I.B.S. coatings on large substrates: Towards an improvement of the mechanical and optical performances

présenté par A. RemillieuxLarge mirrors (350 mm), having extremely low optical loss (absorption, scattering, wavefront) were coated for the VIRGO interferometer. The new mirror generation needs better wavefront and lower mechanical loss. The first results are discussed

Original optical metrologies of large components

présentée par A. RemillieuxThe coating deposition on large optical components (diameter 350 mm) has required the development of new metrology tools at 1064 nm. To give realistic values of the optical performances, the whole surface of the component needs to be scanned. Our scatterometer (commercial system) has been upgraded to support large and heavy samples. The other metrology tools are prototypes we have developed. We can mention the absorption (photothermal effect) and birefringence bench, a control interferometer equipped with an original stitching option, the optical profilometer (RMS roughness and small defect measurements). A detailed description of these metrology benches will be exposed. Their sensitivity, accuracy and capability to map the optical properties of substrates or mirrors will be discussed. We will describe the recent developments: the stitching option adapted to the Micromap profilometer to measure the RMS roughness on larger area (exploration of a new spatial frequency domain), the accurate bulk absorption calibration

A hysteresis model with dipole interaction: one more devil-staircase

Magnetic properties of 2D systems of magnetic nanoobjects (2D regular lattices of the magnetic nanoparticles or magnetic nanostripes) are considered. The analytical calculation of the hysteresis curve of the system with interaction between nanoobjects is provided. It is shown that during the magnetization reversal system passes through a number of metastable states. The kinetic problem of the magnetization reversal was solved for three models. The following results have been obtained. 1) For 1D system (T=0) with the long-range interaction with the energy proportional to $r^{-p}$, the staircase-like shape of the magnetization curve has self-similar character. The nature of the steps is determined by interplay of the interparticle interaction and coercivity of the single nanoparticle. 2) The influence of the thermal fluctuations on the kinetic process was examined in the framework of the nearest-neighbor interaction model. The thermal fluctuations lead to the additional splitting of the steps on the magnetization curve. 3) The magnetization curve for system with interaction and coercivity dispersion was calculated in mean field approximation. The simple method to experimentally distinguish the influence of interaction and coercivity dispersion on the magnetization curve is suggested.Comment: 22 pages, 8 figure

Design, Implementation and First Measurements with the Medipix Neutron Camera in CMS

The Medipix detector is the first device dedicated to measuring mixed-field radiation in the CMS cavern and able to distinguish between different particle types. Medipix2-MXR chips bump bonded to silicon sensors with various neutron conversion layers developed by the IEAP CTU in Prague were successfully installed for the 2008 LHC start-up in the CMS experimental and services caverns to measure the flux of various particle types, in particular neutrons. They have operated almost continuously during the 2010 run period, and the results shown here are from the proton run between the beginning of July and the end of October 2010. Clear signals are seen and different particle types have been observed during regular LHC luminosity running, and an agreement in the measured flux rate is found with the simulations. These initial results are promising, and indicate that these devices have the potential for further and future LHC and high energy physics applications as radiation monitoring devices for mixed field environments, including neutron flux monitoring. Further extensions are foreseen in the near future to increase the performance of the detector and its coverage for monitoring in CMS.Comment: 15 pages, 16 figures, submitted to JINS

ESCO1 and CTCF enable formation of long chromatin loops by protecting cohesinSTAG1 from WAPL.

Eukaryotic genomes are folded into loops. It is thought that these are formed by cohesin complexes via extrusion, either until loop expansion is arrested by CTCF or until cohesin is removed from DNA by WAPL. Although WAPL limits cohesin's chromatin residence time to minutes, it has been reported that some loops exist for hours. How these loops can persist is unknown. We show that during G1-phase, mammalian cells contain acetylated cohesinSTAG1 which binds chromatin for hours, whereas cohesinSTAG2 binds chromatin for minutes. Our results indicate that CTCF and the acetyltransferase ESCO1 protect a subset of cohesinSTAG1 complexes from WAPL, thereby enable formation of long and presumably long-lived loops, and that ESCO1, like CTCF, contributes to boundary formation in chromatin looping. Our data are consistent with a model of nested loop extrusion, in which acetylated cohesinSTAG1 forms stable loops between CTCF sites, demarcating the boundaries of more transient cohesinSTAG2 extrusion activity

Growth and structural characterization of YMnO3 thin films grown by pulsed liquid injection MOCVD on Si and SrTiO3 substrates

International audienceOptimum parameters for the growing of YMnO3 films by pulsed liquid injection metalorganic chemical vapor deposition have been studied. Si substrates were used for the optimization of the deposition process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that polycrystalline single phase YMnO3 films can be obtained for an optimal ratio of Y and Mn on the injected solution and either amorphous, metastable orthorhombic, and/or hexagonal YMnO3 phases can be obtained depending on the deposition temperature and precursors ratio. In a second stage, YMnO3 films were grown on SrTiO3 substrates. Pure epitaxial orthorhombic YMnO3 phase was confirmed by XRD. The films microstructure, characterized by scanning electron microscopy and TEM, shows a columnar growth. Each columnar grain grows epitaxially with three possible orientations

Substrate dependent growth of highly conductive RuO2 films

We have prepared thin RuO2 films by thermal evaporation metal organic chemical vapour deposition on r-plane Al2O3, MgO, LaAlO3 and SrTiO3 single crystal substrates. The films were grown at deposition temperature TD = 500 °C. X-ray diffraction analysis show different type of preferred growth, depending on a substrate. Atomic force microscopy revealed typical surface morphology for each type of substrate. Room temperature resistivity of the films on various substrates varied between 30 and 40 µΩcm. The best parameters were obtained for epitaxialy grown RuO2 film on the r-plane cut Al2O3 substrate with a room temperature resistivity about 30 µΩcm and residual resistivity ratio (resistivity ratio between room temperature and 4.2 K) close to30

PHEBUS-FPTO Benchmark Calculations

Abstract not availableNA-NOT AVAILABL

Ion beam sputtering coatings on large substrates: toward an improvement of the mechanical and optical performances

Large mirrors (∅350 mm) having extremely low optical loss (absorption, scattering, wavefront) were coated for the VIRGO interferometer. The new generation of mirrors needs to have a better wavefront and lower mechanical loss. To improve the component wavefront, the corrective coating technique was used. By doping the tantalum pentoxide layers, we improved, for the first time to our knowledge, the multilayer mechanical loss. The first results are discussed