Submissões Recentes

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    Preliminary results of a Rossi-alpha experiment in the IPEN/MB-01 research reactor

    1997 - SPRIGGS, GREGORY D.; CARNEIRO, ALVARO L. G.; COELHO, PAULO R. P.; DINIZ, RICARDO; FUGA, RINALDO; JEREZ, ROGERIO; ABE, ALFREDO Y.; MIRANDA, ANSELMO F.; SANTOS, ADIMIR dos

    A preliminary set of Rossi-alpha measurements were performed on the IPEN MB-01 research reactor. The intent of the measurements was to determine if the efficiency of the BF{sub 3} detectors placed in the central region of the core was sufficiently high enough to allow an accurate measurement of the effective delayed neutron fraction, {beta}{sub eff}, and the alpha at delayed critical. In addition, a preliminary measurement of the intrinsic source strength was performed to determine the optimum external/intrinsic source strength that would allow the obtainment of sufficient counting statistics in a reasonable length of time without degrading the signal-to-noise ratio.

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    Sedimentation and growth of volcanic aerosols within the Hunga plume

    2025 - SOUZA, GIOVANNI; VERNIER, JEAN PAUL; QUINTÃO, DEMILSON; BIAZON, BRUNO; LOPES, FABIO; RICARDO, JHONATHA; PANDIT, AMIT K.; CHANDRA, RUBEL das; LIU, HONGYU; KNEPP, TRAVIS N. N.; VERNIER, HAZEL; LANDULFO, EDUARDO

    The Hunga eruption was an unprecedented event which influenced stratospheric aerosols. This study analyzes the unique dynamics of aerosol plumes using balloon measurements from the Brazil Volcano campaign in Bauru (22.36° S, 49.03 °W) and the Stratospheric Aerosol and Gas Experiment III/ISS along with theoretical calculations. They revealed consistent trends in particle sedimentation and spreading. Temporal analysis showed that smaller particles (<225 nm) experienced slower sedimentation rates, with a larger influence by the Brewer-Dobson circulation. Larger particles (>400 nm) exhibited faster sedimentation, descending approximately 3 km by the end of 2022. The descent of the plume into the Upper Troposphere and Lower Stratosphere (UTLS) by February-March 2023 is accompanied by an increase of effective radius from 400 nm to 450 nm due to hygroscopic growth from moist convection. These unique observations suggest that Hunga could have impacted cirrus cloud formation by re-entering the UTLS.

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    Recognizing microplastic deposits on sandy beaches by altimetric positioning, Μ-Raman spectroscopy, and multivariate statistical models

    2024 - FERREIRA, ANDERSON S.; WETTER, NIKLAUS U.; RIBEIRO, MARIA C. H.; ESTEVES, LUCIANA S.; DIAS, ANTÓNIO G.; GROHMANN, CARLOS H.; KUZNETSOVA, MARIA; OLIVEIRA, REGINA C. de; FREITAS, ANDERSON Z. de; SIEGLE, EDUARDO

    This study examines microplastic (MP) pollution along São Paulo State's coast, southeastern Brazil, using geodetic surveys, beach morphometric analyses, sediment collection, µ-RAMAN spectrometry, and multivariate statistical models. The coastline was divided into six compartments (C1 to C6) for sampling. Higher MP concentrations were found in C3 and C2, influenced by industrial and port activities. MP types, including pellets, fragments, and fibers, showed distinct distribution patterns based on their sources and properties. Fragments and foams were most common, constituting 42% and 35% of the 1,026 MPs found. Statistical tests linked MP types to beach morphometric characteristics, with higher elevations correlating with higher MP concentrations, especially pellets and foams. Beaches with intermediate profiles and those facing south accumulated more MPs. The study highlights the complexity of MP dynamics in coastal environments and the need for developing specific monitoring and environmental remediation strategies, supporting Sustainable Development Goal 14 (Life Below Water).

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    Development of a fast simulator for GEM-based neutron detectors

    2022 - SANTOS, RENAN F. dos; MUNHOZ, MARCELO G.; MORALLES, MAURICIO; SERRA FILHO, LUCAS de A.; BREGANT, MARCO; SOUZA, FERNANDO A. de

    Gas Electron Multiplier (GEM)-based detectors using a layer of 10B as a neutron converter is becoming popular for thermal neutron detection. A common strategy to simulate this kind of detector is based on two frameworks: Geant4 and Garfield++. The first one provides the simulation of the nuclear interaction between neutrons and the 10B layer, while the second allows the simulation of the interaction of the reaction products with the detector gas leading to the ionization and excitation of the gas molecules. Given the high ionizing power of these nuclear reaction products, a full simulation is very time consuming and must be optimized to become viable. In this work, we present a strategy to develop a fast simulator based on these two frameworks that will allow us to generate enough data for a proper evaluation of the expected performance and optimization of this kind of detector. We will show the first results obtained with this tool concentrating on its validation and performance.