1,721,008 research outputs found
Analysis of the application of the shadow cone technique for the determination of neutron spectrum with Bonner sphere spectrometer
No full textIn this study, shadow cones were examined with Bonner sphere spectrometer (BSS) for the measurement of neutron spectrum of an 241Am-Be source. Our BSS consists of a set of nine polyethylene spheres with a centeral 6LiI(Eu) scintillator sensitive to thermal neutron. The energy response matrix of the BSS was determined by Monte Carlo simulations for the neutron energies from 10-8 to 100 MeV. A crucial problem in neutron measurements is determining the contribution of scattered neutrons coming from the structures and materials surrounding a source. Two shadow cones were manufactured and positioned between the source and the detector. Experiments were performed to select the optimal source to shadow-cone distance. An unfolding code was used to obtain neutron spectra. The difference between the unfolded spectra obtained by using the shadow cones and the ISO reference spectra was considered as a parameter to select the optimum condition for the shadow cone technique application. The unfolded spectra obtained with the shadow-cone technique showed a satisfactory agreement with the ISO 8529-1241Am–Be neutron spectrum
L'intervento della banca per lo sviluppo dell'impresa e il principio della sussidiarietà
No full textIl contrbuto sottolinea la particolare attitudine della banca, in date condizioni, a sostenere l'efficiente allocazione delle risorse e lo sviluppo delle imprese, soffermandosi sui principi della sissidiarietà con riferimento allo svolgimento della funzione finanziaria in realtà produttive caratterizzate dalla presenza di imprese di ridotte dimensioni
Localizzazione e valutazione dell’attività di una sorgente gamma incognita all’interno di un automezzo carico di rifiuti solidi urbani
No full textA new active method for continuous radon measurements based on a multiple cell proportional counter
No full textA new active method for continuous airborne radon activity concentration measurements is developed. It is based upon the use of a specially designed radon Multiple Cell Proportional Counter (MCPC). The constructed MCPC prototype is described and its operation principle presented. This gas-flow counter is a pile-up of 20 adjacent multiwire proportional counters. It uses argon–propane (1%) as the main counting gas mixture to which an appropriate fraction of ambient air is admixed. The airborne radon activity concentration is to be continuously measured through a periodic integral counting of the a particles emitted by 222Rn and its short-lived decay products within the sensitive volume. A Monte Carlo simulation program, taking into account the major physical processes that determine directly the detector performances, has been written and used for design optimization purposes. The simulation results show that the admixture of 10% of ambient air seems to be sufficient to continuously assess radon activity concentration levels ranging from about 15 Bqm3 up to 2.6105kBqm3 for an integral counting time period of 10 min. The expected radon sensitivity is about 1.16 cpm/10 Bqm3 with a radon counting efficiency of about 180%. The detector a-pulse height spectra obtained by simulation show a very good agreement with those delivered by the constructed MCPC prototype in its minimal configuration
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