1,503 research outputs found

    An improved method for estimating the neutron background in measurements of neutron capture reactions

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    The relation between the neutron background in neutron capture measurements and the neutron sensitivity related to the experimental setup is examined. It is pointed out that a proper estimate of the neutron background may only be obtained by means of dedicated simulations taking into account the full framework of the neutron-induced reactions and their complete temporal evolution. No other presently available method seems to provide reliable results, in particular under the capture resonances. An improved neutron background estimation technique is proposed, the main improvement regarding the treatment of the neutron sensitivity, taking into account the temporal evolution of the neutron-induced reactions. The technique is complemented by an advanced data analysis procedure based on relativistic kinematics of neutron scattering. The analysis procedure allows for the calculation of the neutron background in capture measurements, without requiring the time-consuming simulations to be adapted to each particular sample. A suggestion is made on how to improve the neutron background estimates if neutron background simulations are not available.Comment: 11 pages, 9 figure

    Analysis of charged particle emission sources and coalescence in E/A = 61 MeV 36^{36}Ar + 27^{27}Al, 112^{112}Sn and 124^{124}Sn collisions

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    Single-particle kinetic energy spectra and two-particle small angle correlations of protons (pp), deuterons (dd) and tritons (tt) have been measured simultaneously in 61A MeV 36^{36}Ar + 27^{27}Al, 112^{112}Sn and 124^{124}Sn collisions. Characteristics of the emission sources have been derived from a ``source identification plot'' (ő≤source\beta_{source}--ECME_{CM} plot), constructed from the single-particle invariant spectra, and compared to the complementary results from two-particle correlation functions. Furthermore, the source identification plot has been used to determine the conditions when the coalescence mechanism can be applied for composite particles. In our data, this is the case only for the Ar + Al reaction, where pp, dd and tt are found to originate from a common source of emission (from the overlap region between target and projectile). In this case, the coalescence model parameter, p~0\tilde{p}_0 -- the radius of the complex particle emission source in momentum space, has been analyzed.Comment: 20 pages, 5 figures, submitted to Nuclear Physics

    The impact of heavy vehicle traffic trends on the overdesign of flexible asphalt pavements

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    Given their environmental impact, the careful design of asphalt pavements is crucial. Previous research has highlighted the influence of several parameters on the outputs of different pavement design methods. In this study, the focus is on heavy vehicle trends, considering both the percentage of heavy vehicles in the average traffic flow and its evolution over time, which is usually included as a growth factor in the design inputs. Since these factors are very often assumed to be based on old estimates, the first aim of this study was to update them by exploring a recent series of continuous data collected on the Italian motorway network and showing how to infer estimates from historical traffic data. Subsequently, the variability of these input factors is introduced in standard pavement design methods to assess their influence on the design process and to quantify the risk of overdesign. While the analysis of historical heavy vehicle traffic data may reveal an overall zero-growth traffic tendency, different scenarios should be considered and assessed in cost-benefit analyses given the not negligible influence of growth factors on pavement thicknesses. This influence is shown here in different simulated design conditions, with different initial traffic volumes, share of heavy vehicles, and resilient moduli

    On the optimal energy of epithermal neutron beams for BNCT

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    The optimal neutron energy for the treatment of deep-seated tumours using boron neutron capture therapy is studied by analysing various figures of merit. In particular, analysis of the therapeutic gain as a function of the neutron energy indicates that, with the currently available 10 B carriers, the most useful neutrons for the treatment of deep-seated tumours, in particular glioblastoma multiforme, are those with an energy of a few keV. Based on the results of the simulations, a method is presented which allows us to evaluate the quality of epithermal neutron beams of known energy spectrum, thus allowing us to compare different neutron-producing reactions and beam-shaping assembly configurations used for accelerator-based neutron sources

    Mechanical and chemical spinodal instabilities in finite quantum systems

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    Self consistent quantum approaches are used to study the instabilities of finite nuclear systems. The frequencies of multipole density fluctuations are determined as a function of dilution and temperature, for several isotopes. The spinodal region of the phase diagrams is determined and it appears that instabilities are reduced by finite size effects. The role of surface and volume instabilities is discussed. It is indicated that the important chemical effects associated with mechanical disruption may lead to isospin fractionation.Comment: 4 pages, 4 figure
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