224 research outputs found
Volcanoes muon imaging using Cherenkov telescopes
A detailed understanding of a volcano inner structure is one of the
key-points for the volcanic hazards evaluation. To this aim, in the last
decade, geophysical radiography techniques using cosmic muon particles have
been proposed. By measuring the differential attenuation of the muon flux as a
function of the amount of rock crossed along different directions, it is
possible to determine the density distribution of the interior of a volcano. Up
to now, a number of experiments have been based on the detection of the muon
tracks crossing hodoscopes, made up of scintillators or nuclear emulsion
planes. Using telescopes based on the atmospheric Cherenkov imaging technique,
we propose a new approach to study the interior of volcanoes detecting the
Cherenkov light produced by relativistic cosmic-ray muons that survive after
crossing the volcano. The Cherenkov light produced along the muon path is
imaged as a typical annular pattern containing all the essential information to
reconstruct particle direction and energy. Our new approach offers the
advantage of a negligible background and an improved spatial resolution. To
test the feasibility of our new method, we have carried out simulations with a
toy-model based on the geometrical parameters of ASTRI SST-2M, i.e. the imaging
atmospheric Cherenkov telescope currently under installation onto the Etna
volcano. Comparing the results of our simulations with previous experiments
based on particle detectors, we gain at least a factor of 10 in sensitivity.
The result of this study shows that we resolve an empty cylinder with a radius
of about 100 m located inside a volcano in less than 4 days, which implies a
limit on the magma velocity of 5 m/h.Comment: 21 pages, 21 figures, in press on Nuclear Inst. and Methods in
Physics Research, A. Final version published online: 3-NOV-201
Microscopic black hole detection in UHECR: the double bang signature
According to recent conjectures on the existence of large extra dimensions in
our universe, black holes may be produced during the interaction of Ultra High
Energy Cosmic Rays with the atmosphere. However, and so far, the proposed
signatures are based on statistical effects, not allowing identification on an
event by event basis, and may lead to large uncertainties. In this note, events
with a double bang topology, where the production and instantaneous decay of a
microscopic black hole (first bang) is followed, at a measurable distance, by
the decay of an energetic tau lepton (second bang) are proposed as an almost
background free signature. The characteristics of these events and the
capability of large cosmic ray experiments to detect them are discussed.Comment: revised version, 5 figure
Dependence on Frequency of the Electromagnetic Field Distribution inside a Cylindrical CavityExcited through an Off-Axis Aperture
To explain the relevant changes in the electron cyclotron resonance ion source behaviour for small variations of the exciting radiation frequency, we determine the spatial distribution of the field within the cavity for every resonant mode
EUSO Operations: Flight and Ground
Abstract The EUSO operations concept is described. Both the on-board and onground systems play an important role on operations. Since no permanent contact with the payload is provided, a considerable autonomy of the on-board system is required. The fulfilment of the scientific goals of the mission and the safety of the instrument require the definition of different operational modes and procedures. On-board, scientific and housekeeping data are collected and sent to ground, and control of the instrument subsystems is performed, based on on-board autonomous procedures and on telecommands sent from ground. On ground, telemetry is received, processed, monitored and archived. Telecommands are prepared for uplink, according to a defined mission activity planning
Rotation Periods of Open Cluster Stars, II
We present the results from a photometric monitoring program of 21 stars observed during 1992 in the Pleiades and Alpha Persei open clusters. Period determinations for 16 stars are given, 13 of which are the first periods reported for these stars. Brightness variations for an additional five cluster stars are also given. One K dwarf member of the a Per cluster is observed to have a period of rotation of only 4.39 hr, perhaps the shortest period currently known among BY Draconis variables. The individual photometric measurements have been deposited with the NSSDC. Combining current X-ray flux determinations with known photometric periods, we illustrate the X-ray activity/rotation relation among Pleiades K dwarfs based on available data
Looking inside volcanoes with the Imaging Atmospheric Cherenkov Telescopes
Cherenkov light is emitted when charged particles travel through a dielectric medium with velocity higher than the speed of light in the medium. The ground-based Imaging Atmospheric Cherenkov Telescopes (IACT), dedicated to the very-high energy Îł-ray Astrophysics, are based on the detection of the Cherenkov light produced by relativistic charged particles in a shower induced by TeV photons interacting with the Earth atmosphere. Usually, an IACT consists of a large segmented mirror which reflects the Cherenkov light onto an array of sensors, placed at the focal plane, equipped by fast electronics. Cherenkov light from muons is imaged by an IACT as a ring, when muon hits the mirror, or as an arc when the impact point is outside the mirror. The Cherenkov ring pattern contains information necessary to assess both direction and energy of the incident muon. Taking advantage of the muon detection capability of IACTs, we present a new application of the Cherenkov technique that can be used to perform the muon radiography of volcanoes. The quantitative understanding of the inner structure of a volcano is a key-point to monitor the stages of the volcano activity, to forecast the next eruptive style and, eventually, to mitigate volcanic hazards. Muon radiography shares the same principle as X-ray radiography: muons are attenuated by higher density regions inside the target so that, by measuring the differential attenuation of the muon flux along different directions, it is possible to determine the density distribution of the interior of a volcano. To date, muon imaging of volcanic structures has been mainly achieved with detectors made up of scintillator planes. The advantage of using Cherenkov telescopes is that they are negligibly affected by background noise and allow a consistently improved spatial resolution when compared to the majority of the current detectors.Published111-1142V. Struttura e sistema di alimentazione dei vulcaniJCR Journa
A new technique for probing the internal structure of volcanoes using cosmic-ray muons
Among the considerable number of studies that can be carried out using muons, we pay specific attention to the radiography of volcanoes based on the same principle of the X-ray radiography of human body. Thanks to their high penetration capability, cosmic-ray muons can be used to reconstruct the density distribution of the interior of huge structures by measuring the attenuation induced by the material on the muon flux. In particular, the quantitative understanding of the inner structure of volcanoes is a key-point to forecast the dangerous stages of activity and mitigate volcanic hazards. The instrumental approach is currently based on the detection of muons crossing hodoscopes made up of scintillator planes. Unfortunately, these detectors are affected by a strong background comprised by accidental coincidence of vertical shower particles, horizontal high-energy electrons and upward going particles. We propose an alternative technique based on the detection of the Cherenkov light produced by muons. This can be achieved with an imaging atmospheric Cherenkov telescope composed of a high reflectivity optical system that focus the Cherenkov light onto a multi-pixel focal camera with fast read-out electronics. The Cherenkov light emitted by a muon is imaged on the camera as an annular pattern which contains information to reconstruct the direction of the incident muon. We have estimated that using the Cherenkov imaging technique for muon radiography of volcanoes gives the advantage of a negligible background and improved spatial resolution, compared to the majority of the particle detectors. We present results of simulations based on a telescope with a positioning resolution of 13.5 m which corresponds to an acceptance of 9 cm2 sr. The telescope is located 1500 m far from a toy-model volcano, namely, a cone with a base diameter of 500 m and a height of 240 m. We test the feasibility of the proposed method by estimating the minimum number of observation nights needed to resolve inner empty conduits of different diameter.Published122–1252V. Struttura e sistema di alimentazione dei vulcaniN/A or not JC
Detection of the Cherenkov light diffused by Sea Water with the ULTRA Experiment
The study of Ultra High Energy Cosmic Rays represents one of the most
challenging topic in the Cosmic Rays and in the Astroparticle Physics fields.
The interaction of primary particles with atmospheric nuclei produces a huge
Extensive Air Shower together with isotropic emission of UV fluorescence light
and highly directional Cherenkov photons, that are reflected/diffused
isotropically by the impact on the Earth's surface or on high optical depth
clouds. For space-based observations, detecting the reflected Cherenkov signal
in a delayed coincidence with the fluorescence light improves the accuracy of
the shower reconstruction in space and in particular the measurement of the
shower maximum, giving a strong signature for discriminating hadrons and
neutrinos, and helping to estimate the primary chemical composition. Since the
Earth's surface is mostly covered by water, the ULTRA (UV Light Transmission
and Reflection in the Atmosphere)experiment has been designed to provide the
diffusing properties of sea water, overcoming the lack of information in this
specific field. A small EAS array, made up of 5 particle detectors, and an UV
optical device, have been coupled to detect in coincidence both electromagnetic
and UV components. The detector was in operation from May to December, 2005, in
a small private harbor in Capo Granitola (Italy); the results of these
measurements in terms of diffusion coefficient and threshold energy are
presented here.Comment: 4 pages, 3 figures, PDF format, Proceedings of 30th ICRC,
International Cosmic Ray Conference 2007, Merida, Yucatan, Mexico, 3-11 July
200
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