crystallization degree of the expanded graphite declined gradually, but after milling more than 16 h, a recrystallization of the expanded graphite toke place, and ordered nanoscale expanded graphite was formed gradually. In the annealing initial stage, the non-crystallization of the graphite occurred, but, beyond an annealing time, recrystallizations of the graphite arise. Higher annealing temperature supported the recrystallization. The milled and annealed expanded graphite still preserved the crystalline structure as raw material and hold high thermal stability.

  5. Graphite crystals grown within electromagnetically levitated metallic droplets

    International Nuclear Information System (INIS)

    Amini, Shaahin; Kalaantari, Haamun; Mojgani, Sasan; Abbaschian, Reza

    2012-01-01

    Various graphite morphologies were observed to grow within the electromagnetically levitated nickel–carbon melts, including primary flakes and spheres, curved surface graphite and eutectic flakes, as well as engulfed and entrapped particles. As the supersaturated metallic solutions were cooled within the electromagnetic (EM) levitation coil, the primary graphite flakes and spheres formed and accumulated near the periphery of the droplet due to EM circulation. The primary graphite islands, moreover, nucleated and grew on the droplet surface which eventually formed a macroscopic curved graphite crystal covering the entire liquid. Upon further cooling, the liquid surrounding the primary graphite went under a coupled eutectic reaction while the liquid in the center formed a divorced eutectic due to EM mixing. This brought about the formation of graphite fine flakes and agglomerated particles close to the surface and in the center of the droplet, respectively. The graphite morphologies, growth mechanisms, defects, irregularities and growth instabilities were interpreted with detailed optical and scanning electron microscopies.

  6. High heat load performance of an inclined crystal monochromator with liquid gallium cooling on the CHESS-ANL undulator

    International Nuclear Information System (INIS)

    Macrander, A.T.; Lee, W.K.; Smither, R.K.; Mills, D.M.

    1992-01-01

    Recent results for the performance of a novel double crystal monochromator subjected to high heat loads on an APS prototype undulator at the Cornell High Energy Synchrotron Source (CHESS) are presented. The monochromator was designed to achieve symmetric diffraction from asymmetric planes to spread out the beam footprint thereby lowering the incident power density. Both crystals had (111) oriented surfaces and were arranged such that the beam was diffracted from the (11 bar 1) planes at 5 KeV. Rocking curves with minimal distortion were obtained at a ring electron current of 100 mA. This corresponded to 380 Watts total power and an average power density of 40 Watts/mm 2 normal to the incident beam. These results are compared to data obtained from the same crystals in the standard geometry (diffracting planes parallel to surface). The footprint area in the inclined case was three times that of the standard case. We also obtained rocking curve data for the (333) reflection at 15 KeV for both standard and inclined cases, and these data also showed a minimal distortion only for the inclined case. In addition, thermal data were obtained via infrared pyrometry. Liquid gallium flow rates of up to 2 gallons per minute were investigated. The diffraction data revealed a dramatically improved performance for the inclined crystal case

  7. Liquid-metal-cooled, curved-crystal monochromator for Advanced Photon Source bending-magnet beamline 1-BM

    International Nuclear Information System (INIS)

    Brauer, S.; Rodricks, B.; Assoufid, L.; Beno, M.A.; Knapp, G.S.

    1996-06-01

    The authors describe a horizontally focusing curved-crystal monochromator that invokes a 4-point bending scheme and a liquid-metal cooling bath. The device has been designed for dispersive diffraction and spectroscopy in the 5--20 keV range, with a predicted focal spot size of ≤ 100 microm. To minimize thermal distortions and thermal equilibration time, the 355 x 32 x 0.8 mm crystal will be nearly half submerged in a bath of Ga-In-Sn-Zn alloy. The liquid metal thermally couples the crystal to the water-cooled Cu frame, while permitting the required crystal bending. Calculated thermal profiles and anticipated focusing properties are discussed

  8. Development of a bent Laue beam-expanding double-crystal monochromator for biomedical X-ray imaging

    International Nuclear Information System (INIS)

    Martinson, Mercedes; Samadi, Nazanin; Belev, George; Bassey, Bassey; Lewis, Rob; Aulakh, Gurpreet; Chapman, Dean

    2014-01-01

    A bent Laue beam-expanding double-crystal monochromator was developed and tested at the Biomedical Imaging and Therapy beamline at the Canadian Light Source. The expander will reduce scanning time for micro-computed tomography and allow dynamic imaging that has not previously been possible at this beamline. The Biomedical Imaging and Therapy (BMIT) beamline at the Canadian Light Source has produced some excellent biological imaging data. However, the disadvantage of a small vertical beam limits its usability in some applications. Micro-computed tomography (micro-CT) imaging requires multiple scans to produce a full projection, and certain dynamic imaging experiments are not possible. A larger vertical beam is desirable. It was cost-prohibitive to build a longer beamline that would have produced a large vertical beam. Instead, it was proposed to develop a beam expander that would create a beam appearing to originate at a source much farther away. This was accomplished using a bent Laue double-crystal monochromator in a non-dispersive divergent geometry. The design and implementation of this beam expander is presented along with results from the micro-CT and dynamic imaging tests conducted with this beam. Flux (photons per unit area per unit time) has been measured and found to be comparable with the existing flat Bragg double-crystal monochromator in use at BMIT. This increase in overall photon count is due to the enhanced bandwidth of the bent Laue configuration. Whilst the expanded beam quality is suitable for dynamic imaging and micro-CT, further work is required to improve its phase and coherence properties

  9. Graphite

    Science.gov (United States)

    Robinson, Gilpin R.; Hammarstrom, Jane M.; Olson, Donald W.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Graphite is a form of pure carbon that normally occurs as black crystal flakes and masses. It has important properties, such as chemical inertness, thermal stability, high electrical conductivity, and lubricity (slipperiness) that make it suitable for many industrial applications, including electronics, lubricants, metallurgy, and steelmaking. For some of these uses, no suitable substitutes are available. Steelmaking and refractory applications in metallurgy use the largest amount of produced graphite; however, emerging technology uses in large-scale fuel cell, battery, and lightweight high-strength composite applications could substantially increase world demand for graphite.Graphite ores are classified as “amorphous” (microcrystalline), and “crystalline” (“flake” or “lump or chip”) based on the ore’s crystallinity, grain-size, and morphology. All graphite deposits mined today formed from metamorphism of carbonaceous sedimentary rocks, and the ore type is determined by the geologic setting. Thermally metamorphosed coal is the usual source of amorphous graphite. Disseminated crystalline flake graphite is mined from carbonaceous metamorphic rocks, and lump or chip graphite is mined from veins in high-grade metamorphic regions. Because graphite is chemically inert and nontoxic, the main environmental concerns associated with graphite mining are inhalation of fine-grained dusts, including silicate and sulfide mineral particles, and hydrocarbon vapors produced during the mining and processing of ore. Synthetic graphite is manufactured from hydrocarbon sources using high-temperature heat treatment, and it is more expensive to produce than natural graphite.Production of natural graphite is dominated by China, India, and Brazil, which export graphite worldwide. China provides approximately 67 percent of worldwide output of natural graphite, and, as the dominant exporter, has the ability to set world prices. China has significant graphite reserves, and

  10. Optimization of bent perfect Si(220)-crystal monochromator for residual strain/stress instrument - Part II

    Czech Academy of Sciences Publication Activity Database

    Moon, MK.; Em, Vt.; Lee, C.H.; Mikula, Pavol; Hong, KP; Choi, YH; Cheon, JK; Nam, UW; Kong, KN; Jin, KC

    2005-01-01

    Roč. 368, 1 2 3 4 (2005), s. 70-75 ISSN 0921-4526 R&D Projects: GA ČR(CZ) GA202/03/0891 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutron monochromator * residual stress measurement * neutron diffractometers Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.796, year: 2005

  11. Suppression of surface effect by using bent-perfect-crystal monochromator in residual strain scanning

    Czech Academy of Sciences Publication Activity Database

    Vrána, Miroslav; Mikula, Pavol

    490/491, - (2005), s. 234-238 ISSN 0255-5476 R&D Projects: GA ČR GA202/03/0891; GA AV ČR KSK1010104 Institutional research plan: CEZ:AV0Z1048901 Keywords : neutron diffraction * residual strain scanning * bent monochromator Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.399, year: 2005

  12. Dislocation density and graphitization of diamond crystals

    International Nuclear Information System (INIS)

    Pantea, C.; Voronin, G.A.; Zerda, T.W.; Gubicza, J.; Ungar, T.

    2002-01-01

    Two sets of diamond specimens compressed at 2 GPa at temperatures varying between 1060 K and 1760 K were prepared; one in which graphitization was promoted by the presence of water and another in which graphitization of diamond was practically absent. X-ray diffraction peak profiles of both sets were analyzed for the microstructure by using the modified Williamson-Hall method and by fitting the Fourier coefficients of the measured profiles by theoretical functions for crystallite size and lattice strain. The procedures determined mean size and size distribution of crystallites as well as the density and the character of the dislocations. The same experimental conditions resulted in different microstructures for the two sets of samples. They were explained in terms of hydrostatic conditions present in the graphitized samples

  13. Neutron transmission measurements of poly and pyrolytic graphite crystals

    Science.gov (United States)

    Adib, M.; Abbas, Y.; Abdel-Kawy, A.; Ashry, A.; Kilany, M.; Kenawy, M. A.

    The total neutron cross-section measurements of polycrystalline graphite have been carried out in a neutron wavelength from 0.04 to 0.78 nm. This work also presents the neutron transmission measurements of pyrolytic graphite (PG) crystal in a neutron wavelength band from 0.03 to 0.50 nm, at different orientations of the PG crystal with regard to the beam direction. The measurements were performed using three time-of-flight (TOF) spectrometers installed in front of three of the ET-RR-1 reactor horizontal channels. The average value of the coherent scattering amplitude for polycrystalline graphite was calculated and found to be bcoh = (6.61 ± 0.07) fm. The behaviour of neutron transmission through the PG crystal, while oriented at different angles with regard to the beam direction, shows dips at neutron wavelengths corresponding to the reflections from (hkl) planes of hexagonal graphite structure. The positions of the observed dips are found to be in good agreement with the calculated ones. It was also found that a 40 mm thick PG crystal is quite enough to reduce the second-order contamination of the neutron beam from 2.81 to 0.04, assuming that the incident neutrons have a Maxwell distribution with neutron gas temperature 330 K.

  14. Neutron transmission measurements of poly and pyrolytic graphite crystals

    International Nuclear Information System (INIS)

    Adib, M.; Abdel-Kawy, A.; Kilany, M.

    1989-01-01

    The total neutron cross-section measurements of polycrystalline graphite have been carried out in a neutron wavelength from 0.04 to 0.78 nm. This work also presents the neutron transmission measurements of pyrolytic graphite (PG) crystal in a neutron wavelength band from 0.03 to 0.50 nm, at different orientations of the PG crystal with regard to the beam direction. The measurements were performed using three time-of-flight (TOF) spectrometers installed in front of three of the ET-RR-1 reactor horizontal channels. The average value of the coherent scattering amplitude for polycrystalline graphite was calculated and found to be b coh = (6.61 ± 0.07) fm. The behaviour of neutron transmission through the PG crystal, while orientated at different angles with regard to the beam direction, shows dips at neutron wavelengths corresponding to the reflections from (hk1) planes of hexagonal graphite structure. The positions of the observed dips are found to be in good agreement with the calculated ones. It was also found that a 40 mm thick PG crystal is quite enough to reduce the second-order contamination of the neutron beam from 2.81 to 0.04, assuming that the incident neutrons have a Maxwell distribution with neutron gas temperature 330 K. (author)

  15. Multi-layer monochromator

    International Nuclear Information System (INIS)

    Schoenborn, B.P.; Caspar, D.L.D.

    1975-01-01

    This invention provides an artificial monochromator crystal for efficiently selecting a narrow band of neutron wavelengths from a neutron beam having a Maxwellian wavelength distribution, by providing on a substrate a plurality of germanium layers, and alternate periodic layers of a different metal having tailored thicknesses, shapes, and volumetric and neutron scattering densities. (U.S.)

  16. Design, Build and Test of a Double Crystal Monochromator for Beamlines I09 and I23 at the Diamond Light Source

    International Nuclear Information System (INIS)

    Kelly, J; Lee, T; Alcock, S; Patel, H

    2013-01-01

    A high stability Double Crystal Monochromator has been developed at The Diamond Light Source for beamlines I09 and I23. The design specification was a cryogenic, fixed exit, energy scanning monochromator, operating over an energy range of 2.1 – 25 keV using a Si(111) crystal set. The novel design concepts are the direct drive, air bearing Bragg axis, low strain crystal mounts and the cooling scheme. The instrument exhibited superb stability and repeatability on the B16 Test Beamline. A 20 keV Si(555), 1.4 μrad rocking curve was demonstrated. The DCM showed good stability without any evidence of vibration or Bragg angle nonlinearity.

  17. Optimization of flat and horizontally curved neutron monochromators for given diffractometer geometries

    International Nuclear Information System (INIS)

    Graf, H.A.

    1983-08-01

    The computer program MONREF was written for calculating the integrated intensity and the k-vector distribution produced by mosaic-crystal monochromators in neutron diffractometers of given geometries. The program treats flat and horizontally curved monochromators in Bragg reflection. Its basic algorithm is derived from Zachariasen's coupled differential equations which were modified to include the case of asymmetrically cut crystals. The calculations are restricted to the scattering in the experimental plane. In the first part of the report the program and its applications are described. In the second part a compilation of intensities is presented, calculated for crystals of Cu, Si, Ge and pyrolytic graphite commonly used as monochromators, in a standard diffractometer configuration. (orig.)

  18. Study of the long-wave neutron monochromator on the base of an artificial mica crystal

    International Nuclear Information System (INIS)

    Zelenyuk, F.M.; Stepanov, S.B.

    1976-01-01

    The reflectivity, integrated reflectivity and mosaic width of a mica monocristal have been investigated for reflectivity of cold neutrons (lama + 8/14 A) by a double crystal spectrometer. The experimental data are compared with the calculated ones obtained with the use of Bacon and Lowde' model

  19. Mirror monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, Marian [Electron Optica, Inc., Palo Alto, CA (United States); Shadman, Khashayar [Electron Optica, Inc., Palo Alto, CA (United States)

    2014-12-02

    In this SBIR project, Electron Optica, Inc. (EOI) is developing a mirror electron monochromator (MirrorChrom) attachment to new and retrofitted electron microscopes (EMs) for improving the energy resolution of the EM from the characteristic range of 0.2-0.5 eV to the range of 10-50 meV. This improvement will enhance the characterization of materials by imaging and spectroscopy. In particular, the monochromator will refine the energy spectra characterizing materials, as obtained from transmission EMs [TEMs] fitted with electron spectrometers, and it will increase the spatial resolution of the images of materials taken with scanning EMs (SEMs) operated at low voltages. EOI’s MirrorChrom technology utilizes a magnetic prism to simultaneously deflect the electron beam off the axis of the microscope column by 90° and disperse the electrons in proportional to their energies into a module with an electron mirror and a knife-edge. The knife-edge cuts off the tails of the energy distribution to reduce the energy spread of the electrons that are reflected, and subsequently deflected, back into the microscope column. The knife-edge is less prone to contamination, and thereby charging, than the conventional slits used in existing monochromators, which improves the reliability and stability of the module. The overall design of the MirrorChrom exploits the symmetry inherent in reversing the electron trajectory in order to maintain the beam brightness – a parameter that impacts how well the electron beam can be focused downstream onto a sample. During phase I, EOI drafted a set of candidate monochromator architectures and evaluated the trade-offs between energy resolution and beam current to achieve the optimum design for three particular applications with market potential: increasing the spatial resolution of low voltage SEMs, increasing the energy resolution of low voltage TEMs (beam energy of 5-20 keV), and increasing the energy resolution of conventional TEMs (beam

  20. A high-energy double-crystal fixed exit monochromator for the X17 superconducting wiggler beam line at the NSLS

    International Nuclear Information System (INIS)

    Garrett, R.F.; Dilmanian, F.A.; Oversluizen, T.; Lenhard, A.; Berman, L.E.; Chapman, L.D.; Stoeber, W.

    1992-01-01

    A high-energy double-crystal x-ray monochromator has been constructed for use on the X-17 beam line at the National Synchrotron Light Source (NSLS). Its design is based on the ''boomerang'' right angle linkage, and features a fixed exit beam, a cooled first crystal, and an energy range of 8--92 keV. The entire mechanism is UHV compatible. The design is described and performance details, obtained in testing at the X17 beam line, are presented

  1. Selection, rejection and optimisation of pyrolytic graphite (PG) crystal analysers for use on the new IRIS graphite analyser bank

    International Nuclear Information System (INIS)

    Marshall, P.J.; Sivia, D.S.; Adams, M.A.; Telling, M.T.F.

    2000-01-01

    This report discusses design problems incurred by equipping the IRIS high-resolution inelastic spectrometer at the ISIS pulsed neutron source, UK with a new 4212 piece pyrolytic graphite crystal analyser array. Of the 4212 graphite pieces required, approximately 2500 will be newly purchased PG crystals with the remainder comprising of the currently installed graphite analysers. The quality of the new analyser pieces, with respect to manufacturing specifications, is assessed, as is the optimum arrangement of new PG pieces amongst old to circumvent degradation of the spectrometer's current angular resolution. Techniques employed to achieve these criteria include accurate calliper measurements, FORTRAN programming and statistical analysis. (author)

  2. A possibility of parallel and anti-parallel diffraction measurements on neu- tron diffractometer employing bent perfect crystal monochromator at the monochromatic focusing condition

    Science.gov (United States)

    Choi, Yong Nam; Kim, Shin Ae; Kim, Sung Kyu; Kim, Sung Baek; Lee, Chang-Hee; Mikula, Pavel

    2004-07-01

    In a conventional diffractometer having single monochromator, only one position, parallel position, is used for the diffraction experiment (i.e. detection) because the resolution property of the other one, anti-parallel position, is very poor. However, a bent perfect crystal (BPC) monochromator at monochromatic focusing condition can provide a quite flat and equal resolution property at both parallel and anti-parallel positions and thus one can have a chance to use both sides for the diffraction experiment. From the data of the FWHM and the Delta d/d measured on three diffraction geometries (symmetric, asymmetric compression and asymmetric expansion), we can conclude that the simultaneous diffraction measurement in both parallel and anti-parallel positions can be achieved.

  3. Recent developments of high quality synthetic diamond single crystals for synchrotron X-ray monochromators

    CERN Document Server

    Freund, A K; Sellschop, J P Friedel; Burns, R C; Rebak, M

    2001-01-01

    For several years now, the ESRF, the University of the Witwatersrand and Messrs. De Beers Industrial Diamonds (Pty) Ltd. through their Diamond Research Laboratory, have pursued a development programme to assess and improve the quality of synthetic diamonds. Recently, in an effort to study the influence of nitrogen impurities on the defect structure, X-ray excited optical luminescence and spatially resolved double-crystal diffractometry were employed as new techniques. The correlation between nitrogen impurities and the raw defect structure was clearly visible. It was confirmed that concentration variations are related to lattice imperfections, where tilts are much more important than lattice constant variations. High reflectivity was observed and quite large zones of a sample bigger than 1 cm sup 2 showed to be perfect to within better than 0.5 arcsec.

  4. Topological Characterization of Carbon Graphite and Crystal Cubic Carbon Structures.

    Science.gov (United States)

    Siddiqui, Wei Gao Muhammad Kamran; Naeem, Muhammad; Rehman, Najma Abdul

    2017-09-07

    Graph theory is used for modeling, designing, analysis and understanding chemical structures or chemical networks and their properties. The molecular graph is a graph consisting of atoms called vertices and the chemical bond between atoms called edges. In this article, we study the chemical graphs of carbon graphite and crystal structure of cubic carbon. Moreover, we compute and give closed formulas of degree based additive topological indices, namely hyper-Zagreb index, first multiple and second multiple Zagreb indices, and first and second Zagreb polynomials.

  5. APS high heat load monochromator

    International Nuclear Information System (INIS)

    Lee, W.K.; Mills, D.

    1993-02-01

    This document contains the design specifications of the APS high heat load (HHL) monochromator and associated accessories as of February 1993. It should be noted that work is continuing on many parts of the monochromator including the mechanical design, crystal cooling designs, etc. Where appropriate, we have tried to add supporting documentation, references to published papers, and calculations from which we based our decisions. The underlying philosophy behind performance specifications of this monochromator was to fabricate a device that would be useful to as many APS users as possible, that is, the design should be as generic as possible. In other words, we believe that this design will be capable of operating on both bending magnet and ID beamlines (with the appropriate changes to the cooling and crystals) with both flat and inclined crystal geometries and with a variety of coolants. It was strongly felt that this monochromator should have good energy scanning capabilities over the classical energy range of about 4 to 20 keywith Si (111) crystals. For this reason, a design incorporating one rotation stage to drive both the first and second crystals was considered most promising. Separate rotary stages for the first and second crystals can sometimes provide more flexibility in their capacities to carry heavy loads (for heavily cooled first crystals or sagittal benders of second crystals), but their tuning capabilities were considered inferior to the single axis approach

  6. A compact low cost “master–slave” double crystal monochromator for x-ray cameras calibration of the Laser MégaJoule Facility

    Energy Technology Data Exchange (ETDEWEB)

    Hubert, S., E-mail: sebastien.hubert@cea.fr; Prévot, V.

    2014-12-21

    The Alternative Energies and Atomic Energy Commission (CEA-CESTA, France) built a specific double crystal monochromator (DCM) to perform calibration of x-ray cameras (CCD, streak and gated cameras) by means of a multiple anode diode type x-ray source for the MégaJoule Laser Facility. This DCM, based on pantograph geometry, was specifically modeled to respond to relevant engineering constraints and requirements. The major benefits are mechanical drive of the second crystal on the first one, through a single drive motor, as well as compactness of the entire device. Designed for flat beryl or Ge crystals, this DCM covers the 0.9–10 keV range of our High Energy X-ray Source. In this paper we present the mechanical design of the DCM, its features quantitatively measured and its calibration to finally provide monochromatized spectra displaying spectral purities better than 98%.

  7. Low-energy electron observation of graphite and molybdenite crystals. Application to the study of graphite oxidation

    International Nuclear Information System (INIS)

    David, G.

    1969-01-01

    The LEED study of cleaved (0001) faces of crystals having a layered structure allowed to investigate flakes free of steps on graphite and molybdenite, to show twinning on natural graphite. By intensity measurements and computation in the case of a kinematical approximation it has been possible to determine an inner potential of 19 eV for graphite and to identify the direction of the Mo-S bond of the surface layer of molybdenite. The oxidation of graphite has been studied by observing changes, in symmetry of the diffraction patterns and by mass spectrometry of the gases evolved during the oxidation. No surface compounds have been detected and the carbon layers appeared to be peeled off one after the other. The oxidation took place at temperatures higher than 520 C under an oxygen pressure of 10 -5 torr. (author) [fr

  8. Single-crystal apatite nanowires sheathed in graphitic shells: synthesis, characterization, and application.

    Science.gov (United States)

    Jeong, Namjo; Cha, Misun; Park, Yun Chang; Lee, Kyung Mee; Lee, Jae Hyup; Park, Byong Chon; Lee, Junghoon

    2013-07-23

    Vertically aligned one-dimensional hybrid structures, which are composed of apatite and graphitic structures, can be beneficial for orthopedic applications. However, they are difficult to generate using the current method. Here, we report the first synthesis of a single-crystal apatite nanowire encapsulated in graphitic shells by a one-step chemical vapor deposition. Incipient nucleation of apatite and its subsequent transformation to an oriented crystal are directed by derived gaseous phosphorine. Longitudinal growth of the oriented apatite crystal is achieved by a vapor-solid growth mechanism, whereas lateral growth is suppressed by the graphitic layers formed through arrangement of the derived aromatic hydrocarbon molecules. We show that this unusual combination of the apatite crystal and the graphitic shells can lead to an excellent osteogenic differentiation and bony fusion through a programmed smart behavior. For instance, the graphitic shells are degraded after the initial cell growth promoted by the graphitic nanostructures, and the cells continue proliferation on the bare apatite nanowires. Furthermore, a bending experiment indicates that such core-shell nanowires exhibited a superior bending stiffness compared to single-crystal apatite nanowires without graphitic shells. The results suggest a new strategy and direction for bone grafting materials with a highly controllable morphology and material conditions that can best stimulate bone cell differentiation and growth.

  9. Variable angle asymmetric cut monochromator

    International Nuclear Information System (INIS)

    Smither, R.K.; Fernandez, P.B.

    1993-09-01

    A variable incident angle, asymmetric cut, double crystal monochromator was tested for use on beamlines at the Advanced Photon Source (APS). For both undulator and wiggler beams the monochromator can expand area of footprint of beam on surface of the crystals to 50 times the area of incident beam; this will reduce the slope errors by a factor of 2500. The asymmetric cut allows one to increase the acceptance angle for incident radiation and obtain a better match to the opening angle of the incident beam. This can increase intensity of the diffracted beam by a factor of 2 to 5 and can make the beam more monochromatic, as well. The monochromator consists of two matched, asymmetric cut (18 degrees), silicon crystals mounted so that they can be rotated about three independent axes. Rotation around the first axis controls the Bragg angle. The second rotation axis is perpendicular to the diffraction planes and controls the increase of the area of the footprint of the beam on the crystal surface. Rotation around the third axis controls the angle between the surface of the crystal and the wider, horizontal axis for the beam and can make the footprint a rectangle with a minimum. length for this area. The asymmetric cut is 18 degrees for the matched pair of crystals, which allows one to expand the footprint area by a factor of 50 for Bragg angles up to 19.15 degrees (6 keV for Si[111] planes). This monochromator, with proper cooling, will be useful for analyzing the high intensity x-ray beams produced by both undulators and wigglers at the APS

  10. A new transmission based monochromator for energy-selective neutron imaging at the ICON beamline

    International Nuclear Information System (INIS)

    Peetermans, S.; Tamaki, M.; Hartmann, S.; Kaestner, A.; Morgano, M.; Lehmann, E.H.

    2014-01-01

    A new type of monochromator has been developed for energy-selective neutron imaging at continuous sources. It combines the use of a mechanical neutron velocity selector with pyrolytic graphite crystals of different mosaicity. The beam can be monochromatized to similar levels as a standard double crystal monochromator. It can flexibly produce different desired spectral shapes, even an asymmetric one. Intrinsically, no higher order contamination of the spectrum is present. Working with the transmitted beam, the beam divergence (and thus the spatial resolution) is uncompromised. The device has been calibrated, characterized and its performance demonstrated with the measurement of Bragg edges for iron and lead, resolving them more sharply than if solely a mechanical velocity selector was used

  11. Design of mirror and monochromator crystals for a high-resolution multiwavelength anomalous diffraction beam line on a bending magnet at the ESRF

    International Nuclear Information System (INIS)

    Roth, M.; Ferrer, J.; Simon, J.; Geissler, E.

    1992-01-01

    High intensity for diffraction experiments with high-energy resolution on an intense x-ray beam, like the bending magnet beam lines at the ESRF, requires a strict control of the curvature of the optical elements placed in the beam for geometrical focusing and for wavelength monochromatization. Unwanted curvatures can come from nonuniform and variable heating of the optical elements produced by the absorption of x rays. To design the CRG/D2AM beam line described in the accompanying paper, some new techniques were developed to control these effects based on geometrical, i.e., topological, considerations. (1) Cooling of the entrance mirror: longitudinal curvature can be strongly reduced by cooling the mirror from the sides (and not from the rear) and only near the reflecting surface (i.e., not over the whole lateral surface). The cooling can be achieved for instance with an isothermal liquid Ga eutectic bath. (2) Cooling of the first single-crystal Si monochromator: because of the size of the crystal, only cooling from the rear is conceivable in this case. It can be shown by calculation that the curvature due to the front-to-rear gradient can be exactly compensated by the thermal expansion of a metallic layer at the rear of the crystal, having a larger expansion coefficient than Si

  12. On the Crystallization of Compacted and Chunky Graphite from Liquid Multicomponent Iron-Carbon-Silicon-Based Melts

    Science.gov (United States)

    Stefanescu, D. M.; Huff, R.; Alonso, G.; Larrañaga, P.; De la Fuente, E.; Suarez, R.

    2016-08-01

    Extensive SEM work was carried out on deep-etched specimens to reveal the evolution of compacted and chunky graphite in magnesium-modified multicomponent Fe-C-Si alloys during early solidification and at room temperature. The findings of this research were then integrated in the current body of knowledge to produce an understanding of the crystallization of compacted and chunky graphite. It was confirmed that growth from the liquid for both compacted and chunky graphite occurs radially from a nucleus, as foliated crystals and dendrites. The basic building blocks of the graphite aggregates are hexagonal faceted graphite platelets with nanometer height and micrometer width. Thickening of the platelets occurs through growth of additional graphene layers nucleated at the ledges of the graphite prism. Additional thickening resulting in complete joining of the platelets may occur from the recrystallization of the amorphous carbon that has diffused from the liquid through the austenite, once the graphite aggregate is enveloped in austenite. With increasing magnesium levels, the foliated graphite platelets progressively aggregate along the c-axis forming clusters. The clusters that have random orientation, eventually produce blocky graphite, as the spaces between the parallel platelets disappear. This is typical for compacted graphite irons and tadpole graphite. The chunky graphite aggregates investigated are conical sectors of graphite platelets stacked along the c-axis. The foliated dendrites that originally develop radially from a common nucleus may aggregate along the c-axis forming blocky graphite that sometimes exhibits helical growth. The large number of defects (cavities) observed in all graphite aggregates supports the mechanism of graphite growth as foliated crystals and dendrites.

  13. DGR, GGR; molecular dynamical codes for simulating radiation damages in diamond and graphite crystals

    International Nuclear Information System (INIS)

    Taji, Yukichi

    1984-06-01

    Development has been made of molecular dynamical codes DGR and GGR to simulate radiation damages yielded in the diamond and graphite structure crystals, respectively. Though the usual molecular dynamical codes deal only with the central forces as the mutual interactions between atoms, the present codes can take account of noncentral forces to represent the effect of the covalent bonds characteristic of diamond or graphite crystals. It is shown that lattice defects yielded in these crystals are stable by themselves in the present method without any supports of virtual surface forces set on the crystallite surfaces. By this effect the behavior of lattice defects has become possible to be simulated in a more realistic manner. Some examples of the simulation with these codes are shown. (author)

  14. Improvement of graphite crystal analyzer for light elements on X-ray fluorescence holography measurement

    Science.gov (United States)

    Happo, Naohisa; Hada, Takuma; Kubota, Atsushi; Ebisu, Yoshihiro; Hosokawa, Shinya; Kimura, Koji; Tajiri, Hiroo; Matsushita, Tomohiro; Hayashi, Kouichi

    2018-05-01

    Using a graphite crystal analyzer, focused monochromatic fluorescent X-rays can be obtained on an X-ray fluorescence holography (XFH) measurement. To measure the holograms of elements lighter than Ti, we improved a cylindrical-type crystal analyzer and constructed a small C-shaped analyzer. Using the constructed C-shaped analyzer, a Ca Kα hologram of a fluorite single crystal was obtained, from which we reconstructed a clear atomic image. The XFH measurements for the K, Ca, and Sc elements become possible using the presently constructed analyzer.

  15. [A new method for evaluating the degree of eyestrain: a comparison between color and monochrome liquid crystal display monitors].

    Science.gov (United States)

    Okumura, Akiyoshi; Koike, Rumi; Onoda, Yui; Matsui, Takurou; Arai, Kazuo; Shimooka, Ryouji; Tsurutani, Hiroshi

    2011-01-01

    Color and monochromatic liquid crystal displays (LCDs) were compared in terms of eyestrain by using a new method that uses Landolt rings for a visual perceptional test. In this method, the difference of the nearest distances to distinguish Landolt rings between before and after the usage of LCD monitors was used as the index of eyestrain. When the nearest distance for distinguishing Landolt rings increased, the eyestrain was considered to be severe. A total of 11 observers (2 physicians and 9 radiological technologists) participated to this observer study. In the observer study, the TG18-QC pattern, a standard clinical image of 400 images, and JESRA X-0093 were observed using color and monochromatic LCD monitors for approximately 30 minutes. In addition to the observer study, the noise power spectrum (NPS) of the color and the monochromatic monitors were measured using the NS2002 method. The ratio of the nearest distance after 30 minutes of reading and that of before reading was larger when the color LCD monitor was used than when the monochromatic LCD monitor was used (pLandolt rings measured before and after readings can be used to evaluate eyestrain in diagnostic radiology.

  16. Electron transfer kinetics on natural crystals of MoS2 and graphite.

    Science.gov (United States)

    Velický, Matěj; Bissett, Mark A; Toth, Peter S; Patten, Hollie V; Worrall, Stephen D; Rodgers, Andrew N J; Hill, Ernie W; Kinloch, Ian A; Novoselov, Konstantin S; Georgiou, Thanasis; Britnell, Liam; Dryfe, Robert A W

    2015-07-21

    Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)6(3-/4-), Ru(NH3)6(3+/2+) and IrCl6(2-/3-) are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications.

  17. Optimization of the bent perfect Si(311)-crystal monochromator for a residual strain/stress instrument at the HANARO reactor - Part I

    Czech Academy of Sciences Publication Activity Database

    Moon, MK; Lee, Ch.H.; Vyacheslav, T.; Mikula, Pavol

    2005-01-01

    Roč. 369, - (2005), s. 1-7 ISSN 0921-4526 R&D Projects: GA ČR GA202/03/0891 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutron monochromator * residual stress measurement * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.796, year: 2005

  18. Kelvin probe characterization of buried graphitic microchannels in single-crystal diamond

    International Nuclear Information System (INIS)

    Bernardi, E.; Battiato, A.; Olivero, P.; Vittone, E.; Picollo, F.

    2015-01-01

    In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of buried graphitic microchannels fabricated in single-crystal diamond by direct MeV ion microbeam writing. Metal deposition of variable-thickness masks was adopted to implant channels with emerging endpoints and high temperature annealing was performed in order to induce the graphitization of the highly-damaged buried region. When an electrical current was flowing through the biased buried channel, the structure was clearly evidenced by KPM maps of the electrical potential of the surface region overlying the channel at increasing distances from the grounded electrode. The KPM profiling shows regions of opposite contrast located at different distances from the endpoints of the channel. This effect is attributed to the different electrical conduction properties of the surface and of the buried graphitic layer. The model adopted to interpret these KPM maps and profiles proved to be suitable for the electronic characterization of buried conductive channels, providing a non-invasive method to measure the local resistivity with a micrometer resolution. The results demonstrate the potential of the technique as a powerful diagnostic tool to monitor the functionality of all-carbon graphite/diamond devices to be fabricated by MeV ion beam lithography

  19. Graphite edge controlled registration of monolayer MoS{sub 2} crystal orientation

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Chun-I; Butler, Christopher John; Yang, Hung-Hsiang; Chu, Yu-Hsun; Luo, Chi-Hung; Sun, Yung-Che; Hsu, Shih-Hao; Yang, Kui-Hong Ou [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Huang, Jing-Kai; Hsing, Cheng-Rong; Wei, Ching-Ming, E-mail: cmw@phys.sinica.edu.tw; Li, Lain-Jong, E-mail: lanceli@gate.sinica.edu.tw [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China); Lin, Minn-Tsong, E-mail: mtlin@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)

    2015-05-04

    Transition metal dichalcogenides such as the semiconductor MoS{sub 2} are a class of two-dimensional crystals. The surface morphology and quality of MoS{sub 2} grown by chemical vapor deposition are examined using atomic force and scanning tunneling microscopy techniques. By analyzing the moiré patterns from several triangular MoS{sub 2} islands, we find that there exist at least five different superstructures and that the relative rotational angles between the MoS{sub 2} adlayer and graphite substrate lattices are typically less than 3°. We conclude that since MoS{sub 2} grows at graphite step-edges, it is the edge structure which controls the orientation of the islands, with those growing from zig-zag (or armchair) edges tending to orient with one lattice vector parallel (perpendicular) to the step-edge.

  20. Enhanced and selective optical trapping in a slot-graphite photonic crystal.

    Science.gov (United States)

    Krishnan, Aravind; Huang, Ningfeng; Wu, Shao-Hua; Martínez, Luis Javier; Povinelli, Michelle L

    2016-10-03

    Applicability of optical trapping tools for nanomanipulation is limited by the available laser power and trap efficiency. We utilized the strong confinement of light in a slot-graphite photonic crystal to develop high-efficiency parallel trapping over a large area. The stiffness is 35 times higher than our previously demonstrated on-chip, near field traps. We demonstrate the ability to trap both dielectric and metallic particles of sub-micron size. We find that the growth kinetics of nanoparticle arrays on the slot-graphite template depends on particle size. This difference is exploited to selectively trap one type of particle out of a binary colloidal mixture, creating an efficient optical sieve. This technique has rich potential for analysis, diagnostics, and enrichment and sorting of microscopic entities.

  1. Surface structure modification of single crystal graphite after slow, highly charged ion irradiation

    Science.gov (United States)

    Alzaher, I.; Akcöltekin, S.; Ban-d'Etat, B.; Manil, B.; Dey, K. R.; Been, T.; Boduch, P.; Rothard, H.; Schleberger, M.; Lebius, H.

    2018-04-01

    Single crystal graphite was irradiated by slow, highly charged ions. The modification of the surface structure was studied by means of Low-Energy Electron Diffraction. The observed damage cross section increases with the potential energy, i.e. the charge state of the incident ion, at a constant kinetic energy. The potential energy is more efficient for the damage production than the kinetic energy by more than a factor of twenty. Comparison with earlier results hints to a strong link between early electron creation and later target atom rearrangement. With increasing ion fluence, the initially large-scale single crystal is first transformed into μ m-sized crystals, before complete amorphisation takes place.

  2. Characterization of a polychromatic neutron beam diffracted by pyrolytic graphite crystals

    CERN Document Server

    Byun, S H; Choi, H D

    2002-01-01

    The beam spectrum for polychromatic neutrons diffracted by pyrolytic graphite crystals was characterized. The theoretical beam spectrum was obtained using the diffraction model for a mosaic crystal. The lattice vibration effects were included in the calculation using the reported vibration amplitude of the crystal and the measured time-of-flight spectra in the thermal region. The calculated beam spectrum was compared with the results obtained in the absence of thermal motion. The lattice vibration effects became more important for the higher diffraction orders and a large decrease in the neutron flux induced by the vibrations was identified in the epithermal region. The validity of the beam spectrum was estimated by comparing with the effective quantities determined from prompt gamma-ray measurements and Cd-ratios measured both for 1/nu and non-1/nu nuclides.

  3. Asymmetric-cut variable-incident-angle monochromator.

    Science.gov (United States)

    Smither, R K; Graber, T J; Fernandez, P B; Mills, D M

    2012-03-01

    A novel asymmetric-cut variable-incident-angle monochromator was constructed and tested in 1997 at the Advanced Photon Source of Argonne National Laboratory. The monochromator was originally designed as a high heat load monochromator capable of handling 5-10 kW beams from a wiggler source. This was accomplished by spreading the x-ray beam out on the surface an asymmetric-cut crystal and by using liquid metal cooling of the first crystal. The monochromator turned out to be a highly versatile monochromator that could perform many different types of experiments. The monochromator consisted of two 18° asymmetrically cut Si crystals that could be rotated about 3 independent axes. The first stage (Φ) rotates the crystal around an axis perpendicular to the diffraction plane. This rotation changes the angle of the incident beam with the surface of the crystal without changing the Bragg angle. The second rotation (Ψ) is perpendicular to the first and is used to control the shape of the beam footprint on the crystal. The third rotation (Θ) controls the Bragg angle. Besides the high heat load application, the use of asymmetrically cut crystals allows one to increase or decrease the acceptance angle for crystal diffraction of a monochromatic x-ray beam and allows one to increase or decrease the wavelength bandwidth of the diffraction of a continuum source like a bending-magnet beam or a normal x-ray-tube source. When the monochromator is used in the doubly expanding mode, it is possible to expand the vertical size of the double-diffracted beam by a factor of 10-15. When this was combined with a bending magnet source, it was possible to generate an 8 keV area beam, 16 mm wide by 26 mm high with a uniform intensity and parallel to 1.2 arc sec that could be applied in imaging experiments.

  4. Extension of self-seeding scheme with single crystal monochromator to lower energy <5 keV as a way to generate multi-TW scale pulses at the European XFEL

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2012-07-15

    We propose a use of the self-seeding scheme with single crystal monochromator to produce high power, fully-coherent pulses for applications at a dedicated bio-imaging beamline at the European X-ray FEL in the photon energy range between 3.5 keV and 5 keV. We exploit the C(111) Bragg reflection ({pi}-polarization) in diamond crystals with a thickness of 0.1 mm, and we show that, by tapering the 40 cells of the SASE3 type undulator the FEL power can reach up to 2 TW in the entire photon energy range. The present design assumes the use of a nominal electron bunch with charge 0.1 nC at nominal electron beam energy 17.5 GeV. The main application of the scheme proposed in this work is for single shot imaging of individual protein molecules. (orig.)

  5. Extension of self-seeding scheme with single crystal monochromator to lower energy <5 keV as a way to generate multi-TW scale pulses at the European XFEL

    International Nuclear Information System (INIS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2012-07-01

    We propose a use of the self-seeding scheme with single crystal monochromator to produce high power, fully-coherent pulses for applications at a dedicated bio-imaging beamline at the European X-ray FEL in the photon energy range between 3.5 keV and 5 keV. We exploit the C(111) Bragg reflection (π-polarization) in diamond crystals with a thickness of 0.1 mm, and we show that, by tapering the 40 cells of the SASE3 type undulator the FEL power can reach up to 2 TW in the entire photon energy range. The present design assumes the use of a nominal electron bunch with charge 0.1 nC at nominal electron beam energy 17.5 GeV. The main application of the scheme proposed in this work is for single shot imaging of individual protein molecules. (orig.)

  6. MONO: A program to calculate synchrotron beamline monochromator throughputs

    International Nuclear Information System (INIS)

    Chapman, D.

    1989-01-01

    A set of Fortran programs have been developed to calculate the expected throughput of x-ray monochromators with a filtered synchrotron source and is applicable to bending magnet and wiggler beamlines. These programs calculate the normalized throughput and filtered synchrotron spectrum passed by multiple element, flat un- focussed monochromator crystals of the Bragg or Laue type as a function of incident beam divergence, energy and polarization. The reflected and transmitted beam of each crystal is calculated using the dynamical theory of diffraction. Multiple crystal arrangements in the dispersive and non-dispersive mode are allowed as well as crystal asymmetry and energy or angle offsets. Filters or windows of arbitrary elemental composition may be used to filter the incident synchrotron beam. This program should be useful to predict the intensities available from many beamline configurations as well as assist in the design of new monochromator and analyzer systems. 6 refs., 3 figs

  7. Minimization of spurious strains by using a Si bent-perfect-crystal monochromator: neutron surface strain scanning of a shot-peened sample

    Science.gov (United States)

    Rebelo Kornmeier, Joana; Gibmeier, Jens; Hofmann, Michael

    2011-06-01

    Neutron strain measurements are critical at the surface. When scanning close to a sample surface, aberration peak shifts arise due to geometrical and divergence effects. These aberration peak shifts can be of the same order as the peak shifts related to residual strains. In this study it will be demonstrated that by optimizing the horizontal bending radius of a Si (4 0 0) monochromator, the aberration peak shifts from surface effects can be strongly reduced. A stress-free sample of fine-grained construction steel, S690QL, was used to find the optimal instrumental conditions to minimize aberration peak shifts. The optimized Si (4 0 0) monochromator and instrument settings were then applied to measure the residual stress depth gradient of a shot-peened SAE 4140 steel sample to validate the effectiveness of the approach. The residual stress depth profile is in good agreement with results obtained by x-ray diffraction measurements from an international round robin test (BRITE-EURAM-project ENSPED). The results open very promising possibilities to bridge the gap between x-ray diffraction and conventional neutron diffraction for non-destructive residual stress analysis close to surfaces.

  8. Minimization of spurious strains by using a Si bent-perfect-crystal monochromator: neutron surface strain scanning of a shot-peened sample

    International Nuclear Information System (INIS)

    Rebelo Kornmeier, Joana; Hofmann, Michael; Gibmeier, Jens

    2011-01-01

    Neutron strain measurements are critical at the surface. When scanning close to a sample surface, aberration peak shifts arise due to geometrical and divergence effects. These aberration peak shifts can be of the same order as the peak shifts related to residual strains. In this study it will be demonstrated that by optimizing the horizontal bending radius of a Si (4 0 0) monochromator, the aberration peak shifts from surface effects can be strongly reduced. A stress-free sample of fine-grained construction steel, S690QL, was used to find the optimal instrumental conditions to minimize aberration peak shifts. The optimized Si (4 0 0) monochromator and instrument settings were then applied to measure the residual stress depth gradient of a shot-peened SAE 4140 steel sample to validate the effectiveness of the approach. The residual stress depth profile is in good agreement with results obtained by x-ray diffraction measurements from an international round robin test (BRITE-EURAM-project ENSPED). The results open very promising possibilities to bridge the gap between x-ray diffraction and conventional neutron diffraction for non-destructive residual stress analysis close to surfaces

  9. 75 FR 27602 - In the Matter of BVR Technologies Ltd. (n/k/a Technoprises Ltd.), Crystal Graphite Corp., Devine...

    Science.gov (United States)

    2010-05-17

    ... SECURITIES AND EXCHANGE COMMISSION [File No. 500-1] In the Matter of BVR Technologies Ltd. (n/k/a Technoprises Ltd.), Crystal Graphite Corp., Devine Entertainment Corp., GEE TEN Ventures, Inc., National Construction, Inc. (n/k/a E.G. Capital, Inc.), SHEP Technologies, Inc., and WHEREVER.Net Holding Corp.; Order...

  10. Gold clusters sliding on graphite: a possible quartz crystal microbalance experiment?

    International Nuclear Information System (INIS)

    Pisov, S; Tosatti, E; Tartaglino, U; Vanossi, A

    2007-01-01

    A large measured two-dimensional (2D) diffusion coefficient of gold nanoclusters on graphite has been known experimentally and theoretically for about a decade. When subjected to a lateral force, these clusters should slide with an amount of friction that can be measured. We examine the hypothetical possibility of measuring by quartz crystal microbalance (QCM) the phononic sliding friction of gold clusters in the size range around 250 atoms on a graphite substrate between 300 and 600 K. Assuming the validity of Einstein's relations of ordinary Brownian motion and making use of the experimentally available activated behaviour of the diffusion coefficients, we can predict the sliding friction and slip times as a function of temperature. It is found that a prototypical deposited gold cluster could yield slip times at the standard measurable size of 10 -9 s for temperatures around 450-500 K, or 200 0 C. Since gold nanoclusters may also melt at around these temperatures, QCM could offer the additional chance of observing this phenomenon through a frictional change

  11. Processing method for high resolution monochromator

    International Nuclear Information System (INIS)

    Kiriyama, Koji; Mitsui, Takaya

    2006-12-01

    A processing method for high resolution monochromator (HRM) has been developed at Japanese Atomic Energy Agency/Quantum Beam Science Directorate/Synchrotron Radiation Research unit at SPring-8. For manufacturing a HRM, a sophisticated slicing machine and X-ray diffractometer have been installed for shaping a crystal ingot and orienting precisely the surface of a crystal ingot, respectively. The specification of the slicing machine is following; Maximum size of a diamond blade is φ 350mm in diameter, φ 38.1mm in the spindle diameter, and 2mm in thickness. A large crystal such as an ingot with 100mm in diameter, 200mm in length can be cut. Thin crystal samples such as a wafer can be also cut using by another sample holder. Working distance of a main shaft with the direction perpendicular to working table in the machine is 350mm at maximum. Smallest resolution of the main shaft with directions of front-and-back and top-and-bottom are 0.001mm read by a digital encoder. 2mm/min can set for cutting samples in the forward direction. For orienting crystal faces relative to the blade direction adjustment, a one-circle goniometer and 2-circle segment are equipped on the working table in the machine. A rotation and a tilt of the stage can be done by manual operation. Digital encoder in a turn stage is furnished and has angle resolution of less than 0.01 degrees. In addition, a hand drill as a supporting device for detailed processing of crystal is prepared. Then, an ideal crystal face can be cut from crystal samples within an accuracy of about 0.01 degrees. By installation of these devices, a high energy resolution monochromator crystal for inelastic x-ray scattering and a beam collimator are got in hand and are expected to be used for nanotechnology studies. (author)

  12. Composite germanium monochromators - results for the TriCS

    Energy Technology Data Exchange (ETDEWEB)

    Schefer, J.; Fischer, S.; Boehm, M.; Keller, L.; Horisberger, M.; Medarde, M.; Fischer, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Composite germanium monochromators are in the beginning of their application in neutron diffraction. We show here the importance of the permanent quality control with neutrons on the example of the 311 wafers which will be used on the single crystal diffractometer TriCS at SINQ. (author) 2 figs., 3 refs.

  13. Evidence for graphite-like hexagonal AlN nanosheets epitaxially grown on single crystal Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Tsipas, P.; Kassavetis, S.; Tsoutsou, D.; Xenogiannopoulou, E.; Golias, E.; Giamini, S. A.; Dimoulas, A. [National Center for Scientific Research “Demokritos,” 15310 Athens (Greece); Grazianetti, C.; Fanciulli, M. [Laboratorio MDM, IMM-CNR, I-20864, Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, I-20126, Milano (Italy); Chiappe, D.; Molle, A. [Laboratorio MDM, IMM-CNR, I-20864, Agrate Brianza (MB) (Italy)

    2013-12-16

    Ultrathin (sub-monolayer to 12 monolayers) AlN nanosheets are grown epitaxially by plasma assisted molecular beam epitaxy on Ag(111) single crystals. Electron diffraction and scanning tunneling microscopy provide evidence that AlN on Ag adopts a graphite-like hexagonal structure with a larger lattice constant compared to bulk-like wurtzite AlN. This claim is further supported by ultraviolet photoelectron spectroscopy indicating a reduced energy bandgap as expected for hexagonal AlN.

  14. A hard X-ray laboratory for monochromator characterisation

    Energy Technology Data Exchange (ETDEWEB)

    Hamelin, B [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Since their installation at ILL during the 1970`s the ILL {gamma}-ray diffractometers have been intensively used in the development of neutron monochromators. However, the ageing of the sources and new developments in hard X-ray diffractometry lead to a decision at the end of 1995 to replace the existing {gamma}-ray laboratory with a hard X-ray laboratory, based on a 420 keV generator, making available in the long term several beam-lines for rapid characterisation of monochromator crystals. The facility is now installed and its characteristics and advantages are outlined. (author). 2 refs.

  15. Cascade self-seeding scheme with wake monochromator for narrow-bandwidth X-ray FELs

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2010-06-15

    Three different approaches have been proposed so far for production of highly monochromatic X-rays from a baseline XFEL undulator: (i) single-bunch selfseeding scheme with a four crystal monochromator in Bragg reflection geometry; (ii) double-bunch self-seeding scheme with a four-crystal monochromator in Bragg reflection geometry; (iii) single-bunch self-seeding scheme with a wake monochromator. A unique element of the X-ray optical design of the last scheme is the monochromatization of X-rays using a single crystal in Bragg-transmission geometry. A great advantage of this method is that the monochromator introduces no path delay of X-rays. This fact eliminates the need for a long electron beam bypass, or for the creation of two precisely separated, identical electron bunches, as required in the other two self-seeding schemes. In its simplest configuration, the self-seeded XFEL consists of an input undulator and an output undulator separated by a monochromator. In some experimental situations this simplest two-undulator configuration is not optimal. The obvious and technically possible extension is to use a setup with three or more undulators separated by monochromators. This amplification-monochromatization cascade scheme is distinguished, in performance, by a small heat-loading of crystals and a high spectral purity of the output radiation. This paper describes such cascade self-seeding scheme with wake monochromators.We present feasibility study and exemplifications for the SASE2 line of the European XFEL. (orig.)

  16. High Heat Load Diamond Monochromator Project at ESRF

    International Nuclear Information System (INIS)

    Van aerenbergh, P.; Detlefs, C.; Haertwig, J.; Lafford, T. A.; Masiello, F.; Roth, T.; Schmid, W.; Wattecamps, P.; Zhang, L.

    2010-01-01

    Due to its outstanding thermal properties, diamond is an attractive alternative to silicon as a monochromator material for high intensity X-ray beams. To date, however, the practical applications have been limited by the small size and relatively poor crystallographic quality of the crystals available. The ESRF Diamond Project Group has studied the perfection of diamonds in collaboration with industry and universities. The group has also designed and tested different stress-free mounting techniques to integrate small diamonds into larger X-ray optical elements. We now propose to develop a water-cooled Bragg-Bragg double crystal monochromator using diamond (111) crystals. It will be installed on the ESRF undulator beamline, ID06, for testing under high heat load. This monochromator will be best suited for the low energy range, typically from ∼3.4 keV to 15 keV, due to the small size of the diamonds available and the size of the beam footprint. This paper presents stress-free mounting techniques studied using X-ray diffraction imaging, and their thermal-mechanical analysis by finite element modelling, as well as the status of the ID06 monochromator project.

  17. Beam-smiling in bent-Laue monochromators

    International Nuclear Information System (INIS)

    Ren, B.; Dilmanian, F. A.; Wu, X. Y.; Huang, X.; Chapman, L. D.; Ivanov, I.; Zhong, Z.; Thomlinson, W. C.

    1997-01-01

    When a wide fan-shaped x-ray beam is diffracted by a bent crystal in the Laue geometry, the profile of the diffracted beam generally does not appear as a straight line, but as a line with its ends curved up or curved down. This effect, referred to as 'beam-smiling', has been a major obstacle in developing bent-Laue crystal monochromators for medical applications of synchrotron x-ray. We modeled a cylindrically bent crystal using the Finite Element Analysis (FEA) method, and we carried out experiments at the National Synchrotron Light Source and Cornell High Energy Synchrotron Source. Our studies show that, while beam-smiling exists in most of the crystal's area because of anticlastic bending effects, there is a region parallel to the bending axis of the crystal where the diffracted beam is 'smile-free'. By applying asymmetrical bending, this smile-free region can be shifted vertically away from the geometric center of the crystal, as desired. This leads to a novel method of compensating for beam-smiling. We will discuss the method of ''differential bending'' for smile removal, beam-smiling in the Cauchios and the polychromatic geometry, and the implications of the method on developing single- and double-bent Laue monochromators. The experimental results will be discussed, concentrating on specific beam-smiling observation and removal as applied to the new monochromator of the Multiple Energy Computed Tomography [MECT] project of the Medical Department, Brookhaven National Laboratory

  18. Designing and commissioning of a prototype double Laue monochromator at CHESS

    Science.gov (United States)

    Ko, J. Y. Peter; Oswald, Benjamin B.; Savino, James J.; Pauling, Alan K.; Lyndaker, Aaron; Revesz, Peter; Miller, Matthew P.; Brock, Joel D.

    2014-03-01

    High-energy X-rays are efficiently focused sagittally by a set of asymmetric Laue (transmission) crystals. We designed, built and commissioned a prototype double Laue monochromator ((111) reflection in Si(100)) optimized for high-energy X-rays (30-60 keV). Here, we report our design of novel prototype sagittal bender and highlight results from recent characterization experiments. The design of the bender combines the tuneable bending control afforded by previous leaf-spring designs with the stability and small size of a four-bar bender. The prototype monochromator focuses a 25 mm-wide white beam incident on the first monochromator crystal to a monochromatized 0.6 mm beam waist in the experimental station. Compared to the flux in the same focal spot with the Bragg crystal (without focusing), the prototype Laue monochromator delivered 85 times more at 30 keV.

  19. Designing and commissioning of a prototype double Laue monochromator at CHESS

    International Nuclear Information System (INIS)

    Ko, J Y Peter; Oswald, Benjamin B; Savino, James J; Pauling, Alan K; Lyndaker, Aaron; Revesz, Peter; Miller, Matthew P; Brock, Joel D

    2014-01-01

    High-energy X-rays are efficiently focused sagittally by a set of asymmetric Laue (transmission) crystals. We designed, built and commissioned a prototype double Laue monochromator ((111) reflection in Si(100)) optimized for high-energy X-rays (30-60 keV). Here, we report our design of novel prototype sagittal bender and highlight results from recent characterization experiments. The design of the bender combines the tuneable bending control afforded by previous leaf-spring designs with the stability and small size of a four-bar bender. The prototype monochromator focuses a 25 mm-wide white beam incident on the first monochromator crystal to a monochromatized 0.6 mm beam waist in the experimental station. Compared to the flux in the same focal spot with the Bragg crystal (without focusing), the prototype Laue monochromator delivered 85 times more at 30 keV.

  20. Local structure of the silicon implanted in a graphite single crystal

    International Nuclear Information System (INIS)

    Baba, Yuji; Shimoyama, Iwao; Sekiguchi, Tetsuhiro

    2002-01-01

    Solid carbon forms two kinds of local structures, i.e., diamond-like and two-dimensional graphite structures. In contrast, silicon carbide tends to prefer only diamond structure that is composed of sp 3 bonds. In order to clarify weather or not two-dimensional graphitic Si x C layer exists, we investigate the local structures of Si x C layer produced by Si + -ion implantation into highly oriented pyrolytic graphite (HOPG) by means of near-edge X-ray absorption fine structure (NEXAFS). The energy of the resonance peak in the Si K-edge NEXAFS spectra for Si + -implanted HOPG is lower than those for any other Si-containing materials. The intensity of the resonance peak showed a strong polarization dependence. These results suggests that the final state orbitals around Si atoms have π*-like character and the direction of this orbital is perpendicular to the graphite plane. It is elucidated that the Si-C bonds produced by the Si + -ion implantation are nearly parallel to the graphite plane, and Si x C phase forms a two-dimensionally spread graphite-like layer with sp 2 bonds. (author)

  1. Design and optical characterization of high-Q guided-resonance modes in the slot-graphite photonic crystal lattice.

    Science.gov (United States)

    Martínez, Luis Javier; Huang, Ningfeng; Ma, Jing; Lin, Chenxi; Jaquay, Eric; Povinelli, Michelle L

    2013-12-16

    A new photonic crystal structure is generated by using a regular graphite lattice as the base and adding a slot in the center of each unit cell to enhance field confinement. The theoretical Q factor in an ideal structure is over 4 × 10(5). The structure was fabricated on a silicon-on-insulator wafer and optically characterized by transmission spectroscopy. The resonance wavelength and quality factor were measured as a function of slot height. The measured trends show good agreement with simulation.

  2. Diamond monochromator for high heat flux synchrotron x-ray beams

    International Nuclear Information System (INIS)

    Khounsary, A.M.; Smither, R.K.; Davey, S.; Purohit, A.

    1992-12-01

    Single crystal silicon has been the material of choice for x-ray monochromators for the past several decades. However, the need for suitable monochromators to handle the high heat load of the next generation synchrotron x-ray beams on the one hand and the rapid and on-going advances in synthetic diamond technology on the other make a compelling case for the consideration of a diamond mollochromator system. In this Paper, we consider various aspects, advantage and disadvantages, and promises and pitfalls of such a system and evaluate the comparative an monochromator subjected to the high heat load of the most powerful x-ray beam that will become available in the next few years. The results of experiments performed to evaluate the diffraction properties of a currently available synthetic single crystal diamond are also presented. Fabrication of diamond-based monochromator is within present technical means

  3. Inclined monochromator for high heat-load synchrotron x-ray radiation

    Science.gov (United States)

    Khounsary, Ali M.

    1994-01-01

    A double crystal monochromator including two identical, parallel crystals, each of which is cut such that the normal to the diffraction planes of interest makes an angle less than 90 degrees with the surface normal. Diffraction is symmetric, regardless of whether the crystals are symmetrically or asymmetrically cut, enabling operation of the monochromator with a fixed plane of diffraction. As a result of the inclination of the crystal surface, an incident beam has a footprint area which is elongated both vertically and horizontally when compared to that of the conventional monochromator, reducing the heat flux of the incident beam and enabling more efficient surface cooling. Because after inclination of the crystal only a fraction of thermal distortion lies in the diffraction plane, slope errors and the resultant misorientation of the diffracted beam are reduced.

  4. Precision mechanical design of an UHV-compatible artificial channel-cut x-ray monochromator

    International Nuclear Information System (INIS)

    Shu, D.; Narayanan, S.; Sandy, A.; Sprung, M.; Preissner, C.; Sullivan, J.

    2007-01-01

    A novel ultra-high-vacuum (UHV)-compatible x-ray monochromator has been designed and commissioned at the undulator beamline 8-ID-I at the Advanced Photon Source (APS) for x-ray photon correlation spectroscopy applications. To meet the challenging stability and x-ray optical requirements, the monochromator integrates two new precision angular positioning mechanisms into its crystal optics motion control system: An overconstrained weak-link mechanism that enables the positioning of an assembly of two crystals to achieve the same performance as a single channel-cut crystal, the so called 'artificial channel-cut crystal'; A ceramic motor driven in-vacuum sine-bar mechanism for the double crystal combined pitch motion. The mechanical design of the monochromator, as well as the test results of its positioning performance are presented in this paper.

  5. Precision mechanical design of an UHV-compatible artificial channel-cut x-ray monochromator.

    Energy Technology Data Exchange (ETDEWEB)

    Shu, D.; Narayanan, S.; Sandy, A.; Sprung, M.; Preissner, C.; Sullivan, J.; APS Engineering Support Division

    2007-01-01

    A novel ultra-high-vacuum (UHV)-compatible x-ray monochromator has been designed and commissioned at the undulator beamline 8-ID-I at the Advanced Photon Source (APS) for x-ray photon correlation spectroscopy applications. To meet the challenging stability and x-ray optical requirements, the monochromator integrates two new precision angular positioning mechanisms into its crystal optics motion control system: An overconstrained weak-link mechanism that enables the positioning of an assembly of two crystals to achieve the same performance as a single channel-cut crystal, the so called 'artificial channel-cut crystal'; A ceramic motor driven in-vacuum sine-bar mechanism for the double crystal combined pitch motion. The mechanical design of the monochromator, as well as the test results of its positioning performance are presented in this paper.

  6. Cryogenically cooled monochromators for the Advanced Photon Source

    International Nuclear Information System (INIS)

    Mills, D.M.

    1996-01-01

    The use of cryogenically cooled monochromators looks to be a very promising possibility for the Advanced Photon Source. This position has recently been bolstered by several experiments performed on beamlines at the ESRF and CHESS. At the ESRF, several crystal geometries have been tested that were designed for high power densities (approx-gt 150 W/mm 2 ) and moderate total absorbed powers (<200 W). These geometries have proven to be very successful at handling these power parameters with measured strains on the arc-second level. The experiments performed at CHESS were focused on high total power (approx-gt 1000 W) but moderate power densities. As with the previously mentioned experiments, the crystals designed for this application performed superbly with no measurable broadening of the rocking curves on the arc-second level. These experiments will be summarized and, based on these results, the performance of cryogenic monochromators for the APS will be assessed. copyright 1996 American Institute of Physics

  7. Monochromated scanning transmission electron microscopy

    International Nuclear Information System (INIS)

    Rechberger, W.; Kothleitner, G.; Hofer, F.

    2006-01-01

    Full text: Electron energy-loss spectroscopy (EELS) has developed into an established technique for chemical and structural analysis of thin specimens in the (scanning) transmission electron microscope (S)TEM. The energy resolution in EELS is largely limited by the stability of the high voltage supply, by the resolution of the spectrometer and by the energy spread of the source. To overcome this limitation a Wien filter monochromator was recently introduced with commercially available STEMs, offering the advantage to better resolve EELS fine structures, which contain valuable bonding information. The method of atomic resolution Z-contrast imaging within an STEM, utilizing a high-angle annular dark-field (HAADF) detector can perfectly complement the excellent energy resolution, since EELS spectra can be collected simultaneously. In combination with a monochromator microscope not only high spatial resolution images can be recorded but also high energy resolution EELS spectra are attainable. In this work we investigated the STEM performance of a 200 kV monochromated Tecnai F20 with a high resolution Gatan Imaging Filter (HR-GIF). (author)

  8. Heat load studies of a water-cooled minichannel monochromator for synchrotron x-ray beams

    Science.gov (United States)

    Freund, Andreas K.; Arthur, John R.; Zhang, Lin

    1997-12-01

    We fabricated a water-cooled silicon monochromator crystal with small channels for the special case of a double-crystal fixed-exit monochromator design where the beam walks across the crystal when the x-ray energy is changed. The two parts of the cooled device were assembled using a new technique based on low melting point solder. The bending of the system produced by this technique could be perfectly compensated by mechanical counter-bending. Heat load tests of the monochromator in a synchrotron beam of 75 W total power, 3 mm high and 15 mm wide, generated by a multipole wiggler at SSRL, showed that the thermal slope error of the crystal is 1 arcsec/40 W power, in full agreement with finite element analysis. The cooling scheme is adequate for bending magnet beamlines at the ESRF and present wiggler beamlines at the SSRL.

  9. Beam-smiling in bent-Laue monochromators

    International Nuclear Information System (INIS)

    Ren, B.; Dilmanian, F.A.; Wu, X.Y.; Huang, X.; Ivanov, I.; Thomlinson, W.C.

    1997-01-01

    When a wide fan-shaped x-ray beam is diffracted by a bent crystal in the Laue geometry, the profile of the diffracted beam generally does not appear as a straight line, but as a line with its ends curved up or curved down. This effect, referred to as ' beam-smiling', has been a major obstacle in developing bent-Laue crystal monochromators for medical applications of synchrotron x-ray. We modeled a cylindrically bent crystal using the Finite Element Analysis (FEA) method, and we carried out experiments at the National Synchrotron Light Source and Cornell High Energy Synchrotron Source. Our studies show that, while beam-smiling exists in most of the crystal close-quote s area because of anticlastic bending effects, there is a region parallel to the bending axis of the crystal where the diffracted beam is ' smile-free'. By applying asymmetrical bending, this smile-free region can be shifted vertically away from the geometric center of the crystal, as desired. This leads to a novel method of compensating for beam-smiling. We will discuss the method of ' differential bending' for smile removal, beam-smiling in the Cauchios and the polychromatic geometry, and the implications of the method on developing single- and double-bent Laue monochromators. The experimental results will be discussed, concentrating on specific beam-smiling observation and removal as applied to the new monochromator of the Multiple Energy Computed Tomography [MECT] project of the Medical Department, Brookhaven National Laboratory. copyright 1997 American Institute of Physics

  10. Brazing graphite to graphite

    International Nuclear Information System (INIS)

    Peterson, G.R.

    1976-01-01

    Graphite is joined to graphite by employing both fine molybdenum powder as the brazing material and an annealing step that together produce a virtually metal-free joint exhibiting properties similar to those found in the parent graphite. Molybdenum powder is placed between the faying surfaces of two graphite parts and melted to form molybdenum carbide. The joint area is thereafter subjected to an annealing operation which diffuses the carbide away from the joint and into the graphite parts. Graphite dissolved by the dispersed molybdenum carbide precipitates into the joint area, replacing the molybdenum carbide to provide a joint of graphite

  11. Design of Double PG Crystal Neutron Diffractometer

    International Nuclear Information System (INIS)

    Adib, M.; Habib, N.; El-Mesiry, M.S.; Fathallah, M.

    2011-01-01

    The design of a diffractometer containing two pyrolytic graphite (PG) crystals to select monochromatic neutrons in the range of wavelengths longer than 0.26 nm is given. The first crystal is high oriented pyrolytic graphite (HOPG) set at glancing angle to reflect monochromatic neutrons with a selected wavelength. The second is a low quality PG crystal filter, set at take-off-angle such that, it transmits the selected monochromatic neutrons and rejects the higher order contaminations accompanying the first order reflection. It was shown that, 2 mm thick of PG crystal having 0.30 FWHM on mosaic spread are the optimum parameters of monochromator PG crystal. While the optimum thickness and mosaic spread of the PG crystal filter were selected to have low contamination factor of higher order reflections. The optimum parameters of the PG filter crystal were calculated using the computer package Graphite recently developed in our laboratory. Calculation shows that, 3 cm thick PG filter (20 on mosaic spread) is sufficient to almost eliminate the higher order contaminations accompanying the main monochromatic neutrons with

  12. Neutron optics with multilayer monochromators

    International Nuclear Information System (INIS)

    Saxena, A.M.; Majkrzak, C.F.

    1984-01-01

    A multilayer monochromator is made by depositing thin films of two materials in an alternating sequence on a glass substrate. This makes a multilayer periodic in a direction perpendicular to the plane of the films, with a d-spacing equal to the thickness of one bilayer. Neutrons of wavelength λ incident on a multilayer will be reflected at an angle phi given by the Bragg relation nλ = 2d sinphi, where n is the order of reflection. The use of thin-film multilayers for monochromating neutrons is discussed. Because of the low flux of neutrons, the samples have to be large, and the width of the incident beam can be as much as 2 cm. Multilayers made earlier were fabricated by resistive heating of the materials in a vacuum chamber. Because of geometrical constraints imposed by the size of the vacuum chamber, limits on the amount of material that can be loaded in a boat, and finite life of the boats, this method of preparation limits the length of a multilayer to ∼ 15 cm and the total number of bilayers in a multilayer to about 200. This paper discusses a thin-film deposition system using RF sputtering for depositing films

  13. Low-energy electron observation of graphite and molybdenite crystals. Application to the study of graphite oxidation; Observation au moyen d'electrons de faible energie de cristaux de graphite et de molybdenite. Application a l'etude de l'oxydation du graphite

    Energy Technology Data Exchange (ETDEWEB)

    David, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    The LEED study of cleaved (0001) faces of crystals having a layered structure allowed to investigate flakes free of steps on graphite and molybdenite, to show twinning on natural graphite. By intensity measurements and computation in the case of a kinematical approximation it has been possible to determine an inner potential of 19 eV for graphite and to identify the direction of the Mo-S bond of the surface layer of molybdenite. The oxidation of graphite has been studied by observing changes, in symmetry of the diffraction patterns and by mass spectrometry of the gases evolved during the oxidation. No surface compounds have been detected and the carbon layers appeared to be peeled off one after the other. The oxidation took place at temperatures higher than 520 C under an oxygen pressure of 10{sup -5} torr. (author) [French] L'etude par diffraction des electrons lents des faces (0001) de cristaux ayant une structure en feuillet a permis de mettre en evidence des plages sans gradins sur des clivages de graphite et de molybdenite caracterisees par la symetrie ternaire des diagrammes, de montrer l'existence de macles sur des cristaux de graphite naturel. Un calcul utilisant une approximation cinematique a ete applique aux intensites mesurees des taches de diffraction; il a ete ainsi possible de determiner un potentiel interne de 19 eV pour le graphite et de preciser la direction de la liaison Mo-S du feuillet superficiel de la molybdenite. L'oxydation du graphite a ete etudiee en mettant en relation des changements de symetrie des diagrammes de diffraction avec l'analyse des gaz provenant de la reaction carbone-oxygene. Il a ete montre qu'il n'y avait pas formation de composes de surface et que les couches de carbone etaient enlevees les unes apres les autres. L'oxydation a ete observee sous une pression d'oxygene de 10{sup -5} torr au-dessus de 520 C. (auteur)

  14. An ultrahigh vacuum monochromator for photophysics beamline

    International Nuclear Information System (INIS)

    Meenakshi Raja Rao, P.; Padmanabhan, Saraswathy; Raja Sekhar, B.N.; Shastri, Aparna; Khan, H.A.; Sinha, A.K.

    2000-08-01

    The photophysics beamline designed for carrying out photoabsorption and fluorescence studies using the 450 MeV Synchrotron Radiation Source (SRS), INDUS-1, uses a 1 metre monochromator as premonochromator for monochromatising the continuum. An ultra high vacuum compatible monochromator in Seya-Namioka mount has been designed and fabricated indigenously. The monochromator was assembled and tested for its performance. Wavelength scanning mechanism was tested for its reproducibility and the monochromator was tested for its resolution using UV and VUV sources. An average spectral resolution of 2.5 A was achieved using a 1200 gr/mm grating. A wavelength repeatability of ± 1A was obtained. An ultra high vacuum of 2 X 10 -8 mbar was also achieved in the monochromator. Details of fabrication, assembly and testing are presented in this report. (author)

  15. Special graphites; Graphites speciaux

    Energy Technology Data Exchange (ETDEWEB)

    Leveque, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    A large fraction of the work undertaken jointly by the Commissariat a l'Energie Atomique (CEA) and the Pechiney Company has been the improvement of the properties of nuclear pile graphite and the opening up of new fields of graphite application. New processes for the manufacture of carbons and special graphites have been developed: forged graphite, pyro-carbons, high density graphite agglomeration of graphite powders by cracking of natural gas, impervious graphites. The physical properties of these products and their reaction with various oxidising gases are described. The first irradiation results are also given. (authors) [French] Ameliorer les proprietes du graphite nucleaire pour empilements et ouvrir de nouveaux domaines d'application au graphite constituent une part importante de l'effort entrepris en commun par le Commissariat a l'Energie Atomique (CEA) et la compagnie PECHINEY. Des procedes nouveaux de fabrication de carbones et graphites speciaux ont ete mis au point: graphite forge, pyrocarbone, graphite de haute densite, agglomeration de poudres de graphite par craquage de gaz naturel, graphites impermeables. Les proprietes physiques de ces produits ainsi que leur reaction avec differents gaz oxydants sont decrites. Les premiers resultats d'irradiation sont aussi donnes. (auteurs)

  16. Effect of additional nickel on crystallization degree evolution of expanded graphite during ball-milling and annealing

    International Nuclear Information System (INIS)

    Wang Liqin; Yue Xueqing; Zhang Fucheng; Zhang Ruijun

    2010-01-01

    Expanded graphite (EG) and a mixture of EG and nickel (EG-Ni system) were ball-milled and subsequently annealed, respectively. The products were characterized by X-ray diffraction (XRD), Raman spectra and transmission electron microscopy (TEM). After 100 h milling, the average crystallite thickness (L c ) of EG and EG-Ni system deceases from 14.5 to 8.0 and 9.6 nm, respectively, while the interlayer spacing (d 002 ) increases from 0.3341 to 0.3371 and 0.3348 nm, respectively. It can be concluded that ball-milling decreases the crystallization degree of EG, while the additional nickel restrains this process. For the samples ball-milled for 80 h, the disorder parameter I D /(I D + I G ) ratio of EG and EG-Ni system is in the range of 20.7-55.8% and 31.7-45.8%, respectively, implying that the presence of nickel is beneficial to more homogeneous ball-milling of EG. When the samples after ball-milling for 80 h were annealed for 4 h, the average crystallite thickness of EG and EG-Ni system increases from 8.5 to 9.0 nm and from 11.8 to 15.5 nm, respectively. It is deduced that annealing improves the crystallization degree of ball-milled EG, and the additional nickel is helpful for this process.

  17. Software feedback for monochromator tuning at UNICAT (abstract)

    Science.gov (United States)

    Jemian, Pete R.

    2002-03-01

    Automatic tuning of double-crystal monochromators presents an interesting challenge in software. The goal is to either maximize, or hold constant, the throughput of the monochromator. An additional goal of the software feedback is to disable itself when there is no beam and then, at the user's discretion, re-enable itself when the beam returns. These and other routine goals, such as adherence to limits of travel for positioners, are maintained by software controls. Many solutions exist to lock in and maintain a fixed throughput. Among these include a hardware solution involving a wave form generator, and a lock-in amplifier to autocorrelate the movement of a piezoelectric transducer (PZT) providing fine adjustment of the second crystal Bragg angle. This solution does not work when the positioner is a slow acting device such as a stepping motor. Proportional integral differential (PID) loops have been used to provide feedback through software but additional controls must be provided to maximize the monochromator throughput. Presented here is a software variation of the PID loop which meets the above goals. By using two floating point variables as inputs, representing the intensity of x rays measured before and after the monochromator, it attempts to maximize (or hold constant) the ratio of these two inputs by adjusting an output floating point variable. These floating point variables are connected to hardware channels corresponding to detectors and positioners. When the inputs go out of range, the software will stop making adjustments to the control output. Not limited to monochromator feedback, the software could be used, with beam steering positioners, to maintain a measure of beam position. Advantages of this software feedback are the flexibility of its various components. It has been used with stepping motors and PZTs as positioners. Various devices such as ion chambers, scintillation counters, photodiodes, and photoelectron collectors have been used as

  18. Nuclear graphite ageing and turnaround

    International Nuclear Information System (INIS)

    Marsden, B.J.; Hall, G.N.; Smart, J.

    2001-01-01

    Graphite moderated reactors are being operated in many countries including, the UK, Russia, Lithuania, Ukraine and Japan. Many of these reactors will operate well into the next century. New designs of High Temperature Graphite Moderated Reactors (HTRS) are being built in China and Japan. The design life of these graphite-moderated reactors is governed by the ageing of the graphite core due to fast neutron damage, and also, in the case of carbon dioxide cooled reactors by the rate of oxidation of the graphite. Nuclear graphites are polycrystalline in nature and it is the irradiation-induced damage to the individual graphite crystals that determines the material property changes with age. The life of a graphite component in a nuclear reactor can be related to the graphite irradiation induced dimensional changes. Graphites typically shrink with age, until a point is reached where the shrinkage stops and the graphite starts to swell. This change from shrinkage to swelling is known as ''turnaround''. It is well known that pre-oxidising graphite specimens caused ''turnaround'' to be delayed, thus extending the life of the graphite, and hence the life of the reactor. However, there was no satisfactory explanation of this behaviour. This paper presents a numerical crystal based model of dimensional change in graphite, which explains the delay in ''turnaround'' in the pre-oxidised specimens irradiated in a fast neutron flux, in terms of crystal accommodation and orientation and change in compliance due to radiolytic oxidation. (author)

  19. Characterisation of a Sr-90 based electron monochromator

    CERN Document Server

    Arfaoui, S; CERN; Casella, C; ETH Zurich

    2015-01-01

    This note describes the characterisation of an energy filtered Sr-90 source to be used in laboratory studies that require Minimum Ionising Particles (MIP) with a kinetic energy of up to approx. 2 MeV. The energy calibration was performed with a LYSO scintillation crystal read out by a digital Silicon Photomultiplier (dSiPM). The LYSO/dSiPM set-up was pre-calibrated using a Na-22 source. After introducing the motivation behind the usage of such a device, this note presents the principle and design of the electron monochromator as well as its energy and momentum characterisation.

  20. Velocity monochromator for macro-ions

    Energy Technology Data Exchange (ETDEWEB)

    Paquin, R; Baril, M [Laval Univ., Quebec City (Canada). Dept. de Physique

    1976-09-15

    We propose the use of a dynamic monochromator to reduce the energy spread of a macroion source. It is shown that the energy aberration can be corrected using linear acceleration after the particles are separated in a field free drift tube. We give a general expression for the resolution of the monochromator. We verify experimentally that the energy distribution of a beam of cesium ions of 160 eV mean energy could be reduced from 20 eV to 4.5 eV, giving an improvement of 4.3, with this monochromator which has an efficiency of 6%. Two suggestions to improve the transmission of the monochromator are also given.

  1. Velocity monochromator for macro-ions

    International Nuclear Information System (INIS)

    Paquin, R.; Baril, M.

    1976-01-01

    We propose the use of a dynamic monochromator to reduce the energy spread of a macroion source. It is shown that the energy aberration can be corrected using linear acceleration after the particles are separated in a field free drift tube. We give a general expression for the resolution of the monochromator. We verify experimentally that the energy distribution of a beam of cesium ions of 160 eV mean energy could be reduced from 20 eV to 4.5 eV, giving an improvement of 4.3, with this monochromator which has an efficiency of 6%. Two suggestions to improve the transmission of the monochromator are also given. (author)

  2. X-ray diffraction characteristics of curved monochromators for sychrotron radiation

    International Nuclear Information System (INIS)

    Boeuf, A.; Rustichelli, F.; Mazkedian, S.; Puliti, P.; Melone, S.

    1978-01-01

    A theoretical study is presented concerning the diffraction characteristics of curved monochromators for X-ray synchrotron radiation used at the laboratories of Hamburg, Orsay and Stanford. The investigation was performed by extending to the X-ray case a simple model recently developed and fruitfully employed to describe the neutron diffraction properties of curved monochromators. Several diffraction patterns were obtained corresponding to different monochromator materials (Ge, Si) used by the different laboratories, for different reflecting planes (111), (220), asymmetry angles, X-ray wave-lengths (Mo Kα, Cu Kα, Cr Kα) and curvature radii. The results are discussed in physical terms and their implications on the design of curved monochromators for synchrotron radiation are presented. In particular, the study shows that all the monochromators used in the different laboratories should behave practically as perfect crystals and therefore should have a very low integrated reflectivity corresponding to an optimized wavelength passband Δlambda/lambda approximately 10 -4 . The gain that can be obtained by increasing the curvature, by introducing a gradient in the lattice spacing or by any other kind of imperfection is quite limited and much lower than the desirable value. The adopted model can help in obtaining a possible moderate gain in intensity by also taking into consideration other parameters, such as crystal material, reflecting plane, asymmetry of the reflection and X-ray wavelength. (Auth.)

  3. Bragg reflection transmission filters for variable resolution monochromators

    International Nuclear Information System (INIS)

    Chapman, D.

    1989-01-01

    There are various methods for improving the angular and spectral resolution of monochromator and analyzer systems. The novel system described here, though limited to higher x-ray energies (>20keV), is based on a dynamical effect occurring on the transmitted beam with a thin perfect crystal plate set in the Bragg reflection case. In the case of Bragg reflection from a perfect crystal, the incident beam is rapidly attenuated as it penetrates the crystal in the range of reflection. This extinction length is of the order of microns. The attenuation length, which determines the amount of normal transmission through the plate is generally much longer. Thus, in the range of the Bragg reflection the attenuation of the transmitted beam can change by several orders of magnitude with a small change in energy or angle. This thin crystal plate cuts a notch in the transmitted beam with a width equal to its Darwin width, thus acting as a transmission filter. When used in a non-dispersive mode with other monochromator crystals, the filter when set at the Bragg angle will reflect the entire Darwin width of the incident beam and transmit the wings of the incident beam distribution. When the element is offset in angle by some fraction of the Darwin width, the filter becomes useful in adjusting the angular width of the transmitted beam and removing a wing. Used in pairs with a symmetric offset, the filters can be used to continuously adjust the intrinsic angular divergence of the beam with good wing reduction. Instances where such filters may be useful are in improving the angular resolution of a small angle scattering camera. These filters may be added to a Bonse-Hart camera with one pair on the incident beam to reduce the intrinsic beam divergence and a second pair on the analyzer arm to improve the analyzer resolution. 2 refs., 3 Figs

  4. MACS low-background doubly focusing neutron monochromator

    CERN Document Server

    Smee, S A; Scharfstein, G A; Qiu, Y; Brand, P C; Anand, D K; Broholm, C L

    2002-01-01

    A novel doubly focusing neutron monochromator has been developed as part of the Multi-Analyzer Crystal Spectrometer (MACS) at the NIST Center for Neutron Research. The instrument utilizes a unique vertical focusing element that enables active vertical and horizontal focusing with a large, 357-crystal (1428 cm sup 2), array. The design significantly reduces the amount of structural material in the beam path as compared to similar instruments. Optical measurements verify the excellent focal performance of the device. Analytical and Monte Carlo simulations predict that, when mounted at the NIST cold-neutron source, the device should produce a monochromatic beam (DELTA E=0.2 meV) with flux phi>10 sup 8 n/cm sup 2 s. (orig.)

  5. Studies Of The (n, γ) Reaction With A Neutron Monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Kane, W. R.; Gardner, D.; Brown, T.; Kevey, A.; Mateosian, E. der; Emery, G. T.; Gelletly, W.; Mariscotti, M. A.J. [Brookhaven National Laboratory, Upton, Long Island, NY (United States); Schröder, I. [National Bureau of Standards, Washington, DC (United States)

    1969-11-15

    A crystal diffraction neutron monochromator has been constructed specifically for studies of the(n, γ) reaction. This equipment plays a complementary role to that of time-of-flight devices in providing a neutron beam with a full duty cycle at a given energy. This feature and the small target size, large geometrical efficiency for y-ray detection, and negligible fast neutron background afford advantages for certain classes of experiments. The useful energy range extends from 0.01 to 20 eV. Novel features of the equipment include a complete reliance upon precision angle encoders for setting arm and crystal angles, the employment of a liquid shield to facilitate the extraction of the diffracted neutron beam, and the use of air bearings to provide for the motion of the target, detection devices, and associated shielding. Results obtained on low energy resonances of {sup 139}La, {sup 189}Os, and {sup 235}U will be presented. (author)

  6. Direct growth of self-crystallized graphene and graphite nanoballs with Ni vapor-assisted growth: From controllable growth to material characterization

    Science.gov (United States)

    Yen, Wen-Chun; Chen, Yu-Ze; Yeh, Chao-Hui; He, Jr-Hau; Chiu, Po-Wen; Chueh, Yu-Lun

    2014-01-01

    A directly self-crystallized graphene layer with transfer-free process on arbitrary insulator by Ni vapor-assisted growth at growth temperatures between 950 to 1100°C via conventional chemical vapor deposition (CVD) system was developed and demonstrated. Domain sizes of graphene were confirmed by Raman spectra from ~12 nm at growth temperature of 1000°C to ~32 nm at growth temperature of 1100°C, respectively. Furthermore, the thickness of the graphene is controllable, depending on deposition time and growth temperature. By increasing growth pressure, the growth of graphite nano-balls was preferred rather than graphene growth. The detailed formation mechanisms of graphene and graphite nanoballs were proposed and investigated in detail. Optical and electrical properties of graphene layer were measured. The direct growth of the carbon-based materials with free of the transfer process provides a promising application at nanoelectronics. PMID:24810224

  7. Direct growth of self-crystallized graphene and graphite nanoballs with Ni vapor-assisted growth: from controllable growth to material characterization.

    Science.gov (United States)

    Yen, Wen-Chun; Chen, Yu-Ze; Yeh, Chao-Hui; He, Jr-Hau; Chiu, Po-Wen; Chueh, Yu-Lun

    2014-05-09

    A directly self-crystallized graphene layer with transfer-free process on arbitrary insulator by Ni vapor-assisted growth at growth temperatures between 950 to 1100 °C via conventional chemical vapor deposition (CVD) system was developed and demonstrated. Domain sizes of graphene were confirmed by Raman spectra from ~12 nm at growth temperature of 1000 °C to ~32 nm at growth temperature of 1100 °C, respectively. Furthermore, the thickness of the graphene is controllable, depending on deposition time and growth temperature. By increasing growth pressure, the growth of graphite nano-balls was preferred rather than graphene growth. The detailed formation mechanisms of graphene and graphite nanoballs were proposed and investigated in detail. Optical and electrical properties of graphene layer were measured. The direct growth of the carbon-based materials with free of the transfer process provides a promising application at nanoelectronics.

  8. Internally cooled V-shape inclined monochromator

    Czech Academy of Sciences Publication Activity Database

    Oberta, Peter; Áč, V.; Hrdý, Jaromír

    2008-01-01

    Roč. 15, - (2008), 8-11 ISSN 0909-0495 R&D Projects: GA AV ČR IAA100100716 Grant - others:VEGA(SK) 1/4134/07 Institutional research plan: CEZ:AV0Z10100522 Keywords : inclined monochromator * heat load * internal cooling Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.333, year: 2008

  9. Performances of synchrotron X-ray monochromators under heat load. Part 2. Application of the Takagi-Taupin diffraction theory

    CERN Document Server

    Mocella, V; Freund, A K; Hoszowska, J; Zhang, L; Epelboin, Y

    2001-01-01

    The aim of this work is to generate the rocking curves of monochromators exposed to heat load in synchrotron radiation beams with a computer code performing diffraction calculations based on the theory of Takagi and Taupin. The model study starts with the calculation of deformation by finite element analysis and from an accurate characterization of the incident wave and includes the simulation of the wavefront propagation between the first and the second crystal (analyzer) of a double crystal monochromator. A monochromatic plane wave as well as a polychromatic spherical wave approach is described. The theoretical predictions of both methods are compared with experimental data measured in Bragg geometry and critically discussed.

  10. Performances of synchrotron X-ray monochromators under heat load. Part 2. Application of the Takagi-Taupin diffraction theory

    International Nuclear Information System (INIS)

    Mocella, V.; Ferrero, C.; Freund, A.K.; Hoszowska, J.; Zhang, L.; Epelboin, Y.

    2001-01-01

    The aim of this work is to generate the rocking curves of monochromators exposed to heat load in synchrotron radiation beams with a computer code performing diffraction calculations based on the theory of Takagi and Taupin. The model study starts with the calculation of deformation by finite element analysis and from an accurate characterization of the incident wave and includes the simulation of the wavefront propagation between the first and the second crystal (analyzer) of a double crystal monochromator. A monochromatic plane wave as well as a polychromatic spherical wave approach is described. The theoretical predictions of both methods are compared with experimental data measured in Bragg geometry and critically discussed

  11. A bent Laue-Laue monochromator for a synchrotron-based computed tomography system

    CERN Document Server

    Ren, B; Chapman, L D; Ivanov, I; Wu, X Y; Zhong, Z; Huang, X

    1999-01-01

    We designed and tested a two-crystal bent Laue-Laue monochromator for wide, fan-shaped synchrotron X-ray beams for the program multiple energy computed tomography (MECT) at the National Synchrotron Light Source (NSLS). MECT employs monochromatic X-ray beams from the NSLS's X17B superconducting wiggler beamline for computed tomography (CT) with an improved image quality. MECT uses a fixed horizontal fan-shaped beam with the subject's apparatus rotating around a vertical axis. The new monochromator uses two Czochralski-grown Si crystals, 0.7 and 1.4 mm thick, respectively, and with thick ribs on their upper and lower ends. The crystals are bent cylindrically, with the axis of the cylinder parallel to the fan beam, using 4-rod benders with two fixed rods and two movable ones. The bent-crystal feature of the monochromator resolved the difficulties we had had with the flat Laue-Laue design previously used in MECT, which included (a) inadequate beam intensity, (b) excessive fluctuations in beam intensity, and (c) i...

  12. Special graphites

    International Nuclear Information System (INIS)

    Leveque, P.

    1964-01-01

    A large fraction of the work undertaken jointly by the Commissariat a l'Energie Atomique (CEA) and the Pechiney Company has been the improvement of the properties of nuclear pile graphite and the opening up of new fields of graphite application. New processes for the manufacture of carbons and special graphites have been developed: forged graphite, pyro-carbons, high density graphite agglomeration of graphite powders by cracking of natural gas, impervious graphites. The physical properties of these products and their reaction with various oxidising gases are described. The first irradiation results are also given. (authors) [fr

  13. Performance limits of direct cryogenically cooled silicon monochromators - experimental results at the APS

    International Nuclear Information System (INIS)

    Lee, W.-K.; Fernandez, P.; Mills, D.M.

    2000-01-01

    The successful use of cryogenically cooled silicon monochromators at third-generation synchrotron facilities is well documented. At the Advanced Photon Source (APS) it has been shown that, at 100 mA operation with the standard APS undulator A, the cryogenically cooled silicon monochromator performs very well with minimal (<2 arcsec) or no observable thermal distortions. However, to date there has not been any systematic experimental study on the performance limits of this approach. This paper presents experimental results on the performance limits of these directly cooled crystals. The results show that if the beam is limited to the size of the radiation central cone then, at the APS, the crystal will still perform well at twice the present 100 mA single 2.4 m-long 3.3 cm-period undulator heat load. However, the performance would degrade rapidly if a much larger incident white-beam size is utilized

  14. Submicrovolt resolution X-ray monochromators

    International Nuclear Information System (INIS)

    Trammell, G.T.; Hannon, J.P.

    1984-01-01

    Two methods are available to obtain monochromatic x-radiation from a white source: wavelength selection and frequency selection. The resolution of wavelength selection methods is limited to 1-10 MeV in the E = 10 KeV range. To exceed this resolution frequency selection methods based on nuclear resonance scattering can be used. Devices which give strong nuclear resonance reflections but weak electronic reflections are candidates for components of frequency selection monochromates. Some examples are discussed

  15. X-ray instrumentation: monochromators and mirrors

    International Nuclear Information System (INIS)

    Rodrigues, A.R.D.

    1983-01-01

    The main type of X-ray monochromators used with Synchrotron Radiation are discussed in relation to the energy resolution and to the spectral contamination, as well special systems for applications which require simultaneously high flux and resolution. The characteristics for X-ray mirrors necessaries for its utilization with synchrotron radiation are also analized, as conformators of the beam geometry and spectrum. (L.C.) [pt

  16. Workshop on cooling of x-ray monochromators on high power beamlines

    International Nuclear Information System (INIS)

    Matsushita, T.; Ishikawa, T.

    1989-03-01

    This report is a Workshop on Cooling of X-ray Monochromators on High Power Beamlines held on August 31, 1988 at the Photon Factory during the Third International Conference on Synchrotron Radiation Instrumentation (SRI88). On high power beamlines, especially on insertion device beamlines, heating of crystal monochromators is becoming a serious problem: Researchers observe that the intensity of the X-ray beam on the sample is not proportional to the source intensity because of thermal distortion of the monochromator crystal. This problem will be even more serious on beamlines for the next generation X-ray rings. In the very tight program of the SRI88 conference, only 2 speakers were able to give invited talks closely related to this problem in the session of OPTICAL COMPONENTS FOR HIGH POWER BEAMLINES on Wednesday morning of August 31, 1988. We held this workshop in the afternoon of the same day with the intention of offering further opportunities to exchange information on efforts underway at various laboratories and to discuss ideas how to solve this problem. We also intended that the workshop would be a 'follow-up' to the X-ray optics workshop held at ESRF, Grenoble in September 1987, where the importance of crystal cooling was strongly pointed out. There were 32 participants from 7 countries. 12 people represented their experiences and ideas for reducing thermal distortion of crystal monochromators. Following those presentations, there were discussions on collaborations for solving this important problem. The attendees agreed that exchange of information should be continued by holding such meetings at reasonable intervals. (J.P.N.)

  17. Vibration measurements of high-heat-load monochromators for DESY PETRA III extension

    Energy Technology Data Exchange (ETDEWEB)

    Kristiansen, Paw, E-mail: paw.kristiansen@fmb-oxford.com [FMB Oxford Ltd, Unit 1 Ferry Mills, Oxford OX2 0ES (United Kingdom); Horbach, Jan; Döhrmann, Ralph; Heuer, Joachim [DESY, Deutsches Elektronen-Synchrotron Hamburg, Notkestrasse 85, 22607 Hamburg (Germany)

    2015-05-09

    Vibration measurements of a cryocooled double-crystal monochromator are presented. The origins of the vibrations are identified. The minimum achieved vibration of the relative pitch between the two crystals is 48 nrad RMS and the minimum achieved absolute vibration of the second crystal is 82 nrad RMS. The requirement for vibrational stability of beamline optics continues to evolve rapidly to comply with the demands created by the improved brilliance of the third-generation low-emittance storage rings around the world. The challenge is to quantify the performance of the instrument before it is installed at the beamline. In this article, measurement techniques are presented that directly and accurately measure (i) the relative vibration between the two crystals of a double-crystal monochromator (DCM) and (ii) the absolute vibration of the second-crystal cage of a DCM. Excluding a synchrotron beam, the measurements are conducted under in situ conditions, connected to a liquid-nitrogen cryocooler. The investigated DCM utilizes a direct-drive (no gearing) goniometer for the Bragg rotation. The main causes of the DCM vibration are found to be the servoing of the direct-drive goniometer and the flexibility in the crystal cage motion stages. It is found that the investigated DCM can offer relative pitch vibration down to 48 nrad RMS (capacitive sensors, 0–5 kHz bandwidth) and absolute pitch vibration down to 82 nrad RMS (laser interferometer, 0–50 kHz bandwidth), with the Bragg axis brake engaged.

  18. Self-seeding scheme with gas monochromator for narrow-bandwidth soft X-ray FELs

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    Self-seeding schemes, consisting of two undulators with a monochromator in between, aim at reducing the bandwidth of SASE X-ray FELs. We recently proposed to use a new method of monochromatization exploiting a single crystal in Bragg transmission geometry for self-seeding in the hard X-ray range. Here we consider a possible extension of this method to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake. In fact, the FEL pulse forces the gas atoms to oscillate in a way consistent with a forward-propagating, monochromatic radiation beam. The radiation power within this wake is much larger than the equivalent shot noise power in the electron bunch. Further on, the monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements. These are the gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation. In this paper we assess the features of gas monochromator based on the use of He and Ne.We analyze the processes in the monochromator gas cell and outside it, touching upon the performance of the differential pumping system as well. We study the feasibility of using the proposed self-seeding technique to generate narrow bandwidth soft X-ray radiation in the LCLS-II soft X-ray beam line. We present conceptual design, technical implementation and expected performances of the gas monochromator self-seeding scheme. (orig.)

  19. Self-seeding scheme with gas monochromator for narrow-bandwidth soft X-ray FELs

    International Nuclear Information System (INIS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2011-03-01

    Self-seeding schemes, consisting of two undulators with a monochromator in between, aim at reducing the bandwidth of SASE X-ray FELs. We recently proposed to use a new method of monochromatization exploiting a single crystal in Bragg transmission geometry for self-seeding in the hard X-ray range. Here we consider a possible extension of this method to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake. In fact, the FEL pulse forces the gas atoms to oscillate in a way consistent with a forward-propagating, monochromatic radiation beam. The radiation power within this wake is much larger than the equivalent shot noise power in the electron bunch. Further on, the monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements. These are the gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation. In this paper we assess the features of gas monochromator based on the use of He and Ne.We analyze the processes in the monochromator gas cell and outside it, touching upon the performance of the differential pumping system as well. We study the feasibility of using the proposed self-seeding technique to generate narrow bandwidth soft X-ray radiation in the LCLS-II soft X-ray beam line. We present conceptual design, technical implementation and expected performances of the gas monochromator self-seeding scheme. (orig.)

  20. Investigation of a monochromator scheme for SPEAR

    International Nuclear Information System (INIS)

    Wille, K.; Chao, A.W.

    1984-08-01

    The possibility of mono-chromatizing SPEAR for the purpose of increasing the hadronic event rate at the narrow resonances was investigated. By using two pairs of electostatic skew quads in monochromator scheme it is found that the event rate can be increased by a factor of 2 for the mini beta optics assuming the luminosity is kept unchanged. An attempt to increase this enhancement factor by major rearrangements of the ring magnets has encountered serious optical difficulties; although enhancement factor of 8 seems possible in principle, this alternative is not recommended

  1. Cam-driven monochromator for QEXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Caliebe, W.A. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973 (United States); So, I. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973 (United States); Lenhard, A. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973 (United States); Siddons, D.P. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2006-11-15

    We have developed a cam-drive for quickly tuning the energy of an X-ray monochromator through an X-ray absorption edge for quick extended X-ray absorption spectroscopy (QEXAFS). The data are collected using a 4-channel, 12-bit multiplexed VME analog to digital converter and a VME angle encoder. The VME crate controller runs a real-time operating system. This system is capable of collecting 2 EXAFS-scans in 1 s with an energy stability of better than 1 eV. Additional improvements to increase the speed and the energy stability are under way.

  2. Cam-driven monochromator for QEXAFS

    Science.gov (United States)

    Caliebe, W. A.; So, I.; Lenhard, A.; Siddons, D. P.

    2006-11-01

    We have developed a cam-drive for quickly tuning the energy of an X-ray monochromator through an X-ray absorption edge for quick extended X-ray absorption spectroscopy (QEXAFS). The data are collected using a 4-channel, 12-bit multiplexed VME analog to digital converter and a VME angle encoder. The VME crate controller runs a real-time operating system. This system is capable of collecting 2 EXAFS-scans in 1 s with an energy stability of better than 1 eV. Additional improvements to increase the speed and the energy stability are under way.

  3. Cam-driven monochromator for QEXAFS

    International Nuclear Information System (INIS)

    Caliebe, W.A.; So, I.; Lenhard, A.; Siddons, D.P.

    2006-01-01

    We have developed a cam-drive for quickly tuning the energy of an X-ray monochromator through an X-ray absorption edge for quick extended X-ray absorption spectroscopy (QEXAFS). The data are collected using a 4-channel, 12-bit multiplexed VME analog to digital converter and a VME angle encoder. The VME crate controller runs a real-time operating system. This system is capable of collecting 2 EXAFS-scans in 1 s with an energy stability of better than 1 eV. Additional improvements to increase the speed and the energy stability are under way

  4. A Single-Element Plane Grating Monochromator

    Directory of Open Access Journals (Sweden)

    Michael C. Hettrick

    2016-01-01

    Full Text Available Concerted rotations of a self-focused varied line-space diffraction grating about its groove axis and surface normal define a new geometric class of monochromator. Defocusing is canceled, while the scanned wavelength is reinforced at fixed conjugate distances and horizontal deviation angle. This enables high spectral resolution over a wide band, and is of particular advantage at grazing reflection angles. A new, rigorous light-path formulation employs non-paraxial reference points to isolate the lateral ray aberrations, with those of power-sum ≤ 3 explicitly expanded for a plane grating. Each of these 14 Fermat equations agrees precisely with the value extracted from numerical raytrace simulations. An example soft X-ray design (6° deviation angle and 2 × 4 mrad aperture attains a resolving power > 25 , 000 over a three octave scan range. The proposed rotation scheme is not limited to plane surfaces or monochromators, providing a new degree of freedom in optical design.

  5. Characterization of un-irradiated and irradiated reactor graphite; Karakterizacija neozracenog i ozracenog reaktorskog grafita

    Energy Technology Data Exchange (ETDEWEB)

    Marinkovic, S [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-11-15

    This report contains three parts: characterization of Yugoslav nuclear graphite development of methods and obtained results, characterization of un-irradiated and irradiated domestic nuclear graphite; calculation of electrical conductivity changes due to vacancies in the graphite crystal lattice.

  6. Investigation of the Microstructure and Mechanical Properties of Copper-Graphite Composites Reinforced with Single-Crystal α-Al₂O₃ Fibres by Hot Isostatic Pressing.

    Science.gov (United States)

    Zhang, Guihang; Jiang, Xiaosong; Qiao, ChangJun; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao; Valcarcel, Victor

    2018-06-11

    Single-crystal α-Al₂O₃ fibres can be utilized as a novel reinforcement in high-temperature composites owing to their high elastic modulus, chemical and thermal stability. Unlike non-oxide fibres and polycrystalline alumina fibres, high-temperature oxidation and polycrystalline particles boundary growth will not occur for single-crystal α-Al₂O₃ fibres. In this work, single-crystal α-Al₂O₃ whiskers and Al₂O₃ particles synergistic reinforced copper-graphite composites were fabricated by mechanical alloying and hot isostatic pressing techniques. The phase compositions, microstructures, and fracture morphologies of the composites were investigated using X-ray diffraction, a scanning electron microscope equipped with an X-ray energy-dispersive spectrometer (EDS), an electron probe microscopic analysis equipped with wavelength-dispersive spectrometer, and a transmission electron microscope equipped with EDS. The mechanical properties have been measured by a micro-hardness tester and electronic universal testing machine. The results show that the reinforcements were unevenly distributed in the matrix with the increase of their content and there were some micro-cracks located at the interface between the reinforcement and the matrix. With the increase of the Al₂O₃ whisker content, the compressive strength of the composites first increased and then decreased, while the hardness decreased. The fracture and strengthening mechanisms of the composite materials were explored on the basis of the structure and composition of the composites through the formation and function of the interface. The main strengthening mechanism in the composites was fine grain strengthening and solid solution strengthening. The fracture type of the composites was brittle fracture.

  7. Plane grating monochromators for synchrotron radiation

    International Nuclear Information System (INIS)

    Howells, M.R.

    1979-01-01

    The general background and theoretical basis of plane grating monochromators (PGM's) is reviewed and the particular case of grazing incidence PGM's suitable for use with synchrotron radiation is considered in detail. The theory of reflection filtering is described and the problem of the finite source distance is shown to be of special importance with high brightness storage rings. The design philosophy of previous instruments is discussed and a new scheme proposed, aimed at dealing with the problem of the finite source distance. This scheme, involving a parabolic collimating mirror fabricated by diamond turning, is considered in the context of Wolter-type telescopes and microscopes. Some practical details concerning an instrument presently under construction using the new design are presented

  8. Vanadium-rich tourmaline from graphitic rocks at Bítovánky, Czech republic; compositional variation, crystal structure

    Czech Academy of Sciences Publication Activity Database

    Cempírek, J.; Houzar, S.; Novák, M.; Selway, J.B.; Šrein, Vladimír

    2006-01-01

    Roč. 28, Spec. pap. (2006), s. 39-41 ISSN 1896-2203. [Central European Mineralogical Conference /1./. Vyšná Boca, 11.09.2006-15.09.2006] Institutional research plan: CEZ:AV0Z30460519 Keywords : V-rich tourmaline * compositional variation * crystal structure Subject RIV: DB - Geology ; Mineralogy

  9. Irradiation Creep in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  10. Bactericidal activity of self-assembled palmitic and stearic fatty acid crystals on highly ordered pyrolytic graphite.

    Science.gov (United States)

    Ivanova, Elena P; Nguyen, Song Ha; Guo, Yachong; Baulin, Vladimir A; Webb, Hayden K; Truong, Vi Khanh; Wandiyanto, Jason V; Garvey, Christopher J; Mahon, Peter J; Mainwaring, David E; Crawford, Russell J

    2017-09-01

    The wings of insects such as cicadas and dragonflies have been found to possess nanostructure arrays that are assembled from fatty acids. These arrays can physically interact with the bacterial cell membranes, leading to the death of the cell. Such mechanobactericidal surfaces are of significant interest, as they can kill bacteria without the need for antibacterial chemicals. Here, we report on the bactericidal effect of two of the main lipid components of the insect wing epicuticle, palmitic (C16) and stearic (C18) fatty acids. Films of these fatty acids were re-crystallised on the surface of highly ordered pyrolytic graphite. It appeared that the presence of two additional CH 2 groups in the alkyl chain resulted in the formation of different surface structures. Scanning electron microscopy and atomic force microscopy showed that the palmitic acid microcrystallites were more asymmetric than those of the stearic acid, where the palmitic acid microcrystallites were observed to be an angular abutment in the scanning electron micrographs. The principal differences between the two types of long-chain saturated fatty acid crystallites were the larger density of peaks in the upper contact plane of the palmitic acid crystallites, as well as their greater proportion of asymmetrical shapes, in comparison to that of the stearic acid film. These two parameters might contribute to higher bactericidal activity on surfaces derived from palmitic acid. Both the palmitic and stearic acid crystallite surfaces displayed activity against Gram-negative, rod-shaped Pseudomonas aeruginosa and Gram-positive, spherical Staphylococcus aureus cells. These microcrystallite interfaces might be a useful tool in the fabrication of effective bactericidal nanocoatings. Nanostructured cicada and dragonfly wing surfaces have been discovered to be able physically kill bacterial cells. Here, we report on the successful fabrication of bactericidal three-dimensional structures of two main lipid

  11. High heat flux x-ray monochromators: What are the limits?

    International Nuclear Information System (INIS)

    Rogers, C.S.

    1997-06-01

    First optical elements at third-generation, hard x-ray synchrotrons, such as the Advanced Photon Source (APS), are subjected to immense heat fluxes. The optical elements include crystal monochromators, multilayers and mirrors. This paper presents a mathematical model of the thermal strain of a three-layer (faceplate, heat exchanger, and baseplate), cylindrical optic subjected to narrow beam of uniform heat flux. This model is used to calculate the strain gradient of a liquid-gallium-cooled x-ray monochromator previously tested on an undulator at the Cornell High Energy Synchrotron Source (CHESS). The resulting thermally broadened rocking curves are calculated and compared to experimental data. The calculated rocking curve widths agree to within a few percent of the measured values over the entire current range tested (0 to 60 mA). The thermal strain gradient under the beam footprint varies linearly with the heat flux and the ratio of the thermal expansion coefficient to the thermal conductivity. The strain gradient is insensitive to the heat exchanger properties and the optic geometry. This formulation provides direct insight into the governing parameters, greatly reduces the analysis time, and provides a measure of the ultimate performance of a given monochromator

  12. Data reduction and analysis for the graphite crystal X-ray spectrometer and polarimeter experiment flown aboard OSO-8 spacecraft

    Science.gov (United States)

    Novick, R.

    1980-01-01

    The documentation and software programs developed for the reception, initial processing (quickbook), and production analysis of data obtained by solar X-ray spectroscopy, stellar spectroscopy, and X-ray polarimetry experiments on OSO-8 are listed. The effectiveness and sensitivity of the Bragg crystal scattering instruments used are assessed. The polarization data polarimetric data obtained shows that some X-ray sources are polarized and that a larger polarimeter of this type is required to perform the measurements necessary to fully understand the physics of X-ray sources. The scanning Bragg crystal spectrometer was ideally suited for studying rapidly changing solar conditions. Observations of the Crab Nebula and pulsar, Cyg X-1, Cyg X-2, Cyg X-3, Sco X-1, Cen X-3, and Her X-1 are discussed as well as of 4U1656-53 and 4U1820-30. Evidence was obtained for iron line emission from Cyg X-3.

  13. Purification and preparation of graphite oxide from natural graphite

    Energy Technology Data Exchange (ETDEWEB)

    Panatarani, C., E-mail: c.panatarani@phys.unpad.ac.id; Muthahhari, N.; Joni, I. Made [Instrumentation Systems and Functional Material Processing Laboratory, Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Padjadjaran University, Jl. Raya Bandung-Sumedang KM 21, Jatinangor, 45363, Jawa Barat (Indonesia); Rianto, Anton [Grafindo Nusantara Ltd., Belagio Mall Lantai 2, Unit 0 L3-19, Kawasan Mega Kuningan, Kav. B4 No.3, Jakarta Selatan (Indonesia)

    2016-03-11

    Graphite oxide has attracted much interest as a possible route for preparation of natural graphite in the large-scale production and manipulation of graphene as a material with extraordinary electronic properties. Graphite oxide was prepared by modified Hummers method from purified natural graphite sample from West Kalimantan. We demonstrated that natural graphite is well-purified by acid leaching method. The purified graphite was proceed for intercalating process by modifying Hummers method. The modification is on the reaction time and temperature of the intercalation process. The materials used in the intercalating process are H{sub 2}SO{sub 4} and KMNO{sub 4}. The purified natural graphite is analyzed by carbon content based on Loss on Ignition test. The thermo gravimetricanalysis and the Fouriertransform infrared spectroscopy are performed to investigate the oxidation results of the obtained GO which is indicated by the existence of functional groups. In addition, the X-ray diffraction and energy dispersive X-ray spectroscopy are also applied to characterize respectively for the crystal structure and elemental analysis. The results confirmed that natural graphite samples with 68% carbon content was purified into 97.68 % carbon content. While the intercalation process formed a formation of functional groups in the obtained GO. The results show that the temperature and reaction times have improved the efficiency of the oxidation process. It is concluded that these method could be considered as an important route for large-scale production of graphene.

  14. Synchrotron Radiation Beam Line of Piezoelectric Monochromator Control

    International Nuclear Information System (INIS)

    Ye Shengan; LIU Ping; Zheng Lifang

    2009-01-01

    It describes a Piezo Amplifier and Servo-controller module applied in the LN2-cooled Monochromator control system. The application of RS232 communication based on EPICS software environment and its software are implemented. (authors)

  15. Artificial graphites

    International Nuclear Information System (INIS)

    Maire, J.

    1984-01-01

    Artificial graphites are obtained by agglomeration of carbon powders with an organic binder, then by carbonisation at 1000 0 C and graphitization at 2800 0 C. After description of the processes and products, we show how the properties of the various materials lead to the various uses. Using graphite enables us to solve some problems, but it is not sufficient to satisfy all the need of the application. New carbonaceous material open application range. Finally, if some products are becoming obsolete, other ones are being developed in new applications [fr

  16. Synchrotron X-ray adaptative monochromator: study and realization of a prototype

    International Nuclear Information System (INIS)

    Dezoret, D.

    1995-01-01

    This work presents a study of a prototype of a synchrotron X-ray monochromator. The spectral qualities of this optic are sensitive to the heat loads which are particularly important on third synchrotron generation like ESRF. Indeed, powers generated by synchrotron beams can reach few kilowatts and power densities about a few tens watts per square millimeters. The mechanical deformations of the optical elements of the beamlines issue issue of the heat load can damage their spectral efficiencies. In order to compensate the deformations, wa have been studying the transposition of the adaptive astronomical optics technology to the x-ray field. First, we have considered the modifications of the spectral characteristics of a crystal induced by x-rays. We have established the specifications required to a technological realisation. Then, thermomechanical and technological studies have been required to transpose the astronomical technology to an x-ray technology. After these studies, we have begun the realisation of a prototype. This monochromator is composed by a crystal of silicon (111) bonded on a piezo-electric structure. The mechanical control is a loop system composed by a infrared light, a Shack-Hartmann CDD and wave front analyser. This system has to compensate the deformations of the crystal in the 5 kcV to 60 kcV energy range with a power density of 1 watt per square millimeters. (authors)

  17. A new flexible monochromator setup for quick scanning x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stoetzel, J.; Luetzenkirchen-Hecht, D.; Frahm, R. [Fachbereich C, Physik, Bergische Universitaet Wuppertal, Gaussstr. 20, 42097 Wuppertal (Germany)

    2010-07-15

    A new monochromator setup for quick scanning x-ray absorption spectroscopy in the subsecond time regime is presented. Novel driving mechanics allow changing the energy range of the acquired spectra by remote control during data acquisition for the first time, thus dramatically increasing the flexibility and convenience of this method. Completely new experiments are feasible due to the fact that time resolution, edge energy, and energy range of the acquired spectra can be changed continuously within seconds without breaking the vacuum of the monochromator vessel and even without interrupting the measurements. The advanced mechanics are explained in detail and the performance is characterized with x-ray absorption spectra of pure metal foils. The energy scale was determined by a fast and accurate angular encoder system measuring the Bragg angle of the monochromator crystal with subarcsecond resolution. The Bragg angle range covered by the oscillating crystal can currently be changed from 0 deg. to 3.0 deg. within 20 s, while the mechanics are capable to move with frequencies of up to ca. 35 Hz, leading to ca. 14 ms/spectrum time resolution. A new software package allows performing programmed scan sequences, which enable the user to measure stepwise with alternating parameters in predefined time segments. Thus, e.g., switching between edges scanned with the same energy range is possible within one in situ experiment, while also the time resolution can be varied simultaneously. This progress makes the new system extremely user friendly and efficient to use for time resolved x-ray absorption spectroscopy at synchrotron radiation beamlines.

  18. Higher harmonics suppression in Fe/Si polarizing neutron monochromators

    Energy Technology Data Exchange (ETDEWEB)

    Merkel, D.G., E-mail: merkel.daniel@wigner.mta.hu [Wigner Research Centre for Physics, P.O. Box 49, H-1525, Budapest (Hungary); Nagy, B.; Sajti, Sz.; Szilágyi, E. [Wigner Research Centre for Physics, P.O. Box 49, H-1525, Budapest (Hungary); Kovács-Mezei, R. [Mirrotron Ltd. Konkoly-Thege M. út 29-33, H-1121 Budapest (Hungary); Bottyán, L. [Wigner Research Centre for Physics, P.O. Box 49, H-1525, Budapest (Hungary)

    2013-03-11

    The reflected neutron beam originating from a crystal monochromator contains higher order wavelength contributions. Multilayer mirror structures with various custom reflectivity curves including monochromatization and/or polarization of the neutron beam constitute a challenge in modern neutron optics. In this work, we present the study of three types of magnetron-sputtered Fe/Si layer structures with the purpose of higher harmonic suppression. First, an approximately sinusoidal profile was achieved directly by carefully controlling the evaporation parameters during sputtering that leads to first-Bragg-peak reflectivity and polarizing efficiency of R{sub c}=82% and P=97%, respectively. Second, a random, quasi-periodic distribution of the layer thicknesses was implemented, in which the layer structure of the structure was derived from a fit to a prescribed simulated spectrum. This solution resulted in R{sub c}=92% and P=88%. Third, a structure of Fe/Si layers with rounded scattering length profile was constructed starting with a step-like profile and applying 350 keV Ne{sup +} irradiation of 0, 0.5, 1.0, 2.7 and 27×10{sup 15}/cm{sup 2} fluence. Disregarding the highest fluence, the increasing fluence improved the monochromatization (decreasing the intensity of higher order reflections from a total of 11.1% to 2.2% and that of the first Bragg peak from 80% to 70%) and increased the polarizing efficiency from P=79% to 91%). In none of the above structures was a contrast matching agent added to the constituents.

  19. Multiple wavelength X-ray monochromators

    International Nuclear Information System (INIS)

    Steinmeyer, P.A.

    1992-01-01

    An improved apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The apparatus includes a crystalline diffractor which includes a first set of parallel crystal planes, where each of the planes is spaced a predetermined first distance from one another. The crystalline diffractor also includes a second set of parallel crystal planes inclined at an angle with respect to the first set of crystal planes where each of the planes of the second set of parallel crystal planes is spaced a predetermined second distance from one another. In one embodiment, the crystalline diffractor is comprised of a single crystal. In a second embodiment, the crystalline diffractor is comprised of a stack of two crystals. In a third embodiment, the crystalline diffractor includes a single crystal that is bent for focusing the separate first and second output x-ray radiation wavelengths into separate focal points. 3 figs

  20. A graphite foam reinforced by graphite particles

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.J.; Wang, X.Y.; Guo, L.F.; Wang, Y.M.; Wang, Y.P.; Yu, M.F.; Lau, K.T.T. [DongHua University, Shanghai (China). College of Material Science and Engineering

    2007-11-15

    Graphite foam was obtained after carbonization and graphitization of a pitch foam formed by the pyrolysis of coal tar based mesophase pitch mixed with graphite particles in a high pressure and temperature chamber. The graphite foam possessed high mechanical strength and exceptional thermal conductivity after adding the graphite particles. Experimental results showed that the thermal conductivity of modified graphite foam reached 110W/m K, and its compressive strength increased from 3.7 MPa to 12.5 MPa with the addition of 5 wt% graphite particles. Through the microscopic observation, it was also found that fewer micro-cracks were formed in the cell wall of the modified foam as compared with pure graphite foam. The graphitization degree of modified foam reached 84.9% and the ligament of graphite foam exhibited high alignment after carbonization at 1200{sup o}C for 3 h and graphitization at 3000{sup o}C for 10 min.

  1. A method for evaluating image quality of monochrome and color displays based on luminance by use of a commercially available color digital camera

    Energy Technology Data Exchange (ETDEWEB)

    Tokurei, Shogo, E-mail: shogo.tokurei@gmail.com, E-mail: junjim@med.kyushu-u.ac.jp [Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan and Department of Radiology, Yamaguchi University Hospital, 1-1-1 Minamikogushi, Ube, Yamaguchi 755-8505 (Japan); Morishita, Junji, E-mail: shogo.tokurei@gmail.com, E-mail: junjim@med.kyushu-u.ac.jp [Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582 (Japan)

    2015-08-15

    Purpose: The aim of this study is to propose a method for the quantitative evaluation of image quality of both monochrome and color liquid-crystal displays (LCDs) using a commercially available color digital camera. Methods: The intensities of the unprocessed red (R), green (G), and blue (B) signals of a camera vary depending on the spectral sensitivity of the image sensor used in the camera. For consistent evaluation of image quality for both monochrome and color LCDs, the unprocessed RGB signals of the camera were converted into gray scale signals that corresponded to the luminance of the LCD. Gray scale signals for the monochrome LCD were evaluated by using only the green channel signals of the camera. For the color LCD, the RGB signals of the camera were converted into gray scale signals by employing weighting factors (WFs) for each RGB channel. A line image displayed on the color LCD was simulated on the monochrome LCD by using a software application for subpixel driving in order to verify the WF-based conversion method. Furthermore, the results obtained by different types of commercially available color cameras and a photometric camera were compared to examine the consistency of the authors’ method. Finally, image quality for both the monochrome and color LCDs was assessed by measuring modulation transfer functions (MTFs) and Wiener spectra (WS). Results: The authors’ results demonstrated that the proposed method for calibrating the spectral sensitivity of the camera resulted in a consistent and reliable evaluation of the luminance of monochrome and color LCDs. The MTFs and WS showed different characteristics for the two LCD types owing to difference in the subpixel structure. The MTF in the vertical direction of the color LCD was superior to that of the monochrome LCD, although the WS in the vertical direction of the color LCD was inferior to that of the monochrome LCD as a result of luminance fluctuations in RGB subpixels. Conclusions: The authors

  2. Attenuation of thermal neutron through graphite

    International Nuclear Information System (INIS)

    Adib, M.; Ismaail, H.; Fathaallah, M.; Abbas, Y.; Habib, N.; Wahba, M.

    2004-01-01

    Calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of graphite temperature and crystalline from for neutron energies from 1 me V< E<10 eV were carried out. Computer programs have been developed which allow calculation for the graphite hexagonal closed-pack structure in its polycrystalline form and pyrolytic one. I The calculated total cross-section for polycrystalline graphite were compared with the experimental values. An overall agreement is indicated between the calculated values and experimental ones. Agreement was also obtained for neutron cross-section measured for oriented pyrolytic graphite at room and liquid nitrogen temperatures. A feasibility study for use of graphite in powdered form as a cold neutron filter is details. The calculated attenuation of thermal neutrons through large mosaic pyrolytic graphite show that such crystals can be used effectively as second order filter of thermal neutron beams and that cooling improve their effectiveness

  3. Periodic magnetic field as a polarized and focusing thermal neutron spectrometer and monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Cremer, J. T.; Williams, D. L.; Fuller, M. J.; Gary, C. K.; Piestrup, M. A. [Adelphi Technology, Inc., 2003 East Bayshore Rd., Redwood City, California 94063 (United States); Pantell, R. H.; Feinstein, J. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Flocchini, R. G.; Boussoufi, M.; Egbert, H. P.; Kloh, M. D.; Walker, R. B. [Davis McClellan Nuclear Radiation Center, University of California, McClellan, California 95652 (United States)

    2010-01-15

    A novel periodic magnetic field (PMF) optic is shown to act as a prism, lens, and polarizer for neutrons and particles with a magnetic dipole moment. The PMF has a two-dimensional field in the axial direction of neutron propagation. The PMF alternating magnetic field polarity provides strong gradients that cause separation of neutrons by wavelength axially and by spin state transversely. The spin-up neutrons exit the PMF with their magnetic spins aligned parallel to the PMF magnetic field, and are deflected upward and line focus at a fixed vertical height, proportional to the PMF period, at a downstream focal distance that increases with neutron energy. The PMF has no attenuation by absorption or scatter, as with material prisms or crystal monochromators. Embodiments of the PMF include neutron spectrometer or monochromator, and applications include neutron small angle scattering, crystallography, residual stress analysis, cross section measurements, and reflectometry. Presented are theory, experimental results, computer simulation, applications of the PMF, and comparison of its performance to Stern-Gerlach gradient devices and compound material and magnetic refractive prisms.

  4. Periodic magnetic field as a polarized and focusing thermal neutron spectrometer and monochromator.

    Science.gov (United States)

    Cremer, J T; Williams, D L; Fuller, M J; Gary, C K; Piestrup, M A; Pantell, R H; Feinstein, J; Flocchini, R G; Boussoufi, M; Egbert, H P; Kloh, M D; Walker, R B

    2010-01-01

    A novel periodic magnetic field (PMF) optic is shown to act as a prism, lens, and polarizer for neutrons and particles with a magnetic dipole moment. The PMF has a two-dimensional field in the axial direction of neutron propagation. The PMF alternating magnetic field polarity provides strong gradients that cause separation of neutrons by wavelength axially and by spin state transversely. The spin-up neutrons exit the PMF with their magnetic spins aligned parallel to the PMF magnetic field, and are deflected upward and line focus at a fixed vertical height, proportional to the PMF period, at a downstream focal distance that increases with neutron energy. The PMF has no attenuation by absorption or scatter, as with material prisms or crystal monochromators. Embodiments of the PMF include neutron spectrometer or monochromator, and applications include neutron small angle scattering, crystallography, residual stress analysis, cross section measurements, and reflectometry. Presented are theory, experimental results, computer simulation, applications of the PMF, and comparison of its performance to Stern-Gerlach gradient devices and compound material and magnetic refractive prisms.

  5. Development of an imaging VUV monochromator in normal incidence region

    Energy Technology Data Exchange (ETDEWEB)

    Koog, Joong-San

    1996-07-01

    This paper describes a development of the two-dimensional imaging monochromator system. A commercial normal incidence monochromator working on off-Rowland circle mounting is used for this purpose. The imaging is achieved with utilizing the pinhole camera effect created by an entrance slit of limited height. The astigmatism in the normal incidence mounting is small compared with a grazing incidence mount, but has a finite value. The point is that for near normal incidence, the vertical focusing with a concave grating is produced at outside across the exit slit. Therefore, by putting a 2-D detector at the position away from the exit slit ({approx}30 cm), a one-to-one correspondence between the position of a point on the detector and where it originated in the source is accomplished. This paper consists of (1) the principle and development of the imaging monochromator using the off-Rowland mounting, including the 2-D detector system, (2) a computer simulation by ray tracing for investigations of the imaging properties of imaging system, and aberration from the spherical concave grating on the exit slit, (3) the plasma light source (TPD-S) for the test experiments, (4) Performances of the imaging monochromator system on the spatial resolution and sensitivity, and (5) the use of this system for diagnostic studies on the JIPP T-IIU tokamak. (J.P.N.)

  6. Modifications to improve entrance slit thermal stability for grasshopper monochromators

    Science.gov (United States)

    Wallace, Daniel J.; Rogers, Gregory C.; Crossley, Sherry L.

    1994-08-01

    As new monochromators are designed for high-flux storage rings, computer modeling and thermal engineering can be done to process increased heat loads and achieve mechanical stability. Several older monochromators, such as the Mark 2 and Mark 5 Grasshopper monochromators, which were designed in 1974, have thermal instabilities in their entrance slit mechanisms. The Grasshoppers operating with narrow slits experience closure of the entrance slit from thermal expansion. In extreme cases, the thermal expansion of the precision components has caused permanent mechanical damage, leaving the slit uncalibrated and/or inoperable. For the Mark 2 and Mark 5 Grasshopper monochromators at the Synchrotron Radiation Center, the original 440 stainless steel entrance slit jaws were retrofitted with an Invar (low expansion Fe, Ni alloy) slit jaw. To transfer the heat from the critical components, two flexible heat straps of Cu were attached. These changes allow safe operation with a 10 μm entrance slit width where the previous limit was 30 μm. After an initial 2 min equilibration, the slit remains stable to 10%, with 100 mA of beam current. Additional improvements in slit thermal stability are planned for a third Grasshopper.

  7. Development of an imaging VUV monochromator in normal incidence region

    International Nuclear Information System (INIS)

    Koog, Joong-San.

    1996-07-01

    This paper describes a development of the two-dimensional imaging monochromator system. A commercial normal incidence monochromator working on off-Rowland circle mounting is used for this purpose. The imaging is achieved with utilizing the pinhole camera effect created by an entrance slit of limited height. The astigmatism in the normal incidence mounting is small compared with a grazing incidence mount, but has a finite value. The point is that for near normal incidence, the vertical focusing with a concave grating is produced at outside across the exit slit. Therefore, by putting a 2-D detector at the position away from the exit slit (∼30 cm), a one-to-one correspondence between the position of a point on the detector and where it originated in the source is accomplished. This paper consists of 1) the principle and development of the imaging monochromator using the off-Rowland mounting, including the 2-D detector system, 2) a computer simulation by ray tracing for investigations of the imaging properties of imaging system, and aberration from the spherical concave grating on the exit slit, 3) the plasma light source (TPD-S) for the test experiments, 4) Performances of the imaging monochromator system on the spatial resolution and sensitivity, and 5) the use of this system for diagnostic studies on the JIPP T-IIU tokamak. (J.P.N.)

  8. Thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  9. Development of an automated scanning monochromator for sensitivity calibration of the MUSTANG instrument

    Science.gov (United States)

    Rivers, Thane D.

    1992-06-01

    An Automated Scanning Monochromator was developed using: an Acton Research Corporation (ARC) Monochromator, Ealing Photomultiplier Tube and a Macintosh PC in conjunction with LabVIEW software. The LabVIEW Virtual Instrument written to operate the ARC Monochromator is a mouse driven user friendly program developed for automated spectral data measurements. Resolution and sensitivity of the Automated Scanning Monochromator System were determined experimentally. The Automated monochromator was then used for spectral measurements of a Platinum Lamp. Additionally, the reflectivity curve for a BaSO4 coated screen has been measured. Reflectivity measurements indicate a large discrepancy with expected results. Further analysis of the reflectivity experiment is required for conclusive results.

  10. Bridged graphite oxide materials

    Science.gov (United States)

    Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

    2010-01-01

    Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

  11. An elastic, low-background vertical focusing element for a doubly focusing neutron monochromator

    International Nuclear Information System (INIS)

    Smee, Stephen A.; Brand, Paul C.; Barry, Dwight D.; Broholm, Collin L.; Anand, Dave K.

    2001-01-01

    A novel, variable radius of curvature, device for the focusing of neutrons is presented. This elastic element consists of a thin variable thickness, constant width, aluminum blade to which diffracting crystals can be attached. When buckled, the blade assumes a circular focal shape, the radius of which is easily controlled by the relative displacement of supporting pivots. Precision electromechanical and optical measurements show that the slope of the buckled blade conforms to a circular arc to within 0.15 degree sign for radii in the range 900 mm< R<10 000 mm. This easily scalable, low mass mechanism is well suited for use in a focusing neutron monochromator, as the parasitic scattering typically associated with traditional lead screw and lever mechanisms is greatly reduced

  12. Performance of synchrotron x-ray monochromators under heat load: How reliable are the predictions?

    International Nuclear Information System (INIS)

    Freund, A.K.; Hoszowska, J.; Migliore, J.-S.; Mocella, V.; Zhang, L.; Ferrero, C.

    2000-01-01

    With the ongoing development of insertion devices with smaller gaps the heat load generated by modern synchrotron sources increases continuously. To predict the overall performance of experiments on beam lines it is of crucial importance to be able to predict the efficiency of x-ray optics and in particular that of crystal monochromators. We report on a detailed comparison between theory and experiment for a water-cooled silicon crystal exposed to bending magnet radiation of up to 237 W total power and 1.3 W/mm2 power density. The thermal deformation has been calculated by the code ANSYS and its output has been injected into a finite difference code based on the Takagi-Taupin diffraction theory for distorted crystals. Several slit settings, filters and reflection orders were used to vary the geometrical conditions and the x-ray penetration depth in the crystal. In general, good agreement has been observed between the calculated and the observed values for the rocking curve width

  13. Process for purifying graphite

    International Nuclear Information System (INIS)

    Clausius, R.A.

    1985-01-01

    A process for purifying graphite comprising: comminuting graphite containing mineral matter to liberate at least a portion of the graphite particles from the mineral matter; mixing the comminuted graphite particles containing mineral matter with water and hydrocarbon oil to form a fluid slurry; separating a water phase containing mineral matter and a hydrocarbon oil phase containing grahite particles; and separating the graphite particles from the hydrocarbon oil to obtain graphite particles reduced in mineral matter. Depending upon the purity of the graphite desired, steps of the process can be repeated one or more times to provide a progressively purer graphite

  14. The in-focus variable line spacing plane grating monochromator

    International Nuclear Information System (INIS)

    Reininger, R.

    2011-01-01

    The in-focus variable line spacing plane grating monochromator is based on only two plane optical elements, a variable line spacing plane grating and a plane pre-mirror that illuminates the grating at the angle of incidence that will focus the required photon energy. A high throughput beamline requires only a third optical element after the exit slit, an aberration corrected elliptical toroid. Since plane elements can be manufactured with the smallest figure errors, this monochromator design can achieve very high resolving power. Furthermore, this optical design can correct the deformations induced by the heat load on the optics along the dispersion plane. This should allow obtaining a resolution of 10 meV at 1 keV with currently achievable figure errors on plane optics. The position of the photon source when an insertion device center is not located at the center of the straight section, a common occurrence in new insertion device beamlines, is investigated.

  15. Recovery, modernization and computerization of the monochromator MDR-23

    International Nuclear Information System (INIS)

    Miranda, L. J.

    2012-01-01

    For use in the Optics Laboratory, newly created in the CEADEN, one of the necessary equipment is the Monochromator MDR-23, which was necessary for recovery, modernization (replacing the power supply and control) and computerization by designing a VI (virtual instrument) to control stepper motor through a PC using Lab VIEW 7.1 that allows users to select the address mode, the number of steps and the engine speed and give the initial value of the position and limits the range of the monochromator to start working with it. The principle of operation of the program is done in detail to facilitate understanding of how to operate and use the graphical programming designed and achieve efficient use of equipment. (Author)

  16. High temperature soldering of graphite

    International Nuclear Information System (INIS)

    Anikin, L.T.; Kravetskij, G.A.; Dergunova, V.S.

    1977-01-01

    The effect is studied of the brazing temperature on the strength of the brazed joint of graphite materials. In one case, iron and nickel are used as solder, and in another, molybdenum. The contact heating of the iron and nickel with the graphite has been studied in the temperature range of 1400-2400 ged C, and molybdenum, 2200-2600 deg C. The quality of the joints has been judged by the tensile strength at temperatures of 2500-2800 deg C and by the microstructure. An investigation into the kinetics of carbon dissolution in molten iron has shown that the failure of the graphite in contact with the iron melt is due to the incorporation of iron atoms in the interbase planes. The strength of a joint formed with the participation of the vapour-gas phase is 2.5 times higher than that of a joint obtained by graphite recrystallization through the carbon-containing metal melt. The critical temperatures are determined of graphite brazing with nickel, iron, and molybdenum interlayers, which sharply increase the strength of the brazed joint as a result of the formation of a vapour-gas phase and deposition of fine-crystal carbon

  17. Spectrum scanning of monochromator by microcontroller ATtiny 2313

    International Nuclear Information System (INIS)

    Veklich, A.M.; Boretskij, V.F.; Kleshich, M.M.; Fesenko, S.O.

    2009-01-01

    The results of interface developing on the base of Atmel microcontroller ATtiny 2313 are shown. This device is dedicated to the spectrum scanning of monochromators by the step motor. The design principles of motor control scheme are analyzed. The original algorithm of microcontroller program was suggested and realized. The principal performance availability of the USB interface for the purpose of the device control by the personal computer is considered.

  18. Mechanism of spark generation from Japanese toy firework (senko-hanabi). ; Structural-Oxidizing reaction of micro graphite crystals in molten K sub 2 Sn. Senko hanabi no jikkenteki kosatsu. ; Yoyu K sub 2 Sn chu no sekiboku bikessho no kozo teki sanka hanno

    Energy Technology Data Exchange (ETDEWEB)

    Ito, H. (The University, of Tokyo, Tokyo (Japan))

    1991-12-20

    Considerations were given on the spark generating mechanism of graphite particles in molten salt polysulfide through experiments on Japanese sparklers. The firework composition mixed consisted of two kinds: KNO{sub 3}, S, amorphous carbons, charcoal and lamp black, and K{sub 2}CO{sub 3}, S, charcoal and lamp black. The main constituent in fire balls is molten salt polysulfide. The O{sub 2} generated from combustion oxidizes C and S, whereas the generated K{sub 2}CO{sub 3} reacts with S to produce K{sub 2}Sn. In the KNO{sub 3} system, the calorific power reaches the maximum with lamp black contained at 10-15%. This is thought because the K{sup +} expands the space between the graphite crystal layers making the oxidation to take place more easily into their inner sides. On the one hand, the calorific power reduced with the lamp black at more than 16% would be because the lamp black clogging the crystalline spaces restricting the oxidation. It is thought that condensation and decomposition of micro graphite crystals occur simultaneously in the fire balls. It is also believed that the micro graphite crystals jumped out as a result of gas pressure from inside the crystals generated with the progress of oxidation break off at once because of the resistance of air together with the effect of the K{sup +} in the salt polysulfide (mutual separation of each layer). 9 refs., 6 figs., 1 tab.

  19. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  20. Wake monochromator in asymmetric and symmetric Bragg and Laue geometry for self-seeding the European X-ray FEL

    International Nuclear Information System (INIS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni; Serkez, Svitozar; Tolkiehn, Martin

    2013-01-01

    We discuss the use of self-seeding schemes with wake monochromators to produce TW power, fully coherent pulses for applications at the dedicated bio-imaging beamline at the European X-ray FEL, a concept for an upgrade of the facility beyond the baseline previously proposed by the authors. We exploit the asymmetric and symmetric Bragg and Laue reflections (sigma polarization) in diamond crystal. Optimization of the bio-imaging beamline is performed with extensive start-to-end simulations, which also take into account effects such as the spatio-temporal coupling caused by the wake monochromator. The spatial shift is maximal in the range for small Bragg angles. A geometry with Bragg angles close to π/2 would be a more advantageous option from this viewpoint, albeit with decrease of the spectral tunability. We show that it will be possible to cover the photon energy range from 3 keV to 13 keV by using four different planes of the same crystal with one rotational degree of freedom.

  1. Wake monochromator in asymmetric and symmetric Bragg and Laue geometry for self-seeding the European X-ray FEL

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni; Serkez, Svitozar; Tolkiehn, Martin [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2013-01-15

    We discuss the use of self-seeding schemes with wake monochromators to produce TW power, fully coherent pulses for applications at the dedicated bio-imaging beamline at the European X-ray FEL, a concept for an upgrade of the facility beyond the baseline previously proposed by the authors. We exploit the asymmetric and symmetric Bragg and Laue reflections (sigma polarization) in diamond crystal. Optimization of the bio-imaging beamline is performed with extensive start-to-end simulations, which also take into account effects such as the spatio-temporal coupling caused by the wake monochromator. The spatial shift is maximal in the range for small Bragg angles. A geometry with Bragg angles close to {pi}/2 would be a more advantageous option from this viewpoint, albeit with decrease of the spectral tunability. We show that it will be possible to cover the photon energy range from 3 keV to 13 keV by using four different planes of the same crystal with one rotational degree of freedom.

  2. A double-multilayer monochromator using a modular design for the Advanced Photon Source

    International Nuclear Information System (INIS)

    Shu, D.; Yun, W.; Lai, B.; Barraza, J.; Kuzay, T.M.

    1994-01-01

    A novel double-multilayer monochromator has been designed for the Advanced Photon Source X-ray undulator beamline at Argonne National Laboratory. The monochromator consists of two ultra high-vacuum (UHV) compatible modular vessels, each with a sine-bar driving structure and a water-cooled multilayer holder. A high precision Y-Z stage is used to provide compensating motion for the second multilayer from outside the vacuum chamber so that the monochromator can fix the output monochromatic beam direction and angle during the energy scan in a narrow range. The design details for this monochromator are presented in this paper

  3. GRAPHITIZATION OF METASEDIMENTARY ROCKS IN THE WESTERN KONYA

    Directory of Open Access Journals (Sweden)

    Hüseyin KURT

    2000-01-01

    Full Text Available The Paleozoic-Mesozoic metasedimentary rocks in the study area are metacarbonate, metachert, metapelite, metasandstone and metaconglomerate. Graphite layers are 1cm to 2m thick, extend laterally for tens of meters and are intercalated with metasedimentary rocks. Generally, the graphite is black in color, with a well developed cleavage which is concordant with the cleavage of the host rocks. In addition, the crystal and flake graphites formed in metasedimentary rocks are mostly aligned parallel to the cleavage planes. These metamorphic rocks are subjected to shearing and granulation providing structural control for the development of graphite. It was probably this phenomenon that first led to emphasize the relationship between graphite and metasedimentary rocks. Graphite mineralization has been controlled by bedding, microfractures and granulations. Briefly, the metamorphism has converted carbonaceous matter into graphite .

  4. Huge magnetoresistance effect of highly oriented pyrolytic graphite

    International Nuclear Information System (INIS)

    Du Youwei; Wang Zhiming; Ni Gang; Xing Dingyu; Xu Qingyu

    2004-01-01

    Graphite is a quasi-two-dimensional semimetal. However, for usual graphite the magnetoresistance is not so high due to its small crystal size and no preferred orientation. Huge positive magnetoresistance up to 85300% at 4.2 K and 4950% at 300 K under 8.15 T magnetic field was found in highly oriented pyrolytic graphite. The mechanism of huge positive magnetoresistance is not only due to ordinary magnetoresistance but also due to magnetic-field-driven semimetal-insulator transition

  5. Optical design of grazing incidence toroidal grating monochromator

    International Nuclear Information System (INIS)

    Pouey, M.; Howells, M.R.; Takacs, P.Z.

    1982-01-01

    Design rules using geometrical optics and physical optics associated with the phase balancing method are discussed for stigmatic toroidal grazing incidence monochromators. To determine the optical performance of devices involving mirrirs and/or gratings, ray tracing programs using exact geometry are quite widely used. It is then desirable to have some way to infer the practical performance of an instrument from a spot diagram created by tracing a limited number of rays. We propose a first approach to this problem involving an estimation of the geometrical intensity distribution in the image plane and the corresponding line spread function. (orig.)

  6. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

    2015-07-15

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  7. Superconductivity in graphite intercalation compounds

    International Nuclear Information System (INIS)

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P.M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

    2015-01-01

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC 6 and YbC 6 in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition

  8. Storage of cold and thermal neutrons with perfect crystals at the pulsed source

    International Nuclear Information System (INIS)

    Jericha, E.

    1996-12-01

    The possibility of storing cold neutrons by sequential Bragg reflections between two parallel perfect crystal plates in backscattering geometry has been implemented as the parasitic instrument VESTA at the pulsed neutron source ISIS. Filling the neutrons into and releasing them from the storage cavity is accomplished by applying a short-pulsed magnetic field at the crystal plates. The method takes advantage of the conservation of the axial component of the neutron wave vector after Bragg reflection and its Zeeman shift in a magnetic field. The setup at ISIS is presented where a monochromatic neutron beam with wavelength 6.27 A and 2.9 x 10 4 n/scm 2 flux is taken out of the neutron guide leading to the IRIS backscattering spectrometer by a pyrolytic graphite crystal monochromator. The longest storage period obtained with the setup was 2.655 s which corresponds to 1574 consecutive Bragg reflections and a distance traveled of 1675 n. The measurements are analyzed by heuristic methods developed for neutron storage experiments. The apparatus is seen as a passive resonator system and characteristics like stored neutron intensity, the efficiency of the storage process, the probability to remain in the system, the mirror reflectivity, the dispersion of the stored distribution, the penetration depth of a neutron into a crystal mirror and the figure of merit of the resonator system are discussed. Monte Carlo simulations of the extracted beam and of the stored neutron distribution were performed to deepen the understanding of the experimental results. (author)

  9. Numerical simulation of distorted crystal Darwin width

    International Nuclear Information System (INIS)

    Wang Li; Xu Zhongmin; Wang Naxiu

    2012-01-01

    A new numerical simulation method according to distorted crystal optical theory was used to predict the direct-cooling crystal monochromator optical properties(crystal Darwin width) in this study. The finite element analysis software was used to calculate the deformed displacements of DCM crystal and to get the local reciprocal lattice vector of distorted crystal. The broadening of direct-cooling crystal Darwin width in meridional direction was estimated at 4.12 μrad. The result agrees well with the experimental data of 5 μrad, while it was 3.89 μrad by traditional calculation method of root mean square (RMS) of the slope error in the center line of footprint. The new method provides important theoretical support for designing and processing of monochromator crystal for synchrotron radiation beamline. (authors)

  10. Three-energy focusing Laue monochromator for the diamond light source x-ray pair distribution function beamline I15-1

    Energy Technology Data Exchange (ETDEWEB)

    Sutter, John P., E-mail: john.sutter@diamond.ac.uk; Chater, Philip A.; Hillman, Michael R.; Keeble, Dean S.; Wilhelm, Heribert [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE (United Kingdom); Tucker, Matt G. [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE (United Kingdom); ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX (United Kingdom)

    2016-07-27

    The I15-1 beamline, the new side station to I15 at the Diamond Light Source, will be dedicated to the collection of atomic pair distribution function data. A Laue monochromator will be used consisting of three silicon crystals diffracting X-rays at a common Bragg angle of 2.83°. The crystals use the (1 1 1), (2 2 0), and (3 1 1) planes to select 40, 65, and 76 keV X-rays, respectively, and will be bent meridionally to horizontally focus the selected X-rays onto the sample. All crystals will be cut to the same optimized asymmetry angle in order to eliminate image broadening from the crystal thickness. Finite element calculations show that the thermal distortion of the crystals will affect the image size and bandpass.

  11. Three-energy focusing Laue monochromator for the diamond light source x-ray pair distribution function beamline I15-1

    International Nuclear Information System (INIS)

    Sutter, John P.; Chater, Philip A.; Hillman, Michael R.; Keeble, Dean S.; Wilhelm, Heribert; Tucker, Matt G.

    2016-01-01

    The I15-1 beamline, the new side station to I15 at the Diamond Light Source, will be dedicated to the collection of atomic pair distribution function data. A Laue monochromator will be used consisting of three silicon crystals diffracting X-rays at a common Bragg angle of 2.83°. The crystals use the (1 1 1), (2 2 0), and (3 1 1) planes to select 40, 65, and 76 keV X-rays, respectively, and will be bent meridionally to horizontally focus the selected X-rays onto the sample. All crystals will be cut to the same optimized asymmetry angle in order to eliminate image broadening from the crystal thickness. Finite element calculations show that the thermal distortion of the crystals will affect the image size and bandpass.

  12. 78 FR 32424 - Notice of Issuance of Final Determination Concerning Monochrome Laser Printers

    Science.gov (United States)

    2013-05-30

    ... 5200DNG/SP 5210DNG monochrome laser printers for purposes of U.S. Government procurement? LAW AND ANALYSIS... procurement purposes is the United States. Notice of this final determination will be given in the Federal... of certain monochrome laser printers. Based upon the facts presented, CBP has concluded in the final...

  13. Phonon scattering in graphite

    International Nuclear Information System (INIS)

    Wagner, P.

    1976-04-01

    Effects on graphite thermal conductivities due to controlled alterations of the graphite structure by impurity addition, porosity, and neutron irradiation are shown to be consistent with the phonon-scattering formulation 1/l = Σ/sub i equals 1/sup/n/ 1/l/sub i/. Observed temperature effects on these doped and irradiated graphites are also explained by this mechanism

  14. Computer Package for Graphite Total Cross-Section Calculations

    International Nuclear Information System (INIS)

    Adib, M.; Fathalla, M.

    2008-01-01

    An additive formula is given which allows calculating the contribution of the total neut.>neutron transmission through crystalline graphite. The formula takes into account the graphite form of poly or pyrolytic crystals and its parameters. Computer package Graphite has been designed in order to provide the required calculations in the neutron energy range from 0.1 MeV to 10 eV. The package includes three codes: PCG (Polycrystalline Graphite), PG (Pyrolytic Graphite) and HOPG (Highly Oriented Pyrolytic Graphite) for calculating neutron transmission through fine graphite powder (polycrystalline), neutron transmission and removal coefficient of PG crystal in terms of its mosaic spread for neutrons incident along its c-axis and the transmission of neutrons incident on HOPG crystal at different angles, respectively. For comparison of the experimental neutron transmission data with the calculated values, the program takes into consideration the effect of both wavelength and neutron beam divergence in either 2 constant wavelength spread mode (δλ=constant) or constant wavelength resolution mode (δλ/λ=constant). In order to check the validity for application of computer package Graphite in cross-section calculations, a comparison between calculated values with the available experimental data were carried out. An overall agreement is indicated with an accuracy sufficient for determine the neutron transmission characteristics

  15. Biological monochromator with a high flux in the visible spectrum

    International Nuclear Information System (INIS)

    Andre, M.; Guerin de Montgareuil, P.

    1965-01-01

    The object is to carry out research into photosynthesis using energetic illuminations similar to those employed with white light studies. The limitations are due mainly to the source. A comparison of various possible solutions has led to the choice of the sun used in conjunction with 4 large gratings. In an intermediate stage, a description is given of a medium-aperture monochromator with a 3 kW xenon arc and a single grating. With this set-up it is possible to obtain the following performance, given as an example; energy illumination, 1.3 mW/cm 2 over a surface of 50 cm 2 and for a bandwidth at half-height of 50 Angstroms. (authors) [fr

  16. Enhanced generation of hydroxyl radicals on well-crystallized molybdenum trioxide/nano-graphite anode with sesame cake-like structure for degradation of bio-refractory antibiotic.

    Science.gov (United States)

    Tang, Bo; Du, Jiannan; Feng, Qingmao; Zhang, Jiaqi; Wu, Dan; Jiang, Xiankai; Dai, Ying; Zou, Jinlong

    2018-05-01

    Anodic electro-catalysis oxidation is a highly effective way to solve the pollution problem of antibiotics in wastewater and receiving water bodies. In this study, for the first time, molybdenum trioxide/Nano-graphite (MoO 3 /Nano-G) composites are synthesized as anodic catalysts by a surfactant-assisted solvothermal method followed by low-temperature calcination. The effects of the proportion of MoO 3 to Nano-G (10, 30 and 50%) on the properties of composites are investigated through structural characterizations and electrochemical measurements. Results indicate that MoO 3 (30)/Nano-G electrode displays the electro-catalysis degradation efficiency of 99.9% towards ceftazidime, which is much higher than those of Nano-G (46.7%) and dimensionally stable anode (69.2%). The degradation mechanism for ceftazidime is studied by investigating the yields and kinds of active species. Results show that all of the OH, O 2- and H 2 O 2 are responsible for the electro-catalytic degradation process, and the produced OH radicals are the major active species for ceftazidime degradation. The synergistic effects between MoO 3 and Nano-G greatly contribute to the activation of H 2 O molecules to produce OH, meanwhile the special sesame cake-like structure facilitates to the exposure of contaminants to OH on active sites to enhance the degradation efficiency. These results suggest that MoO 3 /Nano-G electrodes can be considered as the promising catalysts for treating bio-refractory organic wastewater. Copyright © 2018 Elsevier Inc. All rights reserved.

  17. Synthesis, spectra, and the crystal structure of α-(3,3-dimethyl-3,4-dihydroisoquinolyl-1)-hydroxyiminoacetamide

    International Nuclear Information System (INIS)

    Sokol, V.I.; Davydov, V.V.; Kartashova, I.V.; Zaitsev, B.E.; Shklyaev, Yu.V.; Ryabov, M.A.; Sergienko, V.S.

    1996-01-01

    α-(3,3-Dimethyl-3,4-dihydroisoquinolyl-1)-hydroxyiminoacetamide (I) was synthesized, and its x-ray structure analysis was performed (Enraf-Nonius CAD-4 diffractometer; MoKα radiation; graphite monochromator; θ/2θ scan; 2θmax=56 deg. ; 2496 reflections with I≥2σ(I); and R=0.038). Crystals of I are monoclinic; a=11.67(1), b=8.365(3), and c=15.22(2) A; β=107.7(1) deg.; V=1415.2(2) A 3; ρ(calc)=1.236 g/cm3; Z=4; and sp. gr. P21/n. I crystallizes as a monohydrate, and its formula is C13H15N3O2·H2O. In a crystal, I exists in a azomethineoxime tautomeric form. The planes of amideoxime and dihydroisoquinoline moieties are nearly orthogonal to each other. According to IR and electronic spectra, when passing from crystal to solution the conformation of I changes only slightly. An effect of water molecules on the molecular structure of I is discussed

  18. The development of a 200 kV monochromated field emission electron source

    Energy Technology Data Exchange (ETDEWEB)

    Mukai, Masaki, E-mail: mmukai@jeol.co.jp [JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558 (Japan); Kim, Judy S. [University of Oxford, Department of Materials, Parks Road, Oxford, OX1 3PH (United Kingdom); Omoto, Kazuya; Sawada, Hidetaka; Kimura, Atsushi; Ikeda, Akihiro; Zhou, Jun; Kaneyama, Toshikatsu [JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558 (Japan); Young, Neil P.; Warner, Jamie H.; Nellist, Peter D.; Kirkland, Angus I. [University of Oxford, Department of Materials, Parks Road, Oxford, OX1 3PH (United Kingdom)

    2014-05-01

    We report the development of a monochromator for an intermediate-voltage aberration-corrected electron microscope suitable for operation in both STEM and TEM imaging modes. The monochromator consists of two Wien filters with a variable energy selecting slit located between them and is located prior to the accelerator. The second filter cancels the energy dispersion produced by the first filter and after energy selection forms a round monochromated, achromatic probe at the specimen plane. The ultimate achievable energy resolution has been measured as 36 meV at 200 kV and 26 meV at 80 kV. High-resolution Annular Dark Field STEM images recorded using a monochromated probe resolve Si–Si spacings of 135.8 pm using energy spreads of 218 meV at 200 kV and 217 meV at 80 kV respectively. In TEM mode an improvement in non-linear spatial resolution to 64 pm due to the reduction in the effects of partial temporal coherence has been demonstrated using broad beam illumination with an energy spread of 134 meV at 200 kV. - Highlights: • Monochromator for 200 kV aberration corrected TEM and STEM was developed. • Monochromator produces monochromated and achromatic probe at specimen plane. • Ultimate energy resolution was measured to be 36 meV at 200 kV and 26 meV at 80 kV. • Atomic resolution STEM images were recorded using monochromated electron probe. • Improvements of TEM resolution were confirmed using monochromated illumination.

  19. The development of a 200 kV monochromated field emission electron source

    International Nuclear Information System (INIS)

    Mukai, Masaki; Kim, Judy S.; Omoto, Kazuya; Sawada, Hidetaka; Kimura, Atsushi; Ikeda, Akihiro; Zhou, Jun; Kaneyama, Toshikatsu; Young, Neil P.; Warner, Jamie H.; Nellist, Peter D.; Kirkland, Angus I.

    2014-01-01

    We report the development of a monochromator for an intermediate-voltage aberration-corrected electron microscope suitable for operation in both STEM and TEM imaging modes. The monochromator consists of two Wien filters with a variable energy selecting slit located between them and is located prior to the accelerator. The second filter cancels the energy dispersion produced by the first filter and after energy selection forms a round monochromated, achromatic probe at the specimen plane. The ultimate achievable energy resolution has been measured as 36 meV at 200 kV and 26 meV at 80 kV. High-resolution Annular Dark Field STEM images recorded using a monochromated probe resolve Si–Si spacings of 135.8 pm using energy spreads of 218 meV at 200 kV and 217 meV at 80 kV respectively. In TEM mode an improvement in non-linear spatial resolution to 64 pm due to the reduction in the effects of partial temporal coherence has been demonstrated using broad beam illumination with an energy spread of 134 meV at 200 kV. - Highlights: • Monochromator for 200 kV aberration corrected TEM and STEM was developed. • Monochromator produces monochromated and achromatic probe at specimen plane. • Ultimate energy resolution was measured to be 36 meV at 200 kV and 26 meV at 80 kV. • Atomic resolution STEM images were recorded using monochromated electron probe. • Improvements of TEM resolution were confirmed using monochromated illumination

  20. Construction and characterization of the fringe field monochromator for a field emission gun

    Science.gov (United States)

    Mook; Kruit

    2000-04-01

    Although some microscopes have shown stabilities sufficient to attain below 0.1 eV spectral resolution in high-resolution electron energy loss spectroscopy, the intrinsic energy width of the high brightness source (0.3-0.6 eV) has been limiting the resolution. To lower the energy width of the source to 50 meV without unnecessary loss of brightness, a monochromator has been designed consisting of a short (4 mm) fringe field Wien filter and a 150 nm energy selection slit (nanoslit) both to be incorporated in the gun area of the microscope. A prototype has been built and tested in an ultra-high-vacuum setup (10(-9) mbar). The monochromator, operating on a Schottky field emission gun, showed stable and reproducible operation. The nanoslits did not contaminate and the structure remained stable. By measuring the current through the slit structure a direct image of the beam in the monochromator could be attained and the monochromator could be aligned without the use of a microscope. Good dispersed imaging conditions were found indicating an ultimate resolution of 55 meV. A Mark II fringe field monochromator (FFM) was designed and constructed compatible with the cold tungsten field emitter of the VG scanning transmission microscope. The monochromator was incorporated in the gun area of the microscope at IBM T.J. Watson research center, New York. The monochromator was aligned on 100 kV and the energy distribution measured using the monochromator displayed a below 50 meV filtering capability. The retarding Wien filter spectrometer was used to show a 61 meV EELS system resolution. The FFM is shown to be a monochromator which can be aligned without the use of the electron microscope. This makes it directly applicable for scanning transmission microscopy and low-voltage scanning electron microscopy, where it can lower the resolution loss which is caused by chromatic blur of the spot.

  1. Optimization of Monochromated TEM for Ultimate Resolution Imaging and Ultrahigh Resolution Electron Energy Loss Spectroscopy

    KAUST Repository

    Lopatin, Sergei; Cheng, Bin; Liu, Wei-Ting; Tsai, Meng-Lin; He, Jr-Hau; Chuvilin, Andrey

    2017-01-01

    The performance of a monochromated transmission electron microscope with Wien type monochromator is optimized to achieve an extremely narrow energy spread of electron beam and an ultrahigh energy resolution with spectroscopy. The energy spread in the beam is improved by almost an order of magnitude as compared to specified values. The optimization involves both the monochromator and the electron energy loss detection system. We demonstrate boosted capability of optimized systems with respect to ultra-low loss EELS and sub-angstrom resolution imaging (in a combination with spherical aberration correction).

  2. Optimization of Monochromated TEM for Ultimate Resolution Imaging and Ultrahigh Resolution Electron Energy Loss Spectroscopy

    KAUST Repository

    Lopatin, Sergei

    2017-09-01

    The performance of a monochromated transmission electron microscope with Wien type monochromator is optimized to achieve an extremely narrow energy spread of electron beam and an ultrahigh energy resolution with spectroscopy. The energy spread in the beam is improved by almost an order of magnitude as compared to specified values. The optimization involves both the monochromator and the electron energy loss detection system. We demonstrate boosted capability of optimized systems with respect to ultra-low loss EELS and sub-angstrom resolution imaging (in a combination with spherical aberration correction).

  3. An energy-dispersive X-ray monochromator for measurements in the soft X-ray spectra: design, construction and first measurements. Ein energiedispersiver Roentgenmonochromator mit der Moeglichkeit von Messungen im weichen Roentgenbereich: Entwurf, Aufbau und erste Messungen

    Energy Technology Data Exchange (ETDEWEB)

    Steil, S.

    1993-12-01

    An Energy-Dispersive X-ray Monochromator (EDM) for time-resolved X-ray absorption spectroscopy was built in the Synchrotron radiation laboratory at the 3.5 GeV ELectron Stretcher and Accelerator (ELSA). Bragg angles up to 70 and a specially designed vacuum system allow measurements down to an energy of 2.149 keV (P K-edge) with a Si(111)-crystal. Compared to a standard double crystal monochromator and for an EXAFS spectrum at the Cu K-edge at 8.979 keV for concentrated samples, the EDM boosts time resolution by 3 orders of magnitude. The time resolution increases by a factor of 50 for a XANES spectrum at the S K-edge at 2.472 keV for a rubber sample with 4% sulfur. The energy resolution of the EDM is limited by the Darwin width [Omega] of the Bragg crystal. The harmonics in the 'monochromatized' beam, which increase to lower energies, could be nearly eliminated by using a quartz mirror. The spherical aberration of the focus was described theoretically for a cylindrically bent crystal and compared with measurements. In a first time-resolved measurement at the S K-edge, which comprehended about 120 spectra taken in 40 minutes, the thermal ageing of a rubber sample was investigated to demonstrate the performance of the monochromator. (orig.)

  4. A graphite nanoeraser

    DEFF Research Database (Denmark)

    Liu, Ze; Bøggild, Peter; Yang, Jia-rui

    2011-01-01

    We present here a method for cleaning intermediate-size (up to 50 nm) contamination from highly oriented pyrolytic graphite and graphene. Electron-beam-induced deposition of carbonaceous material on graphene and graphite surfaces inside a scanning electron microscope, which is difficult to remove...... by conventional techniques, can be removed by direct mechanical wiping using a graphite nanoeraser, thus drastically reducing the amount of contamination. We discuss potential applications of this cleaning procedure....

  5. Oxidation Resistant Graphite Studies

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  6. Analysis and design of multilayer structures for neutron monochromators and supermirrors

    International Nuclear Information System (INIS)

    Masalovich, S.

    2013-01-01

    A relatively simple and accurate analytical model for studying the reflectivity of neutron multilayer monochromators and supermirrors is proposed. Design conditions that must be fulfilled in order to reach the maximum reflectivity are considered. The question of the narrowest bandwidth of a monochromator is discussed and the number of layers required to build such a monochromator is derived. Finally, we propose a new and efficient algorithm for synthesis of a supermirror with specified parameters and discuss some inherent restrictions on an attainable reflectivity. -- Highlights: • The inequality (not equation) that defines the thicknesses of layers was obtained. • Ready-to-use formula for the width of the spectral line was found. • Non-quarter-wave monochromators were suggested. • We propose a new algorithm for design of a neutron supermirror. • The problem of minimizing the number of layers in a supermirror is raised

  7. Aberration corrected and monochromated environmental transmission electron microscopy: challenges and prospects for materials science

    DEFF Research Database (Denmark)

    Hansen, Thomas Willum; Wagner, Jakob Birkedal; Dunin-Borkowski, Rafal E.

    2010-01-01

    The latest generation of environmental transmission electron microscopes incorporates aberration correctors and monochromators, allowing studies of chemical reactions and growth processes with improved spatial resolution and spectral sensitivity. Here, we describe the performance of such an instr...

  8. Synchrotron X-ray adaptative monochromator: study and realization of a prototype; Monochromateur adaptatif pour rayonnement X synchrotron: etude et realisation d`un prototype

    Energy Technology Data Exchange (ETDEWEB)

    Dezoret, D.

    1995-12-12

    This work presents a study of a prototype of a synchrotron X-ray monochromator. The spectral qualities of this optic are sensitive to the heat loads which are particularly important on third synchrotron generation like ESRF. Indeed, powers generated by synchrotron beams can reach few kilowatts and power densities about a few tens watts per square millimeters. The mechanical deformations of the optical elements of the beamlines issue issue of the heat load can damage their spectral efficiencies. In order to compensate the deformations, wa have been studying the transposition of the adaptive astronomical optics technology to the x-ray field. First, we have considered the modifications of the spectral characteristics of a crystal induced by x-rays. We have established the specifications required to a technological realisation. Then, thermomechanical and technological studies have been required to transpose the astronomical technology to an x-ray technology. After these studies, we have begun the realisation of a prototype. This monochromator is composed by a crystal of silicon (111) bonded on a piezo-electric structure. The mechanical control is a loop system composed by a infrared light, a Shack-Hartmann CDD and wave front analyser. This system has to compensate the deformations of the crystal in the 5 kcV to 60 kcV energy range with a power density of 1 watt per square millimeters. (authors).

  9. Design and fabrication of a vacuum ultraviolet monochromator using Seya-Namioka mount

    International Nuclear Information System (INIS)

    Krishnamurty, G.; Sarma, Y.A.; Meenakshi Raja Rao, P.; Bhattacharya, S.S.

    1983-01-01

    The design and fabrication of a one meter vacuum ultraviolet monochromator in the Seya-Namioka mounting is described. The monochromator consists of a concave replica grating (1200 grooves/mm) blazed at 1500 A. The grating rotates about a vertical axis through the center of grating by means of sine drive mechanism. An EMI 6256 photomultiplier coupled with a VUV scintillator, sodium salicylate, is used to detect the radiation. (author)

  10. X fluorescence spectrometer including at least one toroidal monochromator with logarithmic spiral

    International Nuclear Information System (INIS)

    Florestan, J.

    1986-01-01

    This spectrometer includes a X-ray source, an entrance diaphragm, a revolution monochromator with monocrystal thin plates and a seal set in its center, an outer diaphragm and a X-ray detector. A second monochromator can be set between the source and the sample. The thin plates are set so as to be a toroidal ring whose cross section in an axial plane describes a logarithmic spiral [fr

  11. Method for producing dustless graphite spheres from waste graphite fines

    Science.gov (United States)

    Pappano, Peter J [Oak Ridge, TN; Rogers, Michael R [Clinton, TN

    2012-05-08

    A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.

  12. Graphite targets at LAMPF

    International Nuclear Information System (INIS)

    Brown, R.D.; Grisham, D.L.

    1983-01-01

    Rotating polycrystalline and stationary pyrolytic graphite target designs for the LAMPF experimental area are described. Examples of finite element calculations of temperatures and stresses are presented. Some results of a metallographic investigation of irradiated pyrolytic graphite target plates are included, together with a brief description of high temperature bearings for the rotating targets

  13. Electrochemical treatment of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Podlovilin, V.I.; Egorov, I.M.; Zhernovoj, A.I.

    1983-01-01

    In the course of investigating various modes of electrochemical treatment (ECT) it has been found that graphite anode treatment begins under the ''glow mode''. A behaviour of some marks of graphite with the purpose of ECT technique development in different electrolytes has been tested. Electrolytes have been chosen of three types: highly alkaline (pH 13-14), neutral (pH-Z) and highly acidic (pH 1-2). For the first time parallel to mechanical electroerosion treatment, ECT of graphite and carbon graphite materials previously considered chemically neutral is proposed. ECT of carbon graphite materials has a number of advantages as compared with electroerrosion and mechanical ones with respect to the treatment rate and purity (ronghness) of the surface. A small quantity of sludge (6-8%) under ECT is in highly alkali electrolytes.

  14. Electrochemical treatment of graphite

    International Nuclear Information System (INIS)

    Podlovilin, V.I.; Egorov, I.M.; Zhernovoj, A.I.

    1983-01-01

    In the course of investigating various modes of electroche-- mical treatment (ECT) it has been found that graphite anode treatment begins under the ''glow mode''. A behaviour of some marks of graphite with the purpose of ECT technique development in different electrolytes has been tested. Electrolytes have been chosen of three types: highly alkaline (pH 13-14), neutral (pH-Z) and highly acidic (pH 1-2). For the first time parallel to mechanical electroerosion treatment ECT graphite and carbon graphite materials previously considered chemically neutral is proposed. ECT of carbon graphite materials has a number of advantages as compared with electroerrosion and mechanical ones this is treatment rate and purity (ronghness) of the surface. A sMall quantity of sludge (6-8%) under ECT is in highly alkali electrolytes

  15. Crystal structure of tveitite-(Y): Fractionation of rare-earth elements between positions and the variety of defects

    International Nuclear Information System (INIS)

    Yakubovich, O. V.; Massa, W.; Pekov, I. V.; Gavrilenko, P. G.

    2007-01-01

    The crystal structure of the mineral tveitite-(Y) (Y 0.883 Na 0.106 ) (Ca 0.841 LREE 0.159 )(Ca 0.716 Na 0.204 HREE 0.080 )(Ca 0.092 Na 0.074 )F 6.952 from amazonite pegmatites of Rov-Gora Mountain (Keivy, Kola Peninsula) is determined using X-ray diffraction (Stoe IPDS diffractometer, λMoK α , graphite monochromator, 2θ max = 63.5 o , R = 0.051 for 1542 reflections). The main crystal data are as follows: a = 17.020(2) A, c = 9.679(2) A, V = 2428.2(4) A 3 , space group R3-bar, Z = 18, and ρ calcd = 4.00 g/cm 3 . The idealized structural formula of the mineral is represented as (Y,Na) 6 (Ca,LREE) 6 (Ca,Na,HREE) 6 (Ca,Na)F 42 (Z = 3). The defect structure of the mineral manifests itself in a mixed occupation of all four independent cation positions and in a randomly disordered distribution of fluorine atoms over the majority of anion positions. It is shown that the crystal structure of tveitite-(Y) fulfills the function of an 'Eratosthenes sieve' for yttrium cations and two groups of lanthanide cations, so that these cations are distributed over three different positions.

  16. Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury

    OpenAIRE

    Philip, Swetha Sara; John, Deepa; John, Sheeja Susan

    2012-01-01

    Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury.

  17. High-heat-load monochromator options for the RIXS beamline at the APS with the MBA lattice

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zunping, E-mail: zpliu@anl.gov; Gog, Thomas, E-mail: gog@aps.anl.gov; Stoupin, Stanislav A.; Upton, Mary H.; Ding, Yang; Kim, Jung-Ho; Casa, Diego M.; Said, Ayman H.; Carter, Jason A.; Navrotski, Gary [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave, Lemont, IL 60439 (United States)

    2016-07-27

    With the MBA lattice for APS-Upgrade, tuning curves of 2.6 cm period undulators meet the source requirements for the RIXS beamline. The high-heat-load monochromator (HHLM) is the first optical white beam component. There are four options for the HHLM such as diamond monochromators with refrigerant of either water or liquid nitrogen (LN{sub 2}), and silicon monochromators of either direct or indirect cooling system. Their performances are evaluated at energy 11.215 keV (Ir L-III edge). The cryo-cooled diamond monochromator has similar performance as the water-cooled diamond monochromator because GaIn of the Cu-GaIn-diamond interface becomes solid. The cryo-cooled silicon monochromators perform better, not only in terms of surface slope error due to thermal deformation, but also in terms of thermal capacity.

  18. Analysis of electrochemical disintegration process of graphite matrix

    International Nuclear Information System (INIS)

    Tian Lifang; Wen Mingfen; Chen Jing

    2010-01-01

    The electrochemical method with ammonium nitrate as electrolyte was studied to disintegrate the graphite matrix from the simulative fuel elements for high temperature gas-cooled reactor. The influences of process parameters, including salt concentration, system temperature and current density, on the disintegration rate of graphite fragments were investigated in the present work. The experimental results showed that the disintegration rate depended slightly on the temperature and salt concentration. The current density strongly affected the disintegration rate of graphite fragments. Furthermore, the content of introduced oxygen in final graphite fragments was independent of the current density and the concentration of electrolyte. Moreover, the structural evolution of graphite was analyzed based on the microstructural parameters determined by X-ray diffraction profile fitting analysis using MAUD (material analysis using diffraction) before and after the disintegration process. It may safely be concluded that the graphite disintegration can be ascribed to the influences of the intercalation of foreign molecules in between crystal planes and the partial oxidation involved. The disintegration process was described deeply composed of intercalate part and further oxidation part of carbon which effected together to lead to the collapse of graphite crystals.

  19. Recent developments in graphite

    International Nuclear Information System (INIS)

    Cunningham, J.E.

    1983-01-01

    Overall, the HTGR graphite situation is in excellent shape. In both of the critical requirements, fuel blocks and support structures, adequate graphites are at hand and improved grades are sufficiently far along in truncation. In the aerospace field, GraphNOL N3M permits vehicle performance with confidence in trajectories unobtainable with any other existing material. For fusion energy applications, no other graphite can simultaneously withstand both extreme thermal shock and neutron damage. Hence, the material promises to create new markets as well as to offer a better candidate material for existing applications

  20. Graphite for fusion energy applications

    International Nuclear Information System (INIS)

    Eatherly, W.P.; Clausing, R.E.; Strehlow, R.A.; Kennedy, C.R.; Mioduszewski, P.K.

    1987-03-01

    Graphite is in widespread and beneficial use in present fusion energy devices. This report reflects the view of graphite materials scientists on using graphite in fusion devices. Graphite properties are discussed with emphasis on application to fusion reactors. This report is intended to be introductory and descriptive and is not intended to serve as a definitive information source

  1. Carbon-14 Graphitization Chemistry

    Science.gov (United States)

    Miller, James; Collon, Philippe; Laverne, Jay

    2014-09-01

    Accelerator Mass Spectrometry (AMS) is a process that allows for the analysis of mass of certain materials. It is a powerful process because it results in the ability to separate rare isotopes with very low abundances from a large background, which was previously impossible. Another advantage of AMS is that it only requires very small amounts of material for measurements. An important application of this process is radiocarbon dating because the rare 14C isotopes can be separated from the stable 14N background that is 10 to 13 orders of magnitude larger, and only small amounts of the old and fragile organic samples are necessary for measurement. Our group focuses on this radiocarbon dating through AMS. When performing AMS, the sample needs to be loaded into a cathode at the back of an ion source in order to produce a beam from the material to be analyzed. For carbon samples, the material must first be converted into graphite in order to be loaded into the cathode. My role in the group is to convert the organic substances into graphite. In order to graphitize the samples, a sample is first combusted to form carbon dioxide gas and then purified and reduced into the graphite form. After a couple weeks of research and with the help of various Physics professors, I developed a plan and began to construct the setup necessary to perform the graphitization. Once the apparatus is fully completed, the carbon samples will be graphitized and loaded into the AMS machine for analysis.

  2. Melting temperature of graphite

    International Nuclear Information System (INIS)

    Korobenko, V.N.; Savvatimskiy, A.I.

    2001-01-01

    Full Text: Pulse of electrical current is used for fast heating (∼ 1 μs) of metal and graphite specimens placed in dielectric solid media. Specimen consists of two strips (90 μm in thick) placed together with small gap so they form a black body model. Quasy-monocrystal graphite specimens were used for uniform heating of graphite. Temperature measurements were fulfilled with fast pyrometer and with composite 2-strip black body model up to melting temperature. There were fulfilled experiments with zirconium and tungsten of the same black body construction. Additional temperature measurements of liquid zirconium and liquid tungsten are made. Specific heat capacity (c P ) of liquid zirconium and of liquid tungsten has a common feature in c P diminishing just after melting. It reveals c P diminishing after melting in both cases over the narrow temperature range up to usual values known from steady state measurements. Over the next wide temperature range heat capacity for W (up to 5000 K) and Zr (up to 4100 K) show different dependencies of heat capacity on temperature in liquid state. The experiments confirmed a high quality of 2-strip black body model used for graphite temperature measurements. Melting temperature plateau of tungsten (3690 K) was used for pyrometer calibration area for graphite temperature measurement. As a result, a preliminary value of graphite melting temperature of 4800 K was obtained. (author)

  3. Mark IV 'Grasshopper' grazing incidence mono-chromator for the Canadian Synchrotron Radiation Facility (CSRF)

    International Nuclear Information System (INIS)

    Tan, K.H.; Bancroft, G.M.; Coatsworth, L.L.; Yates, B.W.

    1982-01-01

    The vacuum, mechanical, and optical characteristics of a 'Grasshopper' grazing incidence monochromator for use with a synchrotron radiation source in the 30-300 eV range is described. The monochromator is compatible with ultrahigh vacuum ( -10 Torr throughout), and the motor driven scan mechanism is linear and reliable. The monchromator has been calibrated using several known absorption edges between 36 and 102 eV and a nonlinear least squares fit to the scan equation. These same absorption edges, plus a scan over zero order, show that the present resolution of the monochromator (with 10 and 16 μm exit and entrance slits respectively) is 0.16 A (0.06 eV at the AlLsub(2,3) edge). With 10 μm entrance and exit slits the resolution will be very close to the theoretical Δlambda = 0.083 A

  4. The SSRL ultrahigh vacuum grazing incidence monochromator: design considerations and operating experience

    International Nuclear Information System (INIS)

    Brown, F.C.; Bachrach, R.Z.; Lien, N.

    1978-01-01

    Considerable experience has now accumulated with the 'grasshopper' monochromator installed on the four degree line at the Stanford Synchrotron Radiation Laboratory. This is one of the first bakeable high vacuum instruments for use with a storage ring source in the photon energy range 25 to 1000 eV. The unique features of this instrument will be discussed from a general point of view, including the source emittance and the transforming properties of the beam line plus monochromator. Actual performance figures will be given in order to better appraise the limits of focusing optics and gratings at two degree grazing incidence. Improvements such as post-monochromator optics, isolation valves and provisions for adjustment will be briefly discussed. (Auth.)

  5. Generating high gray-level resolution monochrome displays with conventional computer graphics cards and color monitors.

    Science.gov (United States)

    Li, Xiangrui; Lu, Zhong-Lin; Xu, Pengjing; Jin, Jianzhong; Zhou, Yifeng

    2003-11-30

    Display systems based on conventional computer graphics cards are capable of generating images with about 8-bit luminance resolution. However, most vision experiments require more than 12 bits of luminance resolution. Pelli and Zhang [Spatial Vis. 10 (1997) 443] described a video attenuator for generating high luminance resolution displays on a monochrome monitor, or for driving just the green gun of a color monitor. Here we show how to achieve a white display by adding video amplifiers to duplicate the monochrome signal to drive all three guns of any color monitor. Because of the lack of the availability of high quality monochrome monitors, our method provides an inexpensive way to achieve high-resolution monochromatic displays using conventional, easy-to-get equipment. We describe the design principles, test results, and a few additional functionalities.

  6. Erosion of pyrolytic graphite and Ti-doped graphite due to high flux irradiation

    International Nuclear Information System (INIS)

    Ohtsuka, Yusuke; Ohashi, Junpei; Ueda, Yoshio; Isobe, Michiro; Nishikawa, Masahiro

    1997-01-01

    The erosion of pyrolytic graphite and titanium doped graphite RG-Ti above 1,780 K was investigated by 5 keV Ar beam irradiation with the flux from 4x10 19 to 1x10 21 m -2 ·s -1 . The total erosion yields were significantly reduced with the flux. This reduction would be attributed to the reduction of RES (radiation enhanced sublimation) yield, which was observed in the case of isotropic graphite with the flux dependence of RES yield of φ -0.26 (φ: flux) obtained in our previous work. The yield of pyrolytic graphite was roughly 30% higher than that of isotropic graphite below the flux of 10 20 m -2 ·s -1 whereas each yield approached to very close value at the highest flux of 1x10 21 m -2 ·s -1 . This result indicated that the effect of graphite structure on the RES yield, which was apparent in the low flux region, would disappear in the high flux region probably due to the disordering of crystal structure. In the case of irradiation to RG-Ti at 1,780 K, the surface undulations evolved with a mean height of about 3 μm at 1.2x10 20 m -2 ·s -1 , while at higher flux of 8.0x10 20 m -2 ·s -1 they were unrecognizable. These phenomena can be explained by the reduction of RES of graphite parts excluding TiC grains. (author)

  7. Performance tests of a 2-meter grasshopper monochromator at photon factory

    International Nuclear Information System (INIS)

    Yanagihara, Mihiro; Maezawa, Hideki; Sasaki, Taizo; Suzuki, Yoshio; Iguchi, Yasuo.

    1984-12-01

    A 2-meter grasshopper monochromator was installed and adjusted at BL-11A in Photon Factory, and performance tests were carried out. The usable photon energy range for the monochromator is 90 to 1000 eV for a 2400 grooves/mm grating, and the flux is 10 8 - 10 9 photons/sec for entrance and exit slit widths of 15 μm. A resolving power of about 2000 is realized at 250 eV for this slit width. (author)

  8. Physical evaluation of color and monochrome medical displays using an imaging colorimeter

    Science.gov (United States)

    Roehrig, Hans; Gu, Xiliang; Fan, Jiahua

    2013-03-01

    This paper presents an approach to physical evaluation of color and monochrome medical grade displays using an imaging colorimeter. The purpose of this study was to examine the influence of medical display types, monochrome or color at the same maximum luminance settings, on diagnostic performance. The focus was on the measurements of physical characteristics including spatial resolution and noise performance, which we believed could affect the clinical performance. Specifically, Modulation Transfer Function (MTF) and Noise Power Spectrum (NPS) were evaluated and compared at different digital driving levels (DDL) between two EIZO displays.

  9. Collimator type monochromator as a possible impurities monitor for fusion plasmas. Preliminary tests on the Tokamak TM-1-MH

    International Nuclear Information System (INIS)

    Musa, G.; Lungu, C.P.; Badalec, J.; Jakubka, K.; Kopecky, V.; Stoeckel, J.; Zacek, F.

    1984-09-01

    A collimator type monochromator has been tested for the first time as the impurity monitor on Tokamak. The possibility to use this type of monochromator in fusion devices is analyzed and a monoslit device is proposed as a convenient monitor for impurities. (authors)

  10. Recompressed exfoliated graphite articles

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  11. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram; Patole, Archana

    2017-01-01

    A method of fabricating a bromine-graphite/metal composite includes intercalating bromine within layers of graphite via liquid-phase bromination to create brominated-graphite and consolidating the brominated-graphite with a metal nanopowder via a

  12. Cesium diffusion in graphite

    International Nuclear Information System (INIS)

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of 137 Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of 137 Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000 0 C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ΔE of the equation D/epsilon = (D/epsilon) 0 exp [-ΔE/RT] are about 4 x 10 -2 cm 2 /s and 30 kcal/mole, respectively

  13. Influence of higher harmonics of the undulator in X-ray polarimetry and crystal monochromator design.

    Science.gov (United States)

    Marx-Glowna, Berit; Schulze, Kai S; Uschmann, Ingo; Kämpfer, Tino; Weber, Günter; Hahn, Christoph; Wille, Hans Christian; Schlage, Kai; Röhlsberger, Ralf; Förster, Eckhart; Stöhlker, Thomas; Paulus, Gerhard G

    2015-09-01

    The spectrum of the undulator radiation of beamline P01 at Petra III has been measured after passing a multiple reflection channel-cut polarimeter. Odd and even harmonics up to the 15th order, as well as Compton peaks which were produced by the high harmonics in the spectrum, could been measured. These additional contributions can have a tremendous influence on the performance of the polarimeter and have to be taken into account for further polarimeter designs.

  14. Optimization of bent perfect Si(220)-crystal monochromator for residual strain/stress instrument - Part II

    Czech Academy of Sciences Publication Activity Database

    Moon, MK; Mikula, Pavol; Hong, K.P.

    2005-01-01

    Roč. 368, - (2005), s. 70-75 ISSN 0921-4526 R&D Projects: GA ČR GA202/03/0891 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutron diffraction * focusing * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.796, year: 2005

  15. Dry Sliding Wear Behavior of Spark Plasma Sintered Fe-Based Bulk Metallic Glass/Graphite Composites

    Directory of Open Access Journals (Sweden)

    Xiulin Ji

    2016-09-01

    Full Text Available Bulk metallic glass (BMG and BMG-graphite composites were fabricated using spark plasma sintering at the sintering temperature of 575 °C and holding time of 15 min. The sintered composites exhibited partial crystallization and the presence of distributed porosity and graphite particles. The effect of graphite reinforcement on the tribological properties of the BMG/graphite composites was investigated using dry ball-on-disc sliding wear tests. The reinforcement of graphite resulted in a reduction in both the wear rate and the coefficient of friction as compared to monolithic BMG samples. The wear surfaces of BMG/graphite composites showed regions of localized wear loss due to microcracking and fracture, as was also the case with the regions covered with graphite-rich protective film due to smearing of pulled off graphite particles.

  16. Intercomparison of graphite irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Hering, H; Perio, P; Seguin, M [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    While fast neutrons only are effective in damaging graphite, results of irradiations are more or less universally expressed in terms of thermal neutron fluxes. This paper attempts to correlate irradiations made in different reactors, i.e., in fluxes of different spectral compositions. Those attempts are based on comparison of 1) bulk length change and volume expansion, and 2) crystalline properties (e.g., lattice parameter C, magnetic susceptibility, stored energy, etc.). The methods used by various authors for determining the lattice constants of irradiated graphite are discussed. (author)

  17. A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements

    Energy Technology Data Exchange (ETDEWEB)

    Seidler, G. T., E-mail: seidler@uw.edu; Mortensen, D. R.; Remesnik, A. J.; Pacold, J. I.; Ball, N. A.; Barry, N.; Styczinski, M.; Hoidn, O. R. [Physics Department, University of Washington, Seattle, Washington 98195-1560 (United States)

    2014-11-15

    We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ∼5 keV to ∼10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 10{sup 6}–10{sup 7} photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species.

  18. Graphite as negative electrode in Li-ion batteries; Le graphite comme electrode negative dans les accumulateurs Li-ion

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F.; Monnier, A. [Timcal SA (France)

    1996-12-31

    The last developments in lithium batteries design have demonstrated the advantages of graphite: competitive cost, flat output curve, high capacity thanks to the obtention of a final compound close to LiC{sub 6}, good behaviour during cycling and a high mass energy. However, these advantages are slightly tarnished by parasite secondary reactions during the evolution of the element. Two different cases are encountered: the formation of a passivation layer (loss of Li ions and formation of irreversible bounds) and the formation of a passivation layer with a reaction between graphite and the solvent (partial destruction of the graphite crystal lattice). In the first case, the theoretical graphite insertion capacity remains at 372 mAh/g while in the second case the insertion capacity is greatly reduced. Abstract only. (J.S.)

  19. Graphite as negative electrode in Li-ion batteries; Le graphite comme electrode negative dans les accumulateurs Li-ion

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F; Monnier, A [Timcal SA (France)

    1997-12-31

    The last developments in lithium batteries design have demonstrated the advantages of graphite: competitive cost, flat output curve, high capacity thanks to the obtention of a final compound close to LiC{sub 6}, good behaviour during cycling and a high mass energy. However, these advantages are slightly tarnished by parasite secondary reactions during the evolution of the element. Two different cases are encountered: the formation of a passivation layer (loss of Li ions and formation of irreversible bounds) and the formation of a passivation layer with a reaction between graphite and the solvent (partial destruction of the graphite crystal lattice). In the first case, the theoretical graphite insertion capacity remains at 372 mAh/g while in the second case the insertion capacity is greatly reduced. Abstract only. (J.S.)

  20. Optics and design of the fringe field monochromator for a Schottky field emission gun

    International Nuclear Information System (INIS)

    Mook, H.W.; Kruit, P.

    1999-01-01

    For the improvement of high-resolution electron energy loss spectroscopy a new electron source monochromator, based on the Wien filter principle, is presented. In the fringe field monochromator the electric and magnetic filter fields are tightly enclosed by field clamps to satisfy the Wien condition, E=vB. The whole monochromator including the 150 nm energy selection slits (Nanoslits) is positioned in the gun area. Its total length is only 42 mm. Using electron trajectory simulation through the filter fields the dispersion and aberrations are determined. The parasitic astigmatism of the gun lens needs to be corrected using an electrostatic quadrupole field incorporated in the filter. Estimations of the influence of filter electrode misalignment show that at least six filter electrodes must be used to loosen the alignment demands sufficiently. Using theoretical estimations of the Coulomb interaction the final energy resolution, beam brightness and current are predicted. For a Schottky field emission electron gun with typical brightness of 10 8 A/sr m 2 V the monochromator is expected to produce a 50 meV 1 nA beam with a brightness of 10 7

  1. High luminance monochrome vs. color displays: impact on performance and search

    Science.gov (United States)

    Krupinski, Elizabeth A.; Roehrig, Hans; Matsui, Takashi

    2011-03-01

    To determine if diagnostic accuracy and visual search efficiency with a high luminance medical-grade color display are equivalent to a high luminance medical-grade monochrome display. Six radiologists viewed DR chest images, half with a solitary pulmonary nodule and half without. Observers reported whether or not a nodule was present and their confidence in that decision. Total viewing time per image was recorded. On a subset of 15 cases eye-position was recorded. Confidence data were analyzed using MRMC ROC techniques. There was no statistically significant difference (F = 0.0136, p = 0.9078) between color (mean Az = 0.8981, se = 0.0065) and monochrome (mean Az = 0.8945, se = 0.0148) diagnostic performance. Total viewing time per image did not differ significantly (F = 0.392, p = 0.5315) as a function of color (mean = 27.36 sec, sd = 12.95) vs monochrome (mean = 28.04, sd = 14.36) display. There were no significant differences in decision dwell times (true and false, positive and negative) overall for color vs monochrome displays (F = 0.133, p = 0.7154). The true positive (TP) and false positive (FP) decisions were associated with the longest dwell times, the false negatives (FN) with slightly shorter dwell times, and the true negative decisions (TN) with the shortest (F = 50.552, p radiology.

  2. Performance of a high resolution monochromator for the vacuum ultraviolet radiation from the DORIS storage ring

    International Nuclear Information System (INIS)

    Saile, V.; Skibowski, M.; Steinmann, W.; Guertler, P.; Koch, E.E.; Kozevnikov, A.

    1976-03-01

    The unique properties of the DORIS storage ring at DESY as a synchrotron radiation source are exploited for high resolution spectroscopy in the vacuum ultraviolet. We describe a new experimental set up with a 3 meter normal incidence monochromator for wavelengths between 3,000 A to 300 A (4 [de

  3. Electron-optical design parameters for a high-resolution electron monochromator

    International Nuclear Information System (INIS)

    Tanaka, H.; Huebner, R.H.

    1976-01-01

    Detailed design parameters of a new, high-resolution electron monochromator are presented. The design utilizes a hemispherical filter as the energy-dispersing element and combines both cylindrical and aperture electrostatic lenses to accelerate, decelerate, transport, and focus the electron beam from the cathode to the interaction region

  4. Principles for the comparison of the proportions of straylight present in monochromators of various types

    International Nuclear Information System (INIS)

    Glock, E.

    1976-03-01

    The origin and propagation of straylight in monochromators is investigated and an expression is derived for the ratio of the straylight and the effective spectral intensity within the exit slit. This expression, for a prescribed resolution and speed, permits to select the design involving the minimum of straylight which can be attained. (orig.) [de

  5. A novel monochromator for high heat-load synchrotron x-ray radiation

    International Nuclear Information System (INIS)

    Khounsary, A.M.

    1992-01-01

    The high heat load associated with the powerful and concentrated x-ray beams generated by the insertion devices at a number of present and many of the future (planned or under construction) synchrotron radiation facilities pose a formidable engineering challenge in the designer of the monochromators and other optical devices. For example, the Undulator A source on the Advanced Photon Source (APS) ring (being constructed at the Argonne National Laboratory) will generate as much as 10 kW of heat deposited on a small area (about 1 cm 2 ) of the first optics located some 24 m from the source. The peak normal incident heat flux can be as high as 500 W/mm 2 . Successful utilization of the intense x-ray beams from insertion devices critically depends on the development, design, and availability of optical elements that provide acceptable performance under high heat load. Present monochromators can handle, at best, heat load levels that are an order of magnitude lower than those generated by such sources. The monochromator described here and referred to as the open-quote inclinedclose quotes monochromator can provide a solution to high heat-load problems

  6. Graphite-based photovoltaic cells

    Science.gov (United States)

    Lagally, Max; Liu, Feng

    2010-12-28

    The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

  7. Thermal neutron spectra measurements in IEAR-1 Reactor, by using a crystal spectrometer

    International Nuclear Information System (INIS)

    Fulfaro, R.; Figueiredo Neto, A.M.; Stasiulevicius, E.; Vinhas, L.A.

    1975-01-01

    The thermal neutron spectrum of the IEN Argonauta reactor has been measured in the wavelength from 0.7 to 1.9A, using a neutron crystal spectrometer. An aluminium single crystal, in transmission, was used as monochromator. The aluminium crystal reflectivity employed in the analysis of the data was calculated for the first five permitted orders. An effective absorption coefficient of the crystal was used to perform the calculations instead of the macroscopic cross section of the element

  8. Development of fracture toughness test method for nuclear grade graphite

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C. H.; Lee, J. S.; Cho, H. C.; Kim, D. J.; Lee, D. J. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2006-02-15

    Because of its high strength and stability at very high temperature, as well as very low thermal neutron absorption cross-section, graphite has been widely used as a structural material in Gas Cooled Reactors (GCR). Recently, many countries are developing the Very High Temperature gas cooled Reactor (VHTR) because of the potentials of hydrogen production, as well as its safety and viable economics. In VHTR, helium gas serves as the primary coolant. Graphite will be used as a reflector, moderator and core structural materials. The life time of graphite is determined from dimensional changes due to neutron irradiation, which closely relates to the changes of crystal structure. The changes of both lattice parameter and crystallite size can be easily measured by X-ray diffraction method. However, due to high cost and long time of neutron irradiation test, ion irradiation test is being performed instead in KAERI. Therefore, it is essential to develop the technique for measurement of ion irradiation damage of nuclear graphite. Fracture toughness of nuclear grade graphite is one of the key properties in the design and development of VHTR. It is important not only to evaluate the various properties of candidate graphite but also to assess the integrity of nuclear grade graphite during operation. Although fracture toughness tests on graphite have been performed in many laboratories, there have been wide variations in values of the calculated fracture toughness, due to the differences in the geometry of specimens and test conditions. Hence, standard test method for nuclear graphite is required to obtain the reliable fracture toughness values. Crack growth behavior of nuclear grade graphite shows rising R-curve which means the increase in crack growth resistance as the crack length increases. Crack bridging and microcracking have been proposed to be the dominant mechanisms of rising R-curve behavior. In this paper, the technique to measure the changes of crystallite size and

  9. Electronic properties of graphite

    International Nuclear Information System (INIS)

    Schneider, J.

    2010-10-01

    In this thesis, low-temperature magneto-transport (T ∼ 10 mK) and the de Haas-van Alphen effect of both natural graphite and highly oriented pyrolytic graphite (HOPG) are examined. In the first part, low field magneto-transport up to B = 11 T is discussed. A Fourier analysis of the background removed signal shows that the electric transport in graphite is governed by two types of charge carriers, electrons and holes. Their phase and frequency values are in agreement with the predictions of the SWM-model. The SWM-model is confirmed by detailed band structure calculations using the magnetic field Hamiltonian of graphite. The movement of the Fermi at B > 2 T is calculated self-consistently assuming that the sum of the electron and hole concentrations is constant. The second part of the thesis deals with high field magneto-transport of natural graphite in the magnetic field range 0 ≤ B ≤ 28 T. Both spin splitting of magneto-transport features in tilted field configuration and the onset of the charge density wave (CDW) phase for different temperatures with the magnetic field applied normal to the sample plane are discussed. Concerning the Zeeman effect, the SWM calculations including the Fermi energy movement require a g-factor of g* equal to 2.5 ± 0.1 to reproduce the spin spilt features. The measurements of the charge density wave state confirm that its onset magnetic field can be described by a Bardeen-Cooper-Schrieffer (BCS)-type formula. The measurements of the de Haas-van Alphen effect are in agreement with the results of the magneto-transport measurements at low field. (author)

  10. Pyrolytic Graphite as a Selective Neutron Filter

    International Nuclear Information System (INIS)

    Adib, M.; Habib, N.; Fathalla, M.

    2006-01-01

    The transmission of neutrons through pyrolytic graphite (PG) crystals, set at different angles with respect to incident beam, were calculated using an additive formula. A computer program HOPG was developed to provide the required calculation. An overall agreement between the calculated neutron transmissions through a slab of 1,85 mm thick PG crystal with an angular spread of c-axes of 0,4 degree, set at different angles to the incident beam, and the available experimental ones in the wavelength range from (0,02 to 1,4) nm were obtained. A feasibility study for use of PG crystal as an efficient second-order neutron filter is detailed in terms of crystal thickness, angular spread of c-axes and its operation with respect to the neutron beam. It was shown that a PG crystal with an angular spread of c-axes and its orientation with respect to the neutron beam. It was shown that a PG crystal with an angular spread of 0,8 degree is sufficient for optimum scattering of second-order neutrons in the wavelength band (0,384-0,183) nm, by adjusting the filter in an appropriate orientation

  11. An adaptive crystal bender for high power synchrotron radiation beams

    International Nuclear Information System (INIS)

    Berman, L.E.; Hastings, J.B.

    1992-01-01

    Perfect crystal monochromators cannot diffract x-rays efficiently, nor transmit the high source brightness available at synchrotron radiation facilities, unless surface strains within the beam footprint are maintained within a few arcseconds. Insertion devices at existing synchrotron sources already produce x-ray power density levels that can induce surface slope errors of several arcseconds on silicon monochromator crystals at room temperature, no matter how well the crystal is cooled. The power density levels that will be produced by insertion devices at the third-generation sources will be as much as a factor of 100 higher still. One method of restoring ideal x-ray diffraction behavior, while coping with high power levels, involves adaptive compensation of the induced thermal strain field. The design and performance, using the X25 hybrid wiggler beam line at the National Synchrotron Light Source (NSLS), of a silicon crystal bender constructed for this purpose are described

  12. Design and optimization of the grating monochromator for soft X-ray self-seeding FELs

    Energy Technology Data Exchange (ETDEWEB)

    Serkez, Svitozar

    2015-10-15

    The emergence of Free Electron Lasers (FEL) as a fourth generation of light sources is a breakthrough. FELs operating in the X-ray range (XFEL) allow one to carry out completely new experiments that probably most of the natural sciences would benefit. Self-amplified spontaneous emission (SASE) is the baseline FEL operation mode: the radiation pulse starts as a spontaneous emission from the electron bunch and is being amplified during an FEL process until it reaches saturation. The SASE FEL radiation usually has poor properties in terms of a spectral bandwidth or, on the other side, longitudinal coherence. Self-seeding is a promising approach to narrow the SASE bandwidth of XFELs significantly in order to produce nearly transformlimited pulses. It is achieved by the radiation pulse monochromatization in the middle of an FEL amplification process. Following the successful demonstration of the self-seeding setup in the hard X-ray range at the LCLS, there is a need for a self-seeding extension into the soft X-ray range. Here a numerical method to simulate the soft X-ray self seeding (SXRSS) monochromator performance is presented. It allows one to perform start-to-end self-seeded FEL simulations along with (in our case) GENESIS simulation code. Based on this method, the performance of the LCLS self-seeded operation was simulated showing a good agreement with an experiment. Also the SXRSS monochromator design developed in SLAC was adapted for the SASE3 type undulator beamline at the European XFEL. The optical system was studied using Gaussian beam optics, wave optics propagation method and ray tracing to evaluate the performance of the monochromator itself. Wave optics analysis takes into account the actual beam wavefront of the radiation from the coherent FEL source, third order aberrations and height errors from each optical element. The monochromator design is based on a toroidal VLS grating working at a fixed incidence angle mounting without both entrance and exit

  13. Design and optimization of the grating monochromator for soft X-ray self-seeding FELs

    International Nuclear Information System (INIS)

    Serkez, Svitozar

    2015-10-01

    The emergence of Free Electron Lasers (FEL) as a fourth generation of light sources is a breakthrough. FELs operating in the X-ray range (XFEL) allow one to carry out completely new experiments that probably most of the natural sciences would benefit. Self-amplified spontaneous emission (SASE) is the baseline FEL operation mode: the radiation pulse starts as a spontaneous emission from the electron bunch and is being amplified during an FEL process until it reaches saturation. The SASE FEL radiation usually has poor properties in terms of a spectral bandwidth or, on the other side, longitudinal coherence. Self-seeding is a promising approach to narrow the SASE bandwidth of XFELs significantly in order to produce nearly transformlimited pulses. It is achieved by the radiation pulse monochromatization in the middle of an FEL amplification process. Following the successful demonstration of the self-seeding setup in the hard X-ray range at the LCLS, there is a need for a self-seeding extension into the soft X-ray range. Here a numerical method to simulate the soft X-ray self seeding (SXRSS) monochromator performance is presented. It allows one to perform start-to-end self-seeded FEL simulations along with (in our case) GENESIS simulation code. Based on this method, the performance of the LCLS self-seeded operation was simulated showing a good agreement with an experiment. Also the SXRSS monochromator design developed in SLAC was adapted for the SASE3 type undulator beamline at the European XFEL. The optical system was studied using Gaussian beam optics, wave optics propagation method and ray tracing to evaluate the performance of the monochromator itself. Wave optics analysis takes into account the actual beam wavefront of the radiation from the coherent FEL source, third order aberrations and height errors from each optical element. The monochromator design is based on a toroidal VLS grating working at a fixed incidence angle mounting without both entrance and exit

  14. Harwell Graphite Calorimeter

    International Nuclear Information System (INIS)

    Linacre, J.K.

    1970-01-01

    The calorimeter is of the steady state temperature difference type. It contains a graphite sample supported axially in a graphite outer jacket, the assembly being contained in a thin stainless steel outer can. The temperature of the jacket and the temperature difference between sample and jacket are measured by chromel-alumel thermocouples. The instrument is calibrated by means of an electric heater of low mass positioned on the axis of the sample. The resistance of the heater is known and both current through the heater and the potential across it may be measured. The instrument is filled with nitrogen at a pressure of one half atmosphere at room temperature. The calorimeter has been designed for prolonged operation at temperatures up to 600°C, and dose rates up to 1 Wg -1 , and instruments have been in use for periods in excess of one year

  15. A standard graphite block

    Energy Technology Data Exchange (ETDEWEB)

    Ivkovic, M; Zdravkovic, Z; Sotic, O [Department of Reactor Physics and Dynamics, Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)

    1966-04-15

    A graphite block was calibrated for the thermal neutron flux of the Ra-Be source using indium foils as detectors. Experimental values of the thermal neutron flux along the central vertical axis of the system were corrected for the self-shielding effect and depression of flux in the detector. The experimental values obtained were compared with the values calculated on the basis of solving the conservation neutron equation by the continuous slowing-down theory. In this theoretical calculation of the flux the Ra-Be source was divided into three resonance energy regions. The measurement of the thermal neutron diffusion length in the standard graphite block is described. The measurements were performed in the thermal neutron region of the system. The experimental results were interpreted by the diffusion theory for point thermal neutron source in the finite system. The thermal neutron diffusion length was calculated to be L= 50.9 {+-}3.1 cm for the following graphite characteristics: density = 1.7 g/cm{sup 3}; boron content = 0.1 ppm; absorption cross section = 3.7 mb.

  16. A standard graphite block

    International Nuclear Information System (INIS)

    Ivkovic, M.; Zdravkovic, Z.; Sotic, O.

    1966-04-01

    A graphite block was calibrated for the thermal neutron flux of the Ra-Be source using indium foils as detectors. Experimental values of the thermal neutron flux along the central vertical axis of the system were corrected for the self-shielding effect and depression of flux in the detector. The experimental values obtained were compared with the values calculated on the basis of solving the conservation neutron equation by the continuous slowing-down theory. In this theoretical calculation of the flux the Ra-Be source was divided into three resonance energy regions. The measurement of the thermal neutron diffusion length in the standard graphite block is described. The measurements were performed in the thermal neutron region of the system. The experimental results were interpreted by the diffusion theory for point thermal neutron source in the finite system. The thermal neutron diffusion length was calculated to be L= 50.9 ±3.1 cm for the following graphite characteristics: density = 1.7 g/cm 3 ; boron content = 0.1 ppm; absorption cross section = 3.7 mb

  17. Monochromator on a synchrotron undulator source for liquid surface studies

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Freund, A.K.

    1992-01-01

    For liquid surface studies a monochromatic beam of relative bandwidth between 0.1% and 1% at a variable angle in the vertical plane between 0-degrees and 10-degrees is needed. The beam should be like a sheet some tens of mu-m thick and some mm wide, and as intense as possible. We discuss a monoch......For liquid surface studies a monochromatic beam of relative bandwidth between 0.1% and 1% at a variable angle in the vertical plane between 0-degrees and 10-degrees is needed. The beam should be like a sheet some tens of mu-m thick and some mm wide, and as intense as possible. We discuss......% of the useful x rays, in full agreement with diffraction theory including secondary extinction. Heat load experiments reported elsewhere in this conference prove that Be crystals can withstand high beam power density and that the thermal deformation is small compared to the mosaic spread. The results...... of the flux calculations are most encouraging: a gain of order 10(3) to 10(4) can be expected as compared to existing liquid surface spectrometers....

  18. Structural disorder of graphite and implications for graphite thermometry

    Science.gov (United States)

    Kirilova, Martina; Toy, Virginia; Rooney, Jeremy S.; Giorgetti, Carolina; Gordon, Keith C.; Collettini, Cristiano; Takeshita, Toru

    2018-02-01

    Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Thus, the degree of graphite crystallinity, or its structural order, has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry, we performed laboratory deformation experiments. We sheared highly crystalline graphite powder at normal stresses of 5 and 25 megapascal (MPa) and aseismic velocities of 1, 10 and 100 µm s-1. The degree of structural order both in the starting and resulting materials was analyzed by Raman microspectroscopy. Our results demonstrate structural disorder of graphite, manifested as changes in the Raman spectra. Microstructural observations show that brittle processes caused the documented mechanical modifications of the aggregate graphite crystallinity. We conclude that the calibrated graphite thermometer is ambiguous in active tectonic settings.

  19. Structural disorder of graphite and implications for graphite thermometry

    Directory of Open Access Journals (Sweden)

    M. Kirilova

    2018-02-01

    Full Text Available Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Thus, the degree of graphite crystallinity, or its structural order, has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry, we performed laboratory deformation experiments. We sheared highly crystalline graphite powder at normal stresses of 5 and 25  megapascal (MPa and aseismic velocities of 1, 10 and 100 µm s−1. The degree of structural order both in the starting and resulting materials was analyzed by Raman microspectroscopy. Our results demonstrate structural disorder of graphite, manifested as changes in the Raman spectra. Microstructural observations show that brittle processes caused the documented mechanical modifications of the aggregate graphite crystallinity. We conclude that the calibrated graphite thermometer is ambiguous in active tectonic settings.

  20. High-flux normal incidence monochromator for circularly polarized synchrotron radiation

    International Nuclear Information System (INIS)

    Schaefers, F.; Peatman, W.; Eyers, A.; Heckenkamp, C.; Schoenhense, G.; Heinzmann, U.

    1986-01-01

    A 6.5-m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low-signal experiments such as spin- and angle-resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk--Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 10 11 photons s -1 bandwidth -1 (0.2--0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved

  1. The use of diffraction efficiency theory in the design of soft x-ray monochromators

    International Nuclear Information System (INIS)

    Padmore, H.A.; Martynov, V.; Hollis, K.; Mount Vernon Hospital, Northwood

    1993-01-01

    In general, the diffraction efficiency of gratings is limited by the constraints imposed by the type of geometry used to scan the photon energy. In the simplest example, the spherical grating monochromator (SGM), the deviation angle, the grating groove width and depth and the groove density are all constrained by considerations of the maximum photon energy and the tuning range for individual gratings. We have examined the case in which these parameters are unconstrained, resulting in predictions of the ultimate performance of lamellar type gratings for groove densities from 300 to 2400 1/mm for gold and nickel coatings. The differential method of Neviere et al was used for modeling the behavior of the gratings and justification is presented for this by rigorous comparison with measurements. The implications of these results for future monochromators based on a variable included angle geometry are discussed

  2. Ultrathin nondoped emissive layers for efficient and simple monochrome and white organic light-emitting diodes.

    Science.gov (United States)

    Zhao, Yongbiao; Chen, Jiangshan; Ma, Dongge

    2013-02-01

    In this paper, highly efficient and simple monochrome blue, green, orange, and red organic light emitting diodes (OLEDs) based on ultrathin nondoped emissive layers (EMLs) have been reported. The ultrathin nondoped EML was constructed by introducing a 0.1 nm thin layer of pure phosphorescent dyes between a hole transporting layer and an electron transporting layer. The maximum external quantum efficiencies (EQEs) reached 17.1%, 20.9%, 17.3%, and 19.2% for blue, green, orange, and red monochrome OLEDs, respectively, indicating the universality of the ultrathin nondoped EML for most phosphorescent dyes. On the basis of this, simple white OLED structures are also demonstrated. The demonstrated complementary blue/orange, three primary blue/green/red, and four color blue/green/orange/red white OLEDs show high efficiency and good white emission, indicating the advantage of ultrathin nondoped EMLs on constructing simple and efficient white OLEDs.

  3. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram

    2017-07-20

    A method of fabricating a bromine-graphite/metal composite includes intercalating bromine within layers of graphite via liquid-phase bromination to create brominated-graphite and consolidating the brominated-graphite with a metal nanopowder via a mechanical pressing operation to generate a bromine-graphite/metal composite material.

  4. Pulse Compression of Phase-matched High Harmonic Pulses from a Time-Delay Compensated Monochromator

    Directory of Open Access Journals (Sweden)

    Ito Motohiko

    2013-03-01

    Full Text Available Pulse compression of single 32.6-eV high harmonic pulses from a time-delay compensated monochromator was demonstrated down to 11±3 fs by compensating the pulse front tilt. The photon flux was intensified up to 5.7×109 photons/s on target by implementing high harmonic generation under a phase matching condition in a hollow fiber used for increasing the interaction length.

  5. Local Treatment for Monochrome Outdoor Painted Metal Sculptures: Assessing the suitability of conservation paints for retouching

    OpenAIRE

    van Basten, Nikki; Defeyt, Catherine; Rivenc, Rachel

    2015-01-01

    When outdoor painted sculptures get chipped, scratched or abraded, conservators might consider local retouching treatments as an option that would protect the exposed metal substrate and restore the aesthetic integrity, thus postponing a very costly and invasive overall repainting. Unfortunately, matching colour gloss and texture on large monochrome surfaces is always challenging. This paper reports on research undertaken to investigate some of the materials and application techniques that co...

  6. Grating monochromator for soft X-ray self-seeding the European XFEL

    Energy Technology Data Exchange (ETDEWEB)

    Serkez, Svitozar; Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany)

    2013-02-15

    Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. The implementation of this method in the soft X-ray wavelength range necessarily involves gratings as dispersive elements. We study a very compact self-seeding scheme with a grating monochromator originally designed at SLAC, which can be straightforwardly installed in the SASE3 type undulator beamline at the European XFEL. The monochromator design is based on a toroidal VLS grating working at a fixed incidence angle mounting without entrance slit. It covers the spectral range from 300 eV to 1000 eV. The optical system was studied using wave optics method (in comparison with ray tracing) to evaluate the performance of the self-seeding scheme. Our wave optics analysis takes into account the actual beam wavefront of the radiation from the coherent FEL source, third order aberrations, and errors from each optical element. Wave optics is the only method available, in combination with FEL simulations, for the design of a self-seeding monochromator without exit slit. We show that, without exit slit, the self-seeding scheme is distinguished by the much needed experimental simplicity, and can practically give the same resolving power (about 7000) as with an exit slit. Wave optics is also naturally applicable to calculations of the self-seeding scheme efficiency, which include the monochromator transmittance and the effect of the mismatching between seed beam and electron beam. Simulations show that the FEL power reaches 1 TW and that the spectral density for a TW pulse is about two orders of magnitude higher than that for the SASE pulse at saturation.

  7. Linac Coherent Light Source soft x-ray materials science instrument optical design and monochromator commissioning

    Czech Academy of Sciences Publication Activity Database

    Heimann, P.; Krupin, O.; Schlotter, W.F.; Turner, J.; Krzywinski, J.; Sorgenfrei, F.; Messerschmidt, M.; Bernstein, D.; Chalupský, Jaromír; Hájková, Věra; Hau-Riege, S.; Holmes, M.; Juha, Libor; Kelez, N.; Lüning, J.; Nordlund, D.; Perea, M.F.; Scherz, A.; Soufli, R.; Wurth, W.; Rowen, M.

    2011-01-01

    Roč. 82, č. 9 (2011), 093104/1-093104/8 ISSN 0034-6748 R&D Projects: GA MŠk(CZ) ME10046 Institutional research plan: CEZ:AV0Z10100523 Keywords : diffraction gratings * light sources * linear accelerators * optical materials * x-ray monochromators * x-ray optics Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.367, year: 2011

  8. Mechanical design aspects of a soft X-ray plane grating monochromator

    Czech Academy of Sciences Publication Activity Database

    Vašina, R.; Kolařík, V.; Doležel, P.; Mynář, M.; Vondráček, Martin; Cháb, Vladimír; Slezák, Jiří; Comicioli, C.; Prince, K. C.

    467-468, 467-468 (2001), s. 561-564 ISSN 0168-9002 R&D Projects: GA ČR GV202/98/K002 Grant - others:-(XE) CIPA-CT94-0217 Institutional research plan: CEZ:AV0Z2041904 Keywords : synchrotron radiation * monochromator * plane grating Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.026, year: 2001

  9. Grating monochromator for soft X-ray self-seeding the European XFEL

    International Nuclear Information System (INIS)

    Serkez, Svitozar; Kocharyan, Vitali; Saldin, Evgeni; Geloni, Gianluca

    2013-02-01

    Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. The implementation of this method in the soft X-ray wavelength range necessarily involves gratings as dispersive elements. We study a very compact self-seeding scheme with a grating monochromator originally designed at SLAC, which can be straightforwardly installed in the SASE3 type undulator beamline at the European XFEL. The monochromator design is based on a toroidal VLS grating working at a fixed incidence angle mounting without entrance slit. It covers the spectral range from 300 eV to 1000 eV. The optical system was studied using wave optics method (in comparison with ray tracing) to evaluate the performance of the self-seeding scheme. Our wave optics analysis takes into account the actual beam wavefront of the radiation from the coherent FEL source, third order aberrations, and errors from each optical element. Wave optics is the only method available, in combination with FEL simulations, for the design of a self-seeding monochromator without exit slit. We show that, without exit slit, the self-seeding scheme is distinguished by the much needed experimental simplicity, and can practically give the same resolving power (about 7000) as with an exit slit. Wave optics is also naturally applicable to calculations of the self-seeding scheme efficiency, which include the monochromator transmittance and the effect of the mismatching between seed beam and electron beam. Simulations show that the FEL power reaches 1 TW and that the spectral density for a TW pulse is about two orders of magnitude higher than that for the SASE pulse at saturation.

  10. Chemical stabilization of graphite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bistrika, Alexander A.; Lerner, Michael M.

    2018-04-03

    Embodiments of a device, or a component of a device, including a stabilized graphite surface, methods of stabilizing graphite surfaces, and uses for the devices or components are disclosed. The device or component includes a surface comprising graphite, and a plurality of haloaryl ions and/or haloalkyl ions bound to at least a portion of the graphite. The ions may be perhaloaryl ions and/or perhaloalkyl ions. In certain embodiments, the ions are perfluorobenzenesulfonate anions. Embodiments of the device or component including stabilized graphite surfaces may maintain a steady-state oxidation or reduction surface current density after being exposed to continuous oxidation conditions for a period of at least 1-100 hours. The device or component is prepared by exposing a graphite-containing surface to an acidic aqueous solution of the ions under oxidizing conditions. The device or component can be exposed in situ to the solution.

  11. Electron oxidation of graphite by fluorospecies

    International Nuclear Information System (INIS)

    Rosenthal, G.L.

    1984-09-01

    The fluoride-ion affinity (A/sub F - /) of phosphorus pentafluoride was determined to be 100 kcal/mole from the heats of reaction of the Lewis bases SF 4 and ClO 2 F with PF 5 near room temperature. The fluoride-ion affinity of boron trifluoride was determined to be 92 kcal/mole from the heat of reaction of ClO 2 F with BF 3 . The crystal structure of ClO 2 BF 4 was determined and a precise lattice energy was calculated from this structure and used to determined A/sub F - /. Both PF 5 and BF 3 were found to react with graphite in the presence of fluorine gas to yield a variety of non-stoichiometric compounds. The fluoride-ion affinity of silicon tetrafluoride is not known, but it does not react with graphite and F 2 except at high pressures. These and previous results suggested a threshold in oxidizing power of intercalating species below which the oxidative intercalation reaction would not occur. The reduction of C/sub x/PF 6 by PF 3 proved that the reaction is thermodynamically controlled to some extent. The displacement of PF 5 in C/sub x/PF 6 by BF 3 (with a smaller A/sub F - /) suggested that two BF 3 molecules may have a larger fluoride-ion affinity than one PF 5 and that B 2 F 7 - may be a stable anion in graphite. Conductivity studies of PF/sub x/ and BF/sub y/ salts showed that a large drop in conductivity when the reaction reaches first stage is due in the most part to direct fluorination of carbon in graphite

  12. Heat exchanger using graphite foam

    Science.gov (United States)

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  13. An Electron Microscopy Study of Graphite Growth in Nodular Cast Irons

    Science.gov (United States)

    Laffont, L.; Jday, R.; Lacaze, J.

    2018-04-01

    Growth of graphite during solidification and high-temperature solid-state transformation has been investigated in samples cut out from a thin-wall casting which solidified partly in the stable (iron-graphite) and partly in the metastable (iron-cementite) systems. Transmission electron microscopy has been used to characterize graphite nodules in as-cast state and in samples having been fully graphitized at various temperatures in the austenite field. Nodules in the as-cast material show a twofold structure characterized by an inner zone where graphite is disoriented and an outer zone where it is well crystallized. In heat-treated samples, graphite nodules consist of well-crystallized sectors radiating from the nucleus. These observations suggest that the disoriented zone appears because of mechanical deformation when the liquid contracts during its solidification in the metastable system. During heat-treatment, the graphite in this zone recrystallizes. In turn, it can be concluded that nodular graphite growth mechanism is the same during solidification and solid-state transformation.

  14. Management of UKAEA graphite liabilities

    International Nuclear Information System (INIS)

    Wise, M.

    2001-01-01

    The UK Atomic Energy Authority (UKAEA) is responsible for managing its liabilities for redundant research reactors and other active facilities concerned with the development of the UK nuclear technology programme since 1947. These liabilities include irradiated graphite from a variety of different sources including low irradiation temperature reactor graphite (the Windscale Piles 1 and 2, British Energy Pile O and Graphite Low Energy Experimental Pile at Harwell and the Material Testing Reactors at Harwell and Dounreay), advanced gas-cooled reactor graphite (from the Windscale Advanced Gas-cooled Reactor) and graphite from fast reactor systems (neutron shield graphite from the Dounreay Prototype Fast Reactor and Dounreay Fast Reactor). The decommissioning and dismantling of these facilities will give rise to over 6,000 tonnes of graphite requiring disposal. The first graphite will be retrieved from the dismantling of Windscale Pile 1 and the Windscale Advanced Gas-cooled Reactor during the next five years. UKAEA has undertaken extensive studies to consider the best practicable options for disposing of these graphite liabilities in a manner that is safe whilst minimising the associated costs and technical risks. These options include (but are not limited to), disposal as Low Level Waste, incineration, or encapsulation and disposal as Intermediate Level Waste. There are a number of technical issues associated with each of these proposed disposal options; these include Wigner energy, radionuclide inventory determination, encapsulation of graphite dust, galvanic coupling interactions enhancing the corrosion of mild steel and public acceptability. UKAEA is currently developing packaging concepts and designing packaging plants for processing these graphite wastes in consultation with other holders of graphite wastes throughout Europe. 'Letters of Comfort' have been sought from both the Low Level Waste and the Intermediate Level Waste disposal organisations to support the

  15. Fabrication of graphene device from graphite intercalation compound

    Science.gov (United States)

    Yagi, Ryuta; Kobara, Hiroaki; Shimomura, Midori; Tahara, Fumiya; Fukada, Seiya

    2012-02-01

    The mechanical exfoliation of graphite is possibly the simplest and practical method in laboratories to obtain graphene flakes for scientific research. However efficiency for obtaining graphene, with desired layer-number and size, depends largely on crystal specific characters, eg., dislocations. To improve the issue, we have adopted graphite intercalation compound (GIC) instead of graphite for a starting material. Generally, GIC is chemically active. We used SbCl5- GIC, which is stable in the atmosphere. Stage structure of SbCl5-GIC could be tuned by temperature of intercalation. We found that considerable number of undoped graphene flakes coexisted with thin SbCl5-GIC flakes, on a substrate where flakes were transferred.?Statistical inspection of number of graphene layer indicated that it is significantly dependent on the stage number of GIC.

  16. Graphite in Science and Nuclear Technique

    OpenAIRE

    Zhmurikov, E. I.; Bubnenkov, I. A.; Dremov, V. V.; Samarin, S. I.; Pokrovsky, A. S.; Harkov, D. V.

    2013-01-01

    The monograph is devoted to the application of graphite and graphite composites in science and technology. The structure and electrical properties, the technological aspects of production of high-strength synthetic graphites, the dynamics of the graphite destruction, traditionally used in the nuclear industry are discussed. It is focuses on the characteristics of graphitization and properties of graphite composites based on carbon isotope 13C. The book is based, generally, on the original res...

  17. Nano-scale orientation mapping of graphite in cast irons

    International Nuclear Information System (INIS)

    Theuwissen, Koenraad; Lacaze, Jacques; Véron, Muriel; Laffont, Lydia

    2014-01-01

    A diametrical section of a graphite spheroid from a ductile iron sample was prepared using the focused ion beam-lift out technique. Characterization of this section was carried out through automated crystal orientation mapping in a transmission electron microscope. This new technique automatically collects electron diffraction patterns and matches them with precalculated templates. The results of this investigation are crystal orientation and phase maps of the specimen, which bring new light to the understanding of growth mechanisms of this peculiar graphite morphology. This article shows that mapping the orientation of carbon-based materials such as graphite, which is difficult to achieve with conventional techniques, can be performed automatically and at high spatial resolution using automated crystal orientation mapping in a transmission electron microscope. - Highlights: • ACOM/TEM can be used to study the crystal orientation of carbon-based materials. • A spheroid is formed by conical sectors radiating from a central nuclei. • Misorientations exist within the conical sectors, defining various orientation domains

  18. Modification of structural graphite machining

    International Nuclear Information System (INIS)

    Lavrenev, M.M.

    1979-01-01

    Studied are machining procedures for structural graphites (GMZ, MG, MG-1, PPG) most widely used in industry, of the article mass being about 50 kg. Presented are dependences necessary for the calculation of cross sections of chip suction tappers and duster pipelines in machine shops for structural graphite machining

  19. Glass-Graphite Composite Materials

    International Nuclear Information System (INIS)

    Mayzan, M.Z.H.; Lloyd, J.W.; Heath, P.G.; Stennett, M.C.; Hyatt, N.C.; Hand, R.J.

    2016-01-01

    A summary is presented of investigations into the potential of producing glass-composite materials for the immobilisation of graphite or other carbonaceous materials arising from nuclear power generation. The methods are primarily based on the production of base glasses which are subsequently sintered with powdered graphite or simulant TRISO particles. Consideration is also given to the direct preparation of glass-graphite composite materials using microwave technology. Production of dense composite wasteforms with TRISO particles was more successful than with powdered graphite, as wasteforms containing larger amounts of graphite were resistant to densification and the glasses tried did not penetrate the pores under the pressureless conditions used. Based on the results obtained it is concluded that the production of dense glassgraphite composite wasteforms will require the application of pressure. (author)

  20. Interaction of boron with graphite: A van der Waals density functional study

    International Nuclear Information System (INIS)

    Liu, Juan; Wang, Chen; Liang, Tongxiang; Lai, Wensheng

    2016-01-01

    Highlights: • A van der Waals density-functional approach is applied to study the interaction of boron with graphite. • VdW-DF functionals give fair agreement of crystal parameters with experiments. • The π electron approaches boron while adsorbing on graphite surface. • The hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. • PBE cannot describe the interstitial boron in graphite because of the ignoring binding of graphite sheets. - Abstract: Boron doping has been widely investigated to improve oxidation resistance of graphite. In this work the interaction of boron with graphite is investigated by a van der Waals density-functional approach (vdW-DF). The traditional density-functional theory (DFT) is well accounted for the binding in boron-substituted graphite. However, to investigate the boron atom on graphite surface and the interstitial impurities require use of a description of graphite interlayer binding. Traditional DFT cannot describe the vdW physics, for instance, GGA calculations show no relevant binding between graphite sheets. LDA shows some binding, but they fail to provide an accurate account of vdW forces. In this paper, we compare the calculation results of graphite lattice constant and cohesive energy by several functionals, it shows that vdW-DF such as two optimized functionals optB88-vdW and optB86b-vdW give much improved results than traditional DFT. The vdW-DF approach is then applied to study the interaction of boron with graphite. Boron adsorption, substitution, and intercalation are discussed in terms of structural parameters and electronic structures. When adsorbing on graphite surface, boron behaves as π electron acceptor. The π electron approaches boron atom because of more electropositive of boron than carbon. For substitution situation, the hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. The B-doped graphite system with the hole has less

  1. Interaction of boron with graphite: A van der Waals density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juan; Wang, Chen [Beijing Key Lab of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Liang, Tongxiang, E-mail: txliang@tsinghua.edu.cn [State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Lai, Wensheng [Advanced Material Laboratory, School of Materials Science & Engineering, Tsinghua University, Beijing, 100084 (China)

    2016-08-30

    Highlights: • A van der Waals density-functional approach is applied to study the interaction of boron with graphite. • VdW-DF functionals give fair agreement of crystal parameters with experiments. • The π electron approaches boron while adsorbing on graphite surface. • The hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. • PBE cannot describe the interstitial boron in graphite because of the ignoring binding of graphite sheets. - Abstract: Boron doping has been widely investigated to improve oxidation resistance of graphite. In this work the interaction of boron with graphite is investigated by a van der Waals density-functional approach (vdW-DF). The traditional density-functional theory (DFT) is well accounted for the binding in boron-substituted graphite. However, to investigate the boron atom on graphite surface and the interstitial impurities require use of a description of graphite interlayer binding. Traditional DFT cannot describe the vdW physics, for instance, GGA calculations show no relevant binding between graphite sheets. LDA shows some binding, but they fail to provide an accurate account of vdW forces. In this paper, we compare the calculation results of graphite lattice constant and cohesive energy by several functionals, it shows that vdW-DF such as two optimized functionals optB88-vdW and optB86b-vdW give much improved results than traditional DFT. The vdW-DF approach is then applied to study the interaction of boron with graphite. Boron adsorption, substitution, and intercalation are discussed in terms of structural parameters and electronic structures. When adsorbing on graphite surface, boron behaves as π electron acceptor. The π electron approaches boron atom because of more electropositive of boron than carbon. For substitution situation, the hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. The B-doped graphite system with the hole has less

  2. Helium generation and diffusion in graphite and some carbides

    International Nuclear Information System (INIS)

    Holt, J.B.; Guinan, M.W.; Hosmer, D.W.; Condit, R.H.; Borg, R.J.

    1976-01-01

    The cross section for the generation of helium in neutron irradiated carbon was found to be 654 mb at 14.4 MeV and 744 mb at 14.9 MeV. Extrapolating to 14.1 MeV (the fusion reactor spectrum) gives 615 mb. The diffusion of helium in dense polycrystalline graphite and in pyrographite was measured and found to be D = 7.2 x 10 -7 m 2 s -1 exp (-80 kJ/RT). It is assumed that diffusion is primarily in the basal plane direction in crystals of the graphite. In polycrystalline graphite the path length is a factor of √2 longer than the measured distance due to the random orientation mismatch between successive grains. Isochronal anneals (measured helium release as the specimen is steadily heated) were run and maximum release rates were found at 200 0 C in polycrystalline graphite, 1000 0 C in pyrographite, 1350 0 C in boron carbide, and 1350 0 and 2400 0 C (two peaks) in silicon carbide. It is concluded that in these candidates for curtain materials in fusion reactors the helium releases can probably occur without bubble formation in graphites, may occur in boron carbide, but will probably cause bubble formation in silicon carbide. 7 figures

  3. Nanosecond formation of diamond and lonsdaleite by shock compression of graphite.

    Science.gov (United States)

    Kraus, D; Ravasio, A; Gauthier, M; Gericke, D O; Vorberger, J; Frydrych, S; Helfrich, J; Fletcher, L B; Schaumann, G; Nagler, B; Barbrel, B; Bachmann, B; Gamboa, E J; Göde, S; Granados, E; Gregori, G; Lee, H J; Neumayer, P; Schumaker, W; Döppner, T; Falcone, R W; Glenzer, S H; Roth, M

    2016-03-14

    The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystalline graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. Our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites.

  4. Crystallization of nodular cast iron with carbides

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2008-12-01

    Full Text Available In this paper a crystallization process of nodular cast iron with carbides having a different chemical composition have been presented. It have been found, that an increase of molybdenum above 0,30% causes the ledeburutic carbides crystallization after (γ+ graphite eutectic phase crystallization. When Mo content is lower, these carbides crystallize as a pre-eutectic phase. In this article causes of this effect have been given.

  5. The graphite deposit at Borrowdale (UK): A catastrophic mineralizing event associated with Ordovician magmatism

    Science.gov (United States)

    Ortega, L.; Millward, D.; Luque, F. J.; Barrenechea, J. F.; Beyssac, O.; Huizenga, J.-M.; Rodas, M.; Clarke, S. M.

    2010-04-01

    The volcanic-hosted graphite deposit at Borrowdale in Cumbria, UK, was formed through precipitation from C-O-H fluids. The δ 13C data indicate that carbon was incorporated into the mineralizing fluids by assimilation of carbonaceous metapelites of the Skiddaw Group by andesite magmas of the Borrowdale Volcanic Group. The graphite mineralization occurred as the fluids migrated upwards through normal conjugate fractures forming the main subvertical pipe-like bodies. The mineralizing fluids evolved from CO 2-CH 4-H 2O mixtures (XCO 2 = 0.6-0.8) to CH 4-H 2O mixtures. Coevally with graphite deposition, the andesite and dioritic wall rocks adjacent to the veins were intensely hydrothermally altered to a propylitic assemblage. The initial graphite precipitation was probably triggered by the earliest hydration reactions in the volcanic host rocks. During the main mineralization stage, graphite precipitated along the pipe-like bodies due to CO 2 → C + O 2. This agrees with the isotopic data which indicate that the first graphite morphologies crystallizing from the fluid (cryptocrystalline aggregates) are isotopically lighter than those crystallizing later (flakes). Late chlorite-graphite veins were formed from CH 4-enriched fluids following the reaction CH 4 + O 2 → C + 2H 2O, producing the successive precipitation of isotopically lighter graphite morphologies. Thus, as mineralization proceeded, water-generating reactions were involved in graphite precipitation, further favouring the propylitic alteration. The structural features of the pipe-like mineralized bodies as well as the isotopic homogeneity of graphite suggest that the mineralization occurred in a very short period of time.

  6. Comparison of the commercial color LCD and the medical monochrome LCD using randomized object test patterns.

    Directory of Open Access Journals (Sweden)

    Jay Wu

    Full Text Available Workstations and electronic display devices in a picture archiving and communication system (PACS provide a convenient and efficient platform for medical diagnosis. The performance of display devices has to be verified to ensure that image quality is not degraded. In this study, we designed a set of randomized object test patterns (ROTPs consisting of randomly located spheres with various image characteristics to evaluate the performance of a 2.5 mega-pixel (MP commercial color LCD and a 3 MP diagnostic monochrome LCD in several aspects, including the contrast, resolution, point spread effect, and noise. The ROTPs were then merged into 120 abdominal CT images. Five radiologists were invited to review the CT images, and receiver operating characteristic (ROC analysis was carried out using a five-point rating scale. In the high background patterns of ROTPs, the sensitivity performance was comparable between both monitors in terms of contrast and resolution, whereas, in the low background patterns, the performance of the commercial color LCD was significantly poorer than that of the diagnostic monochrome LCD in all aspects. The average area under the ROC curve (AUC for reviewing abdominal CT images was 0.717±0.0200 and 0.740±0.0195 for the color monitor and the diagnostic monitor, respectively. The observation time (OT was 145±27.6 min and 127±19.3 min, respectively. No significant differences appeared in AUC (p = 0.265 and OT (p = 0.07. The overall results indicate that ROTPs can be implemented as a quality control tool to evaluate the intrinsic characteristics of display devices. Although there is still a gap in technology between different types of LCDs, commercial color LCDs could replace diagnostic monochrome LCDs as a platform for reviewing abdominal CT images after monitor calibration.

  7. Easily exchangeable x-ray mirrors and hybrid monochromator modules a study of their performance

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Fan. [Philips Analytical, Asia Pacific, Toa Payoh, (Singapore); Kogan, V. [Philips Analytical, EA Almelo, (Netherlands); Saito, K. [Philips Analytical, Tokyo, (Japan)

    1999-12-01

    Full text: PreFix prealigned optical mounts allowing rapid and easily changeover will be presented. The benefits of laterally graded multilayer X-Ray mirrors coupled with these Prefix mounts - conversion of divergent beam to parallel beam, increase of intensity by a factor of 3-7, monochromation to {alpha}1 and {alpha}2 and a dynamic range of 10 {sup 4-5} CpS will be demonstrated in areas such as Thin Film and Powder analysis. Data will be shown on a diffraction profile of thin film (Cr/SiO{sub 2}) with and without a mirror and Si powder with and without a mirror. Further enhancement will be demonstrated by combining a channel cut monochromator-collimator with an X-Ray mirror to produce a high intensity, parallel, pure Cu K{alpha}1 beam with a high intensity of up to 4.5 x 10{sup 8} cps and a divergence down to 0.01 deg. The applicability to various ranging from High Resolution to thin film/reflectivity to Rietveld structural refinement and to phase analysis will be shown. The Rocking curve of HEMT 10nm InGaAs on InP will be presented using various `standard` optics and hybrid optics, also Si powder and a Rietveld refinement of CuS0{sub 4}.5H{sub 2}0 and Aspirin. A comparison of the benefits and application of X-Ray Mirrors and Hybrid Mirror/Monochromators will be given. The data presented will show that by using X-Ray Mirrors and Hybrid modules the performance of standard `Laboratory` Diffractometers can be greatly enhanced to a level previously unachievable with great practical benefits. Copyright (1999) Australian X-ray Analytical Association Inc.

  8. Hypervelocity impacts into graphite

    Science.gov (United States)

    Latunde-Dada, S.; Cheesman, C.; Day, D.; Harrison, W.; Price, S.

    2011-03-01

    Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms-1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

  9. Hypervelocity impacts into graphite

    International Nuclear Information System (INIS)

    Latunde-Dada, S; Cheesman, C; Day, D; Harrison, W; Price, S

    2011-01-01

    Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms -1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

  10. Acoustic emission from polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, I.; Yoda, S.; Oku, T.; Miyamoto, Y.

    1987-01-01

    Acoustic emission was monitored from polycrystalline graphites with different microstructure (pore size and pore volume) subjected to compressive loading. The graphites used in this study comprised five brands, that is, PGX, ISEM-1, IG-11, IG-15, and ISO-88. A root mean square (RMS) voltage and event counts of acoustic emission for graphites were measured during compressive loading. The acoustic emission was measured using a computed-based data acquisition and analysis system. The graphites were first deformed up to 80 % of the average fracture stress, then unloaded and reloaded again until the fracture occured. During the first loading, the change in RMS voltage for acoustic emission was detected from the initial stage. During the unloading, the RMS voltage became zero level as soon as the applied stress was released and then gradually rose to a peak and declined. The behavior indicated that the reversed plastic deformation occured in graphites. During the second loading, the RMS voltage gently increased until the applied stress exceeded the maximum stress of the first loading; there is no Kaiser effect in the graphites. A bicrystal model could give a reasonable explanation of this results. The empirical equation between the ratio of σ AE to σ f and σ f was obtained. It is considered that the detection of microfracture by the acoustic emission technique is effective in macrofracture prediction of polycrystalline graphites. (author)

  11. Radiolytic graphite oxidation revisited

    International Nuclear Information System (INIS)

    Minshall, P.C.; Sadler, I.A.; Wickham, A.J.

    1996-01-01

    The importance of radiolytic oxidation in graphite-moderated CO 2 -cooled reactors has long been recognised, especially in the Advanced Gas-Cooled Reactors where potential rates are higher because of the higher gas pressure and ratings than the earlier Magnox designs. In all such reactors, the rate of oxidation is partly inhibited by the CO produced in the reaction and, in the AGR, further reduced by the deliberate addition of CH 4 . Significant roles are also played by H 2 and H 2 O. This paper reviews briefly the mechanisms of these processes and the data on which they are based. However, operational experience has demonstrated that these basic principles are unsatisfactory in a number of respects. Gilsocarbon graphites produced by different manufacturers have demonstrated a significant difference in oxidation rate despite a similar specification and apparent equivalence in their pore size and distribution, considered to be the dominant influence on oxidation rate for a given coolant-gas composition. Separately, the inhibiting influence of CH 4 , which for many years had been considered to arise from the formation of a sacrificial deposit on the pore walls, cannot adequately be explained by the actual quantities of such deposits found in monitoring samples which frequently contain far less deposited carbon than do samples from Magnox reactors where the only source of such deposits is the CO. The paper also describes the current status of moderator weight-loss predictions for Magnox and AGR Moderators and the validation of the POGO and DIFFUSE6 codes respectively. 2 refs, 5 figs

  12. First operation of an extended range grasshopper monochromator on the Aladdin storage ring

    International Nuclear Information System (INIS)

    Brown, F.C.

    1986-01-01

    First operation of a new extended range monochromator on the 1 GeV storage ring Aladdin is described. Curves are given of output flux as a function of photon energy for the 2 m and for the 5 m gratings as measured with an NBS diode. Relatively low background and flux up to 1500 eV is obtained using a 1200 line/mm 5 m holographic grating. Highly reproducible scans were obtained of the transmission of thin films including the carbon K and titanium L edges. This reproducibility and high throughput is in large part due to the small beam size and excellent stability of Aladdin. (orig.)

  13. Image quality evaluation of medical color and monochrome displays using an imaging colorimeter

    Science.gov (United States)

    Roehrig, Hans; Gu, Xiliang; Fan, Jiahua

    2012-10-01

    The purpose of this presentation is to demonstrate the means which permit examining the accuracy of Image Quality with respect to MTF (Modulation Transfer Function) and NPS (Noise Power Spectrum) of Color Displays and Monochrome Displays. Indications were in the past that color displays could affect the clinical performance of color displays negatively compared to monochrome displays. Now colorimeters like the PM-1423 are available which have higher sensitivity and color accuracy than the traditional cameras like CCD cameras. Reference (1) was not based on measurements made with a colorimeter. This paper focuses on the measurements of physical characteristics of the spatial resolution and noise performance of color and monochrome medical displays which were made with a colorimeter and we will after this meeting submit the data to an ROC study so we have again a paper to present at a future SPIE Conference.Specifically, Modulation Transfer Function (MTF) and Noise Power Spectrum (NPS) were evaluated and compared at different digital driving levels (DDL) between the two medical displays. This paper focuses on the measurements of physical characteristics of the spatial resolution and noise performance of color and monochrome medical displays which were made with a colorimeter and we will after this meeting submit the data to an ROC study so we have again a paper to present at a future Annual SPIE Conference. Specifically, Modulation Transfer Function (MTF) and Noise Power Spectrum (NPS) were evaluated and compared at different digital driving levels (DDL) between the two medical displays. The Imaging Colorimeter. Measurement of color image quality needs were done with an imaging colorimeter as it is shown below. Imaging colorimetry is ideally suited to FPD measurement because imaging systems capture spatial data generating millions of data points in a single measurement operation. The imaging colorimeter which was used was the PM-1423 from Radiant Imaging. It uses

  14. Performance of the SURF-II high-throughput toroidal grating monochromator

    International Nuclear Information System (INIS)

    Kurtz, R.L.; Ederer, D.L.; Barth, J.; Stockbauer, R.

    1988-01-01

    The performance of the 'high-flux' toroidal grating monochromator (HFTGM) at the NBS SURF-II synchrotron storage ring is assessed. Two gratings are studied: One with a ruled profile and the other having a laminar profile. The laminar profile is shown to reduce substantially the intensity of higher-order diffracted light with only a small decrease in the intensity of the first order light. The dependence of the energy resolution as a function of the area of the grating illuminated is also discussed. (orig.)

  15. Raytracing, chopper, and guideline for double-headed Dragon monochromators (invited)

    International Nuclear Information System (INIS)

    Chen, C.T.

    1992-01-01

    The raytracing of the double-headed Dragon, a recently proposed monochromator for producing two simultaneous left and right circularly polarized soft x-ray beams, is presented. The energy resolution and wavelength of these two beams are confirmed to be identical, and the high performance of the original Dragon is found to be preserved in the double-headed configuration. A compact ultra-high vacuum compatible chopper for rapid alternation between left and right helicities is presented, and a guideline for collecting circularly polarized light from bending magnet sources is given

  16. A new gradient monochromator for the IN13 back-scattering spectrometer

    International Nuclear Information System (INIS)

    Ciampolini, L.; Bove, L.E.; Mondelli, C.; Alianelli, L.; Labbe-Lavigne, S.; Natali, F.; Bee, M.; Deriu, A.

    2005-01-01

    We present new McStas simulations of the back-scattering thermal neutron spectrometer IN13 to evaluate the advantages of a new temperature gradient monochromator relative to a conventional one. The simulations show that a flux gain up to a factor 7 can be obtained with just a 10% loss in energy resolution and a 20% increase in beam spot size at the sample. The results also indicate that a moderate applied temperature gradient (ΔT∼16K) is sufficient to obtain this significant flux gain. n

  17. A facility for plastic deformation of germanium single-crystal wafers

    DEFF Research Database (Denmark)

    Lebech, B.; Theodor, K.; Breiting, B.

    1998-01-01

    . All movements and temperature changes are done by a robot via a PLC-control system. Two nine-crystal focusing monochromators (54 x 116 and 70 x 116 mm(2)) made from 100 wafers with average mosaicity similar to 13' have been constructed. Summaries of the test results are presented. (C) 1998 Elsevier...

  18. Effect of iron and chromium on the graphitization behaviour of sulfur-containing carbon

    International Nuclear Information System (INIS)

    Tyumentsev, V.A.; Belenkov, E.A.; Saunina, S.I.; Podkopaev, S.A.; Shvejkin, G.P.

    1998-01-01

    Process of transition of carbonaceous material, containing structurally incorporated sulfur, into graphite and impact of iron and chromium additions are studied. It is established that carbonaceous material, containing more than 1.5 mass % S and also 1.5 mass % Cr 2 O 3 is heterogeneous after thermal treatment at 1300-1600 deg C. It consists of large and sufficiency complete areas of coherent scattering having graphite structure and ultra-dispersed matrix. The number of graphite crystals formed in the presence of dispersed iron within this temperature range, decreases by two times [ru

  19. SURFACE MODIFICATION OF SEMICONDUCTOR THIN FILM OF TiO2 ON GRAPHITE SUBSTRATE BY Cu-ELECTRODEPOSITION

    Directory of Open Access Journals (Sweden)

    Fitria Rahmawati

    2010-06-01

    Full Text Available Surface modification of graphite/TiO2 has been done by mean of Cu electrodeposition. This research aims to study the effect of Cu electrodeposition on photocatalytic enhancing of TiO2. Electrodeposition has been done using CuSO4 0,4 M as the electrolyte at controlled current. The XRD pattern of modified TiO2 thin film on graphite substrate exhibited new peaks at 2θ= 43-44o and 2θ= 50-51o that have been identified as Cu with crystal cubic system, face-centered crystal lattice and crystallite size of 26-30 nm. CTABr still remains in the material as impurities. Meanwhile, based on morphological analysis, Cu particles are dissipated in the pore of thin film. Graphite/TiO2/Cu has higher photoconversion efficiency than graphite/TiO2.   Keywords: semiconductor, graphite/TiO2, Cu electrodeposition

  20. Chemisputtering of interstellar graphite grains

    International Nuclear Information System (INIS)

    Draine, B.T.

    1979-01-01

    The rate of erosion of interstellar graphite grains as a result of chemical reaction with H, N, and O is estimated using the available experiment evidence. It is argued that ''chemical sputtering'' yields for interstellar graphite grains will be much less than unity, contrary to earlier estimates by Barlow and Silk. Chemical sputtering of graphite grains in evolving H II regions is found to be unimportant, except in extremely compact (n/sub H/> or approx. =10 5 cm -3 ) H II regions. Alternative explanations are considered for the apparent weakness of the lambda=2175 A extinction ''bump'' in the direction of several early type stars

  1. Obtention of nuclear grade graphite

    International Nuclear Information System (INIS)

    Ferreira, M.L.

    1984-01-01

    The impurity level of natural graphite found in some of the most important mines of the State of Minas Gerais - Brasil is determined. It is also concerned with the development and use of natural graphite in nuclear reactors. Standard methods for chemical and instrumentsal analysis such as Spectrografic Determination by Emission, Spectrografic Determination by X-Rays, Spectrografic Determination by Atomic Asorption, Photometric Determination, and also chemical and physical methods for separation of impurities as well standard method for Estimating the Thermal Neutron Absorption Cross Section of graphite were employed. Some aditionals methods of purification to the ordinary treatment such as the use of metanol and halogens are also described. (Author) [pt

  2. The irradiation induced creep of graphite under accelerated damage produced by boron doping

    International Nuclear Information System (INIS)

    Brocklehurst, J.E.

    1975-01-01

    The presence of boron enhances fast neutron irradiation damage in graphite by providing nucleation sites for interstitial loop formation. Doping with 11 B casues an increase in the irradiation induced macroscopic dimensional changes, which have been shown to result from an acceleration in the differential crystal growth rate for a given carbon atom displacement rate. Models of irradiation induced creep in graphite have centred around those in which creep is induced by internal stresses due to the anisotopic crystal growth, and those in which creep is activated by atomic displacements. A creep test on boron doped graphite has been performed in an attempt to establish which of these mechanisms is the determining factor. An isotropic nuclear graphite was doped to a 11 B concentration of 0.27 wt.%. The irradiation induced volume shrinkage rate at 750 0 C increased by a factor of 3 over that of the virgin graphite, in agreement with predictions from the earlier work, but the total creep strains were comparable in both doped and virgin samples. This observation supports the view that irradiation induced creep is dependent only on the carbon atom displacement rate and not on the internal stress level determined by the differential crystal growth rate. The implications of this result on the irradiation behaviour of graphite containing significant concentrations of boron are briefly discussed. (author)

  3. Characterization of Ignalina NPP RBMK Reactors Graphite

    International Nuclear Information System (INIS)

    Hacker, P.J.; Neighbour, G.B.; Levinskas, R.; Milcius, D.

    2001-01-01

    The paper concentrates on the investigations of the initial physical properties of graphite used in production of graphite bricks of Ignalina NPP. These graphite bricks are used as nuclear moderator and major core structural components. Graphite bulk density is calculated by mensuration, pore volumes are measured by investigation of helium gas penetration in graphite pore network, the Young's modulus is determined using an ultrasonic time of flight method, the coefficient of thermal expansion is determined using a Netzsch dilatometer 402C, the fractured and machined graphite surfaces are studied using SEM, impurities are investigated qualitatively by EDAX, the degree of graphitization of the material is tested using X-ray diffraction. (author)

  4. Output diagnostics of the grazing incidence plane grating monochromator BUMBLE BEE (15 to 1500 eV)

    Energy Technology Data Exchange (ETDEWEB)

    Jark, W.; Kunz, C.

    1985-09-01

    The BUMBLE BEE is a bakeable uhv compatible plane grating monochromator, with a fixed exit beam, and the capability to suppress higher order radiation in a wide energy range. The instrument was built to be used in connection with a uhv reflectometer and has a differential pumping section between the optical components and the sample, allowing a pressure of 10/sup -5/ torr in the experimental chamber without influencing the uhv in the monochromator. The monochromator is not optimized for resolution. Due to its location at a beamline with a short source distance we achieve only medium resolving power in the order of E/..delta..E approx. = 200. The primary goal is the suppression of higher orders, fortunately the thus selected operating parameters for the coupled rotations of the optical components also give nearly the highest available output. The instrument is characterized in great detail. The performance of the instrument is discussed and compared with extensive theoretical calculations.

  5. Graphite in Science and Nuclear Technology

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This review is devoted to the application of graphite and graphite composites in the science and technology. Structure and electrical properties, technological aspects of producing of high-strength artificial graphite and dynamics of its destruction are considered. These type of graphite are traditionally used in the nuclear industry, so author concentrates on actual problems of application and testing of graphite materials in modern science and technology. Translated from chapters 1 of monog...

  6. Mesostructure of graphite composite and its lifetime

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This review is devoted to the application of graphite and graphite composites in science and technology. Structure and electrical properties, as so technological aspects of producing of high strength artificial graphite and dynamics of its destruction are considered. These type of graphite are traditionally used in the nuclear industry. Generally, the review relies, on the original results and concentrates on actual problems of application and testing of graphite materials in modern nuclear p...

  7. Reflectivity and filtering characteristics of pyrolytic graphite

    International Nuclear Information System (INIS)

    Adib, M.; Abdel-Kawy, A.; Ashry, A.; Abbas, Y.; Wahba, W.

    1988-01-01

    The neutron transmission measurements through oriented pyrolytic graphite (P.G. crystal) were carried out in the wavelength band from 0.15 nm to 6.5 nm at different orientations of the (002) plane of the crystal w.r.t. the neutron beam direction. It was found that the P.G. crystal may be tuned for optimum scattering of second-order neutrons in the wavelength ranging between 0.112 nm and 0.425 nm, by adjusting the filter in an appropriate orientation. The reflectivity of (002), (004) and (006) planes of P.G. were measured and the following results are obtained: the reflectivity of (002) plane was found to be 99% by (transmission method). The ratio of the integrated intensity of the reflected neutrons from (004) and (006) is 3.14+-0.25 and is found to be in agreement with the calculated ratio. The measurements were performed using the fixed scattering angle spectrometer installed in front of the ET-RR-1 reactor horizontal channel

  8. Graphite surveillance in N Reactor

    International Nuclear Information System (INIS)

    Woodruff, E.M.

    1991-09-01

    Graphite dimensional changes in N Reactor during its 24 yr operating history are reviewed. Test irradiation results, block measurements, stack profiles, top of reflector motion monitors, and visual observations of distortion are described. 18 refs., 14 figs., 1 tab

  9. Graphite oxidation in HTGR atmosphere

    International Nuclear Information System (INIS)

    Growcock, F.B.; Barry, J.J.; Finfrock, C.C.; Rivera, E.; Heiser, J.H. III

    1982-01-01

    On-going and recently completed studies of the effect of thermal oxidation on the structural integrity of HTGR candidate graphites are described, and some results are presented and discussed. This work includes the study of graphite properties which may play decisive roles in the graphites' resistance to oxidation and fracture: pore size distribution, specific surface area and impurity distribution. Studies of strength loss mechanisms in addition to normal oxidation are described. Emphasis is placed on investigations of the gas permeability of HTGR graphites and the surface burnoff phenomenon observed during recent density profile measurements. The recently completed studies of catalytic pitting and the effects of prestress and stress on reactivity and ultimate strength are also discussed

  10. Graphite materials for nuclear reactors

    International Nuclear Information System (INIS)

    Oku, Tatsuo

    1991-01-01

    Graphite materials have been used in the nuclear fission reactors from the beginning of the reactor development for the speed reduction and reflection of neutron. Graphite materials are used both as a moderator and as a reflector in the core of high temperature gas-cooled reactors, and both as a radiation shielding material and as a reflector in the surrounding of the core for the fast breeder reactor. On the other hand, graphite materials are being positively used as a first wall of plasma as it is known that low Z materials are useful for holding high temperature plasma in the nuclear fusion devices. In this paper the present status of the application of graphite materials to the nuclear fission reactors and fusion devices (reactors) is presented. In addition, a part of results on the related properties to the structural design and safety evaluation and results examined on the subjects that should be done in the future are also described. (author)

  11. Design and fabrication of an active polynomial grating for soft-X-ray monochromators and spectrometers

    CERN Document Server

    Chen, S J; Perng, S Y; Kuan, C K; Tseng, T C; Wang, D J

    2001-01-01

    An active polynomial grating has been designed for use in synchrotron radiation soft-X-ray monochromators and spectrometers. The grating can be dynamically adjusted to obtain the third-order-polynomial surface needed to eliminate the defocus and coma aberrations at any photon energy. Ray-tracing results confirm that a monochromator or spectrometer based on this active grating has nearly no aberration limit to the overall spectral resolution in the entire soft-X-ray region. The grating substrate is made of a precisely milled 17-4 PH stainless steel parallel plate, which is joined to a flexure-hinge bender shaped by wire electrical discharge machining. The substrate is grounded into a concave cylindrical shape with a nominal radius and then polished to achieve a roughness of 0.45 nm and a slope error of 1.2 mu rad rms. The long trace profiler measurements show that the active grating can reach the desired third-order polynomial with a high degree of figure accuracy.

  12. Intercalation of lanthanide trichlorides in graphite

    International Nuclear Information System (INIS)

    Stumpp, E.; Nietfeld, G.

    1979-01-01

    The reactions of the whole series of lanthanide trichlorides with graphite have been investigated. Intercalation compounds have been prepared with the chlorides of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y whereas LaCl 3 , CeCl 3 , PrCl 3 and NdCl 3 do not intercalate. The compounds were characterized by chemical and X-ray analysis. The amount of c-axis increase is consistent with the assumption that the chlorides are intercalated in form of a chloride layer sandwich resmbling the sheets in YCl 3 . The chlorides which do not intercalate crystallize in the UCl 3 structure having 3 D arrangements of ions. Obviously, these chlorides cannot form sheets between the carbon layers. The ability of AlCl 3 to volatilize lanthanide chlorides through complex formation in the gas phase can be used to increase the intercalation rate strikingly. (author)

  13. Graphite selection for the PBMR reflector

    International Nuclear Information System (INIS)

    Marsden, B.J.; Preston, S.D.

    2000-01-01

    A high temperature, direct cycle gas turbine, graphite moderated, helium cooled, pebble-bed reactor (PBMR) is being designed and constructed in South Africa. One of the major components in the PBMR is the graphite reflector, which must be designed to last thirty-five full power years. Fast neutron irradiation changes the dimensions and material properties of reactor graphite, thus for design purposes a suitable graphite database is required. Data on the effect of irradiation on nuclear graphites has been gathered for many years, at considerable financial cost, but unfortunately these graphites are no longer available due to rationalization of the graphite industry and loss of key graphite coke supplies. However, it is possible, using un-irradiated graphite materials properties and knowledge of the particular graphite microstructure, to determine the probable irradiation behaviour. Three types of nuclear graphites are currently being considered for the PBMR reflector: an isostatically moulded, fine grained, high strength graphite and two extruded medium grained graphites of moderately high strength. Although there is some irradiation data available for these graphites, the data does not cover the temperature and dose range required for the PBMR. The available graphites have been examined to determine their microstructure and some of the key material properties are presented. (authors)

  14. Design of a high-resolution high-stability positioning mechanism for crystal optics

    International Nuclear Information System (INIS)

    Shu, D.; Toellner, T. S.; Alp, E. E.

    1999-01-01

    The authors present a novel miniature multi-axis driving structure that will allow positioning of two crystals with better than 50-nrad angular resolution and nanometer linear driving sensitivity.The precision and stability of this structure allow the user to align or adjust an assembly of crystals to achieve the same performance as does a single channel-cut crystal, so they call it an artificial channel-cut crystal. In this paper, the particular designs and specifications, as well as the test results,for a two-axis driving structure for a high-energy-resolution artificial channel-cut crystal monochromator are presented

  15. Brilliance and flux reduction in imperfect inclined crystals

    International Nuclear Information System (INIS)

    Lee, W.K.; Blasdell, R.C.; Fernandez, P.B.; Macrander, A.T.; Mills, D.M.

    1996-01-01

    The inclined crystal geometry has been suggested as a method of reducing the surface absorbed power density of high-heat-load monochromators for third-generation synchrotron radiation sources. Computer simulations have shown that if the crystals are perfectly aligned and have no strains then the diffraction properties of a pair of inclined crystals are very similar to a pair of conventional flat crystals with only subtle effects differentiating the two configurations. However, if the crystals are strained, these subtle differences in the behavior of inclined crystals can result in large beam divergences causing brilliance and flux losses. This manuscript elaborates on these issues and estimates potential brilliance and flux losses from strained inclined crystals at the APS

  16. Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Marcu, A., E-mail: aurelian.marcu@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania); Avotina, L. [Institute of Chemical Physics, University of Latvia, Kronvalda 4, LV 1010 Riga (Latvia); Porosnicu, C. [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania); Marin, A. [Ilie Murgulescu” Institute of Physical Chemistry, 202 Splaiul Independentei 060021, Bucharest (Romania); Grigorescu, C.E.A. [National Institute R& D for Optoelectronics INOE 2000, 077125 Bucharest (Romania); Ursescu, D. [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania); Lungu, M. [National Institute of Materials Physics Atomistilor Str., 105 bis, 077125, Magurele (Romania); Demitri, N. [Hard X-ray Beamline and Structural Biology, Elettra-Sincrotrone Trieste, Strada Statale 14 - km 163,5 in AREA Science Park, 34149 Basovizza TS Italy (Italy); Lungu, C.P. [National Institute for Laser, Plasma and Radiation Physics, 077125 Bucharest (Romania)

    2015-11-15

    Graphical abstract: - Highlights: • Polycrystalline graphite was irradiated with a high power fs (IR) laser. • Presence of a diamond peak was detected by synchrotron XRD. • XPS and Raman showed in-depth sp{sup 3}% increase at tens of nm below the surface. • sp{sup 3}% is increasing with laser power density but it is independent of photon absorption rate. • Graphite crystallite size locally increase at tens of nanometers below the irradiated spots. - Abstract: A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp{sup 3} bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp{sup 3} percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not on the surface) increase of the crystallite size. Based on the wavelength dependent photon absorption into graphite, the observed effects are correlated with high density photon per atom and attributed to the melting and recrystallization processes taking place tens of nanometers below the target surface.

  17. Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation

    International Nuclear Information System (INIS)

    Marcu, A.; Avotina, L.; Porosnicu, C.; Marin, A.; Grigorescu, C.E.A.; Ursescu, D.; Lungu, M.; Demitri, N.; Lungu, C.P.

    2015-01-01

    Graphical abstract: - Highlights: • Polycrystalline graphite was irradiated with a high power fs (IR) laser. • Presence of a diamond peak was detected by synchrotron XRD. • XPS and Raman showed in-depth sp 3 % increase at tens of nm below the surface. • sp 3 % is increasing with laser power density but it is independent of photon absorption rate. • Graphite crystallite size locally increase at tens of nanometers below the irradiated spots. - Abstract: A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp 3 bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp 3 percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not on the surface) increase of the crystallite size. Based on the wavelength dependent photon absorption into graphite, the observed effects are correlated with high density photon per atom and attributed to the melting and recrystallization processes taking place tens of nanometers below the target surface.

  18. Neutron irradiation damage of nuclear graphite studied by high-resolution transmission electron microscopy and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, R. [Dalton Cumbrian Facility, Dalton Nuclear Institute, The University of Manchester, Westlakes Science & Technology Park, Moor Row, Whitehaven, Cumbria, CA24 3HA (United Kingdom); Jones, A.N., E-mail: Abbie.Jones@manchester.ac.uk [Nuclear Graphite Research Group, School of MACE, The University of Manchester, Manchester, M13 9PL (United Kingdom); McDermott, L.; Marsden, B.J. [Nuclear Graphite Research Group, School of MACE, The University of Manchester, Manchester, M13 9PL (United Kingdom)

    2015-12-15

    Nuclear graphite components are produced from polycrystalline artificial graphite manufacture from a binder and filler coke with approximately 20% porosity. During the operational lifetime, nuclear graphite moderator components are subjected to fast neutron irradiation which contributes to the change of material and physical properties such as thermal expansion co-efficient, young's modulus and dimensional change. These changes are directly driven by irradiation-induced changes to the crystal structure as reflected through the bulk microstructure. It is therefore of critical importance that these irradiation changes and there implication on component property changes are fully understood. This work examines a range of irradiated graphite samples removed from the British Experimental Pile Zero (BEPO) reactor; a low temperature, low fluence, air-cooled Materials Test Reactor which operated in the UK. Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM) have been employed to characterise the effect of increased irradiation fluence on graphite microstructure and understand low temperature irradiation damage processes. HRTEM confirms the structural damage of the crystal lattice caused by irradiation attributed to a high number of defects generation with the accumulation of dislocation interactions at nano-scale range. Irradiation-induced crystal defects, lattice parameters and crystallite size compared to virgin nuclear graphite are characterised using selected area diffraction (SAD) patterns in TEM and Raman Spectroscopy. The consolidated ‘D’peak in the Raman spectra confirms the formation of in-plane point defects and reflected as disordered regions in the lattice. The reduced intensity and broadened peaks of ‘G’ and ‘D’ in the Raman and HRTEM results confirm the appearance of turbulence and disordering of the basal planes whilst maintaining their coherent layered graphite structure. - Highlights: • Irradiated graphite

  19. Neutron irradiation damage of nuclear graphite studied by high-resolution transmission electron microscopy and Raman spectroscopy

    International Nuclear Information System (INIS)

    Krishna, R.; Jones, A.N.; McDermott, L.; Marsden, B.J.

    2015-01-01

    Nuclear graphite components are produced from polycrystalline artificial graphite manufacture from a binder and filler coke with approximately 20% porosity. During the operational lifetime, nuclear graphite moderator components are subjected to fast neutron irradiation which contributes to the change of material and physical properties such as thermal expansion co-efficient, young's modulus and dimensional change. These changes are directly driven by irradiation-induced changes to the crystal structure as reflected through the bulk microstructure. It is therefore of critical importance that these irradiation changes and there implication on component property changes are fully understood. This work examines a range of irradiated graphite samples removed from the British Experimental Pile Zero (BEPO) reactor; a low temperature, low fluence, air-cooled Materials Test Reactor which operated in the UK. Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM) have been employed to characterise the effect of increased irradiation fluence on graphite microstructure and understand low temperature irradiation damage processes. HRTEM confirms the structural damage of the crystal lattice caused by irradiation attributed to a high number of defects generation with the accumulation of dislocation interactions at nano-scale range. Irradiation-induced crystal defects, lattice parameters and crystallite size compared to virgin nuclear graphite are characterised using selected area diffraction (SAD) patterns in TEM and Raman Spectroscopy. The consolidated ‘D’peak in the Raman spectra confirms the formation of in-plane point defects and reflected as disordered regions in the lattice. The reduced intensity and broadened peaks of ‘G’ and ‘D’ in the Raman and HRTEM results confirm the appearance of turbulence and disordering of the basal planes whilst maintaining their coherent layered graphite structure. - Highlights: • Irradiated graphite exhibits

  20. Mechanical design and performance evaluation for plane grating monochromator in a soft X-ray microscopy beamline at SSRF.

    Science.gov (United States)

    Gong, Xuepeng; Lu, Qipeng

    2015-01-01

    A new monochromator is designed to develop a high performance soft X-ray microscopy beamline at Shanghai Synchrotron Radiation Facility (SSRF). But owing to its high resolving power and high accurate spectrum output, there exist many technical difficulties. In the paper presented, as two primary design targets for the monochromator, theoretical energy resolution and photon flux of the beamline are calculated. For wavelength scanning mechanism, primary factors affecting the rotary angle errors are presented, and the measuring results are 0.15'' and 0.17'' for plane mirror and plane grating, which means that it is possible to provide sufficient scanning precision to specific wavelength. For plane grating switching mechanism, the repeatabilities of roll, yaw and pitch angles are 0.08'', 0.12'' and 0.05'', which can guarantee the high accurate switch of the plane grating effectively. After debugging, the repeatability of light spot drift reaches to 0.7'', which further improves the performance of the monochromator. The commissioning results show that the energy resolving power is higher than 10000 at Ar L-edge, the photon flux is higher than 1 × 108 photons/sec/200 mA, and the spatial resolution is better than 30 nm, demonstrating that the monochromator performs very well and reaches theoretical predictions.

  1. Experience with graphite in JET

    International Nuclear Information System (INIS)

    Pick, M.A.; Celentano, G.; Deksnis, E.; Dietz, K.J.; Shaw, R.; Sonnenberg, K.; Walravens, M.

    1987-01-01

    During the current operational period of JET more than 50% of the internal area of the machine is covered in graphite tiles. This includes the 15 m 2 of carbon tiles installed in the new toroidal limiter, the 40 poloidal belts of graphite tiles covering the U-joints and bellows as well as a two metre high ring (-- 20 m 2 ) or carbon tiles on the inner wall of the Torus. A ring of tiles in the equatorial plane (3 tiles high) consists of carbon-carbon fibre tiles. Test bed results indicated that the fine grained graphite tiles cracked at ∼ 1 kW/cm 2 for 2s of irradiation whereas the carbon-carbon fibre tiles were able to sustain a flux, limited by the irradiation facility, of 3.5 kW for 3s without any damage. The authors report on the generally positive experience they have had had with the installed graphite during the present and previous in-vessel configurations. This includes the physical integrity of the tiles under severe conditions such as high energy run-away electron beams, plasma disruptions and high heat fluxes. They report on the importance of the precise positioning of the inner wall and x-point tiles at the very high power fluxes of JET and the effect of deviations on both graphite and carbon-fibre tiles

  2. Porous (Swiss-Cheese Graphite

    Directory of Open Access Journals (Sweden)

    Joseph P. Abrahamson

    2018-05-01

    Full Text Available Porous graphite was prepared without the use of template by rapidly heating the carbonization products from mixtures of anthracene, fluorene, and pyrene with a CO2 laser. Rapid CO2 laser heating at a rate of 1.8 × 106 °C/s vaporizes out the fluorene-pyrene derived pitch while annealing the anthracene coke. The resulting structure is that of graphite with 100 nm spherical pores. The graphitizablity of the porous material is the same as pure anthracene coke. Transmission electron microscopy revealed that the interfaces between graphitic layers and the pore walls are unimpeded. Traditional furnace annealing does not result in the porous structure as the heating rates are too slow to vaporize out the pitch, thereby illustrating the advantage of fast thermal processing. The resultant porous graphite was prelithiated and used as an anode in lithium ion capacitors. The porous graphite when lithiated had a specific capacity of 200 mAh/g at 100 mA/g. The assembled lithium ion capacitor demonstrated an energy density as high as 75 Wh/kg when cycled between 2.2 V and 4.2 V.

  3. Some thoughts on source monochromation and the implications for electron energy loss spectroscopy

    CERN Document Server

    Brydson, R; Brown, A

    2003-01-01

    We briefly outline the factors determining the intrinsic widths of features in electron energy loss near edge structure (ELNES) measured by electron energy loss spectroscopy (EELS) in the transmission electron microscope (TEM). We have made estimates of the differing contributions of both the initial and final state lifetime effects in the ELNES ionisation processes and also show how these may be combined with the instrumental energy resolution. We discuss the potential benefits of source monochromation for ELNES measurements via a comparison of these theoretical estimates with experimental spectra from the literature. We show that for certain core level excitations, solid state broadening mechanisms may be the fundamental limiting factor for resolving fine detail in ELNES. (orig.)

  4. The sapphire backscattering monochromator at the Dynamics beamline P01 of PETRA III

    Energy Technology Data Exchange (ETDEWEB)

    Alexeev, P., E-mail: pavel.alexeev@desy.de [Deutsches Elektronen-Synchrotron DESY (Germany); Asadchikov, V. [Russian Academy of Sciences, A.V. Shubnikov Institute of Crystallography (Russian Federation); Bessas, D. [European Synchrotron Radiation Facility (France); Butashin, A.; Deryabin, A. [Russian Academy of Sciences, A.V. Shubnikov Institute of Crystallography (Russian Federation); Dill, F.-U.; Ehnes, A.; Herlitschke, M. [Deutsches Elektronen-Synchrotron DESY (Germany); Hermann, R. P.; Jafari, A. [JARA-FIT, Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI (Germany); Prokhorov, I. [Kaluga Branch of Shubnikov Institute of Crystallography RAS, Research Center for Space Materials Science (Russian Federation); Roshchin, B. [Russian Academy of Sciences, A.V. Shubnikov Institute of Crystallography (Russian Federation); Röhlsberger, R.; Schlage, K.; Sergueev, I.; Siemens, A.; Wille, H.-C., E-mail: hans.christian.wille@desy.de [Deutsches Elektronen-Synchrotron DESY (Germany)

    2016-12-15

    We report on a high resolution sapphire backscattering monochromator installed at the Dynamics beamline P01 of PETRA III. The device enables nuclear resonance scattering experiments on Mössbauer isotopes with transition energies between 20 and 60 keV with sub-meV to meV resolution. In a first performance test with {sup 119}Sn nuclear resonance at a X-ray energy of 23.88 keV an energy resolution of 1.34 meV was achieved. The device extends the field of nuclear resonance scattering at the PETRA III synchrotron light source to many further isotopes like {sup 151}Eu, {sup 149}Sm, {sup 161}Dy, {sup 125}Te and {sup 121}Sb.

  5. Comparison of elliptical and spherical mirrors for the grasshopper monochromators at SSRL

    International Nuclear Information System (INIS)

    Waldhauer, A.P.

    1989-01-01

    A comparison of the performance of a spherical and elliptical mirror in the grasshopper monochromator is presented. The problem was studied by ray tracing and then tested using visible (λ=633 nm) laser light. Calculations using ideal optics yield an improvement in flux by a factor of up to 2.7, while tests with visible light show an increase by a factor of 5 because the old spherical mirror is compared to a new, perfect elliptical one. The FWHM of the measured focus is 90 μm with a spherical mirror, and 25 μm with an elliptical one. Elliptical mirrors have been acquired and are now being installed in the two grasshoppers at SSRL

  6. The double rotor neutron monochromator facility at the ET-RR-1 reactor

    International Nuclear Information System (INIS)

    Adib, M.; Maayouf, R.M.A.; Abdel-Kawy, A.; Gwaily, S.E.; Hamouda, I.

    1983-01-01

    A double rotor neutron monochromator recently installed in front of one of the ET-RR-1 reactor horizontal channels is described. The system consists of two rotors, suspended in magnetic field, spinning at speeds up to 16000 rpm with a constant phase angle relative to each producing bursts of monochromatic neutrons at the sample. Each of the rotors, 32 cm in diameter and 27 Kg in weight, has two slits to produce two neutron bursts per revolution. The slits are with radius of curvature 65.65 cm and 7 x 10 sq.mm cross-sectional area. The jitters of the phase between the rotors were measured at different rotation rates and were found not to exceed +- 1.5 μsec. The transmission function of one rotor system was measured and found to be in agreement with that theoretically predicted. (Auth.)

  7. Transmission test of the polyethylene shield against 40 and 65 MeV quasi monochrome neutron

    International Nuclear Information System (INIS)

    Nakao, Makoto; Nakamura, Takashi; Sakuya, Yoshimasa; Nauchi, Yasushi; Nakao, Noriaki; Tanaka, Susumu; Sakamoto, Yukio; Nakajima, Hiroshi; Nakane, Yoshihiro.

    1996-01-01

    Using 40 and 65 MeV quasi monochrome neutron of the AVF cyclotron installed at Takasaki Laboratory, Japan Atomic Energy Research Institute, the neutron energy spectra were measured after transmitting the polyethylene shield. Results of the shielding experiments using concrete and iron recognized as main shielding material were proposed previously. As data obtained in the experiments were useful for a bench-mark experiment to investigate for shielding calculation and sectional data set, a shielding calculation simulated with new experiment to compare with and investigate for the previous experimental data. As a result, it was found that calculation result of neutron flux transmitting through the polyethylene shield showed difference with increase of the shield thickness. And, reducing distance of the peak neutron was also found to be over-estimated in its calculation value, such as three and five times on 43 MeV at 120 and 180 cm thick, respectively. (G.K.)

  8. A water-cooled x-ray monochromator for using off-axis undulator beam

    International Nuclear Information System (INIS)

    Khounsary, A.; Maser, J.

    2000-01-01

    Undulator beamlines at third-generation synchrotrons x-ray sources are designed to use the high-brilliance radiation that is contained in the central cone of the generated x-ray beams. The rest of the x-ray beam is often unused. Moreover, in some cases, such as in the zone-plate-based microfocusing beamlines, only a small part of the central radiation cone around the optical axis is used. In this paper, a side-station branch line at the Advanced Photon Source that takes advantage of some of the unused off-axis photons in a microfocusing x-ray beamline is described. Detailed information on the design and analysis of a high-heat-load water-cooled monochromator developed for this beamline is provided

  9. Graphite analyser upgrade for the IRIS spectrometer at ISIS

    International Nuclear Information System (INIS)

    Campbell, S.I.; Telling, M.T.F.; Carlile, C.J.

    1999-01-01

    Complete text of publication follows. The pyrolytic graphite (PG) analyser bank on the IRIS high resolution inelastic spectrometer [1] at ISIS is to be upgraded. At present the analyser consists of 1350 graphite pieces (6 rows by 225 columns) cooled to 25K [2]. The new analyser array, however, will provide a three-fold increase in area and employ 4212 crystal pieces (18 rows by 234 columns). In addition, the graphite crystals will be cooled close to liquid helium temperature to further reduce thermal diffuse scattering (TDS) and improve the sensitivity of the spectrometer [2]. For an instrument such as IRIS, with its analyser in near back-scattering geometry, optical aberration and variation in the time-of-flight of the analysed neutrons is introduced as one moves out from the horizontal scattering plane. To minimise such effects, the profile of the analyser array has been redesigned. The concept behind the design of the new analyser bank and factors that effect the overall resolution of the instrument are discussed. Results of Monte Carlo simulations of the expected resolution and intensity of the complete instrument are presented and compared to the current instrument performance. (author) [1] C.J. Carlile et al, Physica B 182 (1992) 431-440.; [2] C.J. Carlile et al, Nuclear Instruments and Methods In Physics Research A 338 (1994) 78-82

  10. The application of X-ray, γ-ray and neutron diffraction to the characterization of single crystal perfection

    International Nuclear Information System (INIS)

    Freund, A.; Schneider, J.R.

    1976-01-01

    The work is divided into the following three chapters: 1) diffraction by perfect and imperfect crystals, 2) experimental apparatus (describing gamma ray, X-ray and neutron diffractometers), 3) application of diffraction methods to the development of neutron monochromators. (WBU) [de

  11. High-resolution monochromated electron energy-loss spectroscopy of organic photovoltaic materials.

    Science.gov (United States)

    Alexander, Jessica A; Scheltens, Frank J; Drummy, Lawrence F; Durstock, Michael F; Hage, Fredrik S; Ramasse, Quentin M; McComb, David W

    2017-09-01

    Advances in electron monochromator technology are providing opportunities for high energy resolution (10 - 200meV) electron energy-loss spectroscopy (EELS) to be performed in the scanning transmission electron microscope (STEM). The energy-loss near-edge structure in core-loss spectroscopy is often limited by core-hole lifetimes rather than the energy spread of the incident illumination. However, in the valence-loss region, the reduced width of the zero loss peak makes it possible to resolve clearly and unambiguously spectral features at very low energy-losses (photovoltaics (OPVs): poly(3-hexlythiophene) (P3HT), [6,6] phenyl-C 61 butyric acid methyl ester (PCBM), copper phthalocyanine (CuPc), and fullerene (C 60 ). Data was collected on two different monochromated instruments - a Nion UltraSTEM 100 MC 'HERMES' and a FEI Titan 3 60-300 Image-Corrected S/TEM - using energy resolutions (as defined by the zero loss peak full-width at half-maximum) of 35meV and 175meV, respectively. The data was acquired to allow deconvolution of plural scattering, and Kramers-Kronig analysis was utilized to extract the complex dielectric functions. The real and imaginary parts of the complex dielectric functions obtained from the two instruments were compared to evaluate if the enhanced resolution in the Nion provides new opto-electronic information for these organic materials. The differences between the spectra are discussed, and the implications for STEM-EELS studies of advanced materials are considered. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Optimization of a constrained linear monochromator design for neutral atom beams

    International Nuclear Information System (INIS)

    Kaltenbacher, Thomas

    2016-01-01

    A focused ground state, neutral atom beam, exploiting its de Broglie wavelength by means of atom optics, is used for neutral atom microscopy imaging. Employing Fresnel zone plates as a lens for these beams is a well established microscopy technique. To date, even for favorable beam source conditions a minimal focus spot size of slightly below 1 μm was reached. This limitation is essentially given by the intrinsic spectral purity of the beam in combination with the chromatic aberration of the diffraction based zone plate. Therefore, it is important to enhance the monochromaticity of the beam, enabling a higher spatial resolution, preferably below 100 nm. We propose to increase the monochromaticity of a neutral atom beam by means of a so-called linear monochromator set-up – a Fresnel zone plate in combination with a pinhole aperture – in order to gain more than one order of magnitude in spatial resolution. This configuration is known in X-ray microscopy and has proven to be useful, but has not been applied to neutral atom beams. The main result of this work is optimal design parameters based on models for this linear monochromator set-up followed by a second zone plate for focusing. The optimization was performed for minimizing the focal spot size and maximizing the centre line intensity at the detector position for an atom beam simultaneously. The results presented in this work are for, but not limited to, a neutral helium atom beam. - Highlights: • The presented results are essential for optimal operation conditions of a neutral atom microscope set-up. • The key parameters for the experimental arrangement of a neutral microscopy set-up are identified and their interplay is quantified. • Insights in the multidimensional problem provide deep and crucial understanding for pushing beyond the apparent focus limitations. • This work points out the trade-offs for high intensity and high spatial resolution indicating several use cases.

  13. Optimization of a constrained linear monochromator design for neutral atom beams.

    Science.gov (United States)

    Kaltenbacher, Thomas

    2016-04-01

    A focused ground state, neutral atom beam, exploiting its de Broglie wavelength by means of atom optics, is used for neutral atom microscopy imaging. Employing Fresnel zone plates as a lens for these beams is a well established microscopy technique. To date, even for favorable beam source conditions a minimal focus spot size of slightly below 1μm was reached. This limitation is essentially given by the intrinsic spectral purity of the beam in combination with the chromatic aberration of the diffraction based zone plate. Therefore, it is important to enhance the monochromaticity of the beam, enabling a higher spatial resolution, preferably below 100nm. We propose to increase the monochromaticity of a neutral atom beam by means of a so-called linear monochromator set-up - a Fresnel zone plate in combination with a pinhole aperture - in order to gain more than one order of magnitude in spatial resolution. This configuration is known in X-ray microscopy and has proven to be useful, but has not been applied to neutral atom beams. The main result of this work is optimal design parameters based on models for this linear monochromator set-up followed by a second zone plate for focusing. The optimization was performed for minimizing the focal spot size and maximizing the centre line intensity at the detector position for an atom beam simultaneously. The results presented in this work are for, but not limited to, a neutral helium atom beam. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Optimization of a constrained linear monochromator design for neutral atom beams

    Energy Technology Data Exchange (ETDEWEB)

    Kaltenbacher, Thomas

    2016-04-15

    A focused ground state, neutral atom beam, exploiting its de Broglie wavelength by means of atom optics, is used for neutral atom microscopy imaging. Employing Fresnel zone plates as a lens for these beams is a well established microscopy technique. To date, even for favorable beam source conditions a minimal focus spot size of slightly below 1 μm was reached. This limitation is essentially given by the intrinsic spectral purity of the beam in combination with the chromatic aberration of the diffraction based zone plate. Therefore, it is important to enhance the monochromaticity of the beam, enabling a higher spatial resolution, preferably below 100 nm. We propose to increase the monochromaticity of a neutral atom beam by means of a so-called linear monochromator set-up – a Fresnel zone plate in combination with a pinhole aperture – in order to gain more than one order of magnitude in spatial resolution. This configuration is known in X-ray microscopy and has proven to be useful, but has not been applied to neutral atom beams. The main result of this work is optimal design parameters based on models for this linear monochromator set-up followed by a second zone plate for focusing. The optimization was performed for minimizing the focal spot size and maximizing the centre line intensity at the detector position for an atom beam simultaneously. The results presented in this work are for, but not limited to, a neutral helium atom beam. - Highlights: • The presented results are essential for optimal operation conditions of a neutral atom microscope set-up. • The key parameters for the experimental arrangement of a neutral microscopy set-up are identified and their interplay is quantified. • Insights in the multidimensional problem provide deep and crucial understanding for pushing beyond the apparent focus limitations. • This work points out the trade-offs for high intensity and high spatial resolution indicating several use cases.

  15. Graphitized biogas-derived carbon nanofibers as anodes for lithium-ion batteries

    International Nuclear Information System (INIS)

    Cuesta, Nuria; Cameán, Ignacio; Ramos, Alberto; García, Ana B.

    2016-01-01

    The electrochemical performance as potential anodes for lithium-ion batteries of graphitized biogas-derived carbon nanofibers (BCNFs) is investigated by galvanostatic cycling versus Li/Li + at different electrical current densities. These graphitic nanomaterials have been prepared by high temperature treatment of carbon nanofibers produced in the catalytic decomposition of biogas. At low current density, they deliver specific capacities comparable to that of oil-derived micrometric graphite, the capacity retention values being mostly in the range 70-80% and cycling efficiency ∼ 100%. A clear tendency of the anode capacity to increase alongside the BCNFs crystal thickness was observed. Besides the degree of graphitic tri-dimensional structural order, the presence of loops between the adjacent edges planes on the graphene layers, the mesopore volume and the active surface area of the graphitized BCNFs were found to influence on battery reversible capacity, capacity retention along cycling and irreversible capacity. Furthermore, provided that the development of the crystalline structure is comparable, the graphitized BCNFs studied show better electrochemical rate performance than micrometric graphite. Therefore, this result can be associated with the nanometric particle size as well as the larger surface area of the BCNFs which, respectively, reduces the diffusion time of the lithium ions for the intercalation/de-intercalation processes, i.e. faster charge-discharge rate, and increases the contact area at the anode active material/electrolyte interface which may improve the Li + ions access, i.e. charge transfer reaction.

  16. Thermal Pyrolytic Graphite Enhanced Components

    Science.gov (United States)

    Hardesty, Robert E. (Inventor)

    2015-01-01

    A thermally conductive composite material, a thermal transfer device made of the material, and a method for making the material are disclosed. Apertures or depressions are formed in aluminum or aluminum alloy. Plugs are formed of thermal pyrolytic graphite. An amount of silicon sufficient for liquid interface diffusion bonding is applied, for example by vapor deposition or use of aluminum silicon alloy foil. The plugs are inserted in the apertures or depressions. Bonding energy is applied, for example by applying pressure and heat using a hot isostatic press. The thermal pyrolytic graphite, aluminum or aluminum alloy and silicon form a eutectic alloy. As a result, the plugs are bonded into the apertures or depressions. The composite material can be machined to produce finished devices such as the thermal transfer device. Thermally conductive planes of the thermal pyrolytic graphite plugs may be aligned in parallel to present a thermal conduction path.

  17. The behavior of interstitials in irradiated graphite

    International Nuclear Information System (INIS)

    Pedraza, D.F.

    1991-01-01

    A computer model is developed to simulate the behavior of self-interstitials with particular attention to clustering. Owing to the layer structure of graphite, atomistic simulations can be performed using a large parallelepipedic supercell containing a few layers. In particular, interstitial clustering is studied here using a supercell that contains two basal planes only. Frenkel pairs are randomly produced. Interstitials are placed at sites between the crystal planes while vacancies are distributed in the two crystal planes. The size of the computational cell is 20000 atoms and periodic boundary conditions are used in two dimensions. Vacancies are assumed immobile whereas interstitials are given a certain mobility. Two point defect sinks are considered, direct recombination of Frenkel pairs and interstitial clusters. The clusters are assumed to be mobile up to a certain size where they are presumed to become loop nuclei. Clusters can shrink by emission of singly bonded interstitials or by recombination of a peripheral interstitial with a neighboring vacancy. The conditions under which interstitial clustering occurs are reported. It is shown that when clustering occurs the cluster size population gradually shifts towards the largest size cluster. The implications of the present results for irradiation growth and irradiation-induced amorphization are discussed

  18. Friction anisotropy in boronated graphite

    International Nuclear Information System (INIS)

    Kumar, N.; Radhika, R.; Kozakov, A.T.; Pandian, R.; Chakravarty, S.; Ravindran, T.R.; Dash, S.; Tyagi, A.K.

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient

  19. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N., E-mail: niranjan@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Radhika, R. [Crystal Growth Centre, Anna University, Chennai (India); Kozakov, A.T. [Research Institute of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); Pandian, R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Chakravarty, S. [UGC-DAE CSR, Kalpakkam (India); Ravindran, T.R.; Dash, S.; Tyagi, A.K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

  20. High-resolution optical microscopy of carbon and graphite

    International Nuclear Information System (INIS)

    Cook, W.H.; Allen, M.D.; Leslie, B.C.; Gray, R.J.

    1975-01-01

    The ceramographic preparation of carbonaceous materials varying in crystalline quality, amorphous carbon to well crystallized graphite, is described. In a two-step process, using alumina and diamond polishing compounds, one can prepare more samples, obtain a substantial saving in man hours, avoid rounding material around pores, and obtain flatter surfaces than were obtainable with earlier, conventional methods. Improved resolution of microstructural details is achieved without impregnation with epoxy resins or other materials to support the porous structures. Use of rotatable, half-wave retardation (sensitive tint) enhances the microstructural definition in both color and black and white. These innovations were extensively used as part of the examination of nuclear grades of graphite before and after exposure to fast neutrons at temperatures from 650 to 1100 0 C; typical examples are discussed. (auth)

  1. Raman characterization of bulk ferromagnetic nanostructured graphite

    International Nuclear Information System (INIS)

    Pardo, Helena; Divine Khan, Ngwashi; Faccio, Ricardo; Araújo-Moreira, F.M.; Fernández-Werner, Luciana

    2012-01-01

    Raman spectroscopy was used to characterize bulk ferromagnetic graphite samples prepared by controlled oxidation of commercial pristine graphite powder. The G:D band intensity ratio, the shape and position of the 2D band and the presence of a band around 2950 cm -1 showed a high degree of disorder in the modified graphite sample, with a significant presence of exposed edges of graphitic planes as well as a high degree of attached hydrogen atoms.

  2. Fabrication of Graphene by Cleaving Graphite Chemically

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shu-hua; ZHAO Xiao-ting; FAN Hou-gang; YANG Li-li; ZHANG Yong-jun; YANG Jing-hai

    2011-01-01

    Graphite was chemically cleaved to graphene by Billups Reaction,and the morphologies and microstructures of graphene were characterized by SEM,Raman and AFM.The results show that the graphite was first functionalized by l-iodododecane,which led to the cleavage of the graphene layer in the graphite.The second decoration cleaved the graphite further and graphene was obtained.The heights of the graphene layer were larger than 1 nm due to the organic decoration.

  3. Method of Joining Graphite Fibers to a Substrate

    Science.gov (United States)

    Beringer, Durwood M. (Inventor); Caron, Mark E. (Inventor); Taddey, Edmund P. (Inventor); Gleason, Brian P. (Inventor)

    2014-01-01

    A method of assembling a metallic-graphite structure includes forming a wetted graphite subassembly by arranging one or more layers of graphite fiber material including a plurality of graphite fibers and applying a layer of metallization material to ends of the plurality of graphite fibers. At least one metallic substrate is secured to the wetted graphite subassembly via the layer of metallization material.

  4. Molecular and crystal structure of nido-9-C5H5N-11-I-7,8-C2B9H10: supramolecular architecture via hydrogen bonding X-H...I (X = B, C)

    International Nuclear Information System (INIS)

    Polyanskaya, T.M.

    2006-01-01

    A monocrystal X-ray diffraction study of a new iodine-containing cluster compound 9-(pyridine)-11-iodo-decahydro-7,8-dicarba-nido-undecaborane [9-C 5 H 5 N-11-I-7,8-C 2 B 9 H 10 ] has been performed. Crystal data: C 7 H 15 B 9 NI, M = 337.39, monoclinic, space group P2 1 /c, unit cell parameters: a=9.348(1) A, b=11.159(1) A, c=13.442(2) A, β=98.13(1) deg, V=1388.1(5) A 3 , Z=4, d calc = 1.614 g/cm 3 , T = 295 K, F(000)=648, μ=2.276 mm -1 . The structure was solved by a direct method and refined in the full-matrix anisotropic approximation (isotropic for hydrogen atoms) to final agreement factors R 1 = 0.0254, wR 2 = 0.0454 for 2437 I hkl >2σ I from 3590 measured I hkl (an Enraf-Nonius CAD-4 diffractometer, λMoK α , graphite monochromator, θ/2θ-scanning). The molecules are joined into a supramolecular assembly by hydrogen bonds X-H...I (X = B, C) [ru

  5. Photoemission study of K on graphite

    NARCIS (Netherlands)

    Bennich, P.; Puglia, C.; Brühwiler, P.A.; Nilsson, A.; Sandell, A.; Mårtensson, N.; Rudolf, P.

    1999-01-01

    The physical and electronic structure of the dispersed and (2×2) phases of K/graphite have been characterized by valence and core-level photoemission. Charge transfer from K to graphite is found to occur at all coverages, and includes transfer of charge to the second graphite layer. A rigid band

  6. Separation medium containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

    2012-01-01

    A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

  7. NMR studies on graphite-methanol system

    International Nuclear Information System (INIS)

    El-Akkad, T.M.

    1977-01-01

    The nuclear magnetic relaxation times for protons of methanol on graphite have been studied. The perpendicular and the transversal magnetization as a function of temperature were measured. The results show that the presence of graphite slowed down the methanol movement compared with that in the pure alcohol, and that the methanol molecules are attached to the graphite surface via methyl groups. (author)

  8. Hard X-ray diffraction enhanced imaging only using two crystals

    Institute of Scientific and Technical Information of China (English)

    LI Gang; WANG Nan; WU Ziyu

    2004-01-01

    Different configurations for the monochromator crystals and the analyzer crystals have been used in hard X-ray diffraction enhanced imaging (DEI) methods to overcome the complex task to adjust each of them to the ideal position. Here we present a very compact DEI configuration, and preliminary results of experiments performed at the Beijing Synchrotron Radiation Facility (BSRF) using only two crystals: the first one acting as monochromator and the second one as analyzer in the Bragg geometry. Refraction contrast images characterized by high contrast and spatial resolution are obtained and compared with absorption images. Differences among these images will be outlined and discussed emphasizing the potential capabilities of this very simple layout that guarantees a high transmission efficiency.

  9. Graphite oral tattoo: case report.

    Science.gov (United States)

    Moraes, Renata Mendonça; Gouvêa Lima, Gabriela de Morais; Guilhermino, Marinaldo; Vieira, Mayana Soares; Carvalho, Yasmin Rodarte; Anbinder, Ana Lia

    2015-10-16

    Pigmented oral lesions compose a large number of pathological entities, including exogenous pigmentat oral tattoos, such as amalgam and graphite tattoos. We report a rare case of a graphite tattoo on the palate of a 62-year-old patient with a history of pencil injury, compare it with amalgam tattoos, and determine the prevalence of oral tattoos in our Oral Pathology Service. We also compare the clinical and histological findings of grafite and amalgam tattoos. Oral tattoos affect women more frequently in the region of the alveolar ridge. Graphite tattoos occur in younger patients when compared with the amalgam type. Histologically, amalgam lesions represent impregnation of the reticular fibers of vessels and nerves with silver, whereas in cases of graphite tattoos, this impregnation is not observed, but it is common to observe a granulomatous inflammatory response, less evident in cases of amalgam tattoos. Both types of lesions require no treatment, but in some cases a biopsy may be done to rule out melanocytic lesions.

  10. 'In situ' expanded graphite extinguishant

    International Nuclear Information System (INIS)

    Cao Qixin; Shou Yuemei; He Bangrong

    1987-01-01

    This report is concerning the development of the extinguishant for sodium fire and the investigation of its extinguishing property. The experiment result shows that 'in situ' expanded graphite developed by the authors is a kind of extinguishant which extinguishes sodium fire quickly and effectively and has no environment pollution during use and the amount of usage is little

  11. Graphite nanoreinforcements in polymer nanocomposites

    Science.gov (United States)

    Fukushima, Hiroyuki

    Nanocomposites composed of polymer matrices with clay reinforcements of less than 100 nm in size, are being considered for applications such as interior and exterior accessories for automobiles, structural components for portable electronic devices, and films for food packaging. While most nanocomposite research has focused on exfoliated clay platelets, the same nanoreinforcement concept can be applied to another layered material, graphite, to produce nanoplatelets and nanocomposites. Graphite is the stiffest material found in nature (Young's Modulus = 1060 GPa), having a modulus several times that of clay, but also with excellent electrical and thermal conductivity. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. Also, if the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well, opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are requirements. In this research, a new process to fabricate exfoliated nano-scale graphite platelets was established (Patent pending). The size of the resulted graphite platelets was less than 1 um in diameter and 10 nm in thickness, and the surface area of the material was around 100 m2/g. The reduction of size showed positive effect on mechanical properties of composites because of the increased edge area and more functional groups attached with it. Also various surface treatment techniques were applied to the graphite nanoplatelets to improve the surface condition. As a result, acrylamide grafting treatment was found to enhance the dispersion and adhesion of graphite flakes in epoxy matrices. The resulted composites showed better mechanical properties than those with commercially available carbon fibers, vapor grown carbon fibers

  12. Graphite suspension in carbon dioxide

    International Nuclear Information System (INIS)

    Roche, R.

    1965-01-01

    Since 1963 the Atomic Division of SNECMA has been conducting, under a contract with the CEA, an experimental work with a two-component fluid comprised of carbon dioxide and small graphite particles. The primary purpose was the determination of basic engineering information pertaining to the stability and the flowability of the suspension. The final form of the experimental loop consists mainly of the following items: a light-phase compressor, a heavy-phase pump, an electrical-resistance type heater section, a cooling heat exchanger, a hairpin loop, a transparent test section and a separator. During the course of the testing, it was observed that the fluid could be circulated quite easily in a broad range of variation of the suspension density and velocity - density from 30 to 170 kg/m 3 and velocity from 2 to 24 m/s. The system could be restarted and circulation maintained without any difficulty, even with the heavy-phase pump alone. The graphite did not have a tendency to pack or agglomerate during operation. No graphite deposition was observed on the wall of the tubing. A long period run (250 hours) has shown the evolution of the particle dimensions. Starting with graphite of surface area around 20 m 2 /g (graphite particles about 1 μ), the powder surface area reaches an asymptotic value of 300 m 2 /g (all the particles less than 0.3 μ). Moisture effect on flow stability, flow distribution between two parallel channels, pressure drop in straight tubes, recompression ratio in diffusers were also investigated. (author) [fr

  13. Characterisation of Chlorine Behavior in French Graphite

    International Nuclear Information System (INIS)

    Blondel, A.; Moncoffre, N.; Toulhoat, N.; Bererd, N.; Petit, L.; Laurent, G.; Lamouroux, C.

    2016-01-01

    Chlorine 36 is one of the main radionuclides of concern for French graphite waste disposal. In order to help the understanding of its leaching behaviour under disposal conditions, the respective impact of temperature, irradiation and gas radiolysis on chlorine release in reactor has been studied. Chlorine 36 has been simulated through chlorine 37 ion implantation in virgin nuclear graphite samples. Results show that part of chlorine is highly mobile in graphite in the range of French reactors operating temperatures in relation with graphite structural recovering. Ballistic damage generated by irradiation also promotes chlorine release whereas no clear impact of the coolant gas radiolysis was observed in the absence of graphite radiolytic corrosion. (author)

  14. Pyrolytic Graphite as a Tunable Second order Neutron Filter

    International Nuclear Information System (INIS)

    Adib, M.

    2009-01-01

    A study has been carried out on the neutron transmission through pyrolytic graphite (PG) crystals in order to check its applicability as an efficient tunable second order neutron filter. The neutron transmission have been calculated as a function of neutron wavelengths in the range from 0.01 nm up to 0.7 nm at various PG mosaic spread, thickness and orientation of its c-axis with respect to the beam direction The Computer package Graphite has been used to provide the required calculation. It was shown that highly aligned (10 FWHM on mosaic spread) PG crystal ∼2 cm thick, may be tuned for optimum scattering of 2 second order neutrons within some favorable wavelength intervals in the range between 0.112 and 0.425 nm by adjusting the crystal in an appropriate orientation. .However, a less quality and thinner PG was found to almost eliminate 2 second order neutrons at only tuned values of wavelength corresponding to the poison of the triple intersection points of the curves (hkl) ± and (00l)

  15. AGC-2 Graphite Preirradiation Data Package

    Energy Technology Data Exchange (ETDEWEB)

    David Swank; Joseph Lord; David Rohrbaugh; William Windes

    2012-10-01

    The NGNP Graphite R&D program is currently establishing the safe operating envelope of graphite core components for a Very High Temperature Reactor (VHTR) design. The program is generating quantitative data necessary for predicting the behavior and operating performance of the new nuclear graphite grades. To determine the in-service behavior of the graphite for pebble bed and prismatic designs, the Advanced Graphite Creep (AGC) experiment is underway. This experiment is examining the properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences and compressive loads. Each experiment consists of over 400 graphite specimens that are characterized prior to irradiation and following irradiation. Six experiments are planned with the first, AGC-1, currently being irradiated in the Advanced Test Reactor (ATR) and pre-irradiation characterization of the second, AGC-2, completed. This data package establishes the readiness of 512 specimens for assembly into the AGC-2 capsule.

  16. A high-pressure cell for neutron crystal spectrometry

    International Nuclear Information System (INIS)

    Buras, B.; Kofoed, W.; Lebech, B.; Baeckstroem, G.

    1977-04-01

    Three fixed-scattering-angle methods for neutron scattering powder measurements using double- and triple-axis crystal spectrometers were tested: (1) the analyzer-scan method (AS), (2) the monochromator-scan method (MS), and (3) the monochromator-analyzer scan method (MAS). A high-pressure cell, primarily for use in powder diffraction measurements, with scattering angles of 30 0 , 60 0 , 90 0 and 120 0 and a sample volume of about 0.8 cm 3 was constructed and used in conjunction with the MS and MAS methods. At room temperature, this cell makes it possible to make measurements at pressures up to about 40 kbar and up to about 30 kbar at 300 0 C. The report includes a description of the diffraction methods and of the high-pressure cell. A few examples of experimental results are also given. (Auth.)

  17. Evaluation of the Data-Ray DR96L 4 x 3 Aspect Ratio, 22-Inch Diagonal Flat Screen Monochrome CRT Monitor

    National Research Council Canada - National Science Library

    2001-01-01

    .... Based on results of our evaluation of the third sample NIDL cannot certify the Data-Ray DR96L monochrome monitor as being suitable for suitable monoscopic or stereoscopic operation in IEC workstations...

  18. Progress in radioactive graphite waste management

    International Nuclear Information System (INIS)

    2010-07-01

    Radioactive graphite constitutes a major waste stream which arises during the decommissioning of certain types of nuclear installations. Worldwide, a total of around 250 000 tonnes of radioactive graphite, comprising graphite moderators and reflectors, will require management solutions in the coming years. 14 C is the radionuclide of greatest concern in nuclear graphite; it arises principally through the interaction of reactor neutrons with nitrogen, which is present in graphite as an impurity or in the reactor coolant or cover gas. 3 H is created by the reactions of neutrons with 6 Li impurities in graphite as well as in fission of the fuel. 36 Cl is generated in the neutron activation of chlorine impurities in graphite. Problems in the radioactive waste management of graphite arise mainly because of the large volumes requiring disposal, the long half-lives of the main radionuclides involved and the specific properties of graphite - such as stored Wigner energy, graphite dust explosibility and the potential for radioactive gases to be released. Various options for the management of radioactive graphite have been studied but a generally accepted approach for its conditioning and disposal does not yet exist. Different solutions may be appropriate in different cases. In most of the countries with radioactive graphite to manage, little progress has been made to date in respect of the disposal of this material. Only in France has there been specific thinking about a dedicated graphite waste-disposal facility (within ANDRA): other major producers of graphite waste (UK and the countries of the former Soviet Union) are either thinking in terms of repository disposal or have no developed plans. A conference entitled 'Solutions for Graphite Waste: a Contribution to the Accelerated Decommissioning of Graphite Moderated Nuclear Reactors' was held at the University of Manchester 21-23 March 2007 in order to stimulate progress in radioactive graphite waste management

  19. Voronoi-Tessellated Graphite Produced by Low-Temperature Catalytic Graphitization from Renewable Resources.

    Science.gov (United States)

    Zhao, Leyi; Zhao, Xiuyun; Burke, Luke T; Bennett, J Craig; Dunlap, Richard A; Obrovac, Mark N

    2017-09-11

    A highly crystalline graphite powder was prepared from the low temperature (800-1000 °C) graphitization of renewable hard carbon precursors using a magnesium catalyst. The resulting graphite particles are composed of Voronoi-tessellated regions comprising irregular sheets; each Voronoi-tessellated region having a small "seed" particle located near their centroid on the surface. This suggests nucleated outward growth of graphitic carbon, which has not been previously observed. Each seed particle consists of a spheroidal graphite shell on the inside of which hexagonal graphite platelets are perpendicularly affixed. This results in a unique high surface area graphite with a high degree of graphitization that is made with renewable feedstocks at temperatures far below that conventionally used for artificial graphites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Sagittal focusing of synchrotron radiation on the walls of a longitudinal hole drilled into a single-crystal monochromator

    Czech Academy of Sciences Publication Activity Database

    Artemiev, Nikolai; Hrdý, Jaromír; Peredkov, S.; Artemev, A.; Freud, A.; Tucoulou, R.

    2001-01-01

    Roč. 8, - (2001), s. 1207-1213 ISSN 0909-0495. [Syncrotron Radiation Instrumentation. Madison, 22.08.2001-24.08.2001] R&D Projects: GA AV ČR IAA1010104; GA MPO PZ-CH/22; GA MŠk OK 305 Institutional research plan: CEZ:AV0Z1010914 Keywords : focusing of synchrotron radiation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.519, year: 2001

  1. Optimization of Bent Perfect Si(311)-Crystal Monochromator for Residual Strain/Stress Instrument at HANARO Reactor - Part I

    Czech Academy of Sciences Publication Activity Database

    Moon, M. K.; Mikula, Pavol

    2005-01-01

    Roč. 369, 1-4 (2005), s. 1-7 ISSN 0921-4526 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.796, year: 2005

  2. Graphite structure and magnetic parameters of flake graphite cast iron

    Czech Academy of Sciences Publication Activity Database

    Vértesy, G.; Uchimoto, T.; Takagi, T.; Tomáš, Ivan; Kage, H.

    2017-01-01

    Roč. 442, Nov (2017), s. 397-402 ISSN 0304-8853 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:68378271 Keywords : magnetic NDE * magnetic adaptive testing * cast iron * graphite structure * pearlite content Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.630, year: 2016

  3. Luminescent unit computerization to research spectral characteristics of fine film alkali halide crystal

    International Nuclear Information System (INIS)

    Zhalimbetov, T.; Zhabetov, A.; Moldagaliev, A.; Sarmukhanov, E.; Shunkeev, K.; Shunkeev, S.; Abdullin, K.; Tokmoldin, C.

    2002-01-01

    The fundamental optical absorption of ion crystals characterizes the creation of different free low energetic electronic excitation (the excitons and electron-hole pairs), but their straight registration is not possible because of incommensurable big absorption factor of alkali halide monocrystals. So to registration the spectrums of alkali halide monocrystal very fine layers are necessary. We have received fine films of Nal and KCl in system of KCl-Nal-KCl, KCl-KI-KCl on the base of universal vacuum post VUP-4, VUP-5 by thermal evaporation. A unique spectral unit has been created For this on the basic the SDL-2 complex. Complex consists of radiator, systems of condensers, monochromators MDR-12 and MDR-23, receivers of radiation, controller by unit. Connect and control of monochromators by means of IBM-compatible computer has been created. Kinematics schemes of monochromators provide consequent removing on output slot of monochromatic radiation in operating range of each diffraction lattice and indication its wavelength. The tumbling diffraction lattices is done the crossbar engines SHDR-711. For this special plate of control and block of reinforcement for crossbar engines in monochromators MDR-12 and MDR-23 are designed and constructed. Created controller of monochromators consists of double cascade preamplifier on transistors n-p-n type (815G) and logical scheme, constructed on summers and K555 series triggers. The preamplifier is used for reinforcement of signal to available amplifier on transistors KT837D. The logical scheme reduces the number of used categories of bidirectional port and enables unhooking the feeding to the windings of crossbar engine at conservation of previous combination of signals. The connection controller of monochromators is done through controller of port of computer with use the parallel interface. For installing computerized system of collection and data processing is provided marketed by means of modern object-oriented programming

  4. A high throughput 2 m normal incidence monochromator for SURF-II

    International Nuclear Information System (INIS)

    Ederer, D.L.; Cole, B.E.; West, J.B.

    1980-01-01

    The high intrinsic brightness of the circulating electron beam at SURF-II is used as the entrance slit for a two-meter normal incidence monochromator. A typical beam size for the electron beam is 100 μm high by 2 mm wide yielding an obserbed resolution of 0.4 Angstroem with a 200 μm exit slit and a 2400 lines/mm grating. The instrument accepts a beam with a 65 mrad horizontal divergence and a 10 mrad vertical divergence. A plane pre-mirror used near normal incidence reflects the incoming radiation onto the 2 m grating; this combination provides a horizontal exit beam, and enables the experiment to be located three meters from the orbit tangent point. With magnesium fluoride coated aluminium optics a flux of 2 x 10'' photon/s x Angstroem at 1200 Angstroem is observed with a 10 mA circulating current. A flux of 5 x 10 10 photon/s x Angstroem at 600 Angstroem is obserbed with an osmium coated grating and a 10 mA circulating current. Sample spectra of the angle-resolved photoelectron spectrum of CO are presented. (orig.)

  5. Design and fabrication of a Czerny-Turner monochromator-cum-spectrograph

    International Nuclear Information System (INIS)

    Murty, M.V.R.K.; Shukla, R.P.; Bhattacharya, S.S.; Krishnamurthy, G.

    1987-01-01

    The design and fabrication of a Czerny-Turner monochromator cum spectrograph is described. It consists of a classically ruled grating having 1200 grooves/mm. The collimator is a concave spherical mirror having a radius of curvature 1.025 metre while the focusing element is a concave spherical mirror of radius of curvature 0.925 metre. The design of two unequal radii of curvature for collimating and focusing mirrors is chosen to eliminate the chromatic aberration at the wavelength of 5000A. The linear reciprocal dispersion on the focal surface is about 8A/mm. The resolution of the instrument at the coma corrected wavelength i.e. 5000A is 0.1A. The resolution at the other wavelengths is limited by the residual chromatic aberration which increases linearly with wavelength on either side of the 5000A. Therefore the resolution at the wavelength 2000A and 8000A is about 0.2A. 7 figures. (author)

  6. Mechanical design aspects of a soft X-ray plane grating monochromator

    CERN Document Server

    Vasina, R; Dolezel, P; Mynar, M; Vondracek, M; Chab, V; Slezak, J A; Comicioli, C; Prince, K C

    2001-01-01

    A plane grating monochromator based on the SX-700 concept has been constructed for the Materials Science Beamline, Elettra, which is attached to a bending magnet. The tuning range is from 35 to 800 eV with calculated spectral resolving power epsilon/DELTA epsilon better than 4000 in the whole range. The optical elements consist of a toroidal prefocusing mirror, polarization aperture, entrance slit, plane pre-mirror, single plane grating (blazed), spherical mirror, exit slit and toroidal refocusing mirror. The plane grating is operated in the fixed focus mode with C sub f sub f =2.4. Energy scanning is performed by rotation of the plane grating and simultaneous translation and rotation of the plane pre-mirror. A novel solution is applied for the motion of the plane pre-mirror, namely by a translation and mechanically coupling the rotation by a cam. The slits have no moving parts in vacuum to reduce cost and increase ruggedness, and can be fully closed without risk of damage. In the first tests, a resolving pow...

  7. Microwave absorbing property of a hybrid absorbent with carbonyl irons coating on the graphite

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yonggang, E-mail: xuyonggang221@163.com [Science and Technology on Electromagnetic Scattering Laboratory, Shanghai, 200438 (China); Yan, Zhenqiang; Zhang, Deyuan [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China)

    2015-11-30

    Graphical abstract: The absorbing property could be enhanced as the CIPs coated on the graphite. - Highlights: • Absorbers filled with CIPs coating on the graphite was fabricated. • The permittivity and permeability increased as CIPs coated. • The CIP materials enhanced the electromagnetic property. • The graphite coated CIPs were effective in 2–18 GHz. - Abstract: The hybrid absorbent filled with carbonyl iron particles (CIPs) coating on the graphite was prepared using a chemical vapor decomposition (CVD) process. X-ray diffraction (XRD) patterns were done to analyze the particle crystal grain structure. The complex permittivity and permeability were measured using a vector network analyzer in the frequency range of 2–18 GHz. The results showed that α-Fe appeared in the super-lattice diffraction peaks in XRD graph. The composites added CIPs coating on the graphite had a higher permittivity and imaginary permeability due to the superior microwave dielectric loss and magnetic loss of the CIPs. The reflection loss (RL) result showed that composites filled with 5 vol% Fe-graphite had an excellent absorbing property in the 2–18 GHz, the minimum RL was −25.14 dB at 6 mm and −26.52 dB at 8 mm, respectively.

  8. Electrochemical reactivity at graphitic micro-domains on polycrystalline boron doped diamond thin-films electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mahe, E. [LI2C CNRS/UMR 7612, Laboratoire d' Electrochimie, Universite Pierre-et-Marie Curie - case courrier 51, 4, Place Jussieu, 75252 Paris Cedex 05 (France); Devilliers, D. [LI2C CNRS/UMR 7612, Laboratoire d' Electrochimie, Universite Pierre-et-Marie Curie - case courrier 51, 4, Place Jussieu, 75252 Paris Cedex 05 (France); Comninellis, Ch. [Unite de Genie Electrochimique, Institut de sciences des procedes chimiques et biologiques, Ecole Polytechnique Federale de Lausanne, 1015, Lausanne (Switzerland)

    2005-04-01

    This paper deals with the electrochemical reactivity of boron doped diamond (BDD) electrodes. A comparative study has been carried out to show the influence of the presence of graphitic micro-domains upon the surface of these films. Those graphitic domains are sometimes present on as-grown boron doped diamond electrodes. The effect of doping a pure Csp{sup 3} diamond electrode is established by highly oriented pyrolytic graphite (HOPG) abrasion onto the diamond surface. In order to establish the effect of doping on a pure Csp{sup 3} diamond electrode, the amount of graphitic domains was increased by means of HOPG crystals grafted onto the BDD surface. Indeed that method allows the enrichment of the Csp{sup 2} contribution of the electrode. The presence of graphitic domains can be correlatively associated with the presence of kinetically active redox sites. The electrochemical reactivity of boron doped diamond electrodes shows a distribution of kinetic constants on the whole surface of the electrode corresponding to different active sites. In this paper, we have studied by cyclic voltammetry and electrochemical impedance spectroscopy the kinetics parameters of the ferri/ferrocyanide redox couple in KCl electrolyte. A method is proposed to diagnose the presence of graphitic domains on diamond electrodes, and an electrochemical 'pulse cleaning' procedure is proposed to remove them.

  9. Electrochemical reactivity at graphitic micro-domains on polycrystalline boron doped diamond thin-films electrodes

    International Nuclear Information System (INIS)

    Mahe, E.; Devilliers, D.; Comninellis, Ch.

    2005-01-01

    This paper deals with the electrochemical reactivity of boron doped diamond (BDD) electrodes. A comparative study has been carried out to show the influence of the presence of graphitic micro-domains upon the surface of these films. Those graphitic domains are sometimes present on as-grown boron doped diamond electrodes. The effect of doping a pure Csp 3 diamond electrode is established by highly oriented pyrolytic graphite (HOPG) abrasion onto the diamond surface. In order to establish the effect of doping on a pure Csp 3 diamond electrode, the amount of graphitic domains was increased by means of HOPG crystals grafted onto the BDD surface. Indeed that method allows the enrichment of the Csp 2 contribution of the electrode. The presence of graphitic domains can be correlatively associated with the presence of kinetically active redox sites. The electrochemical reactivity of boron doped diamond electrodes shows a distribution of kinetic constants on the whole surface of the electrode corresponding to different active sites. In this paper, we have studied by cyclic voltammetry and electrochemical impedance spectroscopy the kinetics parameters of the ferri/ferrocyanide redox couple in KCl electrolyte. A method is proposed to diagnose the presence of graphitic domains on diamond electrodes, and an electrochemical 'pulse cleaning' procedure is proposed to remove them

  10. Graphite moderated 252Cf source

    International Nuclear Information System (INIS)

    Sajo B, L.; Barros, H.; Greaves, E. D.; Vega C, H. R.

    2014-08-01

    The thorium molten salt reactor is an attractive and affordable nuclear power option for developing countries with insufficient infrastructure and limited technological capability. In the aim of personnel training and experience gathering at the Universidad Simon Bolivar there is in progress a project of developing a subcritical thorium liquid fuel reactor. The neutron source to run this subcritical reactor is a 252 Cf source and the reactor will use high-purity graphite as moderator. Using the MCNP5 code the neutron spectra of the 252 Cf in the center of the graphite moderator has been estimated along the channel where the liquid thorium salt will be inserted; also the ambient dose equivalent due to the source has been determined around the moderator. (Author)

  11. Fission Product Sorptivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Tompson, Jr., Robert V. [Univ. of Missouri, Columbia, MO (United States); Loyalka, Sudarshan [Univ. of Missouri, Columbia, MO (United States); Ghosh, Tushar [Univ. of Missouri, Columbia, MO (United States); Viswanath, Dabir [Univ. of Missouri, Columbia, MO (United States); Walton, Kyle [Univ. of Missouri, Columbia, MO (United States); Haffner, Robert [Univ. of Missouri, Columbia, MO (United States)

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few μm in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one

  12. Graphite for high-temperature reactors

    International Nuclear Information System (INIS)

    Hammer, W.; Leushacke, D.F.; Nickel, H.; Theymann, W.

    1976-01-01

    The different graphites necessary for HTRs are being developed, produced and tested within the Federal German ''Development Programme Nuclear Graphite''. Up to now, batches of the following graphite grades have been manufactured and fully characterized by the SIGRI Company to demonstrate reproducibility: pitch coke graphite AS2-500 for the hexagonal fuel elements and exchangeable reflector blocks; special pitch coke graphite ASI2-500 for reflector blocks of the pebble-bed reactor and as back-up material for the hexagonal fuel elements; graphite for core support columns. The material data obtained fulfill most of the requirements under present specifications. Production of large-size blocks for the permanent side reflector and the core support blocks is under way. The test programme covers all areas important for characterizing and judging HTR-graphites. In-pile testing comprises evaluation of the material for irradiation-induced changes of dimensions, mechanical and thermal properties - including behaviour under temperature cycling and creep behaviour - as well as irradiating fuel element segments and blocks. Testing out-of-pile includes: evaluation of corrosion rates and influence of corrosion on strength; strength measurements; including failure criteria. The test programme has been carried out extensively on the AS2-graphite, and the results obtained show that this graphite is suitable as HTGR fuel element graphite. (author)

  13. Investigation on the formation of lonsdaleite from graphite

    Energy Technology Data Exchange (ETDEWEB)

    Greshnyakov, V. A.; Belenkov, E. A., E-mail: belenkov@csu.ru [Chelyabinsk State University (Russian Federation)

    2017-02-15

    Structural stability and the possible pathways to experimental formation of lonsdaleite—a hexagonal 2H polytype of diamond—have been studied in the framework of the density functional theory (DFT). It is established that the structural transformation of orthorhombic Cmmm graphite to 2H polytype of diamond must take place at a pressure of 61 GPa, while the formation of lonsdaleite from hexagonal P6/mmm graphite must take place at 56 GPa. The minimum potential barrier height separating the 2H polytype state from graphite is only 0.003 eV/atom smaller than that for the cubic diamond. The high potential barrier is indicative of the possibility of stable existence of the hexagonal diamond under normal conditions. In this work, we have also analyzed the X-ray diffraction and electron-microscopic data available for nanodiamonds found in meteorite impact craters in search for the presence of hexagonal diamond. Results of this analysis showed that pure 3C and 2H polytypes are not contained in the carbon materials of impact origin, the structure of nanocrystals found representing diamonds with randomly packed layers. The term “lonsdaleite,” used to denote carbon materials found in meteorite impact craters and diamond crystals with 2H polytype structure, is rather ambiguous, since no pure hexagonal diamond has been identified in carbon phases found at meteorite fall sites.

  14. AGC-3 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; David Swank; David Rohrbaugh; Joseph Lord

    2013-09-01

    This report describes the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the third Advanced Graphite Capsule (AGC-3) irradiation capsule. The AGC-3 capsule is third in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. The general design of AGC-3 test capsule is similar to the AGC-2 test capsule, material property tests were conducted on graphite specimens prior to loading into the AGC-3 irradiation assembly. However the 6 major nuclear graphite grades in AGC-2 were modified; two previous graphite grades (IG-430 and H-451) were eliminated and one was added (Mersen’s 2114 was added). Specimen testing from three graphite grades (PCEA, 2114, and NBG-17) was conducted at Idaho National Laboratory (INL) and specimen testing for two grades (IG-110 and NBG-18) were conducted at Oak Ridge National Laboratory (ORNL) from May 2011 to July 2013. This report also details the specimen loading methodology for the graphite specimens inside the AGC-3 irradiation capsule. The AGC-3 capsule design requires "matched pair" creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-3 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce "matched pairs" of graphite samples above and below the AGC-3 capsule elevation mid-point to

  15. Neutron diffraction studies of a double-crystal ( plus n,-m) setting containing a fully asymmetric diffraction geometry (FAD) of a bent perfect crystal (BPC)

    Czech Academy of Sciences Publication Activity Database

    Mikula, Pavol; Vrána, Miroslav; Šaroun, Jan; Em, V.

    2017-01-01

    Roč. 32, Supl-1 (2017), s. 13-18 ISSN 0885-7156 R&D Projects: GA ČR GC16-08803J; GA MŠk LM2015048 Institutional support: RVO:61389005 Keywords : neutron diffraction * monochromator * bent perfect crystal Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.674, year: 2016

  16. Ab initio and Molecular Dynamic models of displacement damage in crystalline and turbostratic graphite

    Science.gov (United States)

    McKenna, Alice

    One of the functions of graphite is as a moderator in several nuclear reactor designs, including the Advanced Gas-cooled Reactor (AGR). In the reactor graphite is used to thermalise the neutrons produced in the fission reaction thus allowing a self-sustained reaction to occur. The graphite blocks, acting as the moderator, are constantly irradiated and consequently suffer damage. This thesis examines the types of damage caused using molecular dynamic (MD) simulations and ab intio calculations. Neutron damage starts with a primary knock-on atom (PKA), which is travelling so fast that it creates damage through electronic and thermal excitation (this is addressed with thermal spike simulations). When the PKA has lost energy the subsequent cascade is based on ballistic atomic displacement. These two types of simulations were performed on single crystal graphite and other carbon structures such as diamond and amorphous carbon as a comparison. The thermal spike in single crystal graphite produced results which varied from no defects to a small number of permanent defects in the structure. It is only at the high energy range that more damage is seen but these energies are less likely to occur in the nuclear reactor. The thermal spike does not create damage but it is possible that it can heal damaged sections of the graphite, which can be demonstrated with the motion of the defects when a thermal spike is applied. The cascade simulations create more damage than the thermal spike even though less energy is applied to the system. A new damage function is found with a threshold region that varies with the square root of energy in excess of the energy threshold. This is further broken down in to contributions from primary and subsequent knock-on atoms. The threshold displacement energy (TDE) is found to be Ed=25eV at 300K. In both these types of simulation graphite acts very differently to the other carbon structures. There are two types of polycrystalline graphite structures

  17. Environmentally benign graphite intercalation compound composition for exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Jang, Bor Z.

    2014-06-17

    A carboxylic-intercalated graphite compound composition for the production of exfoliated graphite, flexible graphite, or nano-scaled graphene platelets. The composition comprises a layered graphite with interlayer spaces or interstices and a carboxylic acid residing in at least one of the interstices, wherein the composition is prepared by a chemical oxidation reaction which uses a combination of a carboxylic acid and hydrogen peroxide as an intercalate source. Alternatively, the composition may be prepared by an electrochemical reaction, which uses a carboxylic acid as both an electrolyte and an intercalate source. Exfoliation of the invented composition does not release undesirable chemical contaminants into air or drainage.

  18. Energy-momentum density of graphite by electron-momentum spectroscopy

    International Nuclear Information System (INIS)

    Vos, M.; Fang, Z.; Canney, S.; Kheifets, A.; McCarthy, I.E.; Weigold, E.

    1996-11-01

    The energy-resolved electron momentum density of graphite has been measured along a series of well-defined directions using electron momentum spectroscopy (EMS). This is the first measurement of this kind performed on a single-crystal target with a thoroughly controlled orientation which clearly demonstrates the different nature of the σ and π bands in graphite. Good agreement between the calculated density and the measured one is found, further establishing that fact that EMS yields more direct and complete information on the valence electronic structure that any other method. 12 refs., 2 figs

  19. Electrochemical Ultracapacitors Using Graphitic Nanostacks

    Science.gov (United States)

    Marotta, Christopher

    2012-01-01

    Electrochemical ultracapacitors (ECs) have been developed using graphitic nanostacks as the electrode material. The advantages of this technology will be the reduction of device size due to superior power densities and relative powers compared to traditional activated carbon electrodes. External testing showed that these materials display reduced discharge response times compared to state-of-the-art materials. Such applications are advantageous for pulsed power applications such as burst communications (satellites, cell phones), electromechanical actuators, and battery load leveling in electric vehicles. These carbon nanostructures are highly conductive and offer an ordered mesopore network. These attributes will provide more complete electrolyte wetting, and faster release of stored charge compared to activated carbon. Electrochemical capacitor (EC) electrode materials were developed using commercially available nanomaterials and modifying them to exploit their energy storage properties. These materials would be an improvement over current ECs that employ activated carbon as the electrode material. Commercially available graphite nanofibers (GNFs) are used as precursor materials for the synthesis of graphitic nanostacks (GNSs). These materials offer much greater surface area than graphite flakes. Additionally, these materials offer a superior electrical conductivity and a greater average pore size compared to activated carbon electrodes. The state of the art in EC development uses activated carbon (AC) as the electrode material. AC has a high surface area, but its small average pore size inhibits electrolyte ingress/egress. Additionally, AC has a higher resistivity, which generates parasitic heating in high-power applications. This work focuses on fabricating EC from carbon that has a very different structure by increasing the surface area of the GNF by intercalation or exfoliation of the graphitic basal planes. Additionally, various functionalities to the GNS

  20. Pyrolytic graphite gauge for measuring heat flux

    Science.gov (United States)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  1. Uranium Oxide Aerosol Transport in Porous Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, Jeremy; Gerlach, David C.; Scheele, Randall D.; Stewart, Mark L.; Reid, Bruce D.; Gauglitz, Phillip A.; Bagaasen, Larry M.; Brown, Charles C.; Iovin, Cristian; Delegard, Calvin H.; Zelenyuk, Alla; Buck, Edgar C.; Riley, Brian J.; Burns, Carolyn A.

    2012-01-23

    The objective of this paper is to investigate the transport of uranium oxide particles that may be present in carbon dioxide (CO2) gas coolant, into the graphite blocks of gas-cooled, graphite moderated reactors. The transport of uranium oxide in the coolant system, and subsequent deposition of this material in the graphite, of such reactors is of interest because it has the potential to influence the application of the Graphite Isotope Ratio Method (GIRM). The GIRM is a technology that has been developed to validate the declared operation of graphite moderated reactors. GIRM exploits isotopic ratio changes that occur in the impurity elements present in the graphite to infer cumulative exposure and hence the reactor’s lifetime cumulative plutonium production. Reference Gesh, et. al., for a more complete discussion on the GIRM technology.

  2. Influence of Particle Size on Properties of Expanded Graphite

    Directory of Open Access Journals (Sweden)

    Kurajica, S

    2010-02-01

    Full Text Available Expanded graphite has been applied widely in thermal insulation, adsorption, vibration damping, gasketing, electromagnetic interference shielding etc. It is made by intercalation of natural flake graphite followed by thermal expansion. Intercalation is a process whereby an intercalant material is inserted between the graphene layers of a graphite crystal. Exfoliation, a huge unidirectional expansion of the starting intercalated flakes, occurs when the graphene layers are forced apart by the sudden decomposition and vaporization of the intercalated species by thermal shock. Along with production methodologies, such as the intercalation process and heat treatment, the raw material characteristics, especially particle size, strongly influence the properties of the final product.This report evaluates the influence of the particle size of the raw material on the intercalation and expansion processes and consequently the properties of the exfoliated graphite. Natural crystalline flake graphite with wide particle diameter distribution (between dp = 80 and 425 µm was divided into four size-range portions by sieving. Graphite was intercalated via perchloric acid, glacial acetic acid and potassium dichromate oxidation and intercalation procedure. 5.0 g of graphite, 7.0 g of perchloric acid, 4.0 g of glacial acetic acid and 2.0 g of potassium dichromate were placed in glass reactor. The mixture was stirred with n = 200 min–1 at temperature of 45 °C during 60 min. Then it was filtered and washed with distilled water until pH~6 and dried at 60 °C during 24 h. Expansion was accomplished by thermal shock at 1000 °C for 1 min. The prepared samples were characterized by means of exfoliation volume measurements, simultaneous differential thermal analysis and thermo-gravimetry (DTA/TGA, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, BET measurements and scanning electron microscopy (SEM.X-ray diffraction indicated a change of distance

  3. Dynamics of graphite flake on a liquid

    Science.gov (United States)

    Miura, K.; Tsuda, D.; Kaneta, Y.; Harada, R.; Ishikawa, M.; Sasaki, N.

    2006-11-01

    One-directional motion, where graphite flakes are driven by a nanotip on an octamethylcyclotetrasiloxane (OMCTS) liquid surface, is presented. A transition from quasiperiodic to chaotic motions occurs in the dynamics of a graphite flake when its velocity is increased. The dynamics of graphite flakes pulled by the nanotip on an OMCTS liquid surface can be treated as that of a nanobody on a liquid.

  4. Sealing nuclear graphite with pyrolytic carbon

    International Nuclear Information System (INIS)

    Feng, Shanglei; Xu, Li; Li, Li; Bai, Shuo; Yang, Xinmei; Zhou, Xingtai

    2013-01-01

    Pyrolytic carbon (PyC) coatings were deposited on IG-110 nuclear graphite by thermal decomposition of methane at ∼1830 °C. The PyC coatings are anisotropic and airtight enough to protect IG-110 nuclear graphite against the permeation of molten fluoride salts and the diffusion of gases. The investigations indicate that the sealing nuclear graphite with PyC coating is a promising method for its application in Molten Salt Reactor (MSR)

  5. Nanostructured carbon films with oriented graphitic planes

    International Nuclear Information System (INIS)

    Teo, E. H. T.; Kalish, R.; Kulik, J.; Kauffmann, Y.; Lifshitz, Y.

    2011-01-01

    Nanostructured carbon films with oriented graphitic planes can be deposited by applying energetic carbon bombardment. The present work shows the possibility of structuring graphitic planes perpendicular to the substrate in following two distinct ways: (i) applying sufficiently large carbon energies for deposition at room temperature (E>10 keV), (ii) utilizing much lower energies for deposition at elevated substrate temperatures (T>200 deg. C). High resolution transmission electron microscopy is used to probe the graphitic planes. The alignment achieved at elevated temperatures does not depend on the deposition angle. The data provides insight into the mechanisms leading to the growth of oriented graphitic planes under different conditions.

  6. Production of nuclear graphite in France

    International Nuclear Information System (INIS)

    Legendre, P.; Mondet, L.; Arragon, Ph.; Cornuault, P.; Gueron, J.; Hering, H.

    1955-01-01

    The graphite intended for the construction of the reactors is obtained by the usual process: confection of a cake from coke of oil and tar, cooked (in a electric oven) then the product of cook is graphitized, also by electric heating. The use of the air transportation and the control of conditions cooking and graphitization have permitted to increase the nuclear graphite production as well as to better control their physical and mechanical properties and to reduce to the minimum the unwanted stains. (M.B.) [fr

  7. AC induction field heating of graphite foam

    Science.gov (United States)

    Klett, James W.; Rios, Orlando; Kisner, Roger

    2017-08-22

    A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam. An energy conversion device utilizes heat energy from the heated graphite foam to perform a heat energy consuming function. A device for heating a fluid and a method of converting energy are also disclosed.

  8. Nuclear graphite for high temperature reactors

    International Nuclear Information System (INIS)

    Marsden, B.J.

    2001-01-01

    The cores and reflectors in modern High Temperature Gas Cooled Reactors (HTRs) are constructed from graphite components. There are two main designs; the Pebble Bed design and the Prism design. In both of these designs the graphite not only acts as a moderator, but is also a major structural component that may provide channels for the fuel and coolant gas, channels for control and safety shut off devices and provide thermal and neutron shielding. In addition, graphite components may act as a heat sink or conduction path during reactor trips and transients. During reactor operation, many of the graphite component physical properties are significantly changed by irradiation. These changes lead to the generation of significant internal shrinkage stresses and thermal shut down stresses that could lead to component failure. In addition, if the graphite is irradiated to a very high irradiation dose, irradiation swelling can lead to a rapid reduction in modulus and strength, making the component friable.The irradiation behaviour of graphite is strongly dependent on its virgin microstructure, which is determined by the manufacturing route. Nevertheless, there are available, irradiation data on many obsolete graphites of known microstructures. There is also a well-developed physical understanding of the process of irradiation damage in graphite. This paper proposes a specification for graphite suitable for modern HTRs. (author)

  9. Structural analysis of polycrystalline (graphitized) materials

    International Nuclear Information System (INIS)

    Efremenko, M.M.; Kravchik, A.E.; Osmakov, A.S.

    1993-01-01

    Specific features of the structure of polycrystal carbon materials (CM), characterized by high enough degree of structural perfection and different genesis are analyzed. From the viewpoint of fine and supercrystallite structure analysis of the most characteristic groups of graphitized CM: artificial graphites, and natural graphites, as well, has been carried out. It is ascertained that in paracrystal CM a monolayer of hexagonally-bound carbon atoms is the basic element of the structure, and in graphitized CM - a microlayer. The importance of the evaluation of the degree of three-dimensional ordering of the microlayer is shown

  10. Principle design and data of graphite components

    International Nuclear Information System (INIS)

    Ishihara, Masahiro; Sumita, Junya; Shibata, Taiju; Iyoku, Tatsuo; Oku, Tatsuo

    2004-01-01

    The High Temperature Engineering Test Reactor (HTTR) constructed by Japan Atomic Energy Research Institute (JAERI) is a graphite-moderated and helium-gas-cooled reactor with prismatic fuel elements of hexagonal blocks. The reactor internal structures of the HTTR are mainly made up of graphite components. As well known, the graphite is a brittle material and there were no available design criteria for brittle materials. Therefore, JAERI had to develop the design criteria taking account of the brittle fracture behavior. In this paper, concept and key specification of the developed graphite design criteria is described, and also an outline of the quality control specified in the design criteria is mentioned

  11. Low temperature vapor phase digestion of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Robert A.

    2017-04-18

    A method for digestion and gasification of graphite for removal from an underlying surface is described. The method can be utilized to remove graphite remnants of a formation process from the formed metal piece in a cleaning process. The method can be particularly beneficial in cleaning castings formed with graphite molding materials. The method can utilize vaporous nitric acid (HNO.sub.3) or vaporous HNO.sub.3 with air/oxygen to digest the graphite at conditions that can avoid damage to the underlying surface.

  12. The Fracture Toughness of Nuclear Graphites Grades

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Erdman, III, Donald L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lowden, Rick R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hunter, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hannel, Cara C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-04-01

    New measurements of graphite mode I critical stress intensity factor, KIc (commonly referred to as the fracture toughness) and the mode II critical shear stress intensity, KIIc, are reported and compared with prior data for KIc and KIIc. The new data are for graphite grades PCEA, IG-110 and 2114. Variations of KIc and acoustic emission (AE) data with graphite texture are reported and discussed. The Codes and Standards applications of fracture toughness, KIc, data are also discussed. A specified minimum value for nuclear graphite KIc is recommended.

  13. Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

    International Nuclear Information System (INIS)

    Shu, Deming; Shvyd’ko, Yuri V.; Stoupin, Stanislav; Kim, Kwang-Je

    2016-01-01

    A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

  14. Mechanical design of thin-film diamond crystal mounting apparatus for coherence preservation hard x-ray optics

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Deming, E-mail: shu@aps.anl.gov; Shvyd’ko, Yuri V.; Stoupin, Stanislav; Kim, Kwang-Je [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, U.S.A (United States)

    2016-07-27

    A new thin-film diamond crystal mounting apparatus has been designed at the Advanced Photon Source (APS) for coherence preservation hard x-ray optics with optimized thermal contact and minimized crystal strain. This novel mechanical design can be applied to new development in the field of: x-ray optics cavities for hard x-ray free-electron laser oscillators (XFELOs), self-seeding monochromators for hard x-ray free-electron laser (XFEL) with high average thermal loading, high heat load diamond crystal monochromators and beam-sharing/beam-split-and-delay devices for XFEL facilities and future upgraded high-brightness coherent x-ray source in the MBA lattice configuration at the APS.

  15. Electrolysis of acidic sodium chloride solution with a graphite anode. I. Graphite electrode

    NARCIS (Netherlands)

    Janssen, L.J.J.; Hoogland, J.G.

    1969-01-01

    A graphite anode evolving Cl from a chloride soln. is slowly oxidized to CO and CO2. This oxidn. causes a change in the characteristics of the electrode in aging, comprising a change of the nature of the graphite surface and an increase of the surface area. It appears that a new graphite electrode

  16. Advantages of a monochromated transmission electron microscope for solid state physics

    International Nuclear Information System (INIS)

    Grogger, W.; Kothleitner, G.; Hofer, F.

    2006-01-01

    Full text: The characterization of nanostructured devices and functional materials at a nanometer scale is paramount for the understanding of their physical and chemical properties. Transmission electron microscopy (TEM) plays a central role, especially in terms of structural and chemical analysis on a nearly atomic scale. In particular, electron energy-loss spectrometry (EELS) can obtain information not only about the chemical composition of a thin sample, but also about chemical bonding and electronic structure (ionization edge fine structures) and optical properties (through valence loss EELS). Recent instrumental advances like monochromators for the electron gun in the TEM have made it possible to reduce the energy resolution to 0.15 eV at an acceleration voltage of 200 kV. Another strong point of the method lies in the combination with a fine electron probe (0.2 nm) which allows to record EELS spectra with high energy resolution and spatial resolution in the range of 1 nm. The improved energy resolution opens new possibilities for studying detailed electronic structure and bonding effects in solids such as transmission metal oxides. The experimental results will be compared with x-ray absorption spectroscopy and band structure calculations. A better energy-resolution is particularly important for measurements in the low loss region of the EELS spectrum which provides the information about the band gap and the dielectric function. We will highlight the potential of the method for studying metallic nanoparticles and semiconducting devices. Additionally, the influence of the intrinsic effects like core-hole and excited lifetime broadening and delocalization of the inelastically scattered electrons will be discussed. (author)

  17. Hydrogen storage in graphitic nanofibres

    OpenAIRE

    McCaldin, Simon Roger

    2007-01-01

    There is huge need to develop an alternative to hydrocarbons fuel, which does not produce CO2 or contribute to global warming - 'the hydrogen economy' is such an alternative, however the storage of hydrogen is the key technical barrier that must be overcome. The potential of graphitic nanofibres (GNFs) to be used as materials to allow the solid-state storage of hydrogen has thus been investigated. This has been conducted with a view to further developing the understanding of the mechanism(s) ...

  18. Nano-cracks in a synthetic graphite composite for nuclear applications

    Science.gov (United States)

    Liu, Dong; Cherns, David

    2018-05-01

    Mrozowski nano-cracks in nuclear graphite were studied by transmission electron microscopy and selected area diffraction. The material consisted of single crystal platelets typically 1-2 nm thick and stacked with large relative rotations around the c-axis; individual platelets had both hexagonal and cubic stacking order. The lattice spacing of the (0002) planes was about 3% larger at the platelet boundaries which were the source of a high fraction of the nano-cracks. Tilting experiments demonstrated that these cracks were empty, and not, as often suggested, filled by amorphous material. In addition to conventional Mrozowski cracks, a new type of nano-crack is reported, which originates from the termination of a graphite platelet due to crystallographic requirements. Both types are crucial to understanding the evolution of macro-scale graphite properties with neutron irradiation.

  19. Towards graphite-free hot zone for directional solidification of silicon

    Science.gov (United States)

    Dropka, Natasha; Buchovska, Iryna; Herrmann-Geppert, Iris; Klimm, Detlef; Kiessling, Frank M.; Degenhardt, Ulrich

    2018-06-01

    The reduction of SiC, Si3N4 and transition metals impurities in directionally solidified Si ingots poses one of the crucial challenges in the solar cells production. Particularly strong contamination comes from the graphite parts in the hot zone. Therefore, we selected three massive ceramic materials to replace graphite, developed the novel design of the crucible support and cover and compared the crystals grown in them with ingots from the standard graphite design. The experiments were performed for phosphorus n-doped silicon of G0 size. The ingots were compared with respect to O- and C-content, metal impurities, resistivity and lifetime. The superior performance of TiC relative to other ceramics was observed, particularly due to the lower concentration of substitutional carbon in Si ingot (up to 2.6 times) and the higher minority carrier lifetime of (up to 4.4 times) with narrow red zones.

  20. Mixed graphite cast iron for automotive exhaust component applications

    OpenAIRE

    De-lin Li

    2017-01-01

    Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard speci...

  1. Nuclear graphite waste management. Proceedings of a technical committee meeting

    International Nuclear Information System (INIS)

    2001-05-01

    The purpose of the seminar was to bring together the specialists dealing with various aspects of radioactive graphite waste management to exchange and review information on the decommissioning, characterisation, processing and disposal of irradiated graphite from reactor cores and other graphite waste associated with reactor operation. The seminar covered radioactive graphite characterisation, the effect of irradiation on graphite components, Wigner energy, radioactive graphite waste treatment, conditioning, interim storage and long term disposal options. Individual papers presented at the seminar were indexed separately

  2. Graphite as an indicator of contact influence of Western Keivy alkaline granite intrusion, the Kola Peninsula

    Directory of Open Access Journals (Sweden)

    Fomina E. N.

    2017-03-01

    Full Text Available The results of complex petro-mineragraphic, Raman and isotope- geochemical study of three types of graphite- bearing rocks circulated at different distances from the alkaline granites: (1 kyanite schists of Bolshiye Keivy, sampled at a considerable distance from a contact with alkaline gran ites; (2 sillimanite schists, sampled close to the contact, and (3 silexites, located in the inner part of th e alkaline granite massif Western Keivy have been presented. Five morphogenetic types of graphite have been revealed in the rocks under consideration: fine- grained Gr-1, intergranular Gr-2, nest-shaped Gr-3, vein Gr- 4 and spherulitic Gr-5. Current study demonstrates that these five types of graphite distinctly vary not only i n morphology, but also in temperature of crystallization, as determined by RSCM-Raman geothermometer, and in carbon isotop e composition. The most likely source for the anomalous "light" graphite Gr-1 and Gr-2 [δ 13 C(PDB = −43...−45 ‰] from kyanite schists is a water- methane fluid originating from sedimentary rocks with org anic compounds. The carbon of graphite Gr-5 of the silexites selected at the inner part of alkaline granite massif West ern Keivy, on the contrary, proved to be most "heavy" [δ 13 C(PDB = −8 ‰], which indicates its origin from the lower crustal or mantle carbon dioxide fluid. Thus, carbon extracted into the rocks of Keivy structure from at least two contrasting isotope sources. Graphite Gr-3, that makes up the bulk of graphite of exocontact sil limanite schists, is also isotopically light, but not anomalously [δ 13 C(PDB = −17...−28 ‰]. The crystallization temperature of the gi ven graphite (435−520 ºC, and its structural relationships with other minerals of th e rock evidence of its synmetamorphic origin. The presence of veinlets of isotopically heavy [δ 13 C(PDB = −10 ‰...−11 ‰] high-temperature (570−670 ºC graphite intersecting minerals of the metamorphic paragenesis (i

  3. Analysis of Wigner energy release process in graphite stack of shut-down uranium-graphite reactor

    OpenAIRE

    Bespala, E. V.; Pavliuk, A. O.; Kotlyarevskiy, S. G.

    2015-01-01

    Data, which finding during thermal differential analysis of sampled irradiated graphite are presented. Results of computational modeling of Winger energy release process from irradiated graphite staking are demonstrated. It's shown, that spontaneous combustion of graphite possible only in adiabatic case.

  4. A study of the coefficient of thermal expansion of nuclear graphites

    International Nuclear Information System (INIS)

    Hacker, P.J.

    2001-02-01

    This thesis presents the results of a study of the Coefficient of Thermal Expansion (CTE) of two grades of nuclear graphite that are used as the moderator in the Magnox and Advanced Gas-Cooled reactors operated in the UK. This work has two main aims, the first is to characterise those elements of the graphite microstructure that control CTE within these materials and to relate these to the effects induced within the reactor. The second is to develop a microstructural model, of general applicability, that can initially be applied to model the CTE changes within the graphites under reactor conditions (neutron irradiation and radiolytic oxidation). These aims have been met by study in three interlinked areas, theoretical, experimental and modelling. Previous to this study, a loose assembly of single crystals together with changes in small scale nanometric porosity (Mrozowski cracks) were used to describe CTE behaviour of nuclear graphite both as-received and under reactor conditions. Within the experimental part of this thesis the graphite nanostructure was studied using, primarily, Transmission Electron Microscopy (TEM). This work concluded that structure on this scale was complex and that the loose assembly of single crystals was a poor microstructural approximation for modelling the CTE of these materials. Other experimental programmes measured the CTE of highly oxidised samples and simulated the effects of irradiation. The former discovered that CTE remained largely unaffected to high weight losses. This insensitivity was explained by ''The Continuous Network Hypothesis'' that was also related to classical percolation theory. The final part of the thesis modelled an abstraction of the key microstructural features identified in the previous parts of the thesis. This approach has been applied to AGR moderator graphite where it has successfully modelled the thermal expansion behaviour of the as-received, irradiated and oxidised material. (author)

  5. Mixed graphite cast iron for automotive exhaust component applications

    Directory of Open Access Journals (Sweden)

    De-lin Li

    2017-11-01

    Full Text Available Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard specification (A1095 has been created for compacted, mixed, and spheroidal graphite silicon-molybdenum iron castings. This paper attempts to outline the latest progress in mixed graphite iron published.

  6. X-ray monochromators for high-power synchrotron radiation sources

    Science.gov (United States)

    Hart, Michael

    1990-11-01

    Exact solutions to the problems of power flow from a line source of heat into a semicylinder and of uniform heat flow normal to a flat surface are discussed. These lead to bounds on feasible designs and the boundary layer problem can be placed in proper perspective. While finite element calculations are useful if the sample boundaries are predefined, they are much less help in establishing design principles. Previous work on hot beam X-ray crystal optics has emphasised the importance of coolant hydraulics and boundary layer heat transfer. Instead this paper emphasises the importance of the elastic response of crystals to thermal strainfields and the importance of maintaining the Darwin reflectivity. The conclusions of this design study are that the diffracting crystal region should be thin, but not very thin, similar in area to the hot beam footprint, part of a thin-walked buckling crystal box and remote from the support to which the crystal is rigidly clamped. Prototype 111 and 220 cooled silicon crystals tested at the National Synchrotron Light Source at Brookhaven have almost perfect rocking curves under a beam heat load of {1}/{3}kW.

  7. Measurement of the velocity of sound in crystals by pulsed neutron diffraction

    International Nuclear Information System (INIS)

    Willis, B.T.M.; Carlile, C.J.; Ward, R.C.; David, W.I.F.; Johnson, M.W.

    1986-03-01

    The diffraction method of observing elementary excitations in crystals has been applied to the study of one-phonon thermal diffuse scattering from pyrolytic graphite on a high resolution pulsed neutron diffractometer. The variation of the phase velocity of sound as a function of direction in the crystal and efficient method of determining sound velocities in crystals under extreme conditions. (author)

  8. Methodology of characterization of radioactive graphite

    International Nuclear Information System (INIS)

    Pina, G.; Rodriguez, M.; Lara, E.; Magro, E.; Gascon, J. L.; Leganes, J. L.

    2014-01-01

    Since the dismantling of Vandellos I, ENRESA has promoted the precise knowledge of the inventory of irradiated graphite (graphite-i) through establishing methodologies for radiological characterization of the vector of radionuclides of interest and their correlations as the primary means of characterization strategy to establish the safer management of this material in its life cycle. (Author)

  9. Significance of primary irradiation creep in graphite

    CSIR Research Space (South Africa)

    Erasmus, C

    2013-05-01

    Full Text Available Traditionally primary irradiation creep is introduced into graphite analysis by applying the appropriate amount of creep strain to the model at the initial time-step. This is valid for graphite components that are subjected to high fast neutron flux...

  10. Inhibition of oxidation in nuclear graphite

    International Nuclear Information System (INIS)

    Winston, Philip L.; Sterbentz, James W.; Windes, William E.

    2015-01-01

    Graphite is a fundamental material of high-temperature gas-cooled nuclear reactors, providing both structure and neutron moderation. Its high thermal conductivity, chemical inertness, thermal heat capacity, and high thermal structural stability under normal and off-normal conditions contribute to the inherent safety of these reactor designs. One of the primary safety issues for a high-temperature graphite reactor core is the possibility of rapid oxidation of the carbon structure during an off-normal design basis event where an oxidising atmosphere (air ingress) can be introduced to the hot core. Although the current Generation IV high-temperature reactor designs attempt to mitigate any damage caused by a postulated air ingress event, the use of graphite components that inhibit oxidation is a logical step to increase the safety of these reactors. Recent experimental studies of graphite containing between 5.5 and 7 wt% boron carbide (B 4 C) indicate that oxidation is dramatically reduced even at prolonged exposures at temperatures up to 900 deg. C. The proposed addition of B 4 C to graphite components in the nuclear core would necessarily be enriched in B-11 isotope in order to minimise B-10 neutron absorption and graphite swelling. The enriched boron can be added to the graphite during billet fabrication. Experimental oxidation rate results and potential applications for borated graphite in nuclear reactor components will be discussed. (authors)

  11. Metal/graphite - composites in fusion engineering

    International Nuclear Information System (INIS)

    Staffler, R.; Kneringer, G.; Kny, E.; Reheis, N.

    1989-01-01

    Metal/graphite composites have been well known in medical industry for many years. X-ray tubes used in modern radiography, particularly in computerized tomography are equipped with rotating targets able to absorb a maximum of heat in a given time. Modern rotating targets consist of a refractory metal/graphite composite. Today the use of graphite as a plasma facing material is one predominant concept in fusion engineering. Depending on the thermal load, the graphite components have to be directly cooled (i.e. divertor plates) or inertially cooled (i.e. firstwall tiles). In case of direct cooling a metallurgical joining such as high temperature brazing between graphite and a metallic cooling structure shows the most promising results /1/. Inertially cooled graphite tiles have to be joined to a metallic backing plate in order to get a stable attachment to the supporting structure. The main requirements on the metallic partner of a metal/graphite composite used in the first wall area are: high melting point, high thermal strength, high thermal conductivity, low vapor pressure and a thermal expansion matching that of graphite. These properties are typical for the refractory metals such as molybdenum, tungsten and their alloys. 4 refs., 13 figs., 1 tab

  12. Metal/graphite - composites in fusion engineering

    International Nuclear Information System (INIS)

    Staffler, R.; Kneringer, G.; Kny, E.; Reheis, N.

    1995-01-01

    Metal/graphite composites have been well known in medical industry for many years. X-ray tubes used in modern radiography, particulary in computerized tomography are equipped with rotating targets able to absorb a maximum of heat in a given time. Modern rotating targets consist of a refractory metal/graphite composite. Today the use of graphite as a plasma facing material is one predominant concept in fusion engineering. Depending on the thermal load, the graphite components have to be directly cooled (i.e. divertor plates) or inertially cooled (i.e. firstwall tiles). In case of direct cooling a metallurgical joining such as high temperature brazing between graphite and a metalic cooling structure shows the most promising results /1/. Inertially cooled graphite tiles have to be joined to a metallic backing plate in order to get a stable attachment to the supporting structure. The main requirements on the metallic partner of a metal/graphite composite and in the first wall area are: high melting point, high thermal strength, high thermal conductivity, low vapour pressure and a thermal expansion matching that of graphite. These properties are typical for the refractory metals such as molybdenum, tungsten and their alloys. (author)

  13. Tire containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

  14. Effect of graphite target power density on tribological properties of graphite-like carbon films

    Science.gov (United States)

    Dong, Dan; Jiang, Bailing; Li, Hongtao; Du, Yuzhou; Yang, Chao

    2018-05-01

    In order to improve the tribological performance, a series of graphite-like carbon (GLC) films with different graphite target power densities were prepared by magnetron sputtering. The valence bond and microstructure of films were characterized by AFM, TEM, XPS and Raman spectra. The variation of mechanical and tribological properties with graphite target power density was analyzed. The results showed that with the increase of graphite target power density, the deposition rate and the ratio of sp2 bond increased obviously. The hardness firstly increased and then decreased with the increase of graphite target power density, whilst the friction coefficient and the specific wear rate increased slightly after a decrease with the increasing graphite target power density. The friction coefficient and the specific wear rate were the lowest when the graphite target power density was 23.3 W/cm2.

  15. Hydrogen storage in graphite nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Park, C.; Tan, C.D.; Hidalgo, R.; Baker, R.T.K.; Rodriguez, N.M. [Northeastern Univ., Boston, MA (United States). Chemistry Dept.

    1998-08-01

    Graphite nanofibers (GNF) are a type of material that is produced by the decomposition of carbon containing gases over metal catalyst particles at temperatures around 600 C. These molecularly engineered structures consist of graphene sheets perfectly arranged in a parallel, perpendicular or at angle orientation with respect to the fiber axis. The most important feature of the material is that only edges are exposed. Such an arrangement imparts the material with unique properties for gas adsorption because the evenly separated layers constitute the most ordered set of nanopores that can accommodate an adsorbate in the most efficient manner. In addition, the non-rigid pore walls can also expand so as to accommodate hydrogen in a multilayer conformation. Of the many varieties of structures that can be produced the authors have discovered that when gram quantities of a selected number of GNF are exposed to hydrogen at pressures of {approximately} 2,000 psi, they are capable of adsorbing and storing up to 40 wt% of hydrogen. It is believed that a strong interaction is established between hydrogen and the delocalized p-electrons present in the graphite layers and therefore a new type of chemistry is occurring within these confined structures.

  16. Angular distribution measurement of fragment ions from a molecule using a new beamline consisting of a Grasshopper monochromator

    Science.gov (United States)

    Saito, Norio; Suzuki, Isao H.; Onuki, Hideo; Nishi, Morotake

    1989-07-01

    Optical characteristics of a new beamline consisting of a premirror, a Grasshopper monochromator, and a refocusing mirror have been investigated. The intensity of the monochromatic soft x-ray was estimated to be about 108 photons/(s 100 mA) at 500 eV with the storage electron energy of 600 MeV and the minimum slit width. This slit width provides a resolution of about 500. Angular distributions of fragment ions from an inner-shell excited nitrogen molecule have been measured with a rotatable time-of-flight mass spectrometer by using this beamline.

  17. Angular distribution measurement of fragment ions from a molecule using a new beamline consisting of a Grasshopper monochromator

    International Nuclear Information System (INIS)

    Saito, N.; Suzuki, I.H.; Onuki, H.; Nishi, M.

    1989-01-01

    Optical characteristics of a new beamline consisting of a premirror, a Grasshopper monochromator, and a refocusing mirror have been investigated. The intensity of the monochromatic soft x-ray was estimated to be about 10 8 photons/(s 100 mA) at 500 eV with the storage electron energy of 600 MeV and the minimum slit width. This slit width provides a resolution of about 500. Angular distributions of fragment ions from an inner-shell excited nitrogen molecule have been measured with a rotatable time-of-flight mass spectrometer by using this beamline

  18. Use of a GPGPU means for the development of search programs of defects of monochrome half-tone pictures

    International Nuclear Information System (INIS)

    Dudnik, V.A.; Kudryavtsev, V.I.; Sereda, T.M.; Us, S.A.; Shestakov, M.V.

    2013-01-01

    Application of a GPGPU means for the development of search programs of defects of monochrome half-tone pictures is described. The description of realization of algorithm of search of images' defects by the means of technology CUDA (Compute Unified Device Architecture - the unified hardware-software decision for parallel calculations on GPU) companies NVIDIA is resulted. It is done the comparison of the temporary characteristics of performance of images' updating without application GPU and with use of opportunities of graphic processor GeForce 8800.

  19. Methane generated from graphite--tritium interaction

    International Nuclear Information System (INIS)

    Coffin, D.O.; Walthers, C.R.

    1979-01-01

    When hydrogen isotopes are separated by cryogenic distillation, as little as 1 ppM of methane will eventually plug the still as frost accumulates on the column packings. Elemental carbon exposed to tritium generates methane spontaneously, and yet some dry transfer pumps, otherwise compatible with tritium, convey the gas with graphite rotors. This study was to determine the methane production rate for graphite in tritium. A pump manufacturer supplied graphite samples that we exposed to tritium gas at 0.8 atm. After 137 days we measured a methane synthesis rate of 6 ng/h per cm 2 of graphite exposed. At this rate methane might grow to a concentration of 0.01 ppM when pure tritium is transferred once through a typical graphite--rotor transfer pump. Such a low methane level will not cause column blockage, even if the cryogenic still is operated continuously for many years

  20. Chemical sputtering of graphite by H+ ions

    International Nuclear Information System (INIS)

    Busharov, N.P.; Gorbatov, E.A.; Gusev, V.M.; Guseva, M.I.; Martynenko, Y.V.

    1976-01-01

    In a study of the sputtering coefficient S for the sputtering of graphite by 10-keV H + ions as a function of the graphite temperature during the bombardment, it is found that at T> or =750degreeC the coefficient S is independent of the target temperature and has an anomalously high value, S=0.085 atom/ion. The high rate of sputtering of graphite by atomic hydrogen ions is shown to be due to chemical sputtering of the graphite, resulting primarily in the formation of CH 4 molecules. At T=1100degreeC, S falls off by a factor of about 3. A model for the chemical sputtering of graphite is proposed

  1. Graphite selection for the FMIT test cell

    International Nuclear Information System (INIS)

    Morgan, W.C.

    1982-06-01

    This document provides the basis for procuring a grade of graphite, at minimum cost, having minimum dimensional changes at low irradiation temperatures (nominal range 90 to 140 0 C). In light of those constraints, the author concludes that the most feasible approach is to attempt to reproduce a grade of graphite (TSGBF) which has exhibited a high degree of dimensional stability during low-temperature irradiations and on which irradiation-induced changes in other physical properties have been measured. The effects of differences in raw materials, especially coke morphology, and processing conditions, primarily graphitization temperture are briefly reviewed in terms of the practicality of producing a new grade of graphite with physical properties and irradiation-induced changes which would be very similar to those of TSGBF graphite. The production history and physical properties of TSGBF are also reviewed; no attempt is made, to project changes in dimensions or physical properties under the projected irradiation conditions

  2. Pressure and graphite effects on electrical conductivity in pyroxene

    Science.gov (United States)

    Wang, D.; Liu, T.; Shen, K.; Li, B.

    2017-12-01

    The geophysical observations including magnetotelluric (MT) and geomagnetic deep sounding show the distribution of electrical conductivity in the Earth's interior. The laboratory-based conductivity measurements of minerals and rocks are usually used to interpret the geophysical observations. Pyroxene is the second most abundant components in the upper mantle, and the electrical conductivity of pyroxene is important to understanding the bulk electrical conductivity. The electrical conductivity of a mineral is affected by many factors, such as its chemical composition, temperature, pressure. Here we report the effects of pressure and graphite on the electrical conductivity of pyroxene and applied to interpretation of MT observation. The starting materials are natural of orthopyroxene and clinopyroxe crystals. A powder sample with grain size 10 um was packed in a Mo capsule and hot-pressed at high pressures and temperatures using a 1000-ton Walker-type uniaxial split-cylinder apparatus. A mixture of pyroxene and a few percent of diamond was annealed at high pressure and temperature. All the hot-pressed samples before and after electrical conductivity measurements, were characterized by scanning electron microscopy, Fourier-Transform Infrared and Raman spectroscopy. High pressure conductivity experiments were carried out in a Walker-type multi-anvil apparatus using a 14/8 assembly. We use a Solartron 1260 Impedance/Gain -phase analyzer with 1V applied voltage within a frequency range of 1M-0.1 Hz to collect data. Complex impedance data on were collected in several heating and cooling cycles The electrical conductivity of pyroxene was made at 4,7,10 GPa, and electrical conductivity of the graphite-bearing pyroxene was measured at 4GPa. The results show the electrical conductivity decrease with the increasing of pressure, which may correspond to the transform from orthopyroxene to clinopyroxene. The results can be used to explain a drop of the electrical conductivity in

  3. AGC-2 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; W. David Swank; David Rohrbaugh; Joseph Lord

    2013-08-01

    This report described the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the second Advanced Graphite Capsule (AGC-2) irradiation capsule. The AGC-2 capsule is the second in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. Similar to the AGC-1 specimen pre-irradiation examination report, material property tests were conducted on specimens from 18 nuclear graphite types but on an increased number of specimens (512) prior to loading into the AGC-2 irradiation assembly. All AGC-2 specimen testing was conducted at Idaho National Laboratory (INL) from October 2009 to August 2010. This report also details the specimen loading methodology for the graphite specimens inside the AGC-2 irradiation capsule. The AGC-2 capsule design requires “matched pair” creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-2 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce “matched pairs” of graphite samples above and below the AGC-2 capsule elevation mid-point to provide specimens with similar neutron dose levels.

  4. Modeling Fission Product Sorption in Graphite Structures

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-01-01

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high-temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products

  5. Enhanced microwave absorption properties of graphite nanoflakes by coating hexagonal boron nitride nanocrystals

    KAUST Repository

    Zhong, Bo; Liu, Wei; Yu, Yuanlie; Xia, Long; Zhang, Jiulin; Chai, Zhenfei; Wen, Guangwu

    2017-01-01

    We report herein the synthesis of a novel hexagonal boron nitride nanocrystal/graphite nanoflake (h-BNNC/GNF) composite through a wet-chemistry coating of graphite nanoflakes and subsequent in-situ thermal treatment process. The characterization results of X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy demonstrate that h-BNNCs with diameter of tens of nanometers are highly crystallized and anchored on the surfaces of graphite nanoflakes without obvious aggregation. The minimum reflection loss (RL) value of the h-BNNC/GNF based absorbers could reach −32.38dB (>99.99% attenuation) with the absorber thickness of 2.0mm. This result is superior to the other graphite based and some dielectric loss microwave absorption materials recently reported. Moreover, the frequency range where the RL is less than −10dB is 3.49-17.28GHz with the corresponding thickness of 5.0 to 1.5mm. This reveals a better electromagnetic microwave absorption performance of h-BNNC/GNFs from the X-band to the Ku-band. The remarkable enhancement of the electromagnetic microwave absorption properties of h-BNNC/GNFs can be assigned to the increase of multiple scattering, interface polarization as well as the improvement of the electromagnetic impedance matching of graphite nanoflakes after being coated with h-BNNCs.

  6. Enhanced microwave absorption properties of graphite nanoflakes by coating hexagonal boron nitride nanocrystals

    KAUST Repository

    Zhong, Bo

    2017-05-31

    We report herein the synthesis of a novel hexagonal boron nitride nanocrystal/graphite nanoflake (h-BNNC/GNF) composite through a wet-chemistry coating of graphite nanoflakes and subsequent in-situ thermal treatment process. The characterization results of X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy demonstrate that h-BNNCs with diameter of tens of nanometers are highly crystallized and anchored on the surfaces of graphite nanoflakes without obvious aggregation. The minimum reflection loss (RL) value of the h-BNNC/GNF based absorbers could reach −32.38dB (>99.99% attenuation) with the absorber thickness of 2.0mm. This result is superior to the other graphite based and some dielectric loss microwave absorption materials recently reported. Moreover, the frequency range where the RL is less than −10dB is 3.49-17.28GHz with the corresponding thickness of 5.0 to 1.5mm. This reveals a better electromagnetic microwave absorption performance of h-BNNC/GNFs from the X-band to the Ku-band. The remarkable enhancement of the electromagnetic microwave absorption properties of h-BNNC/GNFs can be assigned to the increase of multiple scattering, interface polarization as well as the improvement of the electromagnetic impedance matching of graphite nanoflakes after being coated with h-BNNCs.

  7. Positron annihilation study of graphite, glassy carbon and C60/C70 fullerene

    International Nuclear Information System (INIS)

    Hasegawa, Masayuki; Kajino, Masahiro; Yamaguchi, Sadae; Iwata, Tadao; Kuramoto, Eiichi; Takenaka, Minoru.

    1992-01-01

    ACAR (Angular Correlation of Annihilation Radiation) and positron lifetime measurements have been made on, HOPG (Highly Oriented Pyrolytic Graphite), isotropic fine-grained graphite, glassy carbons and C 60 /C 70 powder. HOPG showed marked bimodality along the c-axis and anisotropy in ACAR momentum distribution, which stem from characteristic annihilation between 'interlayer' positrons and π-electrons in graphite. ACAR curves of the isotropic graphite and glassy carbons are even narrower than that of HOPG perpendicular to the c-axis. Positron lifetime of 420 and 390 - 480 psec, much longer than that of 221 psec in HOPG, were observed for the isotropic graphite and glassy carbons respectively, which are due to positron trapping in structural voids in them. Positron lifetime and ACAR width (FWHM) can be well correlated to void sizes (1.7 to 5.0 nm) of glassy carbons which have been determined by small angle neutron (SAN) scattering measurements. ACAR curves and positron lifetime of C 60 /C 70 powder agree well with those of glassy carbons. This shows that positron wave functions extend, as in the voids of glassy carbons, much wider than open spaces of the octahedral interstices of the face-centered cubic (FCC) structure of C 60 crystal and strongly suggests positron trapping in the 'soccer ball' vacancy. Possible positron states in the carbon materials are discussed with a simple model of void volume-trapping. Preliminary results on neutron irradiation damage in HOPG are also presented. (author)

  8. A comparison of absolute calibrations of a radiation thermometer based on a monochromator and a tunable source

    Energy Technology Data Exchange (ETDEWEB)

    Keawprasert, T. [National Institute of Metrology Thailand, Pathum thani (Thailand); Anhalt, K.; Taubert, D. R.; Sperling, A.; Schuster, M.; Nevas, S. [Physikalisch Technische Bundesanstalt, Braunschweig and Berlin (Germany)

    2013-09-11

    An LP3 radiation thermometer was absolutely calibrated at a newly developed monochromator-based set-up and the TUneable Lasers in Photometry (TULIP) facility of PTB in the wavelength range from 400 nm to 1100 nm. At both facilities, the spectral radiation of the respective sources irradiates an integrating sphere, thus generating uniform radiance across its precision aperture. The spectral irradiance of the integrating sphere is determined via an effective area of a precision aperture and a Si trap detector, traceable to the primary cryogenic radiometer of PTB. Due to the limited output power from the monochromator, the absolute calibration was performed with the measurement uncertainty of 0.17 % (k= 1), while the respective uncertainty at the TULIP facility is 0.14 %. Calibration results obtained by the two facilities were compared in terms of spectral radiance responsivity, effective wavelength and integral responsivity. It was found that the measurement results in integral responsivity at the both facilities are in agreement within the expanded uncertainty (k= 2). To verify the calibration accuracy, the absolutely calibrated radiation thermometer was used to measure the thermodynamic freezing temperatures of the PTB gold fixed-point blackbody.

  9. A comparison of absolute calibrations of a radiation thermometer based on a monochromator and a tunable source

    International Nuclear Information System (INIS)

    Keawprasert, T.; Anhalt, K.; Taubert, D. R.; Sperling, A.; Schuster, M.; Nevas, S.

    2013-01-01

    An LP3 radiation thermometer was absolutely calibrated at a newly developed monochromator-based set-up and the TUneable Lasers in Photometry (TULIP) facility of PTB in the wavelength range from 400 nm to 1100 nm. At both facilities, the spectral radiation of the respective sources irradiates an integrating sphere, thus generating uniform radiance across its precision aperture. The spectral irradiance of the integrating sphere is determined via an effective area of a precision aperture and a Si trap detector, traceable to the primary cryogenic radiometer of PTB. Due to the limited output power from the monochromator, the absolute calibration was performed with the measurement uncertainty of 0.17 % (k= 1), while the respective uncertainty at the TULIP facility is 0.14 %. Calibration results obtained by the two facilities were compared in terms of spectral radiance responsivity, effective wavelength and integral responsivity. It was found that the measurement results in integral responsivity at the both facilities are in agreement within the expanded uncertainty (k= 2). To verify the calibration accuracy, the absolutely calibrated radiation thermometer was used to measure the thermodynamic freezing temperatures of the PTB gold fixed-point blackbody

  10. Graphite Oxidation Thermodynamics/Reactions

    International Nuclear Information System (INIS)

    Propp, W.A.

    1998-01-01

    The vulnerability of graphite-matrix spent nuclear fuel to oxidation by the ambient atmosphere if the fuel canister is breached was evaluated. Thermochemical and kinetic data over the anticipated range of storage temperatures (200 to 400 C) were used to calculate the times required for a total carbon mass loss of 1 mgcm-2 from a fuel specimen. At 200 C, the time required to produce even this small loss is large, 900,000 yr. However, at 400 C the time required is only 1.9 yr. The rate of oxidation at 200 C is negligible, and the rate even at 400 C is so small as to be of no practical consequence. Therefore, oxidation of the spent nuclear fuel upon a loss of canister integrity is not anticipated to be a concern based upon the results of this study

  11. Low cost sic coated erosion resistant graphite

    International Nuclear Information System (INIS)

    Zafar, M.F.; Nicholls, J.R.

    2007-01-01

    The development of materials with unique and improved properties using low cost processes is essential to increase performance and reduce cost of the solid rocket motors. Specifically advancements are needed for boost phase nozzle. As these motors operate at very high pressure and temperatures, the nozzle must survive high thermal stresses with minimal erosion to maintain performance. Currently three material choices are being exploited; which are refractory metals, graphite and carbon-carbon composites. Of these three materials graphite is the most attractive choice because of its low cost, light weight, and easy forming. However graphite is prone to erosion, both chemical and mechanical, which may affect the ballistic conditions and mechanical properties of the nozzle. To minimize this erosion high density graphite is usually preferred; which is again very expensive. Another technique used to minimize the erosion is Pyrolytic Graphite (PG) coating inside the nozzle. However PG coating is prone to cracking and spallation along with very cumbersome deposition process. Another possible methodology to avoid this erosion is to convert the inside surface of the rocket nozzle to Silicon Carbide (SiC), which is very erosion resistant and have much better thermal stability compared to graphite and even PG. Due to its functionally gradient nature such a layer will be very adherent and resistant to spallation. The current research is focused on synthesizing, characterizing and oxidation testing of such a converted SiC layer on commercial grade graphite. (author)

  12. Design of a high-efficiency grazing incidence monochromator with multilayer-coated laminar gratings for the 1-6 keV region

    International Nuclear Information System (INIS)

    Koike, Masato; Ishino, Masahiko; Sasai, Hiroyuki

    2006-01-01

    A grazing incidence objective monochromator consisting of a spherical mirror, a varied-line-spacing plane grating with multilayered coating, a movable plane multilayered mirror, and a fixed exit slit for the 1-6 keV region has been designed. The included angle at the grating was chosen to satisfy the grating equation and extended Bragg condition simultaneously. The aberration was corrected by means of a hybrid design method. A spectral resolving power of ∼600-∼6000 and a throughput of ∼2%-∼40% is expected for the monochromator when used in an undulator beamline

  13. Physics of radiation effects in crystals

    CERN Document Server

    Johnson, RA

    1986-01-01

    ``Physics of Radiation Effects in Crystals'' is presented in two parts. The first part covers the general background and theory of radiation effects in crystals, including the theory describing the generation of crystal lattice defects by radiation, the kinetic approach to the study of the disposition of these defects and the effects of the diffusion of these defects on alloy compositions and phases. Specific problems of current interest are treated in the second part and include anisotropic dimensional changes in x-uranium, zirconium and graphite, acceleration of thermal creep in reactor ma

  14. Channel uranium-graphite reactor mounting

    International Nuclear Information System (INIS)

    Polushkin, K.K.; Kuznetsov, A.G.; Zheleznyakov, B.N.

    1981-01-01

    According to theoretical principles of general engineering technology the engineering experience of construction-mounting works at the NPP with channel uranium-graphite reactors is systematized. Main parameters and structural features of the 1000 MW channel uranium-graphite reactors are considered. The succession of mounting operations, premounting equipment and pipelines preparation and mounting works technique are described. The most efficient methods of fitting, welding and machining of reactor elements are recommended. Main problems of technical control service are discussed. A typical netted diagram of main equipment of channel uranium-graphite reactors mounting is given

  15. Synthesis of soluble graphite and graphene.

    Science.gov (United States)

    Kelly, K F; Billups, W E

    2013-01-15

    Because of graphene's anticipated applications in electronics and its thermal, mechanical, and optical properties, many scientists and engineers are interested in this material. Graphene is an isolated layer of the π-stacked hexagonal allotrope of carbon known as graphite. The interlayer cohesive energy of graphite, or exfoliation energy, that results from van der Waals attractions over the interlayer spacing distance of 3.34 Å (61 meV/C atom) is many times weaker than the intralayer covalent bonding. Since graphene itself does not occur naturally, scientists and engineers are still learning how to isolate and manipulate individual layers of graphene. Some researchers have relied on the physical separation of the sheets, a process that can sometimes be as simple as peeling of sheets from crystalline graphite using Scotch tape. Other researchers have taken an ensemble approach, where they exploit the chemical conversion of graphite to the individual layers. The typical intermediary state is graphite oxide, which is often produced using strong oxidants under acidic conditions. Structurally, researchers hypothesize that acidic functional groups functionalize the oxidized material at the edges and a network of epoxy groups cover the sp(2)-bonded carbon network. The exfoliated material formed under these conditions can be used to form dispersions that are usually unstable. However, more importantly, irreversible defects form in the basal plane during oxidation and remain even after reduction of graphite oxide back to graphene-like material. As part of our interest in the dissolution of carbon nanomaterials, we have explored the derivatization of graphite following the same procedures that preserve the sp(2) bonding and the associated unique physical and electronic properties in the chemical processing of single-walled carbon nanotubes. In this Account, we describe efficient routes to exfoliate graphite either into graphitic nanoparticles or into graphene without

  16. Adsorption of lead over graphite oxide.

    Science.gov (United States)

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M; Oki, Aderemi

    2014-01-24

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water. Published by Elsevier B.V.

  17. Interface structure between tetraglyme and graphite

    Science.gov (United States)

    Minato, Taketoshi; Araki, Yuki; Umeda, Kenichi; Yamanaka, Toshiro; Okazaki, Ken-ichi; Onishi, Hiroshi; Abe, Takeshi; Ogumi, Zempachi

    2017-09-01

    Clarification of the details of the interface structure between liquids and solids is crucial for understanding the fundamental processes of physical functions. Herein, we investigate the structure of the interface between tetraglyme and graphite and propose a model for the interface structure based on the observation of frequency-modulation atomic force microscopy in liquids. The ordering and distorted adsorption of tetraglyme on graphite were observed. It is found that tetraglyme stably adsorbs on graphite. Density functional theory calculations supported the adsorption structure. In the liquid phase, there is a layered structure of the molecular distribution with an average distance of 0.60 nm between layers.

  18. Status of Chronic Oxidation Studies of Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Contescu, Cristian I. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mee, Robert W. [Univ. of Tennessee, Knoxville, TN (United States)

    2016-05-01

    Graphite will undergo extremely slow, but continuous oxidation by traces of moisture that will be present, albeit at very low levels, in the helium coolant of HTGR. This chronic oxidation may cause degradation of mechanical strength and thermal properties of graphite components if a porous oxidation layer penetrates deep enough in the bulk of graphite components during the lifetime of the reactor. The current research on graphite chronic oxidation is motivated by the acute need to understand the behavior of each graphite grade during prolonged exposure to high temperature chemical attack by moisture. The goal is to provide the elements needed to develop predictive models for long-time oxidation behavior of graphite components in the cooling helium of HTGR. The tasks derived from this goal are: (1) Oxidation rate measurements in order to determine and validate a comprehensive kinetic model suitable for prediction of intrinsic oxidation rates as a function of temperature and oxidant gas composition; (2) Characterization of effective diffusivity of water vapor in the graphite pore system in order to account for the in-pore transport of moisture; and (3) Development and validation of a predictive model for the penetration depth of the oxidized layer, in order to assess the risk of oxidation caused damage of particular graphite grades after prolonged exposure to the environment of helium coolant in HTGR. The most important and most time consuming of these tasks is the measurement of oxidation rates in accelerated oxidation tests (but still under kinetic control) and the development of a reliable kinetic model. This report summarizes the status of chronic oxidation studies on graphite, and then focuses on model development activities, progress of kinetic measurements, validation of results, and improvement of the kinetic models. Analysis of current and past results obtained with three grades of showed that the classical Langmuir-Hinshelwood model cannot reproduce all

  19. Superhydrophilic graphite surfaces and water-dispersible graphite colloids by electrochemical exfoliation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli, 320 Taiwan (China); Chen, Shih-Ming; Lai, Wei-Hao [Materials and Chemical Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu, 31040 Taiwan (China); Sheng, Yu-Jane [Department of Chemical Engineering, National Taiwan University, Taipei, 106 Taiwan (China); Tsao, Heng-Kwong [Department of Chemical and Materials Engineering, Department of Physics, National Central University, Jhongli, 320 Taiwan (China)

    2013-08-14

    Superhydrophilic graphite surfaces and water-dispersible graphite colloids are obtained by electrochemical exfoliation with hydrophobic graphite electrodes. Such counterintuitive characteristics are caused by partial oxidation and investigated by examining both graphite electrodes and exfoliated particles after electrolysis. The extent of surface oxidation can be explored through contact angle measurement, scanning electron microscope, electrical sheet resistance, x-ray photoelectron spectroscopy, zeta-potential analyzer, thermogravimetric analysis, UV-visible, and Raman spectroscopy. The degree of wettability of the graphite anode can be altered by the electrolytic current and time. The water contact angle declines generally with increasing the electrolytic current or time. After a sufficient time, the graphite anode becomes superhydrophilic and its hydrophobicity can be recovered by peeling with adhesive tape. This consequence reveals that the anodic graphite is oxidized by oxygen bubbles but the oxidation just occurs at the outer layers of the graphite sheet. Moreover, the characteristics of oxidation revealed by UV peak shift, peak ratio between D and G bands, and negative zeta-potential indicate the presence of graphite oxide on the outer shell of the exfoliated colloids. However, thermogravimetric analysis for the extent of decomposition of oxygen functional groups verifies that the amount of oxygen groups is significantly less than that of graphite oxide prepared via Hummer method. The structure of this partially oxidized graphite may consist of a graphite core covered with an oxidized shell. The properties of the exfoliated colloids are also influenced by pH of the electrolytic solution. As pH is increased, the extent of oxidation descends and the thickness of oxidized shell decreases. Those results reveal that the degree of oxidation of exfoliated nanoparticles can be manipulated simply by controlling pH.

  20. Performance of AC/graphite capacitors at high weight ratios of AC/graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki [Advanced Research Center, Department of Applied Chemistry, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan)

    2008-03-01

    The effect of negative to positive electrode materials' weight ratio on the electrochemical performance of both activated carbon (AC)/AC and AC/graphite capacitors has been investigated, especially in the terms of capacity and cycle-ability. The limited capacity charge mode has been proposed to improve the cycle performance of AC/graphite capacitors at high weight ratios of AC/graphite. (author)

  1. Emission from Crystals Irradiated with a Beam of Runaway Electrons

    Science.gov (United States)

    Buranchenko, A. G.; Tarasenko, V. F.; Beloplotov, D. V.; Baksht, E. Kh.

    2018-01-01

    An investigation of the spectral and amplitude-temporal characteristics of emission from different crystals, promising in terms of their application as detectors of runaway electrons, is performed. This emission is excited by subnanosecond electron beams generated in a gas diode. It is found out that at the electron energies of tens-hundreds of kiloelectronvolts, the main contribution into the emission from CsI, ZnS, type IIa artificial and natural diamonds, sapphire, CaF2, ZrO2, Ga2O3, CaCO3, CdS, and ZnSe crystals comes from the cathodoluminescence; the radiation pulse duration depends on the crystal used and sufficiently exceeds the Cherenkov radiation pulse duration. It is demonstrated that the latter radiation exhibits low intensity and can be detected in the short-wave region of the spectrum in the cases where a monochromator and a high-sensitivity photomultiplier tube (PMT) are used.

  2. Management of radioactive waste in nuclear power: handling of irradiated graphite from water-cooled graphite reactors

    International Nuclear Information System (INIS)

    Anfimov, S.S.

    2001-01-01

    In this paper an radioactive waste processing of graphite from graphite moderated nuclear reactors at its decommissioning is discussed. Methods of processing of irradiated graphite are presented. It can be concluded that advanced methods for graphite radioactive waste handling are available nowadays. Implementation of these methods will allow to enhance environmental safety of nuclear power that will benefit its progress in the future

  3. A Graphite Isotope Ratio Method: A Primer on Estimating Plutonium Production in Graphite Moderated Reactors

    International Nuclear Information System (INIS)

    Gesh, Christopher J.

    2004-01-01

    The Graphite Isotope Ratio Method (GIRM) is a technique used to estimate the total plutonium production in a graphite-moderated reactor. The cumulative plutonium production in that reactor can be accurately determined by measuring neutron irradiation induced isotopic ratio changes in certain impurity elements within the graphite moderator. The method does not require detailed knowledge of a reactor's operating history, although that knowledge can decrease the uncertainty of the production estimate. The basic premise of the Graphite Isotope Ratio Method is that the fluence in non-fuel core components is directly related to the cumulative plutonium production in the nuclear fuel

  4. Synthesis of graphene nanoplatelets from peroxosulfate graphite intercalation compounds

    OpenAIRE

    MELEZHYK A.V.; TKACHEV A.G.

    2014-01-01

    Ultrasonic exfoliation of expanded graphite compound obtained by cold expansion of graphite intercalated with peroxodisulfuric acid was shown to allow the creation of graphene nanoplatelets with thickness of about 5-10 nm. The resulting graphene material contained surface oxide groups. The expanded graphite intercalation compound was exfoliated by ultrasound much easier than thermally expanded graphite. A mechanism for the cleavage of graphite to graphene nanoplatelets is proposed. It include...

  5. Graphite reactor physics; Physique des piles a graphite

    Energy Technology Data Exchange (ETDEWEB)

    Bacher, P; Cogne, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Noc, B [Electricite de France (EDF), 75 - Paris (France)

    1964-07-01

    The study of graphite-natural uranium power reactor physics, undertaken ten years ago when the Marcoule piles were built, has continued to keep in step with the development of this type of pile. From 1960 onwards the critical facility Marius has been available for a systematic study of the properties of lattices as a function of their pitch, of fuel geometry and of the diameter of cooling channels. This study has covered a very wide field: lattice pitch varying from 19 to 38 cm. uranium rods and tubes of cross-sections from 6 to 35 cm{sup 2}, channels with diameters between 70 and 140 mm. The lattice calculation methods could thus be checked and where necessary adapted. The running of the Marcoule piles and the experiments carried out on them during the last few years have supplied valuable information on the overall evolution of the neutronic properties of the fuel as a function of irradiation. More detailed experiments have also been performed in Marius with plutonium-containing fuels (irradiated or synthetic fuels), and will be undertaken at the beginning of 1965 at high temperature in the critical facility Cesar, which is just being completed at Cadarache. Spent fuel analyses complement these results and help in their interpretation. The thermalization and spectra theories developed in France can thus be verified over the whole valid temperature range. The efficiency of control rods as a function of their dimensions, the materials of which they are made and the lattices surrounding them has been measured in Marius, and the results compared with calculation on the one hand and with the measurements carried out in EDF 1 on the other. Studies on the control proper of graphite piles were concerned essentially with the risks of spatial instability and the means of detecting and controlling them, and with flux distortions caused by the control rods. (authors) [French] Entreprise il y a dix ans a l'occasion de la construction des piles de Marcoule, l'etude de la

  6. Seismic research on graphite reactor core

    International Nuclear Information System (INIS)

    Lai Shigang; Sun Libin; Zhang Zhengming

    2013-01-01

    Background: Reactors with graphite core structure include production reactor, water-cooled graphite reactor, gas-cooled reactor, high-temperature gas-cooled reactor and so on. Multi-body graphite core structure has nonlinear response under seismic excitation, which is different from the response of general civil structure, metal connection structure or bolted structure. Purpose: In order to provide references for the designing and construction of HTR-PM. This paper reviews the history of reactor seismic research evaluation from certain countries, and summarizes the research methods and research results. Methods: By comparing the methods adopted in different gas-cooled reactor cores, inspiration for our own HTR seismic research was achieved. Results and Conclusions: In this paper, the research ideas of graphite core seismic during the process of designing, constructing and operating HTR-10 are expounded. Also the project progress of HTR-PM and the research on side reflection with the theory of similarity is introduced. (authors)

  7. Review: BNL Tokamak graphite blanket design concepts

    International Nuclear Information System (INIS)

    Fillo, J.A.; Powell, J.R.

    1976-01-01

    The BNL minimum activity graphite blanket designs are reviewed, and three are discussed in the context of an experimental power reactor (EPR) and commercial power reactor. Basically, the three designs employ a 30 cm or thicker graphite screen. Bremsstrahlung energy is deposited on the graphite surface and re-radiated away as thermal radiation. Fast neutrons are slowed down in the graphite, depositing most of their energy, which is then radiated to a secondary blanket with coolant tubes, as in types A and B, or removed by intermittent direct gas cooling (type C). In types A and B, radiation damage to the coolant tubes in the secondary blanket is reduced by one or two orders of magnitude, while in type C, the blanket is only cooled when the reactor is shut down, so that coolant cannot quench the plasma. (Auth.)

  8. Immobilization of Rocky Flats Graphite Fines Residue

    International Nuclear Information System (INIS)

    Rudisill, T.S.

    1999-01-01

    The development of the immobilization process for graphite fines has proceeded through a series of experimental programs. The experimental procedures and results from each series of experiments are discussed in this report

  9. Optical motion control of maglev graphite.

    Science.gov (United States)

    Kobayashi, Masayuki; Abe, Jiro

    2012-12-26

    Graphite has been known as a typical diamagnetic material and can be levitated in the strong magnetic field. Here we show that the magnetically levitating pyrolytic graphite can be moved in the arbitrary place by simple photoirradiation. It is notable that the optical motion control system described in this paper requires only NdFeB permanent magnets and light source. The optical movement is driven by photothermally induced changes in the magnetic susceptibility of the graphite. Moreover, we demonstrate that light energy can be converted into rotational kinetic energy by means of the photothermal property. We find that the levitating graphite disk rotates at over 200 rpm under the sunlight, making it possible to develop a new class of light energy conversion system.

  10. Study on graphite samples for nuclear usage

    International Nuclear Information System (INIS)

    Suarez, J.C.M.; Silva Roseira, M. da

    1994-01-01

    Available as short communication only. The graphite, due to its properties (mechanical strength, thermal conductivity, high-temperature stability, machinability etc.) have many industrial applications, and consequently, an important strategic value. In the nuclear area, it has been used as moderator and reflector of neutrons in the fission process of uranium. The graphite can be produced from many types of carbonaceous materials by a variety of process dominated by the manufactures. This is the reason why there are in the world market a lot of graphite types with different physical and mechanical properties. The present investigation studies some physical characteristics of the graphite samples destined to use in a nuclear reactor. (author). 8 refs, 1 fig, 1 tab

  11. Collective modes in superconducting rhombohedral graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kauppila, Ville [O.V. Lounasmaa Laboratory, Aalto University (Finland); Hyart, Timo; Heikkilae, Tero [University of Jyvaeskylae (Finland)

    2015-07-01

    Recently it was realized that coupling particles with a Dirac dispersion (such as electrons in graphene) can lead to a topologically protected state with flat band dispersion. Such a state could support superconductivity with unusually high critical temperatures. Perhaps the most promising way to realize such coupling in real materials is in the surface of rhombohedrally stacked graphite. We consider collective excitations (i.e. the Higgs modes) in surface superconducting rhombohedral graphite. We find two amplitude and two phase modes corresponding to the two surfaces of the graphite where the superconductivity lives. We calculate the dispersion of these modes. We also derive the Ginzburg-Landau theory for this material. We show that in superconducting rhombohedral graphite, the collective modes, unlike in conventional BCS superconductors, give a large contribution to thermodynamic properties of the material.

  12. Large Scale Reduction of Graphite Oxide

    Data.gov (United States)

    National Aeronautics and Space Administration — This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction...

  13. Analysis of picosecond pulsed laser melted graphite

    International Nuclear Information System (INIS)

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M.S.; Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.

    1986-01-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm -1 and the disorder-induced mode at 1360 cm -1 , the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nonosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence

  14. Vapour pressure of caesium over nuclear graphite

    International Nuclear Information System (INIS)

    Faircloth, R.L.; Pummery, F.C.W.

    1976-01-01

    The vapour pressure of caesium over a fine-grained isotropic moulded gilsocarbon nuclear graphite intended for use in the manufacture of fuel tubes for the high temperature reactor has been determined as a function of temperature and concentration by means of the Knudsen effusion technique. The concentration range 0 to 10 μg caesium/g graphite was investigated and it was concluded that a Langmuir adsorption situation exists under these conditions. (author)

  15. Elastic properties of graphite and interstitial defects

    International Nuclear Information System (INIS)

    Ayasse, J.-B.

    1977-01-01

    The graphite elastic constants C 33 and C 44 , reflecting the interaction of the graphitic planes, were experimentally measured as a function of irradiation and temperature. A model of non-central strength atomic interaction was established to explain the experimental results obtained. This model is valid at zero temperature. The temperature dependence of the elastic properties was analyzed. The influence of the elastic property variations on the specific heat of the lattice at very low temperature was investigated [fr

  16. Energy evaluations, graphite corrosion in Bugey I

    International Nuclear Information System (INIS)

    Brisbois, J.; Fiche, C.

    1967-01-01

    Bugey I presents a problem of radiolytic corrosion of the graphite by the CO 2 under pressure at high temperature. This report aims to evaluate the energy transferred to the gas by a Bugey I core cell, in normal operating conditions. The water, the carbon oxides and the hydrogen formed quantities are deduced as the consumed graphite and methane. Experimental studies are realized in parallel to validate the presented results. (A.L.B.)

  17. High temperature tests for graphite materials

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This study was performed within the framework of the EURISOL for facilities SPIRAL-II (GANIL, France) and SPES (LNL, Italy), and aims to investigate the anticipated strength properties of fine-grained graphite at elevated temperatures. It appears that the major parameters that affect to the lifetime of a graphite target of this IP are the temperature and heating time. High temperature tests were conducted to simulate the heating under the influence of a beam of heavy particles by passing thro...

  18. Pulsed Laser Deposition of Tungsten Thin Films on Graphite

    International Nuclear Information System (INIS)

    Kassem, W.; Tabbal, M.; Roumie, M.

    2011-01-01

    Thin coatings of Tungsten were deposited on substrates fabricated by pre-depositing graphite thin layers on Si(100) wafers. We ablate pure W target using a 20 ns KrF excimer laser (248 nm) in an Ar ambient. The effect of background gas pressure, substrate temperature, and laser fluence, on the properties of the deposited W layers is studied using several techniques including X-Ray Diffraction, Atomic Force Microscopy, surface profilometry, and Rutherford Back-Scattering spectrometry. Our results indicate that the deposited layers consist of the well-crystallized body-centered-cubic α-W phase with bulk-like properties, particularly for films deposited at a substrate temperature of 450 0 C, laser fluence greater than 400mJ, and pressure of about 10mTorr. (author)

  19. Graphite Composite Panel Polishing Fixture

    Science.gov (United States)

    Hagopian, John; Strojny, Carl; Budinoff, Jason

    2011-01-01

    The use of high-strength, lightweight composites for the fixture is the novel feature of this innovation. The main advantage is the light weight and high stiffness-to-mass ratio relative to aluminum. Meter-class optics require support during the grinding/polishing process with large tools. The use of aluminum as a polishing fixture is standard, with pitch providing a compliant layer to allow support without deformation. Unfortunately, with meter-scale optics, a meter-scale fixture weighs over 120 lb (.55 kg) and may distort the optics being fabricated by loading the mirror and/or tool used in fabrication. The use of composite structures that are lightweight yet stiff allows standard techniques to be used while providing for a decrease in fixture weight by almost 70 percent. Mounts classically used to support large mirrors during fabrication are especially heavy and difficult to handle. The mount must be especially stiff to avoid deformation during the optical fabrication process, where a very large and heavy lap often can distort the mount and optic being fabricated. If the optic is placed on top of the lapping tool, the weight of the optic and the fixture can distort the lap. Fixtures to support the mirror during fabrication are often very large plates of aluminum, often 2 in. (.5 cm) or more in thickness and weight upwards of 150 lb (68 kg). With the addition of a backing material such as pitch and the mirror itself, the assembly can often weigh over 250 lb (.113 kg) for a meter-class optic. This innovation is the use of a lightweight graphite panel with an aluminum honeycomb core for use as the polishing fixture. These materials have been used in the aerospace industry as structural members due to their light weight and high stiffness. The grinding polishing fixture consists of the graphite composite panel, fittings, and fixtures to allow interface to the polishing machine, and introduction of pitch buttons to support the optic under fabrication. In its

  20. Structure and functionality of bromine doped graphite.

    Science.gov (United States)

    Hamdan, Rashid; Kemper, A F; Cao, Chao; Cheng, H P

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br2). However, with increased compression (decreased layer-layer separation) Br2 molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.

  1. Interface of the transport systems research vehicle monochrome display system to the digital autonomous terminal access communication data bus

    Science.gov (United States)

    Easley, W. C.; Tanguy, J. S.

    1986-01-01

    An upgrade of the transport systems research vehicle (TSRV) experimental flight system retained the original monochrome display system. The original host computer was replaced with a Norden 11/70, a new digital autonomous terminal access communication (DATAC) data bus was installed for data transfer between display system and host, while a new data interface method was required. The new display data interface uses four split phase bipolar (SPBP) serial busses. The DATAC bus uses a shared interface ram (SIR) for intermediate storage of its data transfer. A display interface unit (DIU) was designed and configured to read from and write to the SIR to properly convert the data from parallel to SPBP serial and vice versa. It is found that separation of data for use by each SPBP bus and synchronization of data tranfer throughout the entire experimental flight system are major problems which require solution in DIU design. The techniques used to accomplish these new data interface requirements are described.

  2. Sintered tantalum carbide coatings on graphite substrates: Highly reliable protective coatings for bulk and epitaxial growth

    International Nuclear Information System (INIS)

    Nakamura, Daisuke; Suzumura, Akitoshi; Shigetoh, Keisuke

    2015-01-01

    Highly reliable low-cost protective coatings have been sought after for use in crucibles and susceptors for bulk and epitaxial film growth processes involving wide bandgap materials. Here, we propose a production technique for ultra-thick (50–200 μmt) tantalum carbide (TaC) protective coatings on graphite substrates, which consists of TaC slurry application and subsequent sintering processes, i.e., a wet ceramic process. Structural analysis of the sintered TaC layers indicated that they have a dense granular structure containing coarse grain with sizes of 10–50 μm. Furthermore, no cracks or pinholes penetrated through the layers, i.e., the TaC layers are highly reliable protective coatings. The analysis also indicated that no plastic deformation occurred during the production process, and the non-textured crystalline orientation of the TaC layers is the origin of their high reliability and durability. The TaC-coated graphite crucibles were tested in an aluminum nitride (AlN) sublimation growth process, which involves extremely corrosive conditions, and demonstrated their practical reliability and durability in the AlN growth process as a TaC-coated graphite. The application of the TaC-coated graphite materials to crucibles and susceptors for use in bulk AlN single crystal growth, bulk silicon carbide (SiC) single crystal growth, chemical vapor deposition of epitaxial SiC films, and metal-organic vapor phase epitaxy of group-III nitrides will lead to further improvements in crystal quality and reduced processing costs

  3. Sintered tantalum carbide coatings on graphite substrates: Highly reliable protective coatings for bulk and epitaxial growth

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Daisuke; Suzumura, Akitoshi; Shigetoh, Keisuke [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan)

    2015-02-23

    Highly reliable low-cost protective coatings have been sought after for use in crucibles and susceptors for bulk and epitaxial film growth processes involving wide bandgap materials. Here, we propose a production technique for ultra-thick (50–200 μmt) tantalum carbide (TaC) protective coatings on graphite substrates, which consists of TaC slurry application and subsequent sintering processes, i.e., a wet ceramic process. Structural analysis of the sintered TaC layers indicated that they have a dense granular structure containing coarse grain with sizes of 10–50 μm. Furthermore, no cracks or pinholes penetrated through the layers, i.e., the TaC layers are highly reliable protective coatings. The analysis also indicated that no plastic deformation occurred during the production process, and the non-textured crystalline orientation of the TaC layers is the origin of their high reliability and durability. The TaC-coated graphite crucibles were tested in an aluminum nitride (AlN) sublimation growth process, which involves extremely corrosive conditions, and demonstrated their practical reliability and durability in the AlN growth process as a TaC-coated graphite. The application of the TaC-coated graphite materials to crucibles and susceptors for use in bulk AlN single crystal growth, bulk silicon carbide (SiC) single crystal growth, chemical vapor deposition of epitaxial SiC films, and metal-organic vapor phase epitaxy of group-III nitrides will lead to further improvements in crystal quality and reduced processing costs.

  4. Production of nuclear graphite in France; Production de graphite nucleaire en France

    Energy Technology Data Exchange (ETDEWEB)

    Legendre, P; Mondet, L [Societe Pechiney, 74 - Chedde (France); Arragon, Ph; Cornuault, P; Gueron, J; Hering, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    The graphite intended for the construction of the reactors is obtained by the usual process: confection of a cake from coke of oil and tar, cooked (in a electric oven) then the product of cook is graphitized, also by electric heating. The use of the air transportation and the control of conditions cooking and graphitization have permitted to increase the nuclear graphite production as well as to better control their physical and mechanical properties and to reduce to the minimum the unwanted stains. (M.B.) [French] Le graphite destine a la construction des reacteurs est obtenu par le procede usuel: confection d'une pate a partir de coke de petrole et de brai, cuisson de cette pate (au four electrique) puis graphitation du produit cuit, egalement par chauffage electrique. L'usage du transport pneumatique et le controle des conditions cuisson et de graphitation ont permit d'augmenter la production de graphite nucleaire ainsi que de mieux controler ses proprietes physiques et mecaniques et de reduire au minimum les souillures accidentelles. (M.B.)

  5. Temperature distribution in graphite during annealing in air cooled reactors

    International Nuclear Information System (INIS)

    Oliveira Avila, C.R. de.

    1989-01-01

    A model for the evaluation temperature distributions in graphite during annealing operation in graphite. Moderated an-cooled reactors, is presented. One single channel and one dimension for air and graphite were considered. A numerical method based on finite control volumes was used for partioning the mathematical equations. The problem solution involves the use of unsteady equations of mass, momentum and energy conservation for air, and energy conservation for graphite. The source term was considered as stored energy release during annealing for describing energy conservation in the graphite. The coupling of energy conservation equations in air and graphite is performed by the heat transfer term betwen air and graphite. The results agree with experimental data. A sensitivity analysis shown that the termal conductivity of graphite and the maximum inlet channel temperature have great effect on the maximum temperature reached in graphite during the annealing. (author)

  6. Graphite matrix materials for nuclear waste isolation

    International Nuclear Information System (INIS)

    Morgan, W.C.

    1981-06-01

    At low temperatures, graphites are chemically inert to all but the strongest oxidizing agents. The raw materials from which artificial graphites are produced are plentiful and inexpensive. Morover, the physical properties of artificial graphites can be varied over a very wide range by the choice of raw materials and manufacturing processes. Manufacturing processes are reviewed herein, with primary emphasis on those processes which might be used to produce a graphite matrix for the waste forms. The approach, recommended herein, involves the low-temperature compaction of a finely ground powder produced from graphitized petroleum coke. The resultant compacts should have fairly good strength, low permeability to both liquids and gases, and anisotropic physical properties. In particular, the anisotropy of the thermal expansion coefficients and the thermal conductivity should be advantageous for this application. With two possible exceptions, the graphite matrix appears to be superior to the metal alloy matrices which have been recommended in prior studies. The two possible exceptions are the requirements on strength and permeability; both requirements will be strongly influenced by the containment design, including the choice of materials and the waste form, of the multibarrier package. Various methods for increasing the strength, and for decreasing the permeability of the matrix, are reviewed and discussed in the sections in Incorporation of Other Materials and Elimination of Porosity. However, it would be premature to recommend a particular process until the overall multi-barrier design is better defined. It is recommended that increased emphasis be placed on further development of the low-temperature compacted graphite matrix concept

  7. Method of producing exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z.

    2010-11-02

    The present invention provides a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm. The method comprises (a) dispersing particles of graphite, graphite oxide, or a non-graphite laminar compound in a liquid medium containing therein a surfactant or dispersing agent to obtain a stable suspension or slurry; and (b) exposing the suspension or slurry to ultrasonic waves at an energy level for a sufficient length of time to produce separated nano-scaled platelets. The nano-scaled platelets are candidate reinforcement fillers for polymer nanocomposites. Nano-scaled graphene platelets are much lower-cost alternatives to carbon nano-tubes or carbon nano-fibers.

  8. EEL Calculations and Measurements of Graphite and Graphitic-CNx Core-Losses

    International Nuclear Information System (INIS)

    Seepujak, A; Bangert, U; Harvey, A J; Blank, V D; Kulnitskiy, B A; Batov, D V

    2006-01-01

    Core EEL spectra of MWCNTs (multi-wall carbon nanotubes) grown in a nitrogen atmosphere were acquired utilising a dedicated STEM equipped with a Gatan Enfina system. Splitting of the carbon K-edge π* resonance into two peaks provided evidence of two nondegenerate carbon bonding states. In order to confirm the presence of a CN x bonding state, a full-potential linearised augmented plane-wave method was utilised to simulate core EEL spectra of graphite and graphitic-CN x compounds. The simulations confirmed splitting of the carbon K-edge π* resonance in graphitic-CN x materials, with the pristine graphite π* resonance remaining unsplit. The simulations also confirmed the increasing degree of amorphicity with higher concentrations (25%) of substitutional nitrogen in graphite

  9. Removal of 14C from Irradiated Graphite for Graphite Recycle and Waste Volume Reduction

    International Nuclear Information System (INIS)

    Dunzik-Gougar, Mary Lou; Windes, Will; Marsden, Barry

    2014-01-01

    The aim of the research presented here was to identify the chemical form of 14 C in irradiated graphite. A greater understanding of the chemical form of this longest-lived isotope in irradiated graphite will inform not only management of legacy waste, but also development of next generation gas-cooled reactors. Approximately 250,000 metric tons of irradiated graphite waste exists worldwide, with the largest single quantity originating in the Magnox and AGR reactors of UK. The waste quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation I gas-cooled, graphite moderated reactors. Of greatest concern for long-term disposal of irradiated graphite is carbon-14 14 C, with a half-life of 5730 years.

  10. Effect of Graphite Doped TiO_2 Nanoparticles on Smoke Degradation

    International Nuclear Information System (INIS)

    Roshasnorlyza Hazan; Mohamad Shahrizal Md Zain; Natrah Syafiqah Rosli

    2016-01-01

    Secondhand smoke affects in the same way as regular smoker. The best solution is to purify the air efficiently and effectively. In this study, we were successfully doped TiO_2 nanoparticle with graphite to accelerate the degradation of cigarette smoke. The graphite doped and undoped TiO_2 nanoparticles were prepared from synthetic rutile using alkaline fusion method and their photo catalytic activity were investigated under visible light irradiation. The photo catalytic activity of the TiO_2 nanoparticles was analyzed in terms of their particle size analysis, crystallization and optical band gap. TiO_2 nanoparticle act as photo catalyzer by utilization of light energy to excite electron-hole pairs in smoke degradation processes. With the aided from graphite in TiO_2 nanoparticles, the smoke degradation was accelerate up to 44.4 %. In this case, graphite helps to reduce optical band gap of TiO_2 nanoparticle, thus increasing excitation of electron from valence band to conduction band. (author)

  11. Mechanochemical formation of heterogeneous diamond structures during rapid uniaxial compression in graphite

    Science.gov (United States)

    Kroonblawd, Matthew P.; Goldman, Nir

    2018-05-01

    We predict mechanochemical formation of heterogeneous diamond structures from rapid uniaxial compression in graphite using quantum molecular dynamics simulations. Ensembles of simulations reveal the formation of different diamondlike products starting from thermal graphite crystal configurations. We identify distinct classes of final products with characteristic probabilities of formation, stress states, and electrical properties and show through simulations of rapid quenching that these products are nominally stable and can be recovered at room temperature and pressure. Some of the diamond products exhibit significant disorder and partial closure of the energy gap between the highest-occupied and lowest-unoccupied molecular orbitals (i.e., the HOMO-LUMO gap). Seeding atomic vacancies in graphite significantly biases toward forming products with small HOMO-LUMO gap. We show that a strong correlation between the HOMO-LUMO gap and disorder in tetrahedral bonding configurations informs which kinds of structural defects are associated with gap closure. The rapid diffusionless transformation of graphite is found to lock vacancy defects into the final diamond structure, resulting in configurations that prevent s p3 bonding and lead to localized HOMO and LUMO states with a small gap.

  12. Gas transport in graphitic materials

    International Nuclear Information System (INIS)

    Hoinkis, E.

    1995-02-01

    The characterization of the gas transport properties of porous solids is of interest in several fields of science and technology. Many catalysts, adsorbents, soils, graphites and carbons are porous. The gas transport through most porous solids can be well described by the dusty gas model invented by Evans, Watson and Mason. This model includes all modes of gas tranport under steady-state conditions, which are Knudsen diffusion, combined Knudsen/continuum diffusion and continuum diffusion, both for gas pairs with equal and different molecular weights. In the absence of a pressure difference gas transport in a pore system can be described by the combined Knudsen/continuum diffusion coefficient D 1 for component 1 in the pores, the Knudsen diffusion coefficient D 1K in the pores, and the continuum diffusion coefficient D 12 for a binary mixture in the pores. The resistance to stationary continuum diffusion of the pores is characterized by a geometrical factor (ε/τ) 12 = (ε/τ)D 12 , were D 12 is the continuum diffusion coefficient for a binary mixture in free space. The Wicke-Kallenbach method was often used to measure D 1 as function of pressure. D 12 and D 1K can be derived from a plot 1/D 1 νs P, and ε/τcan be calculated since D 12 is known. D 1K and the volume of dead end pores can be derived from transient measurements of the diffusional flux at low pressures. From D 1K the expression (ε/τ c ) anti l por may be calculated, which characterizes the pore system for molecular diffusion, where collisions with the pore walls are predominant. (orig.)

  13. Influence of Metal-Coated Graphite Powders on Microstructure and Properties of the Bronze-Matrix/Graphite Composites

    Science.gov (United States)

    Zhao, Jian-hua; Li, Pu; Tang, Qi; Zhang, Yan-qing; He, Jian-sheng; He, Ke

    2017-02-01

    In this study, the bronze-matrix/x-graphite (x = 0, 1, 3 and 5%) composites were fabricated by powder metallurgy route by using Cu-coated graphite, Ni-coated graphite and pure graphite, respectively. The microstructure, mechanical properties and corrosive behaviors of bronze/Cu-coated-graphite (BCG), bronze/Ni-coated-graphite (BNG) and bronze/pure-graphite (BPG) were characterized and investigated. Results show that the Cu-coated and Ni-coated graphite could definitely increase the bonding quality between the bronze matrix and graphite. In general, with the increase in graphite content in bronze-matrix/graphite composites, the friction coefficients, ultimate density and wear rates of BPG, BCG and BNG composites all went down. However, the Vickers microhardness of the BNG composite would increase as the graphite content increased, which was contrary to the BPG and BCG composites. When the graphite content was 3%, the friction coefficient of BNG composite was more stable than that of BCG and BPG composites, indicating that BNG composite had a better tribological performance than the others. Under all the values of applied loads (10, 20, 40 and 60N), the BCG and BNG composites exhibited a lower wear rate than BPG composite. What is more, the existence of nickel in graphite powders could effectively improve the corrosion resistance of the BNG composite.

  14. Slow neutron total cross-section, transmission and reflection calculation for poly- and mono-NaCl and PbF2 crystals

    Science.gov (United States)

    Mansy, Muhammad S.; Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.

    2016-10-01

    A detailed study about the calculation of total neutron cross-section, transmission and reflection from crystalline materials was performed. The developed computer code is approved to be sufficient for the required calculations, also an excellent agreement has been shown when comparing the code results with the other calculated and measured values. The optimal monochromator and filter parameters were discussed in terms of crystal orientation, mosaic spread, and thickness. Calculations show that 30 cm thick of PbF2 poly-crystal is an excellent cold neutron filter producing neutron wavelengths longer than 0.66 nm needed for the investigation of magnetic structure experiments. While mono-crystal filter PbF2 cut along its (1 1 1), having mosaic spread (η = 0.5°) and thickness 10 cm can only transmit thermal neutrons of the desired wavelengths and suppress epithermal and γ-rays forming unwanted background, when it is cooled to liquid nitrogen temperature. NaCl (2 0 0) and PbF2 (1 1 1) monochromator crystals having mosaic spread (η = 0.5°) and thickness 10 mm shows high neutron reflectivity for neutron wavelengths (λ = 0.114 nm and λ = 0.43 nm) when they used as a thermal and cold neutron monochromators respectively with very low contamination from higher order reflections.

  15. Glassy carbon coated graphite for nuclear applications

    International Nuclear Information System (INIS)

    Delpeux S; Cacciaguerra T; Duclaux L

    2005-01-01

    Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF 2 , ThF 4 , and UF 4 ) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin or polyvinyl chloride precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm 3 and closed pores with nano-metric size (∼ 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons, in good agreement with the proposed texture model for glassy carbon. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry of the graphite substrate. The deposit regions where

  16. Glassy carbon coated graphite for nuclear applications

    Energy Technology Data Exchange (ETDEWEB)

    Delpeux, S.; Cacciaguerra, T.; Duclaux, L. [Orleans Univ., CRMD, CNRS, 45 (France)

    2005-07-01

    Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF{sub 2}, ThF{sub 4}, and UF{sub 4}) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin [1,2] or polyvinyl chloride [3] precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm{sup 3} and closed pores with nano-metric size ({approx} 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons (Fig 1), in good agreement with the proposed texture model for glassy carbon (Fig 2) [4]. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry

  17. Hydrogen adsorption on and solubility in graphites

    International Nuclear Information System (INIS)

    Kanashenko, S.L.; Wampler, W.R.

    1996-01-01

    The experimental data on adsorption and solubility of hydrogen isotopes in graphite over a wide range of temperatures and pressures are reviewed. Langmuir adsorption isotherms are proposed for the hydrogen-graphite interaction. The entropy and enthalpy of adsorption are estimated, allowing for effects of relaxation of dangling sp 2 bonds. Three kinds of traps are proposed: edge carbon atoms of interstitial loops with an adsorption enthalpy relative to H 2 gas of -4.4 eV/H 2 (unrelaxed, Trap 1), edge carbon atoms at grain surfaces with an adsorption enthalpy of -2.3 eV/H 2 (relaxed, Trap 2), and basal plane adsorption sites with an enthalpy of +2.43 eV/H 2 (Trap 3). The adsorption capacity of different types of graphite depends on the concentration of traps which depends on the crystalline microstructure of the material. The number of potential sites for the 'true solubility' (Trap 3) is assumed to be about one site per carbon atom in all types of graphite, but the endothermic character of this solubility leads to a negligible H inventory compared to the concentration of hydrogen in type 1 and type 2 traps for temperatures and gas pressures used in the experiments. Irradiation with neutrons or carbon atoms increases the concentration of type 1 and type 2 traps from about 20 and 200 appm respectively for unirradiated (POCO AXF-5Q) graphite to about 1500 and 5000 appm, respectively, at damage levels above 1 dpa. (orig.)

  18. Irradiation-induced amorphization process in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Hiroaki [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    1996-04-01

    Effects of the element process of irradiation damage on irradiation-induced amorphization processes of graphite was studied. High orientation thermal decomposed graphite was cut about 100 nm width and used as samples. The irradiation experiments are carried out under the conditions of electronic energy of 100-400 KeV, ion energy of 200-600 KeV, ionic species Xe, Ar, Ne, C and He and the irradiation temperature at from room temperature to 900 K. The critical dose ({phi}a) increases exponentially with increasing irradiation temperature. The displacement threshold energy of graphite on c-axis direction was 27 eV and {phi}a{sup e} = 0.5 dpa. dpa is the average number of displacement to atom. The critical dose of ion irradiation ({phi}a{sup i}) was 0.2 dpa at room temperature, and amorphous graphite was produced by less than half of dose of electronic irradiation. Amorphization of graphite depending upon temperature is discussed. (S.Y.)

  19. X-ray optics for 50-100 keV undulator radiation using crystals and refractive lenses

    International Nuclear Information System (INIS)

    Shastri, S. D.; Mashayekhi, A.; Cremer, J. T.; Piestrup, M. A.

    2003-01-01

    Compound refractive lenses (CRLs) are effective for collimating or focusing high-energy x-ray beams (50 - 100 keV) and can be used in conjunction with crystal optics in a variety of configurations, as demonstrated at the 1-ID undulator beamline of the Advanced Photon Source. As a primary example, this article describes the quadrupling of the output flux when a collimating CRL, composed of cylindrical holes in aluminum, is inserted in between two successive monochromators -- a modest energy resolution premonochromator followed by a high-resolution monochromator. The premonochromator is a cryogenically cooled, divergence-preserving, bent double-Laue Si(111) crystal device delivering an energy width ΔE/E ∼ 10 -3 , sufficient for most experiments. The high-resolution monochromator is a four-reflection, flat Si(111) crystal system resembling two channel-cuts in a dispersive arrangement, reducing the bandwidth to ΔE/E -4 , as required for some applications. Tests with 67 keV and 81 keV photon energies show that the high-resolution monochromator, having a narrow angular acceptance of a few erad, exhibits, a four-fold throughput enhancement due to the insertion of a CRL which reduces the premonochromatized beam's vertical divergence from 29 erad to a few erad. The ability to focus high-energy x-rays with CRLs having long focal lengths (tens of meters) is also shown by creating a line focus of 70 - 90 μ m beam height in the beamline end-station with both the modest-energy-resolution and high-energy- resolution monochromatic x-rays

  20. Pyrolytic graphite as an efficient second-order neutron filter at tuned positions of boundary crossing

    International Nuclear Information System (INIS)

    Adib, M.; Abdel Kawy, A.; Habib, N.; El Mesiry, M.

    2010-01-01

    An investigation of pyrolytic graphite (PG) crystal as an efficient second order neutron filter at tuned boundary crossings has been carried out. The neutron transmission through PG crystal at these tuned crossing points as a function of first- and second-order wavelengths were calculated in terms of PG mosaic spread and thickness. The filtering features of PG crystals at these tuned boundary crossings were deduced. It was shown that, there are a large number of tuned positions at double and triple boundary crossings of the curves (hkl) are very promising as tuned filter positions. However, only fourteen of them are found to be most promising ones. These tuned positions are found to be within the neutron wavelengths from 0.133 up to 0.4050 nm. A computer package GRAPHITE has been used in order to provide the required calculations in the whole neutron wavelength range in terms of PG mosaic spread and its orientation with respect to incident neutron beam direction. It was shown that 0.5 cm thick PG crystal with angular mosaic spread of 2 0 is sufficient to remove 2nd-order neutrons at the wavelengths corresponding to the positions of the intersection boundaries curves (hkl).

  1. Nuclear quadrupole interaction measurements of 19F* and 22Na* on Graphite

    International Nuclear Information System (INIS)

    Djoko-Surono, Th; Martin, Peter W

    1996-01-01

    Time differential perturbed angular distribution (TDPAD) technique has been used to investigate nuclear quadrupole interactions of 19 F * and 22 Na * in graphite. We concentrated the measurements on pseudo single crystal graphite called Highly Oriented Pyrolytic Graphite for it has an ordered structure in which the c-axes of the microcrystals aligned in a certain direction with the mosaic spread less than 1 o , while the a- and b-axes randomly oriented on a plane perpendicular to the c-axes. Interactions between quadrupole moment of 19 F * and 22 Na * with its surroundings electric field gradient were studied by detecting the γ-rays distribution, W(Θ,t). For 1 9F * we found one static interaction. The corresponding electric field gradient was V zz =3.24(19)x10 22 V/m 2 . In the case of 22 Na * we found no evidence of nuclear quadrupole interaction, however, we were able to conclude that |QV 22 | 19 bV/m 2 . Using theoretical calculation Q=0.06 barn, we find that |V zz | 20 V/m 2 . These results indicate that the value efg depend on two factors, the host crystal and the core electrons. The core electrons contribution to the total efg is considerably large

  2. Variable-metric diffraction crystals for x-ray optics

    International Nuclear Information System (INIS)

    Smither, R.K.; Fernandez, P.B.

    1992-01-01

    A variable-metric (VM) crystal is one in which the spacing between the crystalline planes changes with position in the crystal. This variation can be either parallel to the crystalline planes or perpendicular to the crystalline planes of interest and can be produced by either introducing a thermal gradient in the crystal or by growing a crystal made of two or more elements and changing the relative percentages of the two elements as the crystal is grown. A series of experiments were performed in the laboratory to demonstrate the principle of the variable-metric crystal and its potential use in synchrotron beam lines. One of the most useful applications of the VM crystal is to increase the number of photons per unit bandwidth in a diffracted beam without losing any of the overall intensity. In a normal synchrotron beam line that uses a two-crystal monochromator, the bandwidth of the diffracted photon beam is determined by the vertical opening angle of the beam which is typically 0.10--0.30 mrad or 20--60 arcsec. When the VM crystal approach is applied, the bandwidth of the beam can be made as narrow as the rocking curve of the diffracting crystal, which is typically 0.005--0.050 mrad or 1--10 arcsec. Thus a very large increase of photons per unit bandwidth (or per unit energy) can be achieved through the use of VM crystals. When the VM principle is used with bent crystals, new kinds of x-ray optical elements can be generated that can focus and defocus x-ray beams much like simple lenses where the focal length of the lens can be changed to match its application. Thus both large magnifications and large demagnifications can be achieved as well as parallel beams with narrow bandwidths

  3. Graphitic encapsulation of MgO and Fe3C nanoparticles in the reaction of iron pentacarbonyl with magnesium

    International Nuclear Information System (INIS)

    Dyjak, Sławomir; Cudziło, Stanisław; Polański, Marek; Budner, Bogusław; Bystrzycki, Jerzy

    2013-01-01

    A simple method to produce highly ordered carbon nanostructures by combustion synthesis is presented. Graphite-encapsulated magnesium oxide, iron carbide nanoparticles and carbon nanobelts were synthesized by the one-step reduction of iron pentacarbonyl with magnesium. High-resolution transmission electron microscopy analysis of the products revealed nanocrystalline MgO and Fe 3 C particles surrounded by a well-crystallized, tight graphite film. The possible formation mechanism is presented and discussed. - Highlights: • We present a simple method to produce highly ordered carbon nanostructures by combustion synthesis. • The cubic MgO particles are completely coated by tight graphitic shells. • The mechanism of formation a distant carbon film on MgO surface has been discussed. • The presented method can be applied to synthesis of other core-shell structures

  4. Spherical cauliflower-like carbon dust formed by interaction between deuterium plasma and graphite target and its internal structure

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, N. [Department of Energy Engineering and Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)], E-mail: ohno@ees.nagoya-u.ac.jp; Yoshimi, M. [Department of Energy Engineering and Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Tokitani, M. [National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292 (Japan); Takamura, S. [Department of Electronics, Aichi Institute of Technology, Yakusa-cho, Toyota 470-0392 (Japan); Tokunaga, K.; Yoshida, N. [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)

    2009-06-15

    Simulated experiments to produce carbon dust particles with cauliflower structure have been performed in a liner plasma device, NAGDIS-II by exposing high density deuterium plasma to a graphite sample (IG-430U). Formation of carbon dust depends on the surface temperature and the incident ion energy. At a surface temperature 600-700 K, a lot of isolated spherical dust particles are observed on the graphite target. The internal structure of an isolated dust particle was observed with Focused Ion Beam (FIB) system and Transmission Electron Microscope (TEM) in detail. FIB analysis clearly shows there exist honey-combed cell structure with thin carbon walls in the dust particle and the dust particle grows from the graphite surface. TEM image also shows that the dust particle is made of amorphous carbon with crystallized grains with diameters of 10-50 nm.

  5. Capacitive behavior of highly-oxidized graphite

    Science.gov (United States)

    Ciszewski, Mateusz; Mianowski, Andrzej

    2014-09-01

    Capacitive behavior of a highly-oxidized graphite is presented in this paper. The graphite oxide was synthesized using an oxidizing mixture of potassium chlorate and concentrated fuming nitric acid. As-oxidized graphite was quantitatively and qualitatively analyzed with respect to the oxygen content and the species of oxygen-containing groups. Electrochemical measurements were performed in a two-electrode symmetric cell using KOH electrolyte. It was shown that prolonged oxidation causes an increase in the oxygen content while the interlayer distance remains constant. Specific capacitance increased with oxygen content in the electrode as a result of pseudo-capacitive effects, from 0.47 to 0.54 F/g for a scan rate of 20 mV/s and 0.67 to 1.15 F/g for a scan rate of 5 mV/s. Better cyclability was observed for the electrode with a higher oxygen amount.

  6. Reactivity of lithium exposed graphite surface

    International Nuclear Information System (INIS)

    Harilal, S.S.; Allain, J.P.; Hassanein, A.; Hendricks, M.R.; Nieto-Perez, M.

    2009-01-01

    Lithium as a plasma-facing component has many attractive features in fusion devices. We investigated chemical properties of the lithiated graphite surfaces during deposition using X-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy. In this study we try to address some of the known issues during lithium deposition, viz., the chemical state of lithium on graphite substrate, oxide layer formation mechanisms, Li passivation effects over time, and chemical change during exposure of the sample to ambient air. X-ray photoelectron studies indicate changes in the chemical composition with various thickness of lithium on graphite during deposition. An oxide layer formation is noticed during lithium deposition even though all the experiments were performed in ultrahigh vacuum. The metal oxide is immediately transformed into carbonate when the deposited sample is exposed to air.

  7. Reduced graphite oxide in supercapacitor electrodes.

    Science.gov (United States)

    Lobato, Belén; Vretenár, Viliam; Kotrusz, Peter; Hulman, Martin; Centeno, Teresa A

    2015-05-15

    The current energy needs have put the focus on highly efficient energy storage systems such as supercapacitors. At present, much attention focuses on graphene-like materials as promising supercapacitor electrodes. Here we show that reduced graphite oxide offers a very interesting potential. Materials obtained by oxidation of natural graphite and subsequent sonication and reduction by hydrazine achieve specific capacitances as high as 170 F/g in H2SO4 and 84F/g in (C2H5)4NBF4/acetonitrile. Although the particle size of the raw graphite has no significant effect on the physico-chemical characteristics of the reduced materials, that exfoliated from smaller particles (materials may suffer from a drop in their specific surface area upon fabrication of electrodes with features of the existing commercial devices. This should be taken into account for a reliable interpretation of their performance in supercapacitors. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. Graphite core design in UK reactors

    International Nuclear Information System (INIS)

    Davies, M.W.

    1996-01-01

    The cores in the first power producing Magnox reactors in the UK were designed with only a limited amount of information available regarding the anisotropic dimensional change behaviour of Pile Grade graphite. As more information was gained it was necessary to make modifications to the design, some minor, some major. As the cores being built became larger, and with the switch to the Advanced Gas-cooled Reactor (AGR) with its much higher power density, additional problems had to be overcome such as increased dimensional change and radiolytic oxidation by the carbon dioxide coolant. For the AGRs a more isotropic graphite was required, with a lower initial open pore volume and higher strength. Gilsocarbon graphite was developed and was selected for all the AGRs built in the UK. Methane bearing coolants are used to limit radiolytic oxidation. (author). 5 figs

  9. Sensing capabilities of graphite based MR elastomers

    International Nuclear Information System (INIS)

    Tian, T F; Li, W H; Deng, Y M

    2011-01-01

    This paper presents both experimental and theoretical investigations of the sensing capabilities of graphite based magnetorheological elastomers (MREs). In this study, eight MRE samples with varying graphite weight fractions were fabricated and their resistance under different magnetic fields and external loadings were measured with a multi-meter. With an increment of graphite weight fraction, the resistance of MRE sample decreases steadily. Higher magnetic fields result in a resistance increase. Based on an ideal assumption of a perfect chain structure, a mathematical model was developed to investigate the relationship between the MRE resistance with external loading. In this model, the current flowing through the chain structure consists of both a tunnel current and a conductivity current, both of which depend on external loadings. The modelling parameters have been identified and reconstructed from comparison with experimental results. The comparison indicates that both experimental results and modelling predictions agree favourably well

  10. Cluster Ion Implantation in Graphite and Diamond

    DEFF Research Database (Denmark)

    Popok, Vladimir

    2014-01-01

    Cluster ion beam technique is a versatile tool which can be used for controllable formation of nanosize objects as well as modification and processing of surfaces and shallow layers on an atomic scale. The current paper present an overview and analysis of data obtained on a few sets of graphite...... and diamond samples implanted by keV-energy size-selected cobalt and argon clusters. One of the emphases is put on pinning of metal clusters on graphite with a possibility of following selective etching of graphene layers. The other topic of concern is related to the development of scaling law for cluster...... implantation. Implantation of cobalt and argon clusters into two different allotropic forms of carbon, namely, graphite and diamond is analysed and compared in order to approach universal theory of cluster stopping in matter....

  11. Graphite based Schottky diodes formed semiconducting substrates

    Science.gov (United States)

    Schumann, Todd; Tongay, Sefaattin; Hebard, Arthur

    2010-03-01

    We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs) or 4H-silicon carbide (4H-SiC). The fabrication can be as easy as allowing a dab of graphite paint to air dry on any one of the investigated semiconductors. Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky-Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.

  12. Graphite moderated reactor for thermoelectric generation

    International Nuclear Information System (INIS)

    Akazawa, Issei; Yamada, Akira; Mizogami, Yorikata

    1998-01-01

    Fuel rods filled with cladded fuel particles distributed and filled are buried each at a predetermined distance in graphite blocks situated in a reactor core. Perforation channels for helium gas as coolants are formed to the periphery thereof passing through vertically. An alkali metal thermoelectric power generation module is disposed to the upper lid of a reactor container while being supported by a securing receptacle. Helium gas in the coolant channels in the graphite blocks in the reactor core absorbs nuclear reaction heat, to be heated to a high temperature, rises upwardly by the reduction of the specific gravity, and then flows into an upper space above the laminated graphite block layer. Then the gas collides against a ceiling and turns, and flows down in a circular gap around the circumference of the alkali metal thermoelectric generation module. In this case, it transfers heat to the alkali metal thermoelectric generation module. (I.N.)

  13. Nondestructive evaluation of nuclear-grade graphite

    Science.gov (United States)

    Kunerth, D. C.; McJunkin, T. R.

    2012-05-01

    The material of choice for the core of the high-temperature gas-cooled reactors being developed by the U.S. Department of Energy's Next Generation Nuclear Plant Program is graphite. Graphite is a composite material whose properties are highly dependent on the base material and manufacturing methods. In addition to the material variations intrinsic to the manufacturing process, graphite will also undergo changes in material properties resulting from radiation damage and possible oxidation within the reactor. Idaho National Laboratory is presently evaluating the viability of conventional nondestructive evaluation techniques to characterize the material variations inherent to manufacturing and in-service degradation. Approaches of interest include x-ray radiography, eddy currents, and ultrasonics.

  14. Electrostatic Manipulation of Graphene On Graphite

    Science.gov (United States)

    Untiedt, Carlos; Rubio-Verdu, Carmen; Saenz-Arce, Giovanni; Martinez-Asencio, Jesús; Milan, David C.; Moaied, Mohamed; Palacios, Juan J.; Caturla, Maria Jose

    2015-03-01

    Here we report the use of a Scanning Tunneling Microscope (STM) under ambient and vacuum conditions to study the controlled exfoliation of the last layer of a graphite surface when an electrostatic force is applied from a STM tip. In this work we have focused on the study of two parameters: the applied voltage needed to compensate the graphite interlayer attractive force and the one needed to break atomic bonds to produce folded structures. Additionally, we have studied the influence of edge structure in the breaking geometry. Independently of the edge orientation the graphite layer is found to tear through the zig-zag direction and the lifled layer shows a zig-zag folding direction. Molecular Dinamics simulations and DFT calculations have been performed to understand our results, showing a strong correlation with the experiments. Comunidad Valenciana through Prometeo project.

  15. THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE

    Energy Technology Data Exchange (ETDEWEB)

    Bragg, R H; Crooks, D D; Fenn, Jr, R W; Hammond, M L

    1963-06-15

    Metallographic and x-ray diffraction studies were made of the effect of applied stress at high temperature on the structure of pyrolytic graphite (PG). The dominant factor was whether the PG was above or below its graphitization temperature, which, in turn, was not strongly dependent on applied stress. Below the graphitization temperature, the PG showed a high proportion of disordered layers (0.9), a fairly large mean tilt angle (20 deg ) and a small crystailite size (La --150 A). Fracture occurred at low stress and strain and the materiai exhibited a high apparent Young's modulus ( approximates 4 x 10/sup 6/ psi). Above the graphitization temperature, graphitization was considerably enhanced by strain up to about 8%. The disorder parameter was decreased from a zero strain value of 0.3 to 0.l5 with strain, the mean tilt angle was decreased to 4 deg , and a fivefold increase in crystallite size occurred. When the strainenhanced graphitization was complete, the material exhibited a low apparent modulus ( approximates 0.5 x 10/sup 6/ psi) and large plastic strains (>100%) for a constant stress ( approximates 55 ksi). Graphitization was shown to be a spontaneous process that is promoted by breaking cross-links thermally, and the process is furthered by chemical attack and plastic strain. (auth)

  16. Crystals in crystals

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.

    2005-01-01

    A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion....... As representative examples, a metal (Pt), an alloy (PtSn), and a metal carbide (beta-Mo2C) were supported on conventional and mesoporous zeolite carriers, respectively, and the degree of particle dispersion was compared by TEM imaging. On conventional zeolites, the supported material aggregated on the outer surface...

  17. Cementation of Nuclear Graphite Using Geopolymers

    International Nuclear Information System (INIS)

    Girke, N.A.; Steinmetz, H-J.; Bukaemsky, A.; Bosbach, D.; Hermann, E.; Griebel, I.

    2016-01-01

    Geopolymers are solid aluminosilicate materials usually formed by alkali hydroxide or alkali silicate activation of solid precursors such as coal fly ash, calcined clay and/or metallurgical slag. Today the primary application of geopolymer technology is in the development of alternatives to Portland-based cements. Variations in the ratio of aluminium to silicon, and alkali to silicon or addition of structure support, produce geopolymers with different physical and mechanical properties. These materials have an amorphous three-dimensional structure that gives geopolymers certain properties, such as fire and acid resistance, low leach rate, which make them an ideal substitute for ordinary Portland cement (OPC) in a wide range of applications especially in conditioning and storage of radioactive waste. Therefore investigations have been initiated on how and to which amount graphite as a hydrophobic material can be mixed with cement or concrete to form stable waste products and which concretes fulfil the necessary specifications best. As a result, geopolymers have been identified as a promising matrix for graphite containing nuclear wastes. With geopolymers, both favourable properties in the cementation process and a high long time structural stability of the products can be achieved. Investigations include: • direct mixing of graphite with geopolymers with or without sand as a mechanically stabilizing medium; • production of cement-graphite granulates as intermediate products and embedding of these granulates in geopolymer; • coating of formed graphite pieces with geopolymer.The report shows that carbon in the form of graphite can both be integrated with different grain size spectra as well as shaped in the hydraulic binder geopolymer and meets the requirements for a stable long-term immobilisation. (author)

  18. Virtual Crystallizer

    Energy Technology Data Exchange (ETDEWEB)

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  19. single crystals

    Indian Academy of Sciences (India)

    2018-05-18

    May 18, 2018 ... Abstract. 4-Nitrobenzoic acid (4-NBA) single crystals were studied for their linear and nonlinear optical ... studies on the proper growth, linear and nonlinear optical ..... between the optic axes and optic sign of the biaxial crystal.

  20. Crystal Systems.

    Science.gov (United States)

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)