3,815 research outputs found
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
Simulation of guard ring influence on the performance of ATLAS pixel detectors for inner layer replacement
Electric field magnitude and depletion in the bulk of silicon pixel detectors, which influence its breakdown behaviour, was studied using finite-element method to solve the drift-diffusion equation coupled to Poisson's equation in a simplified two dimensional model of the ATLAS pixel sensor. Based on this model, the number of guard rings and dead edges width were modified to investigate their influence on the detector's depletion at the edge and on its internal electrical field distribution. Final ly, the 3 level model was implemented into the simulation to study the behaviour of such detector under different level of irradiation
Behavior of Droplets in Microfluidic System with T-Junction
Micro droplet formation is considered as a growing
emerging area of research due to its wide-range application in
chemistry as well as biology. The mechanism of micro droplet
formation using two immiscible liquids running through a T-junction
has been widely studied.
We believe that the flow of these two immiscible phases can be of
greater important factor that could have an impact on out-flow
hydrodynamic behavior, the droplets generated and the size of the
droplets. In this study, the type of the capillary tubes used also
represents another important factor that can have an impact on the
generation of micro droplets.
The tygon capillary tubing with hydrophilic inner surface doesn't
allow regular out-flows due to the fact that the continuous phase
doesn't adhere to the wall of the capillary inner surface.
Teflon capillary tubing, presents better wettability than tygon
tubing, and allows to obtain steady and regular regimes of out-flow,
and the micro droplets are homogeneoussize.
The size of the droplets is directly dependent on the flows of the
continuous and dispersed phases. Thus, as increasing the flow of the
continuous phase, to flow of the dispersed phase stationary, the size
of the drops decreases. Inversely, while increasing the flow of the
dispersed phase, to flow of the continuous phase stationary, the size
of the droplet increases
Accessing the purity of a single photon by the width of the Hong-Ou-Mandel interference
We demonstrate a method to determine the spectral purity of single photons.
The technique is based on the Hong-Ou-Mandel (HOM) interference between a
single photon state and a suitably prepared coherent field. We show that the
temporal width of the HOM dip is not only related to reciprocal of the spectral
width but also to the underlying quantum coherence. Therefore, by measuring the
width of both the HOM dip and the spectrum one can directly quantify the degree
of spectral purity. The distinct advantage of our proposal is that it obviates
the need for perfect mode matching, since it does not rely on the visibility of
the interference. Our method is particularly useful for characterizing the
purity of heralded single photon states.Comment: Extended version, 16 pages, 9 figure
OMEGAPIX: 3D integrated circuit prototype dedicated to the ATLAS upgrade Super LHC pixel project
In late 2008, an international consortium for development of vertically integrated (3D) readout electronics was created to explore features available from this technology. In this paper, the OMEGAPIX circuit is presented. It is the first front-end ASIC prototype designed at LAL in 3D technology. It has been submitted on May 2009. At first, a short reminder of 3D technology is presented. Then the IC design is explained: analogue tier, digital tier and testability
Topological magnons driven by the Dzyaloshinskii-Moriya interaction in the centrosymmetric ferromagnet MnGe
The phase of the quantum-mechanical wave function can encode a topological
structure with wide-ranging physical consequences, such as anomalous transport
effects and the existence of edge states robust against perturbations. While
this has been exhaustively demonstrated for electrons, properties associated
with the elementary quasiparticles in magnetic materials are still
underexplored. Here, we show theoretically and via inelastic neutron scattering
experiments that the bulk ferromagnet MnGe hosts gapped topological
Dirac magnons. Although inversion symmetry prohibits a net
Dzyaloshinskii-Moriya interaction in the unit cell, it is locally allowed and
is responsible for the gap opening in the magnon spectrum. This gap is
predicted and experimentally verified to close by rotating the magnetization
away from the -axis with an applied magnetic field. Hence, MnGe
realizes a gapped Dirac magnon material in three dimensions. Its tunability by
chemical doping or by thin film nanostructuring defines an exciting new
platform to explore and design topological magnons. More generally, our
experimental route to verify and control the topological character of the
magnons is applicable to bulk centrosymmetric hexagonal materials, which calls
for systematic investigation.Comment: 24 pages, 4 figures. Accepted in Nature Communication
An overview of the spin dynamics of antiferromagnetic MnSi
The metallic compound MnSi hosts a series of antiferromagnetic phases
which can be controlled by external stimuli such as temperature and magnetic
field. In this work, we investigate the spin-excitation spectrum of bulk
MnSi by combining inelastic neutron scattering measurements and density
functional theory calculations. We study the evolution of the dynamical
response under external parameters and demonstrate that the spin dynamics of
each phase is robust against any combination of temperature and magnetic field.
In particular, the high-energy spin dynamics is very characteristic of the
different phases consisting of either spin waves or broad fluctuations
patterns.Comment: 5 figure
KARSTOLOGIE EN ZONE ARIDE : FORMATIONS KARSTIFIEES DU SUD EST ALGERIEN. METHODES ET OUTILS.
Un karst est un espace ouvert sur l’extérieur permettant l’introduction dans une roche compacte peu soluble, de traceurs des événements climatiques d’une période donnée. Un karst est donc un conservatoire, mémoire de l’histoire d’une région, d’un pays, d’un continent, voire d’un espace plus vaste encore. Comme dans tout le Bassin méditerranéen, en Algérie subsistent des formations karstiques. Celles-ci ont été étudiées par quelques auteurs et non des moindres tels : Durozoy G., Collignon B., Coiffait P.E., Quinif Y., Maire R. et plus récemment Abdessalem M., Kardache R. etc. Toutes les informations recueillies, du reste aussi importantes les unes que les autres, ne suffisent toujours pas à cerner la karstologie du SE algérien. Beaucoup de travail reste à accomplir tan t la répartition de ces formations en surface est importante, s’étendant jusqu’au piémont du Sahara algérien. Un seul chercheur ne peut y suffire.A cet effet, il nous semble important de tenter une reconstitution des événements qui ont atteint ces formations.En première approche, les karsts du SE de l’Algérie, s’inscrivant dans un milieu aride où règnent une pluviosité extrêmement irrégulière et de très longuespériodes sèches, sont cités comme exemple.L’étude, en l’absence du recours aux techniques de mesures isotopiques, s’est principalement basée sur l’histoire géologique de la région en insistant davantage sur la paléosédimentologie, les phases tectoniques, les épisodes d’érosion, d’émersion et d’accumulation des corps sédimentaires, le paléoclimat enfin
Fast Purcell-enhanced single photon source in 1,550-nm telecom band from a resonant quantum dot-cavity coupling
High-bit-rate nanocavity-based single photon sources in the 1,550-nm telecom
band are challenges facing the development of fibre-based long-haul quantum
communication networks. Here we report a very fast single photon source in the
1,550-nm telecom band, which is achieved by a large Purcell enhancement that
results from the coupling of a single InAs quantum dot and an InP photonic
crystal nanocavity. At a resonance, the spontaneous emission rate was enhanced
by a factor of 5 resulting a record fast emission lifetime of 0.2 ns at 1,550
nm. We also demonstrate that this emission exhibits an enhanced anti-bunching
dip. This is the first realization of nanocavity-enhanced single photon
emitters in the 1,550-nm telecom band. This coupled quantum dot cavity system
in the telecom band thus provides a bright high-bit-rate non-classical single
photon source that offers appealing novel opportunities for the development of
a long-haul quantum telecommunication system via optical fibres.Comment: 16 pages, 4 figure
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