907 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
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
A mechanistic protrusive-based model for 3D cell migration
Cell migration is essential for a variety of biological processes, such as embryogenesis, wound healing, and the immune response. After more than a century of research—mainly on flat surfaces—, there are still many unknowns about cell motility. In particular, regarding how cells migrate within 3D matrices, which more accurately replicate in vivo conditions. We present a novel in silico model of 3D mesenchymal cell migration regulated by the chemical and mechanical profile of the surrounding environment. This in silico model considers cell’s adhesive and nuclear phenotypes, the effects of the steric hindrance of the matrix, and cells ability to degradate the ECM. These factors are crucial when investigating the increasing difficulty that migrating cells find to squeeze their nuclei through dense matrices, which may act as physical barriers. Our results agree with previous in vitro observations where fibroblasts cultured in collagen-based hydrogels did not durotax toward regions with higher collagen concentrations. Instead, they exhibited an adurotactic behavior, following a more random trajectory. Overall, cell’s migratory response in 3D domains depends on its phenotype, and the properties of the surrounding environment, that is, 3D cell motion is strongly dependent on the context
A Micromegas-based low-background x-ray detector coupled to a slumped-glass telescope for axion research
We report on the design, construction and operation of a low background x-ray
detection line composed of a shielded Micromegas (micromesh gaseous structure)
detector of the microbulk technique. The detector is made from radiopure
materials and is placed at the focal point of a ~5 cm diameter, 1.3 m
focal-length, cone-approximation Wolter I x-ray telescope (XRT) comprised of
thermally-formed (or "slumped") glass substrates deposited with multilayer
coatings. The system has been conceived as a technological pathfinder for the
future International Axion Observatory (IAXO), as it combines two of the
techniques (optic and detector) proposed in the conceptual design of the
project. It is innovative for two reasons: it is the first time an x-ray optic
has been designed and fabricated specifically for axion research, and the first
time a Micromegas detector has been operated with an x-ray optic. The line has
been installed at one end of the CERN Axion Solar Telescope (CAST) magnet and
is currently looking for solar axions. The combination of the XRT and
Micromegas detector provides the best signal-to-noise ratio obtained so far by
any detection system of the CAST experiment with a background rate of
5.410counts per hour in the energy region-of-interest and
signal spot area.Comment: 21 pages, 16 figure
Lessons from the operation of the "Penning-Fluorescent" TPC and prospects
We have recently reported the development of a new type of high-pressure
Xenon time projection chamber operated with an ultra-low diffusion mixture and
that simultaneously displays Penning effect and fluorescence in the
near-visible region (300 nm). The concept, dubbed `Penning-Fluorescent' TPC,
allows the simultaneous reconstruction of primary charge and scintillation with
high topological and calorimetric fidelity
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