3,651 research outputs found
Experimental study of a liquid Xenon PET prototype module
A detector using liquid Xenon in the scintillation mode is studied for
Positron Emission Tomography (PET). The specific design aims at taking full
advantage of the liquid Xenon properties. It does feature a promising
insensitive to any parallax effect. This work reports on the performances of
the first LXe prototype module, equipped with a position sensitive PMT
operating in the VUV range (178 nm).Comment: Proc. of the 7th International Workshops on Radiation Imaging
Detectors (IWORID-7), Grenoble, France 4-7 July 200
Mode structure and ray dynamics of a parabolic dome microcavity
We consider the wave and ray dynamics of the electromagnetic field in a
parabolic dome microcavity. The structure of the fundamental s-wave involves a
main lobe in which the electromagnetic field is confined around the focal point
in an effective volume of the order of a cubic wavelength, while the modes with
finite angular momentum have a structure that avoids the focal area and have
correspondingly larger effective volume. The ray dynamics indicates that the
fundamental s-wave is robust with respect to small geometrical deformations of
the cavity, while the higher order modes are associated with ray chaos and
short-lived. We discuss the incidence of these results on the modification of
the spontaneous emission dynamics of an emitter placed in such a parabolic dome
microcavity.Comment: 50 pages, 17 figure
Evidence for sinistral strike-slip deformation in the Solomon Island arc
6 pages, 4 figuresDuring the SOPACMAPS 2 crusie carried out by IFREMER (Institut Français de Recherche pour l'Exploitation de la Mer) and ORSTOM (Institut Français de Recherche Scientifique pour le dévelopement en Coopération) on theR/V L'Atalante, in the Central Solomon Arc area, multibeam bathymetric and imagery data and single-channel seismic reflection profiles were collected from an area of about 3500 km2, to evaluate regional tectonics. Structural data geophysical profiles interpretation provide evidence for left-lateral transtensional tectonics on the southern edge of the Central Solomon Trough. This transtensional deformation is represented by faulting, block tilting, and rhombohedral deformation. The regional geology and the analysis of the sedimentary cover allow us to demonstrate that this tectonic occurred in two different phases during Oligocene to Miocene and Pliocene to Pleistocene timesPeer reviewe
Seabeam survey at the southern end of the Manila trench : transition between subduction and collision processes, offshore Mindoro island, Philippines
Crustal structure of the Peruvian continental margin from wide-angle seismic studies
Active seismic investigations along the Pacific margin off Peru were carried out using ocean bottom hydrophones and seismometers. The structure and the P-wave velocities of the obliquely subducting oceanic Nazca Plate and overriding South American Plate from 8°S to 15°S were determined by modelling the wide-angle seismic data combined with the analysis of reflection seismic data. Three detailed cross-sections of the subduction zone of the Peruvian margin and one strike-line across the Lima Basin are presented here.
The oceanic crust of the Nazca Plate, with a thin pelagic sediment cover, ranging from 0â200 m, has an average thickness of 6.4 km. At 8°S it thins to 4 km in the area of Trujillo Trough, a graben-like structure. Across the margin, the plate boundary can be traced to 25 km depth. As inferred from the velocity models, a frontal prism exists adjacent to the trench axis and is associated with the steep lower slope. Terrigeneous sediments are proposed to be transported downslope due to gravitational forces and comprise the frontal prism, characterized by low seismic P-wave velocities. The lower slope material accretes against a backstop structure, which is defined by higher seismic P-wave velocities, 3.5â6.0 km sâ1. The large variations in surface slope along one transect may reflect basal removal of upper plate material, thus steepening the slope surface. Subduction processes along the Peruvian margin are dominated by tectonic erosion indicated by the large margin taper, the shape and bending of the subducting slab, laterally varying slope angles and the material properties of the overriding continental plate. The erosional mechanisms, frontal and basal erosion, result in the steepening of the slope and consequent slope failure
Position resolution and particle identification with the ATLAS EM calorimeter
In the years between 2000 and 2002 several pre-series and series modules of
the ATLAS EM barrel and end-cap calorimeter were exposed to electron, photon
and pion beams. The performance of the calorimeter with respect to its finely
segmented first sampling has been studied. The polar angle resolution has been
found to be in the range 50-60 mrad/sqrt(E (GeV)). The neutral pion rejection
has been measured to be about 3.5 for 90% photon selection efficiency at pT=50
GeV/c. Electron-pion separation studies have indicated that a pion fake rate of
(0.07-0.5)% can be achieved while maintaining 90% electron identification
efficiency for energies up to 40 GeV.Comment: 32 pages, 22 figures, to be published in NIM
Development of an analogue optical link for the front-end read-out of the ATLAS electromagnetic calorimeter
We have developed an analogue optical data transmission system intended to meet the read-out requirements of the ATLAS liquid argon electromagnetic calorimeter. Eight-way demonstrators have been built and tested. The link uses arrays of VCSEL diodes as the optical emitters, coupled to a 70 m long fibre ribbon to simulate the distance between the detector and the control room. The receiver is based around a custom-designed PIN photodiode array. We describe here the final results of laboratory tests on a demonstrator, laying stress on the VCSEL-to-fibre coupling issues, and the overall performance of the full link. A 9-bit dynamic range is achieved, with a 5on-linearity
Energy Linearity and Resolution of the ATLAS Electromagnetic Barrel Calorimeter in an Electron Test-Beam
A module of the ATLAS electromagnetic barrel liquid argon calorimeter was
exposed to the CERN electron test-beam at the H8 beam line upgraded for
precision momentum measurement. The available energies of the electron beam
ranged from 10 to 245 GeV. The electron beam impinged at one point
corresponding to a pseudo-rapidity of eta=0.687 and an azimuthal angle of
phi=0.28 in the ATLAS coordinate system. A detailed study of several effects
biasing the electron energy measurement allowed an energy reconstruction
procedure to be developed that ensures a good linearity and a good resolution.
Use is made of detailed Monte Carlo simulations based on Geant which describe
the longitudinal and transverse shower profiles as well as the energy
distributions. For electron energies between 15 GeV and 180 GeV the deviation
of the measured incident electron energy over the beam energy is within 0.1%.
The systematic uncertainty of the measurement is about 0.1% at low energies and
negligible at high energies. The energy resolution is found to be about 10%
sqrt(E) for the sampling term and about 0.2% for the local constant term
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