669 research outputs found

    Estimation of fluence rate and absorbed dose rate due to gas bremsstrahlung from electron storage rings

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    Abstract Bremsstrahlung produced in electron storage rings by interactions with residual gas has been studied in the energy range 100–1000 MeV using the PLUKA code. Photon spectra and quantitative estimates of fluence rate and tissue absorbed dose rate are given. Simple equations are proposed for the fluence rate and the absorbed dose rate according to the results obtained

    Sterile neutrinos: the necessity for a 5 sigma definitive clarification

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    Several different experiments have hinted to the existence of "anomalies" in the neutrino sector, implying the possible presence of additional sterile neutrinos or of other options. A definitive experimental search, capable to clarify either in favour or against all these anomalies at the appropriate > 5 sigma level has been proposed by the ICARUS-NESSIE Collaboration. The technique is based on two innovative concepts, namely (1) a large mass Liquid Argon Time Projection Chamber (LAr-TPC) now in full operation at LNGS and (2) the search for spectral differences in two identical detectors at different distances along the (anti-)neutrino line(s).Comment: 7 pages, 4 figures, 1 tabl

    Monolithic GaAs current-sensitive cryogenic preamplifier for calorimetry applications

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    We have realized low-noise monolithic GaAs preamplifiers using ion- implanted technology , to operate under low temperature and high radiation field conditions. The evaluation of noise, amplitude and timing distributions of a batch taken after first mass-production run is presented. The current-sensitive preamplifier is linear up to 8 mA of input current and able to cope a 2.2 nF detector capacitance, showing fast response ( GBW product ∼ 1.7GHz) and very low series noise. Very good noise performance at LAr temperature is obtained by using large area MESFET ( l · w = 3. 24000μm 2 ) as a head transistor, which exhibits at 8mA standing current and only 10mW power dissipation, intrinsic gain μ = g m · r ds = 15 and noise referred to the input 0.30 ÷ 0.35 H z n ¯ V According to our estimation, second stage noise contribution is negligible. Radiation damage from neutrons and γ-irradiations as well as protection network against HV discharges are discussed

    Precise measurement of the Bragg curve for 800 MeV/u 238^{238}U ions stopping in polyethylene and its implications for calculation of heavy ion ranges

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    Stopping power predictions in radiation transport codes are based on the Bethe-Bloch formula and different corrections. For very heavy ions at relativistic energies the available experimental data are scarce and therefore verification of stopping power predictions is only possible to a limited extent. In this work, a full experimental Bragg curve for 800 MeV/u 238^{238}U ions stopping in polyethylene is presented. The measurements were conducted at the experimental area Cave A at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The 800 MeV/u 238^{238}U beam was provided by the SIS18 heavy ion synchrotron. The Bragg curve was measured with a setup consisting of a binary range shifter and two large area parallel plate ionization chambers. Complementary Monte Carlo simulations using the FLUKA code were performed and compared with the experimental Bragg curve. The mean ionization potential of polyethylene was fine-tuned to match the measured primary ion range with FLUKA simulations. The impact of the Bloch and Mott corrections to the stopping power calculation were studied by switching them off intentionally in separate simulations. A detailed description of the implementation of the stopping power formulae and the Mott correction in FLUKA is provided

    Performances and potential of a productive urban green infrastructure

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    Negli ultimi anni si sta diffondendo anche nelle grandi città Europee, un fenomeno complesso che coinvolge la disciplina dell’architettura: l’agricoltura urbana, ovvero la pratica della coltivazione, di prodotti orticoli “nella città, per la città”. La produzione agricola, trasportata in un contesto urbano, diviene ad oggi una strategia concreta per la riqualificazione delle città grazie a: l’innesco di una rete di attività sociali, ricreative e commerciali, la possibilità di rifunzionalizzazione di spazi privati e pubblici (soprattutto quelli inutilizzati), di creazione di verde condiviso, la possibilità di integrazione con l’ambiente costruito, la valorizzazione di stili di vita sostenibili, l’occasione di educazione e collante sociale, il potenziamento e nuove possibilità all’infrastruttura verde (produttiva). Questo fenomeno necessita dunque di essere studiato per comprenderne e definirne le potenzialità, poiché l’architetto è chiamato a concepire spazi per rispondere a nuove esigenze ed a progettare soluzioni innovative alle diverse scale. Sulla base di tale consapevolezza è stata condotta una ricerca sul tema della riqualificazione della città in chiave sostenibile e sulle nuove tecnologie da mettere in atto finalizzata ad analizzare ed individuare le possibilità dell’agricoltura urbana come strategia innovativa per il potenziamento delle reti verdi nella città, definendo lo spettro di possibilità che questa offre al progettista, e di rimando alla pubblica amministrazione, per una nuova interpretazione della funzione sia dello spazio aperto che del patrimonio costruito
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