2,882 research outputs found
Novel Single Photon Detectors for UV Imaging
There are several applications which require high position resolution UV
imaging. For these applications we have developed and successfully tested a new
version of a 2D UV single photon imaging detector based on a microgap RPC. The
main features of such a detectors is the high position resolution - 30 micron
in digital form and the high quantum efficiency (1-8% in the spectral interval
of 220-140 nm). Additionally, they are spark- protected and can operate without
any feedback problems at high gains, close to a streamer mode. In attempts to
extend the sensitivity of RPCs to longer wavelengths we have successfully
tested the operation of the first sealed parallel-plate gaseous detectors with
CsTe photocathodes. Finally, the comparison with other types of photosensitive
detectors is given and possible fields of applications are identified.Comment: Presented at the 5th International Workshop on RICH detectors Playa
del Carmen, Mexico, November 200
Permeability sets the linear path instability of buoyancy-driven disks
The prediction of trajectories of buoyancy-driven objects immersed in a viscous fluid is a key problem in fluid dynamics. Simple-shaped objects, such as disks, present a great variety of trajectories, ranging from zig-zag to tumbling and chaotic motions. Yet, similar studies are lacking when the object is permeable. We perform a linear stability analysis of the steady vertical path of a thin permeable disk, whose flow through the microstructure is modelled via a stress-jump model based on homogenization theory. The relative velocity of the flow associated with the vertical steady path presents a recirculation region detached from the body, which shrinks and eventually disappears as the disk becomes more permeable. In analogy with the solid disk, one non-oscillatory and several oscillatory modes are identified and found to destabilize the fluid-solid coupled system away from its straight trajectory. Permeability progressively filters out the wake dynamics in the instability of the steady vertical path. Modes dominated by wake oscillations are first stabilized, followed by those characterized by weaker, or absent, wake oscillations, in which the wake is typically a tilting induced by the disk inclined trajectory. For sufficiently large permeabilities, the disk first undergoes a non-oscillatory divergence instability, which is expected to lead to a steady oblique path with a constant disk inclination, in the nonlinear regime. A further permeability increase reduces the unstable range of all modes until quenching of all linear instabilities
A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery
The standard model of particle physics1-4 describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model is a field that permeates all of space and interacts with fundamental particles5-9. The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN10,11. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons-the carriers of the strong, electromagnetic and weak forces-are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (τ)) are well measured and indications of interactions with a second-generation particle (muons, μ) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model
Evaluation of the imaging performance of the TECNOMUSE muon tomograph and its feasibility in a real scenario
Muon tomography is a very promising imaging technique for the control of cargo
containers. It takes advantage of cosmic muons and their interaction mechanisms to reconstruct
images of the volume traversed by these particles. In the present work, the imaging
performance of a novelmuon tomography scanner based on resistive plate chambers detectors
is investigated. By means of several Monte Carlo simulations, some imaging parameters are
evaluated. The results in terms of spatial resolution, field-of-view and volume and material
recognition make the presented scanner and its geometry suitable for muon tomograph
A splitting approach for the fully nonlinear and weakly dispersive Green-Naghdi model
The fully nonlinear and weakly dispersive Green-Naghdi model for shallow
water waves of large amplitude is studied. The original model is first recast
under a new formulation more suitable for numerical resolution. An hybrid
finite volume and finite difference splitting approach is then proposed. The
hyperbolic part of the equations is handled with a high-order finite volume
scheme allowing for breaking waves and dry areas. The dispersive part is
treated with a classical finite difference approach. Extensive numerical
validations are then performed in one horizontal dimension, relying both on
analytical solutions and experimental data. The results show that our approach
gives a good account of all the processes of wave transformation in coastal
areas: shoaling, wave breaking and run-up
Optimization of RPCs read-out panel with electromagnetic simulation
With the upgrade of the RPCs [1]-[2] and the increase of its performances,
the study and the optimization of the read-out panel is necessary in order to
maintain the signal integrity and to reduce the intrinsic crosstalk. Through
Electromagnetic Simulation, performed with CST Studio Suite, new panels design
are tested and their crosstalk property are studied. The behavior of different
type of panel is shown, in particular a panel with the decoupling strip
connected through their characteristic impedance to the ground plane is
simulated
High Resolution RPC's for Large TOF Systems
Here we report on a particular type of RPC that presents up to 99% efficiency
for minimum ionizing particles and a very sharp time resolution, below 50 ps
sigma in the most optimized conditions. Our 9 cm2 cells, made with glass and
metal electrodes that form accurately spaced gaps of a few hundred micrometers,
are operated at atmospheric pressure in non-flammable gases and can be
economically produced in large quantities, opening perspectives for the
construction of large area time of flight systems.Comment: 10 pages, 8 figure
- …