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  • 1
    Electronic Resource
    Electronic Resource
    Variable-metric diffraction crystals for x-ray opticsa) (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 1755-1762 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143335
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  • 2
    Electronic Resource
    Electronic Resource
    Variable-metric diffraction crystals for x-ray optics (abstract)a) (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 941-941 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A variable-metric (V-M) 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 was 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 V-M 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 band width 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 V-M crystal approach is applied, the band width 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 V-M crystals. When the V-M 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143814
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  • 3
    Electronic Resource
    Electronic Resource
    Performance limits of direct cryogenically cooled silicon monochromators – experimental results at the APS (2000)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 7 (2000), S. 12-17 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599014478
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  • 4
    Electronic Resource
    Electronic Resource
    Parametric down conversion of X-ray photons (2000)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 7 (2000), S. 81-88 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Parametric down conversion of X-ray photons in diamond crystals was detected in two experiments, both using the phase-matching scheme first employed in the X-ray regime by Eisenberger & McCall [Phys. Rev. Lett. (1971), 26, 684–688]. The conversion events were detected by a combination of time-correlation spectroscopy and energy discrimination, using Si drift-chamber detectors. The time-correlation spectra give a direct comparison of the conversion rate over the accidental coincidence rate. Mechanisms for possible detection of false events and ways to cross check against them are discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049599015113
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  • 5
    Electronic Resource
    Electronic Resource
    Performance limits of indirectly cryogenically cooled silicon monochromators – experimental results at the APS (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 22-25 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The results of high-heat-load tests of indirectly cryogenically cooled silicon monochromators are presented. The measurements show that, provided that the total power absorbed by the crystal is less than ∼150 W, indirect cryogenically cooled silicon monochromators will perform well, with thermal-induced slope errors of less than 2 arcsec. At the Advanced Photon Source, this corresponds to the undulator closed-gap (11 mm) condition at 100 mA with white-beam slit sizes slightly larger than the full width at half-maximum of the radiation central cones. The dependence of the slope errors on the thermomechanical properties of silicon are discussed and clearly demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500013868
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  • 6
    Electronic Resource
    Electronic Resource
    Nonlinear thermal-distortion predictions of a silicon monochromator using the finite element method (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 1140-1148 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Silicon crystal monochromators at cryogenic temperatures have been used with great success at third-generation synchrotron radiation sources. At the Advanced Photon Source the unique characteristics of silicon at liquid nitrogen temperatures (80 K) have been leveraged to significantly reduce the thermally induced distortions on beamline monochromators. Finite element simulations of the nonlinear (temperature-dependent material properties) thermal stress problem were performed and compared with the experimental measurements. Several critical finite element modeling considerations are discussed for their role in accurately predicting the highly coupled thermal and structural response of the optical component's surface distortion to the high thermal heat flux. Once an understanding of the effects of (i) local element mesh size, (ii) area/surface heat flux versus volumetric heat generation, and (iii) uniform volumetric absorbed power versus a depth-dependent absorbed power, a final series of simulations was performed. Depending on the estimated convection heat-transfer coefficient, the final refined finite element model's predictions correlated well with the experimental measurements. In general, the use of the finite element method in predicting the overall thermal and structural behavior of the surface of the optical components with a high heat flux was shown to be quite effective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049501012006
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  • 7
    Electronic Resource
    Electronic Resource
    Review of crystal diffraction and its application to focusing energetic gamma rays (1995)
    Springer
    Experimental astronomy 6 (1995), S. 47-56 
    Details
    ISSN: 1572-9508
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The basic features of crystal diffraction and their application to the construction of a crystal diffraction lens for focusing energetic gamma rays are described using examples from the work performed at the Argonne National Laboratory. Both on-axis and off-axis performance are discussed. The review includes the use of normal crystals, bent crystals, and crystals with variable crystal-plane spacing to develop both condenser-type lenses and point-to-point imaging lenses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00419257
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  • 8
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    Santuario de Fauna y Flora Malpelo: descubrimiento en marcha. (2018)
    Dirección General Marítima | Tumaco, Colombia
    Details
    Publication Date: 2021-05-19
    Description: ‘Santuario de Fauna y Flora Malpelo: descubrimiento en marcha’ Los ocho capítulos que suceden esta presentación abren ante sus ojos temas de diversos ámbitos de ciencia desarrollados durante los años 2003 y 2004 a bordo del buque ARC Malpelo, plataforma oceanográfica de la Dirección General Marítima que anualmente arriba a esta zona de estudio haciendo investigación científica, con la orientación de expertos oceanógrafos del Centro Control Contaminación del Pacífico, CCCP. Junto a ellos trabajaron científicos de diferentes áreas, vinculados a otras instituciones como es el caso de la Dirección Territorial Suroccidental del Sistema de Parques Nacionales Naturales, la Fundación Malpelo y Otros Ecosistemas Marinos, el Centro de Investigaciones Marinas y Costeras ‘José Benito Vives de Andréis’, la Fundación Yubarta y la Asociación Calidris, entre otras instituciones conscientes de la trascendencia de la conservación natural de esta isla que alberga particulares especies de fauna marina y terrestre, algunos endemismos y formaciones coralinas que han capturado la atención de conservacionistas propios y foráneos. Así el lector encontrará página tras otra, aspectos generales de la isla; análisis sobre su oceanografía; estudios de calidad de aguas, fitoplancton e ictioplancton; resultados arrojados por la implementación de estaciones del Sistema Nacional de Monitoreo de Arrecifes Coralinos Colombianos; estudios sobre la ecología de los mamíferos marinos que circundan la isla, en especial las ballenas yubartas; además del Piquero de Nazca, cuya colonia reproductiva más grande del planeta se haya en esta isla.
    Description: Published
    Keywords: Ecosistema ; Calidad del agua ; Mamífero ; Ecología ; Circulación oceánica ; ASFA_2015::E::Ecosystems ; ASFA_2015::M::Marine water
    Repository Name: AquaDocs
    Type: Report , Not Known
    Format: 142pp
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  • 9
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    Santuario de Fauna y Flora Malpelo: descubrimiento en marcha (2023)
    Ed. DImar | Tumaco, Nariño. Colombia
    Details
    Publication Date: 2023-10-10
    Description: Santuario de Fauna y Flora Malpelo: descubrimiento en marcha’ reúne a un connotado grupo de investigadores y científicos colombianos inquietos y comprometidos con la conservación de la biodiversidad del lugar. Empuje reconocido por la Dirección General Marítima, DIMAR, y la Unidad Administrativa Especial del Sistema de Parques Nacionales Naturales, UAESPNN, en la unión de esfuerzos para liderar este producto editorial con el que se espera entregar nuevo conocimiento acerca de la segunda área protegida del país declarada Patrimonio Natural de la Humanidad, después del Parque Nacional Natural Los Katíos. Los ocho capítulos que suceden esta presentación abren ante sus ojos temas de diversos ámbitos de ciencia desarrollados durante los años 2003 y 2004 a bordo del buque ARC Malpelo, plataforma oceanográfica de la Dirección General Marítima que anualmente arriba a esta zona de estudio haciendo investigación científica, con la orientación de expertos oceanógrafos del Centro Control Contaminación del Pacífico, CCCP. Junto a ellos trabajaron científicos de diferentes áreas, vinculados a otras instituciones como es el caso de la Dirección Territorial Suroccidental del Sistema de Parques Nacionales Naturales, la Fundación Malpelo y Otros Ecosistemas Marinos, el Centro de Investigaciones Marinas y Costeras ‘José Benito Vives de Andréis’, la Fundación Yubarta y la Asociación Calidris, entre otras instituciones conscientes de la trascendencia de la conservación natural de esta isla que alberga particulares especies de fauna marina y terrestre, algunos endemismos y formaciones coralinas que han capturado la atención de conservacionistas propios y foráneos. Así el lector encontrará página tras otra, aspectos generales de la isla; análisis sobre su oceanografía; estudios de calidad de aguas, fitoplancton e ictioplancton; resultados arrojados por la implementación de estaciones del Sistema Nacional de Monitoreo de Arrecifes Coralinos Colombianos; estudios sobre la ecología de los mamíferos marinos que circundan la isla, en especial las ballenas yubartas; además del Piquero de Nazca, cuya colonia reproductiva más grande del planeta se haya en esta isla.
    Description: Published
    Description: Not Known
    Keywords: Ecosistema ; Calidad del agua ; Mamífero ; Ecología ; Circulación oceánica ; ASFA_2015::P::Physical oceanography ; ASFA_2015::M::Marine ecology ; ASFA_2015::E::Ecosystems ; ASFA_2015::W::Water quality
    Repository Name: AquaDocs
    Type: Book/Monograph/Conference Proceedings
    Format: 142pp.
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  • 10
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    Bragg–Fresnel optics for hard x-ray microscopy: Development of fabrication process and x-ray characterization at the Advanced Photon Source (1998)
    American Institute of Physics
    Details
    Publication Date: 1998-08-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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