186 research outputs found
Contenido polínico de la familia Pinaceae en la atmósfera de Córdoba, España
XV lnternational A.P.L.E. Symposium of Palynolog
La Educación Superior en el Siglo XXI. Nuevas características profesionales y científicas
UMET Press is an imprint of the Universidad Metropolitana (SUAGM).Postprin
Radiopurity of Micromegas readout planes
Micromesh Gas Amplification Structures (Micromegas) are being used in an
increasing number of Particle Physics applications since their conception
fourteen years ago. More recently, they are being used or considered as readout
of Time Projection Chambers (TPCs) in the field of Rare Event searches (dealing
with dark matter, axions or double beta decay). In these experiments, the
radiopurity of the detector components and surrounding materials is measured
and finely controlled in order to keep the experimental background as low as
possible. In the present paper, the first measurement of the radiopurity of
Micromegas planes obtained by high purity germanium spectrometry in the low
background facilities of the Canfranc Underground Laboratory (LSC) is
presented. The obtained results prove that Micromegas readouts of the microbulk
type are currently manufactured with radiopurity levels below 30 microBq/cm2
for Th and U chains and ~60 microBq/cm2 for 40K, already comparable to the
cleanest detector components of the most stringent low background experiments
at present. Taking into account that the studied readouts were manufactured
without any specific control of the radiopurity, it should be possible to
improve these levels after dedicated development.Comment: 15 pages, 2 figure
Gaseous time projection chambers for rare event detection: Results from the T-REX project. II. Dark matter
As part of the T-REX project, a number of R&D and prototyping activities have
been carried out during the last years to explore the applicability of
Micromegas-read gaseous TPCs in rare event searches like double beta decay
(DBD), axion research and low-mass WIMP searches. While in the companion paper
we focus on DBD, in this paper we focus on the results regarding the search for
dark matter candidates, both axions and WIMPs. Small ultra-low background
Micromegas detectors are used to image the x-ray signal expected in axion
helioscopes like CAST at CERN. Background levels as low as
c keVcms have already been achieved in CAST while values
down to c keVcms have been obtained in a
test bench placed underground in the Laboratorio Subterr\'aneo de Canfranc.
Prospects to consolidate and further reduce these values down to
c keVcmswill be described. Such detectors, placed at the
focal point of x-ray telescopes in the future IAXO experiment, would allow for
10 better signal-to-noise ratio than CAST, and search for solar axions with
down to few 10 GeV, well into unexplored axion
parameter space. In addition, a scaled-up version of these TPCs, properly
shielded and placed underground, can be competitive in the search for low-mass
WIMPs. The TREX-DM prototype, with 0.300 kg of Ar at 10 bar, or
alternatively 0.160 kg of Ne at 10 bar, and energy threshold well below 1
keV, has been built to test this concept. We will describe the main technical
solutions developed, as well as the results from the commissioning phase on
surface. The anticipated sensitivity of this technique might reach
cm for low mass ( GeV) WIMPs, well beyond current
experimental limits in this mass range.Comment: Published in JCAP. New version with erratum incorporated (new figure
14
CAST microbulk micromegas in the Canfranc Underground Laboratory
During the last taking data campaigns of the CAST experiment, the micromegas
detectors have achieved background levels of keVcms between 2 and 9 keV. This performance has
been possible thanks to the introduction of the microbulk technology, the
implementation of a shielding and the development of discrimination algorithms.
It has motivated new studies towards a deeper understanding of CAST detectors
background. One of the working lines includes the construction of a replica of
the set-up used in CAST by micromegas detectors and its installation in the
Canfranc Underground Laboratory. Thanks to the comparison between the
performance of the detectors underground and at surface, shielding upgrades,
etc, different contributions to the detectors background have been evaluated.
In particular, an upper limit keVcms
for the intrinsic background of the detector has been obtained. This work means
a first evaluation of the potential of the newest micromegas technology in an
underground laboratory, the most suitable environment for Rare Event Searches.Comment: 6 pages, 8 figures. To appear in the proceedings of the 2nd
International Conference on Technology and Instrumentation for Particle
Physics (TIPP 2011
Problemas en educación superior en el estado de Veracruz al aplicar programación lineal
In operational research, the linear programming technique applies various methods to solve mathematical programming models, it relies on matrix algebra to arrive at the solution of the problem, however, a problem that arises during the optimization process is the need to work with rational numbers, which causes that the ignorance to carry out the operations and the inadequate handling of the calculating machines causes that the solution of the problem in question is wrong. This problem impacts on the learning of the operations or related research subject, taught in the educational programs of the Technological Institutes of the State of Veracruz.En investigación operativa, la técnica de programación lineal aplica diversos métodos para resolver modelos de programación matemática, se basa en álgebra matricial para llegar a la solución del problema, sin embargo, un problema que se presenta durante el proceso de optimización es la necesidad de trabajar con números racionales, lo que ocasiona que el desconocimiento para realizar las operaciones y el manejo inadecuado de las maquinas calculadoras provoque que la solución del problema en cuestión sea errónea. Este problema impacta en el aprendizaje de la asignatura de investigación de operaciones o afines, impartidas en los programas educativos de los Institutos Tecnológicos del Estado de Veracruz
X-ray detection with Micromegas with background levels below 10 keVcms
Micromegas detectors are an optimum technological choice for the detection of
low energy x-rays. The low background techniques applied to these detectors
yielded remarkable background reductions over the years, being the CAST
experiment beneficiary of these developments. In this document we report on the
latest upgrades towards further background reductions and better understanding
of the detectors' response. The upgrades encompass the readout electronics, a
new detector design and the implementation of a more efficient cosmic muon veto
system. Background levels below 10keVcms have been
obtained at sea level for the first time, demonstrating the feasibility of the
expectations posed by IAXO, the next generation axion helioscope. Some results
obtained with a set of measurements conducted in the x-ray beam of the CAST
Detector Laboratory will be also presented and discussed
Performance of micromegas detectors in the CAST Experiment
CERN Axion Solar Telescope (CAST) experiment is searching for axions coming from the Sun. Inside transverse magnetic fields, axions can be converted into X-rays, which can be detected by X-ray detectors. The expected energy of the signal in CAST is in the 1-10 keV range. Low noise and low background detectors are necessary to increase the sensitivity of the experiment. Micro Mesh Gaseous Structure (micromegas) detectors have been used in CAST since the beginning, providing good energy and spatial resolution for CAST's needs. CAST has been intensely studying micromegas detectors to develop new technologies. Initially, CAST detectors consisted of a micromegas, a Time Projection Chamber (TPC) and a Charged Couple Device (CCD), however the improvements in micromegas technologies encouraged CAST to replace the TPC with 2 new micromegas detectors. In some periods during CAST run, ultra low background has been observed in one of the micromegas detectors and it is being investigated through simulations and laboratory tests carried out at Canfranc Underground Laboratory. If this low background is indeed not a systematic effect, it can open new possibilities on rare event searches
The Koskobilo (Olazti, Navarre, Northern Iberian Peninsula) paleontological collection: New insights for the Middle and Late Pleistocene in Western Pyrenees
The destroyed site(s) of Koskobilo (Olazti, Navarre, Northern Iberian Peninsula) have yielded unique archaeo-paleontological evidence in the Western Pyrenees region. The quarry uncovered a karstic site with faunal remains in 1940, and fossils were recovered both in situ and from the quarry dump. Ten years later, while the quarry was still working, a new visit to the dump yielded a large lithic assemblage and additional fossil remains with a different taphonomic pattern, which has been interpreted as the remains coming from a different site or zone within the same karst system. Here we re-study the paleontological evidence and provide new dating on a speleothem covering a Stephanorhinus hemitoechus tooth, which has yielded a minimum date of c. 220 ka for part of the assemblage. In total, the fossil assemblage comprises 38 mammal and six avian taxa and three fish remains. The faunal evidence indicates that in 1940 a mix of taxa from both the Middle and Upper Pleistocene were recovered, and it is difficult to assign most of them to a concrete period. However, based on biochronological criteria some of the identified taxa (e.g., Ursus thibetanus, Ursus cf. deningeri, Cuon cf. priscus, Macaca sylvanus, cf. Megaceroides) could be roughly contemporaneous with the dated rhino tooth, which would provide a new window to the Middle Pleistocene of the region, with deposits from MIS 7d and/or older. Despite the difficulties in studying this collection, recovered without stratigraphic context and in a salvage operation, Koskobilo has yielded an important paleontological assemblage which helps to understand the paleoecology of the Middle Pleistocene human occupations in the Western Pyrenees
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