Time-resolved spectroscopic diagnostic of laser-induced plasma on germanium targets

The following article appeared in Journal of Applied Physics 109.10 (2011): 103304 and may be found at http://scitation.aip.org/content/aip/journal/jap/109/10/10.1063/1.3590159Time-resolved optical emission measurements have been made in laser-induced plasma plumes following CO2 pulsed-laser (10.591 µm, 64 ns and intensity from 0.27 to 4.9 GW cm-2) irradiation of germanium targets. The temporal behavior of Ge atoms and ionized excited species Ge3+, Ge2+, and Ge+ is reported. The results show a faster decay of the continuum emission and Ge3+, Ge2+ ionic species than in the case of Ge and neutral Ge atoms. The velocity distributions for Ge3+, Ge2+, Ge, and Ge species are obtained from time-of-flight measurements. Electron density in the laser-induced plasma was estimated from the analysis of spectral data at various times from the CO2 laser pulse incidence. From the intensity decay with the delay time for Ge, Ge2+, and Ge3+, we estimated the three-body electron-ion recombination rate constants for these species.We gratefully acknowledge the support received in part by the DGICYT (Spain) Projects: MEC: CTQ2008-05393/ BQU and MEC: CTQ2010-15680/BQU for this research

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

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

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

Precision measurement of the electron energy-loss function in tritium and deuterium gas for the KATRIN experiment

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 KATRIN experiment is designed for a direct and model-independent determination of the effective electron anti-neutrino mass via a high-precision measurement of the tritium β-decay endpoint region with a sensitivity on mν of 0.2 eV /c 2 (90% CL). For this purpose, the β-electrons from a high-luminosity windowless gaseous tritium source traversing an electrostatic retarding spectrometer are counted to obtain an integral spectrum around the endpoint energy of 18.6 keV. A dominant systematic effect of the response of the experimental setup is the energy loss of β -electrons from elastic and inelastic scattering off tritium molecules within the source. We determined the energy-loss function in-situ with a pulsed angular-selective and monoenergetic photoelectron source at various tritium-source densities. The data was recorded in integral and differential modes; the latter was achieved by using a novel time-of-flight technique. We developed a semi-empirical parametrization for the energy-loss function for the scattering of 18.6-keV electrons from hydrogen isotopologs. This model was fit to measurement data with a 95% T 2 gas mixture at 30 K, as used in the first KATRIN neutrino-mass analyses, as well as a D 2 gas mixture of 96% purity used in KATRIN commissioning runs. The achieved precision on the energy-loss function has abated the corresponding uncertainty of σ(mν2) < 10-2eV2 [1] in the KATRIN neutrino-mass measurement to a subdominant leve

Improved eV-scale sterile-neutrino constraints from the second KATRIN measurement campaign

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 UAMWe present the results of the light sterile neutrino search from the second Karlsruhe Tritium Neutrino (KATRIN) measurement campaign in 2019. Approaching nominal activity, 3.76 × 106 tritium β-electrons are analyzed in an energy window extending down to 40 eV below the tritium end point at E0 = 18.57 keV. We consider the 3ν + 1 framework with three active and one sterile neutrino flavors. The analysis is sensitive to a fourth mass eigenstate m42 ≲ 1600 eV2 and active-to-sterile mixing |Ue4|2 ≳ 6 × 10-3. As no sterile-neutrino signal was observed, we provide improved exclusion contours on m42 and |Ue4|2 at 95% C.L. Our results supersede the limits from the Mainz and Troitsk experiments. Furthermore, we are able to exclude the large Δm412 solutions of the reactor antineutrino and gallium anomalies to a great extent. The latter has recently been reaffirmed by the BEST Collaboration and could be explained by a sterile neutrino with large mixing. While the remaining solutions at small Δm412 are mostly excluded by short-baseline reactor experiments, KATRIN is the only ongoing laboratory experiment to be sensitive to relevant solutions at large Δm412 through a robust spectral shape analysi

Digital skills, ICTs and students’ needs: a case study in social work degree, University of Zaragoza (Aragón-Spain)

Technological innovations are related to information and communication technologies (ICTs), which in turn have become a fundamental pillar in the field of education. Social work professionals require new approaches to take on the new type of work demanded by the digital society, specializing in research into the innovation of these new forms of action through technology. This article analyses whether university training is in tune with the new skills and abilities required for professional interventions in the twenty-first century. A total of 288 surveys were carried out on 309 students. Each survey consisted of 25 questions on the five digital skills areas. The results indicate that training in digital skills must gain space in university training plans, just as the pandemic became a starting point for the massive use of ICTs. The conclusions point to the importance of improving training in digital competences and skills for future generations of social workers, who, although they are digital natives, will need to know how to use ICTs in their social work

New constraint on the local relic neutrino background overdensity with the first KATRIN data runs

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 UAMWe report on the direct search for cosmic relic neutrinos using data acquired during the first two science campaigns of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity molecular tritium gas source are analyzed by a high-resolution MAC-E filter around the end point at 18.57 keV. The analysis is sensitive to a local relic neutrino overdensity ratio of η < 9.7 × 1010/α (1.1 × 1011/α) at a 90% (95%) confidence level with α = 1 (0.5) for Majorana (Dirac) neutrinos. A fit of the integrated electron spectrum over a narrow interval around the end point accounting for relic neutrino captures in the tritium source reveals no significant overdensity. This work improves the results obtained by the previous neutrino mass experiments at Los Alamos and Troitsk. We furthermore update the projected final sensitivity of the KATRIN experiment to η < 1 × 1010/α at 90% confidence level, by relying on updated operational condition