3,653 research outputs found
+ / / at ATLAS
The newest results from the ATLAS Collaboration for the production of a
top-quark pair in association with a or boson, and for the production
of four top quarks, are summarised in these proceedings. The measurements were
performed with 36.1 fb of proton-proton collision data from the Large
Hadron Collider at a centre-of-mass energy of 13 TeV.Comment: 7 pages, 3 figures, TOP2018 Conference Proceeding
Measurements and TCAD simulation of novel ATLAS planar pixel detector structures for the HL-LHC upgrade
The LHC accelerator complex will be upgraded between 2020-2022, to the
High-Luminosity-LHC, to considerably increase statistics for the various
physics analyses. To operate under these challenging new conditions, and
maintain excellent performance in track reconstruction and vertex location, the
ATLAS pixel detector must be substantially upgraded and a full replacement is
expected. Processing techniques for novel pixel designs are optimised through
characterisation of test structures in a clean room and also through
simulations with Technology Computer Aided Design (TCAD). A method to study
non-perpendicular tracks through a pixel device is discussed. Comparison of
TCAD simulations with Secondary Ion Mass Spectrometry (SIMS) measurements to
investigate the doping profile of structures and validate the simulation
process is also presented.Comment: 9 pages, 7 figures, PIXEL201
Local boron doping quantification in homoepitaxial diamond structures
The capability of transmission electronmicroscopy (TEM) using the high angle annular dark fieldmode (HAADF,also labelled Z-contrast) to quantify boron concentration, in the high doping range between 1019cm−3 and 1021cm−3, is demonstrated. Thanks to the large relative variation of atomic number Z between carbon and boron, doping concentration maps and profiles are obtained with a nanometer-scale resolution. A novel numerical simulation procedure allows the boron concentration quantification and demonstrates the high sensitivity and
spatial resolution of the technique.4 page
Crystal Structure of the ZrO Phase at Zirconium/Zirconium Oxide Interfaces
Zirconium-based alloys are used in water-cooled nuclear reactors for both nuclear fuel cladding and structural components. Under this harsh environment, the main factor limiting the service life of zirconium cladding, and hence fuel burn-up efficiency, is water corrosion. This oxidation process has recently been linked to the presence of a sub-oxide phase with well-defined composition but unknown structure at the metal–oxide interface. In this paper, the combination of first-principles materials modeling and high-resolution electron microscopy is used to identify the structure of this sub-oxide phase, bringing us a step closer to developing strategies to mitigate aqueous oxidation in Zr alloys and prolong the operational lifetime of commercial fuel cladding alloys
4D STEM: high efficiency phase contrast imaging using a fast pixelated detector
Phase contrast imaging is widely used for imaging beam sensitive and weak phase objects in electron microscopy. In this work we demonstrate the achievement of high efficient phase contrast imaging in STEM using the pnCCD, a fast direct electron pixelated detector, which records the diffraction patterns at every probe position with a speed of 1000 to 4000 frames per second, forming a 4D STEM dataset simultaneously with the incoherent Z-contrast imaging. Ptychographic phase reconstruction has been applied and the obtained complex transmission function reveals the phase of the specimen. The results using GaN and Ti, Nd- doped BiFeO3 show that this imaging mode is especially powerful for imaging light elements in the presence of much heavier elements
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