77 research outputs found
The 1999-2000 seismic experiment of Macas swarm (Ecuador) in relation with rift inversion in Subandean foothills
International audienceWe propose to explain the origin of the double trend in seismicity of the Macas swarm in the Subandean Cordillera of CutucĂş (Ecuador) and characterize the corresponding active deformation of that region. For that purpose, seismological and geological data have been used, with the deployment of a temporary seismological array, with geological field observations and image processing. We found that some earthquakes are aligned on a well known NNE SSW trend corresponding to the orientation of the nodal planes of the reverse focal mechanism of the Mw=7.0 1995 Macas earthquake as for its aftershocks. Nevertheless, many smaller events are aligned on an unexpected NNW SSE trend inside the CutucĂş Cordillera. We interpret these two orientations of the Macas swarm as linked to Subandean basement thrusts inherited from the inversion tectonics of a NNE SSW trending Triassic Jurassic rift, which has been uplifted and partly extruded in the CutucĂş Cordillera. The present partitioning of this part of the Subandean deformation is controlled by pre-existing NNE SSW to NNW SSE Triassic Jurassic normal faults that have been subsequently compressed transpressed and reactivated into reverse faults. Major boundary faults of the rift were NNE SSW oriented and correspond now to some main Subandean thrusts as confirms the focal mechanism of the 1995 main shock located on the eastern border (Morona frontal thrust) and the orientation of its aftershocks. In the CutucĂş Cordillera, the double orientation of present swarm can be interpreted as the result of accommodation of deformation along NNW SSE pre-existing faults inside the inverted rift system, linked to the motion of the Morona frontal NNE SSW thrust
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
Dome C site testing: surface layer, free atmosphere seeing and isoplanatic angle statistics
This paper analyses 3.5 years of site testing data obtained at Dome C,
Antarctica, based on measurements obtained with three DIMMs located at three
different elevations. Basic statistics of the seeing and the isoplanatic angle
are given, as well as the characteristic time of temporal fluctuations of these
two parameters, which we found to around 30 minutes at 8 m. The 3 DIMMs are
exploited as a profiler of the surface layer, and provide a robust estimation
of its statistical properties. It appears to have a very sharp upper limit
(less than 1 m). The fraction of time spent by each telescope above the top of
the surface layer permits us to deduce a median height of between 23 m and 27
m. The comparison of the different data sets led us to infer the statistical
properties of the free atmosphere seeing, with a median value of 0.36 arcsec.
The C_n^2 profile inside the surface layer is also deduced from the seeing data
obtained during the fraction of time spent by the 3 telescopes inside this
turbulence. Statistically, the surface layer, except during the 3-month summer
season, contributes to 95 percent of the total turbulence from the surface
level, thus confirming the exceptional quality of the site above it
Studying the vertical extent of the ground layer turbulence using sonic-anemometers
The optical turbulence above Dome C in winter is mainly concentrated in the first tens of meters above the ground. The properties of this so-called surface layer were investigated during the last two winterover by a set of sonics anemometers placed on a 45 m high tower. These anemometers provide measurements of the temperature and the wind speed vector. The sampling rate of 10 Hz allows to derivate the refractive index structure constant C_n^2. We report here the first analysis of these data
Photometric quality of Dome C for the winter 2008 from ASTEP South
ASTEP South is an Antarctic Search for Transiting Exo- Planets in the South
pole field, from the Concordia station, Dome C, Antarctica. The instrument
consists of a thermalized 10 cm refractor observing a fixed 3.88\degree x
3.88\degree field of view to perform photometry of several thousand stars at
visible wavelengths (700-900 nm). The first winter campaign in 2008 led to the
retrieval of nearly 1600 hours of data. We derive the fraction of photometric
nights by measuring the number of detectable stars in the field. The method is
sensitive to the presence of small cirrus clouds which are invisible to the
naked eye. The fraction of night-time for which at least 50% of the stars are
detected is 74% from June to September 2008. Most of the lost time (18.5% out
of 26%) is due to periods of bad weather conditions lasting for a few days
("white outs"). Extended periods of clear weather exist. For example, between
July 10 and August 10, 2008, the total fraction of time (day+night) for which
photometric observations were possible was 60%. This confirms the very high
quality of Dome C for nearly continuous photometric observations during the
Antarctic winter
Theoretical study and experimental result of the RF coupler prototypes of Spiral2
JACoW web site THPCH160International audienceSpiral2 is a 40 MeV-5mA deuterons and a 14.5 MeV/u-1mA heavy ions superconducting linac under construction at GANIL. The RF couplers have to provide 12 kW CW power to the cavities at 88 MHz for an accelerating field of 6.5 MV/m. Two solutions corresponding to two different technologies have been designed and two prototypes have been built. We present the technical proposals ans issues as well as the results (manufacturing, test at low and high power, multipacting...) leading to the final choice
Design and construction of a Cherenkov imager for charge measurement of nuclear cosmic rays
A proximity focusing Cherenkov imager called CHERCAM, has been built for the
charge measurement of nuclear cosmic rays with the CREAM instrument. It
consists of a silica aerogel radiator plane across from a detector plane
equipped with 1,600 1" diameter photomultipliers. The two planes are separated
by a ring expansion gap. The Cherenkov light yield is proportional to the
charge squared of the incident particle. The expected relative light collection
accuracy is in the few percents range. It leads to an expected single element
separation over the range of nuclear charge Z of main interest 1 < Z < 26.
CHERCAM is designed to fly with the CREAM balloon experiment. The design of the
instrument and the implemented technical solutions allowing its safe operation
in high altitude conditions (radiations, low pressure, cold) are presented.Comment: 24 pages, 19 figure
The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica
The ASTEP (Antarctica Search for Transiting ExoPlanets) program was
originally aimed at probing the quality of the Dome C, Antarctica for the
discovery and characterization of exoplanets by photometry. In the first year
of operation of the 40 cm ASTEP 400 telescope (austral winter 2010), we
targeted the known transiting planet WASP-19b in order to try to detect its
secondary transits in the visible. This is made possible by the excellent
sub-millimagnitude precision of the binned data. The WASP-19 system was
observed during 24 nights in May 2010. The photometric variability level due to
starspots is about 1.8% (peak-to-peak), in line with the SuperWASP data from
2007 (1.4%) and larger than in 2008 (0.07%). We find a rotation period of
WASP-19 of 10.7 +/- 0.5 days, in agreement with the SuperWASP determination of
10.5 +/- 0.2 days. Theoretical models show that this can only be explained if
tidal dissipation in the star is weak, i.e. the tidal dissipation factor Q'star
> 3.10^7. Separately, we find evidence for a secondary eclipse of depth 390 +/-
190 ppm with a 2.0 sigma significance, a phase consistent with a circular orbit
and a 3% false positive probability. Given the wavelength range of the
observations (420 to 950 nm), the secondary transit depth translates into a day
side brightness temperature of 2690(-220/+150) K, in line with measurements in
the z' and K bands. The day side emission observed in the visible could be due
either to thermal emission of an extremely hot day side with very little
redistribution of heat to the night side, or to direct reflection of stellar
light with a maximum geometrical albedo Ag=0.27 +/- 0.13. We also report a
low-frequency oscillation well in phase at the planet orbital period, but with
a lower-limit amplitude that could not be attributed to the planet phase alone,
and possibly contaminated with residual lightcurve trends.Comment: Accepted for publication in Astronomy and Astrophysics, 13 pages, 13
figure
- …