1,720,967 research outputs found
Extreme ultraviolet multilayer for the FERMI@Elettra free electron laser beam transport system
Full text linkIn this work we present the design of a Pd/B4C multilayer structure optimized for high reflectance at 6.67 nm. The structure has been deposited and also characterized along one year in order to investigate itstemporal stability. This coating has been developed for the beam transport system of FERMI@Elettra Free Electron Laser: the use of an additional aperiodic capping layer on top of the structure combines the high reflectance with filter properties useful in rejecting the fundamental harmonic when the goal is to select the third FEL harmonic. ©2012 Optical Society of America
Characterization techniques and qualification tests of glass and optical coatings for space applications
No full textOptical coatings and materials need to be qualified against space environmental agents, such as protons, helium ions and electrons. The induced damage effects are studied in dependence on ion species, energy, flux and fluence. Results show that damages can be dramatically dependent not only by fluence, but also by ions energy, so that qualification should take this factor into account. The significance of results obtained by using gamma-rays in place of ions irradiation to qualify components is briefly discussed. A systematic experimental plan for an extensively study of the irradiation effects induced in a large number of different sample coatings and materials is presented
Phase Characterization of Multilayer Coatings by Photoemission Measurements
No full textAttosecond science, photolithography, synchrotron, and free electron laser physics are new frontiers research and technological areas, where the properties of the beam play a fundamental role in the light-matter interaction. To fully control the properties of a propagating beam, knowledge and control of the efficiency and phase introduced by the optical components upon reflection is mandatory. In this letter, an original method based on photoemission measurements useful to determine the phase shift upon reflection of extreme ultraviolet multilayer mirrors working in a near Brewster's condition has been developed. The method has been also successfully applied to test two different innovative samples specifically designed and proposed for the FERMI@ELETTRA free electron laser beam transport system
Multilayer coatings and their use in spectroscopic applications
No full textMultilayers coatings are widely used in different fields ranging from new generation sources applications to astrophysical observations. Novel materials couples have been recently considered to improve the efficiency performances in different spectral regions. The deposition of capping layer structures onto standard periodic Mo/Si multilayers is used to add specific properties, such as high resistance to aging and different damage processes, or to regulate the reflectance in other spectral regions. This solution is adopted in the development of multilayer to be used in FERMI@ELETTRA FEL beam transport systems for third harmonics selection. (C) 2012 Elsevier B.V. All rights reserved
Iridium/silicon multilayers for extreme ultraviolet applications in the 20-35 nm wavelength range
No full textWe have developed an Ir/Si multilayer for extreme ultraviolet (EUV) applications. Normal incidence reflectance measurements of a prototype film tuned to 30nm wavelength show superior performance relative to a conventional Mo/Si multilayer structure; we also find good stability over time. Transmission electron microscopy and electron dispersive x-ray spectroscopy have been used to examine the microstructure and interface properties of this system: we find amorphous Si layers and polycrystalline Ir layers, with asymmetric interlayer regions of mixed composition. Potential applications of Ir/Si multilayers include instrumentation for solar physics and laboratory EUV beam manipulation
Stability of extreme ultraviolet multilayer coatings to low energy proton bombardment
Full text linkIn this work we present results of an new experiment related to low energy protons bombardments on nano-structured optical coatings. Multilayer structures protected by different capping layers have been fabricated and exposed to low energy protons (1keV). The experimental parameters have been selected considering the potential application of the coatings to solar mission instrumentation. Future solar missions will investigate the Sun from very close distances and optical components are constantly exposed to low energy ion particles irradiation. The experiment was repeated fixing the proton flux while varying the total dose accumulated. Results show that physical processes occurred at the uppermost interfaces can strongly damage the structure
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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