Laser-induced breakdown spectroscopy of trisilane using infrared C O2 laser pulses

The plasma produced in trisilane (Si3 H8) at room temperature and pressures ranging from 50 to 103 Pa by laser-induced breakdown (LIB) has been investigated. The ultraviolet-visible-near infrared emission generated by high-power IR C O2 laser pulses in Si3 H8 has been studied by means of optical emission spectroscopy. Optical breakdown threshold intensities in trisilane at 10.591 μm for laser pulse lengths of 100 ns have been measured as a function of gas pressure. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited atomic H and Si and ionic fragments Si+, Si2+, and Si3+. An excitation temperature Texc =5600±300 K was calculated by means of H atomic lines assuming local thermodynamic equilibrium. The physical processes leading to LIB of trisilane in the power density range 0.28 GW cm-2 <J<3.99 GW cm-2 have been analyzed. From our experimental observations we can propose that, although the first electrons must appear via multiphoton ionization, electron cascade is the main mechanism responsible for the breakdown in trisilane. © 2007 American Institute of Physics.This work was partially supported by the Spanish MEC Project No. CTQ2007-60177/BQU. It is a pleasure to acknowledge the excellent technical support of A. Magro. This work is dedicated in memory of Professor Antonio Pardo Martinez.Peer Reviewe

Substrate influence on the ferroelectric properties of PTCa thin films

[ES] Se han estudiado las propiedades ferroeléctricas de láminas delgadas de titanato de plomo modificado con calcio (Pb0.76Ca0.24)TiO3 (PTCa) preparadas vía sol gel mediante cristalizaciones sucesivas sobre tres tipos de substratos: (A) Pt / Ti / SiO2 / Si (100), (B) Ti / Pt / Ti / SiO2 / Si(100) y (C) Pt / TiO2 / SiO2 /Si (100). Los resultados de la caracterización ferroeléctrica muestran valores del coeficiente piroeléctrico espontáneo entorno a » 5 .10-9 C cm-2 K-1. La baja conmutabilidad de las laminas facilita la estabilización del valor del coeficiente piroeléctrico en el tiempo. Un tratamiento térmico posterior de recocido a 650ºC 1 hora produce cambios en las propiedades ferro-piezoeléctricas que se pueden asociar con modificaciones de la textura en las láminas.[EN] The ferroelectric properties of calcium modified lead titanate (Pb0.76Ca0.24)TiO3 (PTCa) thin films prepared by a sol - gel method with successive crystallisations on three different substrates (A) Pt / Ti / SiO2 / Si (100), (B) Ti / Pt / Ti / SiO2 / Si(100) y (C) Pt / TiO2 / SiO2 /Si (100), have been studied. The results of the ferroelectric characterisation show values of the spontaneous pyroelectric coefficient close to » 5 .10-9 C cm-2 K-1. The low switching properties favour the stabilisation in time of the pyroelectric coefficient value. Alatter annealing thermal treatment (650ºC 1h) produces changes in the ferro - piezoelectric properties that can be related with changes in the texture of the films.Este trabajo ha sido realizado mediante la financiación recibida de los proyectos MAT98 - 1068 (CICYT) y BRPR - CT98 - 0777 (BRITE EURAM de la U.E.).Peer reviewe

Optical Breakdown in Gases Induced by High-power IR CO2 Laser Pulses

This chapter reviews some fundamentals of laser-induced breakdown spectroscopy (LIBS) and describes some experimental studies developed in our laboratory on gases such as nitrogen, oxygen and air. LIBS of these gases at different pressures, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), was excited by using a high-power transverse excitation atmospheric (TEA) CO2 laser (¿=9.621 or 10.591 ¿m; tFWHM=64 ns; and different laser power densities). The spectra of the generated plasmas are dominated by emission of strong atomic, ionic species and molecular bands. Excitation temperatures are estimated from the intensities of atomic and ionic lines. Electron number densities are deduced from the Stark broadening of several ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the gas pressure and laser irradiance. Optical breakdown threshold intensities in different gases have been experimentally measured. The physical processes leading to laser-induced breakdown of gases have been analyzed. Plasma characteristics of LIBS in air are examined in detail on the emission lines of N+, O+ and C by using time-resolved optical-emission spectroscopy (OES) technique. The results show a faster decay of continuum and ionic spectral species than of neutral atomic and molecular ones. The velocity and kinetic energy distributions for the different species are obtained from time-of-flight (TOF) OES measurements. Excitation temperatures and electron densities in the laser-induced plasma are estimated from the analysis of spectral data at various times from the laser pulse incidence. Temporal evolution of electron density has been used for the estimation of the three-body recombination rate constant.Peer Reviewe

Temporal evolution of the laser-induced plasma generated by IR CO 2 pulsed laser on carbon targets

Time-resolved optical emission analysis was carried out for the plasma plume, produced by high-power tunable IR CO2 pulsed laser ablation of graphite, at λ=10.591 μm and in a regime of relatively high laser fluences (123-402 J/ cm2). Wavelength-dispersed spectra of the plasma plume, at medium-vacuum conditions (4 Pa) and at 9.0 mm from the target, show ionized species (C+, C2+, C3+, C4+, N2 +, N+, and O+), neutral atoms (C, H, N, and O), and neutral diatomic molecules (C2, CN, OH, CH, and N2). In this work, we focus our attention on the temporal evolution of different atomic/ionic and molecular species over a broad spectral range from 190 to 1000 nm. The results show a faster decay for ionic fragments than for neutral atomic and molecular species. The velocity and kinetic energy distributions for different species were obtained from time-of-flight measurements using time-resolved optical emission spectroscopy. Possible mechanisms for the production of these distributions are discussed. Excitation temperature, electron density, and vibrational temperature in the laser-induced plasma were estimated from the analysis of spectral data at various times from the laser pulse incidence. © 2009 American Institute of Physics.Peer Reviewe

Analysis methods for the first KATRIN neutrino-mass measurement

We report on the dataset, data handling, and detailed analysis techniques of the first neutrino-mass measurement by the Karlsruhe Tritium Neutrino (KATRIN) experiment, which probes the absolute neutrino-mass scale via the β-decay kinematics of molecular tritium. The source is highly pure, cryogenic T2 gas. The β electrons are guided along magnetic field lines toward a high-resolution, integrating spectrometer for energy analysis. A silicon detector counts β electrons above the energy threshold of the spectrometer, so that a scan of the thresholds produces a precise measurement of the high-energy spectral tail. After detailed theoretical studies, simulations, and commissioning measurements, extending from the molecular final-state distribution to inelastic scattering in the source to subtleties of the electromagnetic fields, our independent, blind analyses allow us to set an upper limit of 1.1 eV on the neutrino-mass scale at a 90% confidence level. This first result, based on a few weeks of running at a reduced source intensity and dominated by statistical uncertainty, improves on prior limits by nearly a factor of two. This result establishes an analysis framework for future KATRIN measurements, and provides important input to both particle theory and cosmolog

Suppression of Penning discharges between the KATRIN spectrometers

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMThe KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective electron (anti)-neutrino mass with a sensitivity of 0.2eV/c2 by precisely measuring the endpoint region of the tritium β-decay spectrum. It uses a tandem of electrostatic spectrometers working as magnetic adiabatic collimation combined with an electrostatic (MAC-E) filters. In the space between the pre-spectrometer and the main spectrometer, creating a Penning trap is unavoidable when the superconducting magnet between the two spectrometers, biased at their respective nominal potentials, is energized. The electrons accumulated in this trap can lead to discharges, which create additional background electrons and endanger the spectrometer and detector section downstream. To counteract this problem, “electron catchers” were installed in the beamline inside the magnet bore between the two spectrometers. These catchers can be moved across the magnetic-flux tube and intercept on a sub-ms time scale the stored electrons along their magnetron motion paths. In this paper, we report on the design and the successful commissioning of the electron catchers and present results on their efficiency in reducing the experimental backgroun

Open-Source Application for Water Supply System Management: Implementation in a Water Transmission System in Southern Spain

Sustainable water use has become a critical issue for the future of the planet in face of highly probable climate change. The drinking water supply sector has made significant progress over the last 20 years, although improvements in the management of urban hydraulic infrastructures are still required. The proposed system, Integrated Tool for Water Supply Systems Management (ITWSM), built on three interconnected modules (QGIS database, Epanet hydraulic model, and Google My Maps app), was developed on open-source software. The core of ITWSM allows analyzing the behavior of water supply systems under several operation/failure scenarios. It facilitates decision making supported by the mobile application ITWSM-app. Information flows easily through the different decision levels involved in the management process, keeping updated the georeferenced database after system changes. ITWSM has been implemented in a real public water supply company and applied to manage breakdown repairs in water transmission systems. The use of the proposed methodology reduces the average cost of failure repair by 13.6%, mainly due to the optimal planning of the resources involved

Electrical conduction mechanisms in graphene nanoplatelet/yttria tetragonal zirconia composites

Yttria tetragonal zirconia polycrystalline (3YTZP) ceramic composites with 5, 10 and 20 vol% graphene nanoplatelets (GNPs) were prepared by spark plasma sintering (SPS) and their electrical conductivity as a function of temperature was characterized. The composites exhibit anisotropic microstructures so the electrical conductivity studies were carried out in two directions: perpendicular (σ⊥) and parallel (σ||) to the SPS pressing axis. The composites with 5 and 10 GNP vol% showed high electrical anisotropy, whereas the composite with 20 GNP vol % exhibited nearly isotropic electrical behavior. σ⊥ shows metallic-type behavior in the composites with 10 and 20 vol% GNP revealing that charge transport takes place through defect-free GNPs. For the composite with 5 vol % GNP the observed semiconductor-type behavior was explained by a two dimensional variable range hopping mechanism. σ|| shows metallic-type conductivity in the composite with 20 GNP vol% and positive dσ||/dT slope in the composites with 5 and 10 GNP vol%.Ministerio de Economía y Competitividad de España y Fondos Europeos FEDER - MAT2015-67889-PPremio Mensual Publicación Científica Destacada de la US. Facultad de Físic

First operation of the KATRIN experiment with tritium

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UA

Perceptions, attitudes, and barriers to obesity management in Spain: Results from the spanish cohort of the international ACTION-IO observation study

The prevalence of obesity is rapidly rising in Spain. The Awareness, Care and Treatment in Obesity Management—An International Observation (ACTION-IO) study (NCT03584191) was an international cross-sectional survey conducted to identify the perceptions, attitudes, behaviors, and barriers to obesity management for people with obesity (PwO) and healthcare professionals (HCPs); results from Spain are presented. In Spain, 1500 PwO (body mass index ≥30 kg/m2 based on self-reported height and weight) and 306 HCPs (in direct patient care for ≥2 years) completed the survey. Fewer PwO (59%) than HCPs (93%) agreed that obesity is a chronic disease. Most PwO (80%) assumed complete responsibility for their own weight loss, whilst 19% of HCPs placed the responsibility on PwO. One-fifth of PwO stated they began struggling with weight before age 15. The mean delay in discussing weight for the first time with an HCP was 6 years. Only 24% of HCPs thought their patients were motivated to lose weight, whilst 45% of PwO reported being motivated. Of the 67% of PwO who had discussed their weight with an HCP in the last 5 years, 66% had been formally diagnosed with obesity. Our Spanish dataset reveals discrepancies in the perceptions and attitudes between PwO and HCPs, thus highlighting the need to improve education about obesity and its clinical management