46 research outputs found
Measurement of the thermal expansion coefficient of an Al-Mg alloy at ultra-low temperatures
We describe a result coming from an experiment based on an Al-Mg alloy (~ 5%
Mg) suspended bar hit by an electron beam and operated above and below the
termperature of transition from superconducting to normal state of the
material. The amplitude of the bar first longitudinal mode of oscillation,
excited by the beam interacting with the bulk, and the energy deposited by the
beam in the bar are the quantities measured by the experiment. These
quantities, inserted in the equations describing the mechanism of the mode
excitation and complemented by an independent measurement of the specific heat,
allow us to determine the linear expansion coefficient of the material.Comment: 13 pages, 4 figure
The tectonic puzzle of the Messina area (Southern Italy): Insights from new seismic reflection data
The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of
the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although
the area is highly populated and important infrastructures are planned there. New seismic reflection data
have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait.
These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian
offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina
Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic
settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction
zone relative to slab advance in the western Sicilian side
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Proximity array device: a novel photon detector working in long wavelengths
We present here an innovative photon detector based on the proximity junction array device (PAD) working at long wavelengths. We show that the vortex dynamics in PAD undergoes a transition from a Mott insulator to a vortex metal state by application of an external magnetic field. The PAD also evidences a Josephson I-V characteristic with the external field dependent tunneling current. At high applied currents, we observe a dissipative regime in which the vortex dynamics is dominated by the quasi-particle contribution from the normal metal. The PAD has a relatively high photo-response even at frequencies below the expected characteristic frequency while, its superconducting properties such as the order parameter and the Josephson characteristic frequency can be modulated via external fields to widen the detection band. This device represents a promising and reliable candidate for new high-sensitivity long-wavelength detectors. © 2020 by the authors. Licensee MDPI, Basel, Switzerland
The Bortoluzzi Mud Volcano (Ionian Sea, Italy) and its potential for tracking the seismic cycle of active faults
The Ionian Sea in southern Italy is at the center
of active interaction and convergence between the Eurasian
and African–Adriatic plates in the Mediterranean. This area
is seismically active with instrumentally and/or historically
recorded Mw > 7:0 earthquakes, and it is affected by recently
discovered long strike-slip faults across the active Calabrian
accretionary wedge. Many mud volcanoes occur on
top of the wedge. A recently discovered one (called the Bortoluzzi
Mud Volcano or BMV) was surveyed during the Seismofaults
2017 cruise (May 2017). Bathymetric backscatter
surveys, seismic reflection profiles, geochemical and earthquake
data, and a gravity core are used here to geologically,
geochemically, and geophysically characterize this structure.
The BMV is a circular feature ' 22m high and ' 1100m in
diameter with steep slopes (up to a dip of 22 ). It sits atop
the Calabrian accretionary wedge and a system of flowerlike
oblique-slip faults that are probably seismically active as
demonstrated by earthquake hypocentral and focal data. Geochemistry
of water samples from the seawater column on top
of the BMV shows a significant contamination of the bottom
waters from saline (evaporite-type) CH4-dominated crustalderived
fluids similar to the fluids collected from a mud volcano
located on the Calabria mainland over the same accretionary
wedge. These results attest to the occurrence of open
crustal pathways for fluids through the BMV down to at least
the Messinian evaporites at about 3000 m. This evidence
is also substantiated by helium isotope ratios and by comparison
and contrast with different geochemical data from
three seawater columns located over other active faults in the
Ionian Sea area. One conclusion is that the BMV may be
useful for tracking the seismic cycle of active faults through
geochemical monitoring. Due to the widespread diffusion of
mud volcanoes in seismically active settings, this study contributes
to indicating a future path for the use of mud volcanoes
in the monitoring and mitigation of natural hazards.Published1-233SR TERREMOTI - AttivitĂ dei CentriJCR Journa
The future search for low-frequency axions and new physics with the FLASH resonant cavity experiment at Frascati National Laboratories
We present a proposal for a new experiment, the FINUDA magnet for Light Axion
SearcH (FLASH), a large resonant-cavity haloscope in a high static magnetic
field which is planned to probe new physics in the form of dark matter (DM)
axions, scalar fields, chameleons, hidden photons, as well as high frequency
gravitational waves (GWs). Concerning the QCD axion, FLASH will search for
these particles as the DM in the mass range (0.49-1.49) ueV, thus filling the
mass gap between the ranges covered by other planned searches. A dedicated
Microstrip SQUID operating at ultra-cryogenic temperatures will amplify the
signal. The frequency range accessible overlaps with the Very High Frequency
(VHF) range of the radio wave spectrum and allows for a search in GWs in the
frequency range (100-300) MHz. The experiment will make use of the cryogenic
plant and magnet of the FINUDA experiment at INFN Frascati National
Laboratories near Rome (Italy); the operations needed to restore the
functionalities of the apparatus are currently underway. We present the setup
of the experiment and the sensitivity forecasts for the detection of axions,
scalar fields, chameleons, hidden photons, and GWs
Validation of techniques to mitigate copper surface contamination in CUORE
In this article we describe the background challenges for the CUORE
experiment posed by surface contamination of inert detector materials such as
copper, and present three techniques explored to mitigate these backgrounds.
Using data from a dedicated test apparatus constructed to validate and compare
these techniques we demonstrate that copper surface contamination levels better
than 10E-07 - 10E-08 Bq/cm2 are achieved for 238U and 232Th. If these levels
are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit
on the number of background counts in the region of interest is 0.02-0.03
counts/keV/kg/y depending on the adopted mitigation technique.Comment: 10 pages, 6 figures, 6 table
Search for 14.4 keV solar axions from M1 transition of Fe-57 with CUORE crystals
We report the results of a search for axions from the 14.4 keV M1 transition
from Fe-57 in the core of the sun using the axio-electric effect in TeO2
bolometers. The detectors are 5x5x5 cm3 crystals operated at about 10 mK in a
facility used to test bolometers for the CUORE experiment at the Laboratori
Nazionali del Gran Sasso in Italy. An analysis of 43.65 kg d of data was made
using a newly developed low energy trigger which was optimized to reduce the
detectors energy threshold. An upper limit of 0.63 c kg-1 d-1 was established
at 95% C.L.. From this value, a lower bound at 95% C.L. was placed on the
Peccei-Quinn energy scale of fa >= 0.76 10**6 GeV for a value of S=0.55 for the
flavor-singlet axial vector matrix element. Bounds are given for the interval
0.15 < S < 0.55.Comment: 14 pages, 6 figures, submitted to JCA