6,778 research outputs found
Alignment procedure of the LHCb Vertex Detector
LHCb is one of the four main experiments of the Large Hadron Collider (LHC)
project, which will start at CERN in 2008. The experiment is primarily
dedicated to B-Physics and hence requires precise vertex reconstruction. The
silicon vertex locator (VELO) has a single hit precision of better than 10
micron and is used both off-line and in the trigger. These requirements place
strict constraints on its alignment. Additional challenges for the alignment
arise from the detector being retracted between each fill of the LHC and from
its unique circular disc r/phi strip geometry. This paper describes the track
based software alignment procedure developed for the VELO. The procedure is
primarily based on a non-iterative method using a matrix inversion technique.
The procedure is demonstrated with simulated events to be fast, robust and to
achieve a suitable alignment precision.Comment: accepted for publication in NIM
LHCb VELO software alignment, Part III: the alignment of the relative sensor positions
The LHCb Vertex Locator contains 42 silicon sensor modules. Each module has
two silicon sensors. A method for determining the relative alignment of the
silicon sensors within each module from data is presented. The software
implementation details are discussed. Monte-Carlo simulation studies are
described that demonstrate an alignment precision of 1.3 micron is obtained in
the sensor plane
Very large spontaneous electric polarization in BiFeO3 single crystals at room temperature and its evolution under cycling fields
Electric polarization loops are measured at room temperature on highly pure
BiFeO3 single crystals synthesized by a flux growth method. Because the
crystals have a high electrical resistivity, the resulting low leakage currents
allow us to measure a large spontaneous polarization reaching 100
microC.cm^{-2}, a value never reported in the bulk. During electric cycling,
the slow degradation of the material leads to an evolution of the hysteresis
curves eventually preventing full saturation of the crystals.Comment: 8 pages, 3 figure
Prediction of novel interface-driven spintronic effects
The recently-proposed coupling between the angular momentum density and
magnetic moment [A. Raeliarijaona et al, Phys. Rev. Lett. 110, 137205 (2013)]
is shown here to result in the prediction of (i) novel spin currents generated
by an electrical current and (ii) new electrical currents induced by a spin
current in systems possessing specific interfaces between two different
materials. Some of these spin (electrical) currents can be reversed near the
interface by reversing the applied electrical (spin) current. Similarities and
differences between these novel spintronic effects and the well-known spin Hall
and inverse spin Hall effects are also discussed.Comment: Accepted in J. Phys.::Condens. Matte
Current induced distortion of a magnetic domain wall
We consider the spin torque induced by a current flowing ballistically
through a magnetic domain wall. In addition to a global pressure in the
direction of the electronic flow, the torque has an internal structure of
comparable magnitude due to the precession of the electrons' spins at the
"Larmor" frequency. As a result, the profile of the domain wall is expected to
get distorted by the current and acquires a periodic sur-structure.Comment: 5 pages, 3 eps figure
Caractérisation de matériaux avancés à faible permittivité par Spectroscopie Temporelle d'Annihilation de Positons (PALS)
Cet exposé présente le principe et la réalisation d'un détecteur PALS (Positron Annihilation Lifetime Spectroscopy). Ce détecteur nous permettra de mesurer le temps de vie d'un positon dans un matériau poreux et de caractériser ainsi la taille des pores. Dans une deuxième partie, nous présentons les caractéristiques de ce détecteur et nous comparons ces performances temporelles avec celles des détecteurs existant
Laser monitoring system for the ATLAS tile calorimeter
International audienc
Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta
We report on a comparative study of spin Hall related effects and
magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements
allow to estimate the characteristic transport parameters of both Pt and Ta
layers juxtaposed to YIG: the spin mixing conductance
at the YIGnormal metal interface, the spin Hall angle , and the
spin diffusion length in the normal metal. The inverse spin Hall
voltages generated in Pt and Ta by the pure spin current pumped from YIG
excited at resonance confirm the opposite signs of spin Hall angles in these
two materials. Moreover, from the dependence of the inverse spin Hall voltage
on the Ta thickness, we extract the spin diffusion length in Ta, found to be
nm. Both the YIG|Pt and YIG|Ta systems
display a similar variation of resistance upon magnetic field orientation,
which can be explained in the recently developed framework of spin Hall
magnetoresistance.Comment: 8 pages, 5 figures, 1 tabl
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