Characterization of Angle Accuracy and Precision of 3-Degree-of-Freedom Absolute Encoder Based on NanoGPS OxyO Technology

An absolute encoder based on vision system nanoGPS OxyO was developed by HORIBA France. This encoder provides three types of position information, namely, two inplane co-ordinates and inplane angular orientation. This paper focuses on the characterization of its angular performance. To this aim, the nanoGPS OxyO system was compared with the national angle standard of the National Metrology Institute of Italy (INRIM) that had evaluated accuracy of about 0.1 urad. The effect of image size and illumination conditions on angular measurements was studied. Precision better than 10 urad and accuracy better than 63 urad over 2π rotation were demonstrated. Moreover, the application of nanoGPS OxyO to the characterization of rotation bearing is presented. Small deviations from pure rotational behavior were evidenced that would have not been possible using laser interferometers. As a consequence of its accuracy and versatility, the nanoGPS OxyO encoder is expected to be useful for laboratory experiments and quality-control tasks

Estimation of the Temperature Fluctuations Harshness Regarding Stability of Structures in the Nanometer Range

International audienceThermally induced distortions are a key contributor to the overall positional and pointing performance of high-stability systems. Though stability scales with temperature fluctuations, there is some hidden complexity is the subject. Firstly, not all temperature oscillations will distort the structure: fast variations will hardly propagate into the structure, little change in overall dimensions but primarily pointing errors. Conversely, slow variations will result in quasi uniform temperature fields that change dimensions, hence mainly positional errors. Secondly, there is randomness in temperature fluctuations which obscures the actual severity of a given environment: randomness occurs timewise, but also space-wise. For highly stable situations, random part of the temperature field becomes prominent, and discarding this component becomes questionable. No harshness indicator exists that could help quantifying the actual severity of a given thermal environment. It is the objective of this paper to provide some insight on the matter, and propose a simple yet efficient numerical method allowing the evaluation of actual structural response to any realistic thermal environment

Chalcogen Atom Interaction with Palladium and the Complex Molecule–Metal Interface in Thiol Self Assembly

In the case of reactive metals, on adsorption of organic chalcogenide molecules like thiols, chalcogenide-C bond scission can occur. Thus, the high reactivity of Pd leads to initial thiol dissociation and formation of a complex PdS interface layer on which thereafter thiol self-assembled monolayers (SAM) can form. In this context we investigate in detail the adsorption of S, Se, alkanethiols, and aromatic dithiols on Pd by photoemission with synchrotron radiation. The nature of the PdS and PdSe layers formed is studied, and thiol adsorption on Pd(111), PdS, and PdSe surfaces is investigated, along with interface characteristics. After initial strong sulfidation (selenization) in Na2S(Se) solutions, a well-ordered surface PdS (PdSe) layer can be obtained by annealing. For S, annealing leads to formation of a PdS (root 7 x root 7)R19.1 degrees layer, whereas for Se, large domains of this structure are formed. Experiments suggest that in thiol adsorption the Pdsulfide interface is not simply similar to the (root 7 x root 7)R19.1 degrees PdS layer but that modifications in this surface sulfide layer are induced. A similar effect is observed on the selenide interface layer. In addition, 1,4-benzenedimethanethiol adsorption on Pd is investigated with the aim of creation of thiol-terminated dithiol molecular layers. Unlike the case of surfaces like Au, no clear indication of a standing-up, thiol-terminated SAM was found. X-ray radiation damage effects are reported

Bromine cycle in subduction zones through in situ Br monitoring in diamond anvil cells

International audienceAbstract The geochemical partitioning of bromine between hydrous haplogranitic melts, initially enriched with respect to Br and aqueous fluids, has been continuously monitored in situ during decompression. Experiments were carried out in diamond anvil cells from 890 °C to room temperature and from 1.7 GPa to room pressure, typically from high P, T conditions corresponding to total miscibility (presence of a supercritical fluid). Br contents were measured in aqueous fluids, hydrous melts and supercritical fluids. Partition coefficients of bromine were characterized at pressure and temperature between fluids, hydrous melts and/or glasses, as appropriate: DBrfluid/melt = (Br)fluid/(Br)melt, ranges from 2.18 to 9.2 ± 0.5 for conditions within the ranges 0.66–1.7 GPa, 590–890 °C; and DBrfluid/glass = (Br)fluid/(Br)glass ranges from 60 to 375 at room conditions. The results suggest that because high pressure melts and fluids are capable of accepting high concentrations of bromine, this element may be efficiently removed from the slab to the mantle source of arc magmas. We show that Br may be highly concentrated in subduction zone magmas and strongly enriched in subduction-related volcanic gases, because its mobility is strongly correlated with that of water during magma degassing. Furthermore, our experimental results suggest that a non negligible part of Br present in the subducted slab may remain in the down-going slab, being transported toward the transition zone. This indicates that the Br cycle in subduction zones is in fact divided in two related but independent parts: (1) a shallower one where recycled Br may leave the slab with a water and silica-bearing “fluid” leading to enriched arc magmas that return Br to the atmosphere. (2) A deeper cycle where Br may be recycled back to the mantle maybe to the transition zone, where it may be present in high pressure water-rich metasomatic fluids

Propanoate grafting on (H,OH)-Si(0 0 1)-2 × 1

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DFT and experimental FTIR investigations of early stages of (0 0 1) and (1 1 1)B GaAs surface nitridation

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Interferometric characterization of rotation stages for X-ray nanotomography

The field of three-dimensional multi-modal X-ray nanoimaging relies not only on high-brilliance X-rays but also on high-precision mechanics and position metrology. Currently available state-of-the-art linear and rotary drives can provide 3D position accuracy within tens to hundreds of nm, which is often insufficient for high resolution imaging with nanofocused X-ray beams. Motion errors are especially troublesome in the case of rotation drives and their correction is more complicated and relies on the metrology grade reference objects. Here we present a method which allows the characterisation and correction of the radial and angular errors of the rotary drives without the need for a highly accurate metrology object. The method is based on multi-probe error separation using fiber-laser interferometry and uses a standard cylindrical sample holder as a reference. The obtained runout and shape measurements are then used to perform the position corrections using additional drives. We demonstrate the results of the characterization for a piezo-driven small rotation stage. The error separation allowed us to measure the axis runout to be approximately ±1.25 μm, and with active runout compensation this could be reduced down to ±42 nm