2,847 research outputs found
Test and characterization of multigap resistive plate chambers for the EEE project
The Extreme Energy Events project is based on the deployment of cosmic-ray telescopes in Italian high schools with the active contribution of students and teachers. Each telescope is made by three Multigap Resistive Plate Chambers
readout by strips. With around 50 telescopes already built and others under construction, specific systems to test and characterize the chambers are needed. In this article I will present a flexible and software-configurable solution to perform chamber efficiency studies with a set of scintillators and hardware to automatically scan detector strips to identify electrical issues. Both systems can provide accurate information but at the same time they can be easily operated by students
The extended halo of NGC 2682 (M 67) from Gaia DR2
Context: NGC 2682 is a nearby open cluster, approximately 3.5 Gyr old.
Dynamically, most open clusters should dissolve on shorter timescales, of ~ 1
Gyr. Having survived until now, NGC 2682 was likely much more massive in the
past, and is bound to have an interesting dynamical history. Aims: We
investigate the spatial distribution of NGC 2682 stars to constrain its
dynamical evolution, especially focusing on the marginally bound stars in the
cluster outskirts. Methods: We use Gaia DR2 data to identify NGC 2682 members
up to a distance of ~150 pc (10 degrees). Two methods (Clusterix and UPMASK)
are applied to this end. We estimate distances to obtain three-dimensional
stellar positions using a Bayesian approach to parallax inversion, with an
appropriate prior for star clusters. We calculate the orbit of NGC 2682 using
the GRAVPOT16 software. Results: The cluster extends up to 200 arcmin (50 pc)
which implies that its size is at least twice as previously believed. This
exceeds the cluster Hill sphere based on the Galactic potential at the distance
of NGC 2682. Conclusions: The extra-tidal stars in NGC 2682 may originate from
external perturbations such as disk shocking or dynamical evaporation from
two-body relaxation. The former origin is plausible given the orbit of NGC
2682, which crossed the Galactic disk ~40 Myr ago.Comment: 9 pages, 5 figures, accepted for publication on A&
Administración digital y teletrabajo
This study addresses the evolution of Spanish regulations on teleworking, from the existing regulations prior to the pandemic to the recent reforms of basic regulations on public employment. Beyond this, it exposes, synthesizes, and critically reflects on the elements of change necessary in said regulations to address a phenomenon that, regardless of specific circumstances experienced throughout those months, should imply a cultural and organizational change in our Public Administrations.El presente estudio aborda la evolución de la normativa española sobre teletrabajo, desde la normativa existente con carácter previo a la pandemia, a las recientes reformas de la normativa básica en materia de empleo público. Más allá de ello, expone, sintetiza, y reflexiona críticamente sobre los elementos de cambio necesarios en dicha normativa para abordar un fenómeno que, con independencia de las concretas circunstancias vividas a lo largo de esos meses, debiera implicar un cambio cultural y organizativo de nuestras Administraciones Públicas
Search for lithium-rich giants in 32 open clusters with high-resolution spectroscopy
Lithium-rich giant stars are rare and their existence challenges our
understanding of stellar structure and evolution. We profit from the
high-quality sample gathered with HARPS and UVES, in order to search for
Li-rich giants and to identify the Li enrichment mechanisms responsible. We
derive stellar parameters for 247 stars belonging to 32 open clusters, with
0.07 Ga < ages < 3.6 Ga. We employed the spectral synthesis technique code
FASMA for the abundance analysis of 228 stars from our sample. We also
determined ages, distances, and extinction using astrometry and photometry from
Gaia and PARSEC isochrones to constrain their evolutionary stage. Our sample
covers a wide range of stellar masses from 1 to more than 6 solar masses where
the majority of the masses are above 2 solar masses. We have found 14 canonical
Li-rich giant stars which have experienced the first dredge-up. This
corresponds to 6% of our total sample, which is higher than what is typically
found for field stars. Apart from the canonical limit, we use the maximum Li
abundance of the progenitor stars as a criterion for Li enrichment. We find Li
enhancement also among eight stars which have passed the first dredge up and
show strong Li lines based on the fact that stars at the same evolutionary
stage in the same cluster have significantly different Li abundances. We
confirm that giants with higher Li abundance correspond to a higher fraction of
fast-rotating giants, suggesting a connection between Li enhancement and
stellar rotation as predicted by stellar models. Our Li-rich giants are found
in various evolutionary stages implying that no unique Li production mechanism
is responsible for Li enrichment but rather different intrinsic or external
mechanisms can be simultaneously at play.Comment: accepted in A&A, online data will be available in CD
Timing performance of a double layer diamond detector
In order to improve the time precision of detectors based on diamonds sensors we have built a detector with two scCVD layers connected in parallel to the same amplifier. This work describes the design and the first measurements of such a prototype performed on a particle beam at CERN. With this different configuration we have obtained an improvement larger than a factor of 1.6-1.7 for the timing precision of the measurement when compared to a one layer scCVD diamond detector.Peer reviewe
Development of FTK architecture: a fast hardware track trigger for the ATLAS detector
The Fast Tracker (FTK) is a proposed upgrade to the ATLAS trigger system that
will operate at full Level-1 output rates and provide high quality tracks
reconstructed over the entire detector by the start of processing in Level-2.
FTK solves the combinatorial challenge inherent to tracking by exploiting the
massive parallelism of Associative Memories (AM) that can compare inner
detector hits to millions of pre-calculated patterns simultaneously. The
tracking problem within matched patterns is further simplified by using
pre-computed linearized fitting constants and leveraging fast DSP's in modern
commercial FPGA's. Overall, FTK is able to compute the helix parameters for all
tracks in an event and apply quality cuts in approximately one millisecond. By
employing a pipelined architecture, FTK is able to continuously operate at
Level-1 rates without deadtime. The system design is defined and studied using
ATLAS full simulation. Reconstruction quality is evaluated for single muon
events with zero pileup, as well as WH events at the LHC design luminosity. FTK
results are compared with the tracking capability of an offline algorithm.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072
The Evolution of FTK, a Real-Time Tracker for Hadron Collider Experiments
We describe the architecture evolution of the highly-parallel dedicated
processor FTK, which is driven by the simulation of LHC events at high
luminosity (1034 cm-2 s-1). FTK is able to provide precise on-line track
reconstruction for future hadronic collider experiments. The processor,
organized in a two-tiered pipelined architecture, execute very fast algorithms
based on the use of a large bank of pre-stored patterns of trajectory points
(first tier) in combination with full resolution track fitting to refine
pattern recognition and to determine off-line quality track parameters. We
describe here how the high luminosity simulation results have produced a new
organization of the hardware inside the FTK processor core.Comment: 11th ICATPP conferenc
Detection of solar-like oscillations in relics of the Milky Way: asteroseismology of K giants in M4 using data from the NASA K2 mission
Asteroseismic constraints on K giants make it possible to infer radii, masses
and ages of tens of thousands of field stars. Tests against independent
estimates of these properties are however scarce, especially in the metal-poor
regime. Here, we report the detection of solar-like oscillations in 8 stars
belonging to the red-giant branch and red-horizontal branch of the globular
cluster M4. The detections were made in photometric observations from the K2
Mission during its Campaign 2. Making use of independent constraints on the
distance, we estimate masses of the 8 stars by utilising different combinations
of seismic and non-seismic inputs. When introducing a correction to the Delta
nu scaling relation as suggested by stellar models, for RGB stars we find
excellent agreement with the expected masses from isochrone fitting, and with a
distance modulus derived using independent methods. The offset with respect to
independent masses is lower, or comparable with, the uncertainties on the
average RGB mass (4-10%, depending on the combination of constraints used). Our
results lend confidence to asteroseismic masses in the metal poor regime. We
note that a larger sample will be needed to allow more stringent tests to be
made of systematic uncertainties in all the observables (both seismic and
non-seismic), and to explore the properties of RHB stars, and of different
populations in the cluster.Comment: 6 pages, 3 figures, accepted for publication in MNRA
Test of Ultra Fast Silicon Detectors for the TOTEM upgrade project
This paper describes the performance of a prototype timing detector, based on 50 mu m thick Ultra Fast Silicon Detector, as measured in a beam test using a 180 GeV/c momentum pion beam. The dependence of the time precision on the pixel capacitance and bias voltage is investigated in this paper. A timing precision from 30 ps to 100 ps (RMS), depending on the pixel capacitance, has been measured at a bias voltage of 180 V.Peer reviewe
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