337 research outputs found
On the Kramers-Kronig transform with logarithmic kernel for the reflection phase in the Drude model
We use the Kramers-Kronig transform (KKT) with logarithmic kernel to obtain
the reflection phase and, subsequently, the complex refractive index of a bulk
mirror from reflectance. However, there remains some confusion regarding the
formulation for this analysis. Assuming the damped Drude model for the
dielectric constant and the oblique incidence case, we calculate the additional
terms: phase at zero frequency and Blashke factor and we propose a reformulated
KKT within this model. Absolute reflectance in the s-polarization case of a
gold film is measured between 40 and 350 eV for various glancing angles using
synchrotron radiation and its complex refractive index is deduced using the
reformulated KKT that we propose. The results are discussed with respect to the
data available in the literature.Comment: 18 pages, piblished in j. Mod. Opt. 57, 1504 (2010
DUVEX: An X-ray counting system based on YAG:Ce scintillator
International audienceA detector system, called DUVEX, has been developed for the soft-X-ray and extreme ultraviolet domain. It consists of a YAG:Ce scintillator coupled to a photomultiplier module working under vacuum in counting mode. The design and the performances of this detector in terms of yield, absolute efficiency, response and noise are reported. Spectra in the soft X-ray range of different elements (W, Ag, Al, Mg, Cu, N, C and B) obtained in WDS mode using this detector are presented. DUVEX appears as a competitive detection tool in terms of cost and easiness of implementation
Exploring a Place-Based Approach to Materials Design: Harakeke Nonwovens in Aotearoa New Zealand
As the interdisciplinary field of materials design expands, pressing environmental, social and economic crises mean that the impacts of materials are more clearly perceived (Drazin 2015). This presents a challenge to activate materials towards positive change. Design practices that are relational, place based and deeply attuned to justice and the Earth are needed (Escobar 2017). What might such practices look like within the field of materials design? And how might they be informed by textiles practice? To address these questions, this paper presents and reflects upon a recent study into the development of harakeke (Phormium Tenax/New Zealand Flax) based nonwovens. The aim of the study was to support the re-establishment of harakeke based industry in Aotearoa New Zealand, which recent research suggests could address a range of environmental, social and economic problems specific to the region (McGruddy 2006). The approach taken drew on notions of place-based design and textile thinking, and was underpinned by a collaboration between university based design researchers, an agricultural and a forestry/ biomaterials research institute, an independent designer and an expert in traditional harakeke weaving. An initial review of materials design, research and developments that are predicated on regionally specific resources and knowledge was undertaken. Processing trials were conducted that brought together knowledge from indigenous harakeke weaving practice, fine art practices, industrially based fibre processing techniques and biopolymer processing. The resulting new materials were qualitatively evaluated using emergent models of experiential characterization (Camere and Karana 2018), which showed potential for the materials to be developed towards applications including architectural surfaces and packaging
Determination of the magnetization profile of Co/Mg periodic multilayers by magneto-optic Kerr effect and X-ray magnetic resonant reflectivity
The resonant magnetic reflectivity of Co/Mg multilayers around the Co L2,3
absorption edge is simulated then measured on a specifically designed sample.
The dichroic signal is obtained when making the difference between the two
reflectivities measured with the magnetic field applied in two opposite
directions parallel to the sample surface. The simulations show that the
existence of magnetic dead layers at the interfaces between the Co and Mg
layers leads to an important increase of the dichroic signal measured in the
vicinity of the third Bragg peak that otherwise should be negligible. The
measurements are in agreement with the model introducing 0.25 nm thick dead
layers. This is attributed to the Co atoms in contact with the Mg layers and
thus we conclude that the Co-Mg interfaces are abrupt from the magnetic point
of view.Comment: 8 page
Cr/Sc multilayer radiator for parametric EUV radiation in "water-window" spectral range
The results of experimental investigation of parametric radiation generated by 5.7 MeV electrons in a multilayer structure consisting of 100 Cr/Sc bi-layers deposited on a Si3N4 membrane are presented. The multilayer structure was specially created for generation of parametric radiation with photon energy in "water-window" spectral rang
Investigation of the thermal stability of Mg/Co periodic multilayers for EUV applications
We present the results of the characterization of Mg/Co periodic multilayers
and their thermal stability for the EUV range. The annealing study is performed
up to a temperature of 400\degree C. Images obtained by scanning transmission
electron microscopy and electron energy loss spectroscopy clearly show the good
quality of the multilayer structure. The measurements of the EUV reflectivity
around 25 nm (~49 eV) indicate that the reflectivity decreases when the
annealing temperature increases above 300\degreeC. X-ray emission spectroscopy
is performed to determine the chemical state of the Mg atoms within the Mg/Co
multilayer. Nuclear magnetic resonance used to determine the chemical state of
the Co atoms and scanning electron microscopy images of cross sections of the
Mg/Co multilayers reveal changes in the morphology of the stack from an
annealing temperature of 305\degreee;C. This explains the observed reflectivity
loss.Comment: Published in Applied Physics A: Materials Science \& Processing
Published at
http://www.springerlink.com.chimie.gate.inist.fr/content/6v396j6m56771r61/ 21
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