535 research outputs found
GC-MS/MS Analysis of Trace Level Dechlorane Flame Retardants in Food and Feed and Possible Exposure Routes to Humans
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Ultra-trace measurement of Dechloranes to investigate food as a route of human exposure
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The Borexino Thermal Monitoring & Management System and simulations of the fluid-dynamics of the Borexino detector under asymmetrical, changing boundary conditions
No full textA comprehensive monitoring system for the thermal environment inside the Borexino neutrino detector was developed and installed in order to reduce uncertainties in determining temperatures throughout the detector. A complementary thermal management system limits undesirable thermal couplings between the environment and Borexino's active sections. This strategy is bringing improved radioactive background conditions to the region of interest for the physics signal thanks to reduced fluid mixing induced in the liquid scintillator. Although fluid-dynamical equilibrium has not yet been fully reached, and thermal fine-tuning is possible, the system has proven extremely effective at stabilizing the detector's thermal conditions while offering precise insights into its mechanisms of internal thermal transport. Furthermore, a Computational Fluid-Dynamics analysis has been performed, based on the empirical measurements provided by the thermal monitoring system, and providing information into present and future thermal trends. A two-dimensional modeling approach was implemented in order to achieve a proper understanding of the thermal and fluid-dynamics in Borexino. It was optimized for different regions and periods of interest, focusing on the most critical effects that were identified as influencing background concentrations. Literature experimental case studies were reproduced to benchmark the method and settings, and a Borexino-specific benchmark was implemented in order to validate the modeling approach for thermal transport. Finally, fully-convective models were applied to understand general and specific fluid motions impacting the detector's Active Volume
Oxygen contamination in liquid argon: combined effects on ionization electron charge and scintillation light
No full textA dedicated test of the effects of Oxygen contamination in liq. Argon has been performed at the INFN-Gran Sasso Lab. (LNGS, Italy) within the WArP R&D program. Two detectors have been used: the WArP 2.3 It prototype and a small (0.7 It) dedicated detector, coupled with a system for the injection of controlled amts. of gaseous Oxygen. O2 contamination in LAr leads to depletion of both the free electron charge (via attachment process) and the scintillation light (via quenching and absorption mechanisms) available for ionization signal detectio
Marking Animals with Micro-Tags of Chemical Elements for Identification by X-Ray Spectroscopy
No full text This report describes a method of marking living organisms. As an illustration of the method, foreign chemical elements are incorporated into small salmon and the analytical technique of X-ray fluorescence spectroscopy is used to detect and measure minute quantities in the tissues. Mixtures of elements, either in equal or varying concentration, are used to generate a code. Decoding is readily accomplished by irradiating the tagged organisms and monitoring the X-ray fluorescence produced. A large number of unique combinations appear possible using the method as described. Mixtures of chemical elements (atomic numbers 37–69) were suspended in silicone rubber and injected directly into fish tissue. In this manner tags 1 mm2 in area were incorporated in the tissue and decoded by nondestructive analysis. </jats:p
Natural Convection and Transport of Background Contamination in the Borexino Neutrino Detector
No full textThe Borexino detector at Gran Sasso National Laboratories (INFN) has obtained extraordinary achievements for solar neutrino and geoneutrino physics during its lifetime. More recently, Borexino has provided the first experimental evidence of the subdominant CNO solar neutrino flux, thanks to an outstanding low background level obtained by means of intense purification campaigns and a continuous improvement of the detector thermal stabilization over the years. In particular, this impressive thermal steadiness has led to a progressive mitigation of the internal convective currents which are responsible for the continuous background contamination of the detector sensitive inner volume. To this purpose, numerical analyses are essential to better comprehend the detector fluid dynamics, the background behavior, and are also important to propose effective countermeasures to further reduce natural convection inside the detector. In this framework, the present work investigates the flow characteristics of the liquid scintillator by means of computational fluid dynamics analyses. In particular, a full 3D model of the Borexino inner vessel is considered in the simulations, addressing the complex nature of the natural convective currents under consideration both in transient and stationary conditions. The calculated flow pattern has been adopted to predict the transport behavior of 210Po, that is fundamental for the independent constraint of 210Bi, the main background constituent affecting CNO measurement. The convection-diffusion analysis demonstrates the applicability of the adopted methodology showing a good agreement between calculation and experimental data
Fluid-dynamics and transport of 210Po in the scintillator Borexino detector: A numerical analysis
No full textMoving beyond the important contributions to neutrino physics obtained by the Borexino experiment during the last years, research activities are ongoing at INFN Gran Sasso National Laboratories to further improve the detector sensitivity in order to perform an accurate measurement of the subdominant CNO solar neutrino rate. To this purpose, the improvement of the detector fluid-dynamic stability is the key to further reduce the 210Po background, that is continuously being transported inside the measurement fiducial volume by convective currents. In this framework, numerical simulations of the detector fluid-dynamics may help to better comprehend the 210Po behaviour, and also to suggest effective countermeasures, able to minimize the natural convection inside the detector. In the present work, two-dimensional numerical simulations have been performed to improve the current understanding of Borexino thermal and fluid-dynamics. Adopted models have been optimized for different regions and periods of interest, focusing on the most critical aspects that were identified as influencing the polonium background concentrations. In particular, a Borexino-specific benchmark was constructed in order to validate the model temperature predictions. The derived inner vessel surface temperatures are successively used as boundary conditions for a more refined convective model of the inner most part of the detector. Based on the calculated convective currents, the transport behaviour of background 210Po inside the detector active volume was investigated by means of a convection–diffusion model, showing a reasonable good agreement between calculations and experimental data
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