155 research outputs found

    Assessment of partial discharge activity and conductivity in IGBT modules as a reliability index

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    Al giorno d’oggi l’elettronica di potenza deve essere in grado di operare in ambienti ostili e in condizioni di lavoro difficili. Il tema dell’affidabilità è diventato fondamentale quanto quello dell’efficienza. Questa tesi si focalizza sull’IGBT, in particolare sul suo sistema d’isolamento. Il primo passo è stato studiare in dettaglio i meccanismi di guasto possibili e più frequenti. Dal momento che le scariche parziali risultano essere un problema per l’affidabilità dei dielettrici solidi, in questo studio si esamina l’attività di PD su moduli IGBT nuovi ed invecchiati, in diverse configurazioni, con forme d’onda di tensione e temperature differenti. Si sono effettuate anche misure di corrente di dispersione su moduli nuovi ed invecchiati alla temperatura di lavoro. I risultati sono stati post-processati statisticamente tentando di ottenere indici di affidabilità per quei moduli. Quasi tutti i moduli invecchiati sono interessati da PD e i risultati mostrano che il PDIV, assieme ad altri fattori, è sicuramente influenzato dall’ageing. I risultati del monitoraggio della corrente di dispersione mostrano una tendenza all'aumento con l'invecchiamento. Si sono svolte anche simulazioni con software agli elementi finiti e rilevazioni ottiche di PD ed entrambe supportano i risultati ottenuti. È necessario effettuare ulteriori indagini su un data set più ampio al fine di migliorare un algoritmo di diagnostica predittiva basato sui valori di PDIV e conducibilità

    NEMO-SN1 Abyssal Cabled Observatory in the Western Ionian Sea

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    The NEutrinoMediterranean Observatory—Submarine Network 1 (NEMO-SN1) seafloor observatory is located in the central Mediterranean Sea, Western Ionian Sea, off Eastern Sicily (Southern Italy) at 2100-m water depth, 25 km from the harbor of the city of Catania. It is a prototype of a cabled deep-sea multiparameter observatory and the first one operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of the European Multidisciplinary Seafloor Observatory (EMSO), one of the incoming European large-scale research infrastructures included in the Roadmap of the European Strategy Forum on Research Infrastructures (ESFRI) since 2006. EMSO will specifically address long-term monitoring of environmental processes related to marine ecosystems, marine mammals, climate change, and geohazards

    Study of cosmogenic activation above ground for the DarkSide-20k experiment

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    The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating / background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods

    Search for dark matter-nucleon interactions via Migdal effect with DarkSide-50

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    Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c2^2 mass dark matter. We present new constraints for sub-GeV/c2^2 dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12306 ±\pm 184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c2^2. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below 3.63.6 GeV/c2^2.Comment: 7 pages, 3 figure

    Search for dark matter annual modulation with DarkSide-50

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    Dark matter induced event rate in an Earth-based detector is predicted to show an annual modulation as a result of the Earth's orbital motion around the Sun. We searched for this modulation signature using the ionization signal of the DarkSide-50 liquid argon time projection chamber. No significant signature compatible with dark matter is observed in the electron recoil equivalent energy range above 40 eVee40~{\rm eV_{ee}}, the lowest threshold ever achieved in such a search.Comment: 8 pages, 4 figure

    Search for dark matter particle interactions with electron final states with DarkSide-50

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    We present a search for dark matter particles with sub-GeV/c2c^2 masses whose interactions have final state electrons using the DarkSide-50 experiment's (12306 ±\pm 184) kg d low-radioactivity liquid argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section σˉe\bar{\sigma}_e, the axioelectric coupling constant gAeg_{Ae}, and the dark photon kinetic mixing parameter κ\kappa. We also set the first dark matter direct-detection constraints on the mixing angle ∣Ue4∣2\left|U_{e4}\right|^2 for keV sterile neutrinos.Comment: 6 pages, 2 figure

    DarkSide-50 532-day dark matter search with low-radioactivity argon

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    FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a (16 660 +/- 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C. L. upper limit on the dark matter-nucleon spin-independent cross section of 1.14 x 10(-44) cm(2) (3.78 x 10(-44) cm(2), 3.43 x 10(-43) cm(2)) for a WIMP mass of 100 GeV/c(2) (1 TeV/c(2), 10 TeV/c(2)).9810117FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2016/09084-0Agências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig

    DarkSide status and prospects

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    Sem informaçãoDarkSide uses a dual-phase Liquid Argon Time Projection Chamber to search for WIMP dark matter. The current detector, DarkSide-50, is running since mid 2015 with a target of 50 kg of Argon from an underground source. Here it is presented the latest results of searches of WIMP-nucleus interactions, with WIMP masses in the GeV-TeV range, and of WIMP-electron interactions, in the sub-GeV mass range. The future of DarkSide with a new generation experiment, involving a global collaboration from all the current Argon based experiments, is presented.422-315Sem informaçãoSem informaçãoSem informaçã

    Constraints on sub-GeV dark-matter-electron scattering from the DarkSide-50 experiment

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    FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOWe present new constraints on sub-GeV dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matterelectron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and 100 MeV/c(2).1211117FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2016/09084-0Agências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig

    Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel

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    Dark matter lighter than 10  GeV/c2 encompasses a promising range of candidates. A conceptual design for a new detector, DarkSide-LowMass, is presented, based on the DarkSide-50 detector and progress toward DarkSide-20k, optimized for a low-threshold electron-counting measurement. Sensitivity to light dark matter is explored for various potential energy thresholds and background rates. These studies show that DarkSide-LowMass can achieve sensitivity to light dark matter down to the solar neutrino fog for GeV-scale masses and significant sensitivity down to 10  MeV/c2 considering the Migdal effect or interactions with electrons. Requirements for optimizing the detector’s sensitivity are explored, as are potential sensitivity gains from modeling and mitigating spurious electron backgrounds that may dominate the signal at the lowest energies
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