arXiv subjects

J. A. García

Publications and source records attributed to J. A. García.

77 records · Page 5Linked to original sources

arXiv2011

New developments in Micromegas Microbulk detectors

A new Micromegas manufacturing technique, based on kapton etching technology, has been recently developed, improving the uniformity and stability of this kind of readouts. Excellent energy resolutions have been obtained, reaching 11% FWHM for the 5.9 keV photon peak of 55Fe source and 1.8% FWHM for the 5.5 MeV alpha peak of the 241Am source. The new detector has other advantages like its flexible structure, low material and high radio-purity. The two actual approaches of this technique will be described and the features of these readouts in argon-isobutane mixtures will be presented. Moreover, the low material present in the amplification gap makes these detectors approximate the Rose and Korff model for the avalanche amplification, which will be discussed for the same type of mixtures. Finally, we will present several applications of the microbulk technique.

physics.ins-det↗

arXiv2011

The discrimination capabilities of Micromegas detectors at low energy

The latest generation of Micromegas detectors show a good energy resolution, spatial resolution and low threshold, which make them idoneous in low energy applications. Two micromegas detectors have been built for dark matter experiments: CAST, which uses a dipole magnet to convert axion into detectable x-ray photons, and MIMAC, which aims to reconstruct the tracks of low energy nuclear recoils in a mixture of CF4 and CHF3. These readouts have been respectively built with the microbulk and bulk techniques, which show different gain, electron transmission and energy resolutions. The detectors and the operation conditions will be described in detail as well as their discrimination capabilities for low energy photons will be discussed.

physics.ins-det↗

arXiv2011

Status of R&D on Micromegas for Rare Event Searches: The T-REX project

The T-REX project aims at developing novel readout techniques for Time Projection Chambers in experiments searching for rare events. The enhanced performance of the latest Micromegas readouts in issues like energy resolution, gain stability, homogeneity, material budget, combined with low background techniques, is opening new windows of opportunity for their application in this field. Here we review the latest results regarding the use and prospects of Micromegas readouts in axion physics (CAST and the future helioscope), as well as the R&D carried out within NEXT, to search for the neutrinoless double-beta decay.

physics.ins-det↗

arXiv2010

Micromegas readouts for double beta decay searches

Double beta $ββ$ decay experiments are one of the most active research topics in Neutrino Physics. The measurement of the neutrinoless mode $0νββ$ could give unique information on the neutrino mass scale and nature. The current generation of experiments aims at detector target masses at the 100 kg scale, while the next generation will need to go to the ton scale in order to completely explore the inverse hierarchy models of neutrino mass. Very good energy resolutions and ultra-low background levels are the two main experimental requirements for a successful experiment. The topological information of the $ββ$ events offered by gaseous detectors like gas Time Projection Chambers (TPC) could provide a very powerful tool of signal identification and background rejection. However only recent advances in TPC readouts may assure the competitiveness of a high pressure gas TPCs for $ββ$ searches, especially regarding the required energy resolution. In this paper we present first results on energy resolution with state-of-the-art microbulk Micromesh Gas Amplification Structure (Micromegas) using a 5.5 MeV alpha source in high pressure pure xenon. Resolutions down to 2 % FWHM have been achieved for pressures up to 5 bar. These results, together with their recently measured radiopurity , prove that Micromegas readouts are not only a viable option but a very competitive one for $ββ$ searches.

physics.ins-det↗

arXiv2007

A Catalogue of Be Stars in the Direction of the Galactic Bulge

Detailed studies of Be stars in environments with different metallicities like the Magellanic Clouds or the Galactic bulge are necessary to understand the formation and evolution mechanisms of the circumstellar disks. However, a detailed study of Be stars in the direction of the bulge of our own galaxy has not been performed until now. We report the first systematic search for Be star candidates in the direction of the Galactic Bulge. We present the catalogue, give a brief description of the stellar variability seen, and show some light curve examples. We searched for stars matching specific criteria of magnitude, color and variability in the I band. Our search was conducted on the 48 OGLE II fields of the Galactic Bulge.This search has resulted in 29053 Be star candidates, 198 of them showing periodic light variations. Nearly 1500 stars in this final sample are almost certainly Be stars, providing an ideal sample for spectroscopic multiobject follow-up studies.

astro-ph↗