37 research outputs found

    Simple strategy for simulation of large area of axially symmetric metasurfaces

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    Metalenses are composed of nanostructures for focusing light and have been widely explored in many exciting applications. However, their expanding dimensions pose simulation challenges. We propose a method to simulate metalenses in a timely manner using vectorial wave and ray tracing models. We sample the metalens' radial phase gradient and locally approximate it by a linear phase response. Each sampling point is modeled as a binary blazed grating, employing the chosen nanostructure, to build a transfer function set. The metalens transmission or reflection is then obtained by applying the corresponding transfer function to the incoming field on the regions surrounding each sampling point. Fourier optics is used to calculate the scattered fields under arbitrary illumination for the vectorial wave method and a Monte Carlo algorithm is used in the ray tracing formalism. We validated our method against finite difference time domain simulations at 632 nm and we were able to simulate metalenses larger than 3000lambda0 in diameter on a personal computer.Comment: 10 page

    The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

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    The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

    VERITAS observations of galactic compact objects

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    VERITAS consists of an array of four 12 m imaging atmospheric telescopes, designed to observe very high energy (VHE) gamma-ray emission between 100 GeV and 30 TeV. In this thesis, galactic compact objects, observed with the VERITAS telescopes, will be presented. Magnetars are highly magnetized neutron stars. Three magnetars were observed by VERITAS: 4U 0142+61, 1E 2259+586 and SGR 0501+4516. No significant gamma-ray emission was observed during the quiescent phase. These results support the current magnetar models, which do not predict any VHE emission. No data were acquired during outburst activity. Magnetar observations during outburst are now part of the VERITAS burst alert program. It is now known that X-ray binaries can emit in the TeV regime. There is no clear correlations with physical properties that could indicate with certainty which ones are TeV emitters. Data on 15 X-ray binaries were retrieved from VERITAS archival data. No gamma-ray emission was observed from any of the systems. Due to the differences between the systems studied and the three known TeV emitters, no conclusions could be made on the physical properties that might be responsible for TeV emission. The SS 433 system, hosting a black hole (BH), exhibits two powerful jets. TeV emission has been predicted from near the BH and from the regions where the jets hit the surrounding medium. VERITAS acquired ~19 h of data on the system, allowing analyses at the BH and at the region where the western jet interacts with the surrounding medium (w2). No significant gamma-ray emission was observed. From the results at the black hole position, constraints were put on a theoretical model of emission. In the case of the w2 region, an excess, lower than the canonical detection level of 5 sigma, was observed. This excess is not attributed yet to gamma-ray emission; more data are required to confirm or refute the excess as a gamma-ray signal. If the excess is treated as a statistical fluctuation, the uppVERITAS est un r√©seau de quatre t√©lescopes Cherenkov √† imagerie de 12 m, con√ß cu pour l'observation de rayons gamma entre 100 GeV et 30 TeV. Dans cette th√®se, plusieurs objets compacts galactiques, observ√©s par VERITAS, seront pr√©sent√©s. Les magn√©tars sont des √©toiles √† neutron fortement magn√©tiques. Trois magn√©tars ont √©t√© observ√©s par VERITAS: 4U 0142+61, 1E 2259+586 et SGR 0501+4516. Aucune √©mission de rayons gamma n'a √©t√© d√©tect√©e. Ces r√©sultats supportent les mod√®les th√©oriques actuels, qui ne pr√©disent aucune √©mission √† ces √©nergies. Aucune donn√©e n'a √©t√© enregistr√©e pendant un √©pisode de sursaut d'activit√©. L'observation de magn√©tars pendant un sursaut fait maintenant partie du programme d'alerte de sursauts de VERITAS. Il est maintenant connu que les binaires √† rayons X peuvent √©mettre dans le r√©gime des TeV. Il n'y a cependant pas de corr√©lations claires entre les propri√©t√©s physiques de ces objets qui pourraient indiquer avec certitude les propri√©t√©s responsables de l'√©mission √† tr√®s haute √©nergie. Des donn√©es sur 15 binaires √† rayons X ont √©t√© retir√©es des archives de VERITAS. Aucune √©mission gamma n'a √©t√© d√©tect√©e dans ces syt√®mes. Aucune conclusion n'a pu √™tre tir√©e sur les propri√©t√©s physiques qui pourraient √™tre responsables de l'√©mission gamma, due aux trop grandes diff√©rences entre les syst√®mes √©tudi√©s et les trois syst√®mes √©mettant dans les TeV. Le syst√®me SS 433, comprenant un trou noir (TN), pr√©sente deux puissants jets. L'√©mission de rayons gamma a √©t√© pr√©dite pr√®s du TN et dans les r√©gions o√Ļ les jets entrent en contact avec le mat√©riel environnant. VERITAS a obtenu ~19 h de donn√©es sur le syst√®me, permettant l'analyse √† la position du TN et √† l'endroit o√Ļ le jet ouest interagit avec le mat√©riel environnant (w2). Aucune √©mission gamma n'a √©t√© d√©tect√©e √† aucun des endroits. Les r√©sultats √† la position du TN ont permis de mettre des contraintes su

    MicroBooNE and the Future SBN Program

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    <p>The Short-Baseline Neutrino (SBN) Program consists of a suite of three liquid argon neutrino detectors, designed to resolve the previous short-baseline anomalies observed by the LSND and MiniBooNE experiments, and to perform highly needed neutrino cross-section measurements on argon. In addition to reviewing the status of the full program, including the progress on the construction and installation of the near detector (SBND) and the far detector (ICARUS), this talk will focus on recent results from the first SBN detector, the MicroBooNE experiment, which has been recording and analyzing neutrino data since October 2015. The first physics results will be presented.</p

    MicroBooNE and the Future SBN Program

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    The Short-Baseline Neutrino (SBN) Program consists of a suite of three liquid argon neutrino detectors, designed to resolve the previous short-baseline anomalies observed by the LSND and MiniBooNE experiments, and to perform highly needed neutrino cross-section measurements on argon. In addition to reviewing the status of the full program, including the progress on the construction and installation of the near detector (SBND) and the far detector (ICARUS), this talk will focus on recent results from the first SBN detector, the MicroBooNE experiment, which has been recording and analyzing neutrino data since October 2015. The first physics results will be presented

    Convolutional neural networks applied to neutrino events in a liquid argon time projection chamber

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    We present several studies of convolutional neural networks applied to data coming from the MicroBooNE detector, a liquid argon time projection chamber (LArTPC). The algorithms studied include the classification of single particle images, the localization of single particle and neutrino interactions in an image, and the detection of a simulated neutrino event overlaid with cosmic ray backgrounds taken from real detector data. These studies demonstrate the potential of convolutional neural networks for particle identification or event detection on simulated neutrino interactions. We also address technical issues that arise when applying this technique to data from a large LArTPC at or near ground level

    Digital Wire Analyzer of Mechanical Tension, Electrical Continuity, and Isolation

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    A digital instrument that allows the measurement of the mechanical tension of an array of wires of known length and density, and the testing of their electrical continuity and isolation, has been developed. The instrument measures wire tension by measuring the fundamental frequency of the wire. Its working principle is to apply direct high voltages on neighboring wires of a wire under test and sweeping the frequency of an alternating high voltage that is also applied on those neighbors. A resonance is observed in the readout signal of the middle wire when the frequency of the alternating high voltage coincides with its fundamental frequency. The instrument automates the process over 128 wires, with eight read out simultaneously. An accuracy of 1% in the measurement of tension is achieved by this digital wire analyzer (DWA).ISSN:0018-9456ISSN:1557-966

    High efficiency glass-based VUV metasurfaces

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    Most advances in metaoptics have been made at visible wavelengths and above; in contrast, the vacuum ultraviolet (VUV) has barely been explored despite numerous scientific and technological opportunities. Creating metaoptic elements at this short wavelength is challenging due to the scarcity of VUV transparent materials and the small sizes of the required nanostructures. Here, we present the first transmissive VUV (175 nm) metalens. By using UV-grade silica and trading-off the Nyquist requirement for subwavelength structures against feasibility of the fabrication process, we achieve a step-change in diffraction efficiencies for wavelengths shorter than 300 nm. Our large numerical aperture (NA = 0.5) metalens shows an average diffraction efficiency of (53.3 +- 1.4)%. This demonstration opens up new avenues for compact flat optic systems operating in the VUV range
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