1,335 research outputs found
TREX-DM: a low background Micromegas-based TPC for low-mass WIMP detection
Dark Matter experiments are recently focusing their detection techniques in
low-mass WIMPs, which requires the use of light elements and low energy
threshold. In this context, we describe the TREX-DM experiment, a low
background Micromegas-based TPC for low-mass WIMP detection. Its main goal is
the operation of an active detection mass 0.3 kg, with an energy
threshold below 0.4 keVee and fully built with previously selected radiopure
materials. This work describes the commissioning of the actual setup situated
in a laboratory on surface and the updates needed for a possible physics run at
the Canfranc Underground Laboratory (LSC) in 2016. A preliminary background
model of TREX-DM is also presented, based on a Geant4 simulation, the
simulation of the detector's response and two discrimination methods: a
conservative muon/electron and one based on a neutron source. Based on this
background model, TREX-DM could be competitive in the search for low-mass
WIMPs. In particular it could be sensitive, e.g., to the low-mass WIMP
interpretation of the DAMA/LIBRA and other hints in a conservative scenario.Comment: Proceedings of the XIV International Conference on Topics in
Astroparticle and Underground Physics (TAUP 2015), 7-11 September 2015,
Torino, Ital
Classification, characterisation and strategies for improvement of cattle and sheep pasture systems in marginal areas of Southern Chile
Pasture-based livestock systems in farms with medium or low size are especially important in less favored areas and are valuable for society. For these systems to survive, it is necessary to obtain an acceptable level of productivity and ensure commercialization of the products. This study was carried out in the district of Rio Ibáñez, General Carrera Province, in the XI (Aysén) Region of Chile. The sample consisted of 28 small-scale livestock farmers with dual-purpose cattle production; 16 of them also produced sheep for meat. The empirical data produced 55 variables which were subjected to multivariate analysis; three main components were obtained which explain 72.1 % of the variance. By cluster analysis it was obtained four groups with characteristics which varied by farm size, age and personal situation of farmers, farm management and farm profitability. The principal problems found are low productivity in the herds and the poor marketing channels of animals produced. In two groups, due to the low size and poor management, the profitability of the farms is very low and this may compromise their future. To improve production systems, the training and advice of farmers should be strengthened, investment should be supported, especially for young people, and the farmer partnership should be promoted. There is also a need to diversify the families' sources of income (sale of other farm products or handicrafts and touristic activities).Ministerio de EconomÃa de Chile Innova-CORFO Project 11 NTEC 1279
Classification, characterisation and strategies for improvement of cattle and sheep pasture systems in marginal areas of Southern Chile
Pasture-based livestock systems in farms with medium or low size are especially important in less favored areas and are valuable for society. For these systems to survive, it is necessary to obtain an acceptable level of productivity and ensure commercialization of the products. This study was carried out in the district of Rio Ibáñez, General Carrera Province, in the XI (Aysén) Region of Chile. The sample consisted of 28 small-scale livestock farmers with dual-purpose cattle production; 16 of them also produced sheep for meat. The empirical data produced 55 variables which were subjected to multivariate analysis; three main components were obtained which explain 72.1 % of the variance. By cluster analysis it was obtained four groups with characteristics which varied by farm size, age and personal situation of farmers, farm management and farm profitability. The principal problems found are low productivity in the herds and the poor marketing channels of animals produced. In two groups, due to the low size and poor management, the profitability of the farms is very low and this may compromise their future. To improve production systems, the training and advice of farmers should be strengthened, investment should be supported, especially for young people, and the farmer partnership should be promoted. There is also a need to diversify the families' sources of income (sale of other farm products or handicrafts and touristic activities).Ministerio de EconomÃa de Chile Innova-CORFO Project 11 NTEC 1279
TREX-DM: a low background Micromegas-based TPC for low mass WIMP detection
Dark Matter experiments are recently focusing their detection techniques in
low-mass WIMPs, which requires the use of light elements and low energy
threshold. In this context, we present the TREX-DM experiment, a low background
Micromegas-based TPC for low-mass WIMP detection. Its main goal is the
operation of an active detection mass 0.300 kg, with an energy threshold
below 0.4 keVee and fully built with previously selected radiopure materials.
This article describes the actual setup, the first results of the comissioning
in Ar+2\%iCH at 1.2 bar and the future updates for a possible
physics run at the Canfranc Underground Laboratory in 2016. A first background
model is also presented, based on Geant4 simulations and a muon/electron
discrimination method. In a conservative scenario, TREX-DM could be sensitive
to DAMA/LIBRA and other hints of positive WIMPs signals, with some space for
improvement with a neutron/electron discrimination method or the use of other
light gases.Comment: Proceedings of the 7th Symposium on Large TPCs for Low-Energy Rare
Event Detectio
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
Modelling the behaviour of microbulk Micromegas in Xenon/trimethylamine gas
We model the response of a state of the art micro-hole single-stage charge
amplication device (`microbulk' Micromegas) in a gaseous atmosphere consisting
of Xenon/trimethylamine at various concentrations and pressures. The amplifying
structure, made with photo-lithographic techniques similar to those followed in
the fabrication of gas electron multipliers (GEMs), consisted of a 100 um-side
equilateral-triangle pattern with 50 um-diameter holes placed at its vertexes.
Once the primary electrons are guided into the holes by virtue of an optimized
field configuration, avalanches develop along the 50 um-height channels etched
out of the original doubly copper-clad polyimide foil. In order to properly
account for the strong field gradients at the holes' entrance as well as for
the fluctuations of the avalanche process (that ultimately determine the
achievable energy resolution), we abandoned the hydrodynamic framework,
resorting to a purely microscopic description of the electron trajectories as
obtained from elementary cross-sections. We show that achieving a satisfactory
description needs additional assumptions about atom-molecule (Penning) transfer
reactions and charge recombination to be made
The Operational Impacts of Chief Supply Chain Officers in Manufacturing Firms
Many firms have elevated their supply chain management decision-making responsibilities through the creation of ‘Chief Supply Chain Officer’ (CSCO) positions. This is widely attributed to the recognition that superior supply chain operations can generate a competitive advantage. Prior studies have found that firms with CSCOs outperform firms without CSCOs along many financial dimensions. However, these prior efforts did not examine the pathways by which these improvements occur. This study addresses this gap in the literature by investigating whether supply chain characteristics of manufacturing firms differ within firms with CSCOs. To explore this, we investigate the relationship between CSCOs and operational dimensions of supply chain performance using data from the 10-year period between 2008 and 2017. We find that the presence of a CSCO in a firm is associated with shorter cash conversion cycles, lower levels of operational slack, and larger buffers of inventory during periods of high market instability
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