382 research outputs found

    On the influence of the mean-free-path parameter on intranuclear cascade calculations

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    In a recent letter GINOCCHIO and BLANN (2) compared results of intranuclear cascade model (ICM) calculations obtained either with a nucleon mean-free-path (mfp) in nuclear matter corresponding to free 3~-2C scattering cross-sections, or with a four times longer mfp. The latter assumption was reported to give far poorer agreement with the experimental data; and this conclusion was reported as evidence in favour of the use of the shorter mfp values in pre-equilibrium decay models, whose alternate formulations have been lately discussed at some length (2.6). We maintain tha t ICI~[ calculations performed with the free ~ ~ scatter mfp in general do not afford an accurate reproduction of the excitation functions of reactions induced by protons of some tens of MeV, and of the energy integrated spectra of the emitted particles. In fact, published results of ICM calculations have shown a systematic tendency to underestimate the emission of high-energy particles, and to overestimate compound-nucleus production. We made this statement, which agrees with an opinion already expressed by MILLER (D, on the basis of the findings of several works cited in ref. (2). Our belief is further supported by other results of BERTINI et al. (S) (e l . Specifically fig. 4 thereof), and even by the figures reported by the authors of ref. (1). However, in spite of such inadequacies of the ICM calculations, the model seems to retain a good measure of appeal as an intui t ive tool much in use for practical purposes

    The level width of atomic nuclei in the continuum energy region: Comparison with the statistical-model previsions

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    In this paper the theoretical expression of the « coherence energy » which characterizes the Ericson flctuations of an excitation function is derived in the framework of the statistical model. It is given by a weighted average over spins, parity and energy of the widths of the levels of the compound nucleus interested in the reaction. The case of purely statistical reactions and the case in which a nonstatistical effect is present are analised

    Study of the 27 Al(d, α) 25 Mg and 27 Al(d, p) 28 al nuclear reactions at 2 MeV deuteron energy

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    Differential excitation functions and angular distributions from 30° to 150° have been measured for the27Al(d, α)26Mg and27Al(d, p)28Al reactions leading to the ground state and to the first excited states of the residual nuclei25Mg and28Al, in the deuteron energy range (1.4â‰Ș2.3) MeV. The overall energy resolution was 10 keV for the differential excitation functions and 2 0 keV for the angular distributions. Fluctuations occurring in the differential excitation functions as well as in the integrated cross-sections have been analysed on the basis of the statistical theory. In particular, with the use of correlation functions, values of Γ=(40±10)keV and Ξ0≃30° have been deduced for the « coherence » energy and the « coherence » angle, respectively. The theoretical values of Γ and the average values of the integrated cross-sections have been evaluated using a consistent set of parameters. The analysis showed that the predictions of the statistical model agree with the experimental results for the27Al(d, α)25Mg reactions. Both statistical and nonstatistioal effects have been found to contribute to the27Al(d, p)28Al reaction for the proton transitions leading to the low-lying levels of the residual nucleus

    Comprehensive study of the reactions induced by 12C on 103Rh up to 33 MeV/nucleon

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    Abstract Fifty-three excitation functions for the production of radioactive residues in the interaction of 12C with 103Rh have been measured from the Coulomb barrier up to 400 MeV by means of the activation technique. These excitation functions have been analyzed considering complete fusion, incomplete fusion of 8Be and α-particle fragments and, above about 200 MeV, the transfer of either one proton or one neutron from 12C to 103Rh. The emission of pre-equilibrium particles during the thermalization of the excited composite nuclei formed in all these processes and, in the case of 8Be and α incomplete fusion, also the re-emission of α-particles after a mean-field interaction or a few interactions with the target nucleons have been taken into account

    The physics models of FLUKA: status and recent development

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    A description of the intermediate and high energy hadronic interaction models used in the FLUKA code is given. Benchmarking against experimental data is also reported in order to validate the model performances. Finally the most recent developments and perspectives for nucleus-nucleus interactions are described together with some comparisons with experimental data.Comment: talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 10 pages, p

    A Monte Carlo approach to study neutron and fragment emission in heavy-ion reactions

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    Quantum Molecular Dynamics models (QMD) are Monte Carlo approaches targeted at the description of nucleon-ion and ion-ion collisions. We have developed a QMD code, which has been used for the simulation of the fast stage of ion-ion collisions, considering a wide range of system masses and system mass asymmetries. The slow stage of the collisions has been described by statistical methods. The combination of both stages leads to final distributions of particles and fragments, which have been compared to experimental data available in literature. A few results of these comparisons, concerning neutron double-differential production cross-sections for C, Ne and Ar ions impinging on C, Cu and Pb targets at 290 - 400 MeV/A bombarding energies and fragment isotopic distributions from Xe + Al at 790 MeV/A, are shown in this paper.Comment: 12 pages, 3 figures, submitted for publication in Adv. Space Re

    The role of nuclear reactions in Monte Carlo calculations of absorbed and biological effective dose distributions in hadron therapy

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    Monte Carlo codes are rapidly spreading among hadron therapy community due to their sophisticated nuclear/electromagnetic models which allow an improved description of the complex mixed radiation field produced by nuclear reactions in therapeutic irradiation. In this contribution results obtained with the Monte Carlo code FLUKA are presented focusing on the production of secondary fragments in carbon ion interaction with water and on CT-based calculations of absorbed and biological effective dose for typical clinical situations. The results of the simulations are compared with the available experimental data and with the predictions of the GSI analytical treatment planning code TRiP

    Shell closure effects studied via cluster decay in heavy nuclei

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    The effects of shell closure in nuclei via the cluster decay is studied. In this context, we have made use of the Preformed Cluster Model (PCMPCM) of Gupta and collaborators based on the Quantum Mechanical Fragmentation Theory. The key point in the cluster radioactivity is that it involves the interplay of close shell effects of parent and daughter. Small half life for a parent indicates shell stabilized daughter and long half life indicates the stability of the parent against the decay. In the cluster decay of trans lead nuclei observed so far, the end product is doubly magic lead or its neighbors. With this in our mind we have extended the idea of cluster radioactivity. We investigated decay of different nuclei where Zirconium is always taken as a daughter nucleus, which is very well known deformed nucleus. The branching ratio of cluster decay and α\alpha-decay is also studied for various nuclei, leading to magic or almost doubly magic daughter nuclei. The calculated cluster decay half-life are in well agreement with the observed data. First time a possibility of cluster decay in 218U^{218}U nucleus is predicted