Over the centuries, the Roman Empire enlarge and restrict its borders, as a consequence of many factors, like different emperor’s policies, wars and conquests.In a general view, we can identify them ...and we can consider the Danubian Limes as one of the most important one.This Limes was mostly characterized by the fact that it was corresponded with the path of the Danube river, from Germany till the Black Sea.Those lands, through centuries, were always threaten by the risk of barbarians’ incursions and this is the reason why the Danubian Limes had always been considered as a fragile border.During the sixth century, in the midst Byzantine Era, Justinian the I was the first emperor able to consider the problem of the military protection not even “site by site”. He felt the need of an (absolutely modern) idea of considering the limes as a network of sites, who need each other to guarantee a strong and efficient result.Speaking about the architectonical choices, the system of military camps and fortress starts to change its identity, becoming cities with specific relations.Focusing on the case study of Serbia, the aim of the work is to map the specific location of each archaeological site, trying to use this network as an index of places. The research would like to highlight the important value of those sites as Cultural Heritage, considering the necessity of their preservation and valorization as historical evidence in a new European and common scenario.
Abstract Quantum tunnelling plays a crucial role in heavy-ion fusion reactions at sub-barrier energies, especially in the context of nuclear physics and astrophysics. The nuclear structure of the ...colliding nuclei and nucleon transfer processes represent intrinsic degrees of freedom. They are coupled to the relative ion motion and, in general, increase the probability of tunnelling. The influence of couplings to nucleon transfer channels relatively to inelastic excitations, on heavy-ion fusion cross sections, is one of the still open problems in this field. We present a new analysis of several systems, based on the combined observation of the energy-weighted excitation functions $$E\sigma $$ E σ in relation to their first energy derivatives $$d(E\sigma )/dE$$ d ( E σ ) / d E . The relation between $$d(E\sigma )/dE$$ d ( E σ ) / d E and $$E\sigma $$ E σ removes the basic differences due to the varying Coulomb barrier when comparing different systems. We show that, depending on the nuclear structure and/or the presence of strong transfer channels, this representation reveals characteristic features below the barrier. The possible presence of cross section oscillations makes this analysis less clear for light- or medium-light systems.
One and two proton transfer channels have been measured in 116Sn+60Ni with the magnetic spectrometer PRISMA by making an excitation function at several bombarding energies, from above to well below ...the Coulomb barrier. The total kinetic energy loss distributions show the predominance of quasi-elastic processes in the sub-barrier regime. The data have been compared with calculations performed with the GRAZING program, based on semiclassical formalism, and in the Distorted Wave Born Approximation (DWBA), which provided a good theoretical description of the extracted transfer probabilities for the one proton transfers. The much larger values of the experimental two proton transfers compared with those evaluated within an independent particle transfer mechanism, indicate the presence of strong proton-proton correlations. The results complement the ones of the previously analyzed one- and two-neutron transfers, providing significant new information on the subject compared to past works.
In the present work the fusion cross section of the 12C+24Mg system has been measured down to energies far below the coulomb barrier around 4μb. This system is slightly heavier than those of ...astrophysical interest, like 12C+12C and 16O+16O. The data points highlight the presence of hindrance in 12C+24Mg because the excitation function is over-estimated by standard Coupled-Channels calculations, and a clear maximum of the S factor has been observed. The cross section at hindrance threshold is found to be remarkably large (σ ≈0.75mb). The S-factor maximum is nicely fitted using both an empirical interpolation in the spirit of the adiabatic model, and the hindrance parametrisation. The data far below the barrier may suggest that the coupling strengths gradually decrease and vanish, so that the excitation function seems to be well reproduced by a simple one-dimensional tunnelling through the potential barrier in that energy range. On the other hand, the equally good fit obtained with the hindrance model, indicates that discriminating between the two approaches would require further precise measurements at slightly lower energies.
The energy loss profiles of different ion beams (6Li, 27Al and 50Ti) impinging on CF4, isobutane and P10 have been measured with the active target ACTAR TPC demonstrator. The pressure of the gas, ...monitored during the experiment, has been chosen in order to stop the ions inside the active zone. Starting from the energy loss calculation produced by the SRIM code, the experimental ion tracks have been simulated, taking into account the effect of the thermal diffusion of electrons during their drift towards the pad plane under the effect of a uniform electric field. The uncertainty in the geometry, mainly due to the thickness and deformation of the mylar interface window between the gas volume and the high vacuum line, has been taken into account. A good agreement is obtained between the experimental and simulated energy loss profiles.
Worldwide efforts to tackle the nature of exotic nuclei comprise the construction of new-generation Radioactive Ion Beam facilities. The Italian community is deeply involved in the process and the ...construction of SPES at Legnaro National Laboratories (INFN) is progressing. This contribution describes the layout of SPES in all its flavours, from Nuclear Physics to Applications in Nuclear Medicine and Neutron Physics. In particular, the status of the SPES-β ISOL facility, together with some of the relevant physics cases and the associated equipment are described.
•The last generation large solid angle magnetic spectrometers for very heavy ions.•Transfer of multiple pairs, providing valuable information on nucleon-nucleon correlations.•The study of the ...properties of the heavy binary partner via transfer reactions.
Significant advances have been achieved in the last years in the field of multinucleon transfer reactions. The advent of the last generation large solid angle magnetic spectrometers pushed the detection efficiency more than an order of magnitude above previous limits, with a significant gain in mass resolution for very heavy ions. Further, the coupling of these spectrometers to large gamma arrays allowed to perform gamma-particle coincidences. One can thus detect the transfer strength to the lowest excited levels of binary products and perform gamma spectroscopy for nuclei moderately far from stability, especially in the neutron-rich region. Via transfer of multiple pairs valuable information on nucleon-nucleon correlations can also be derived, especially from measurements performed below the Coulomb barrier. There is growing interest in the study of the properties of the heavy binary partner, since the transfer mechanism may allow the production of (moderately) neutron rich nuclei in the Pb and in the actinides regions, crucial also for astrophysics. Present studies are relevant for future studies with radioactive beams.
We present some of the recent experimental results in heavy-ion transfer reactions obtained with the large solid angle magnetic spectrometer PRISMA at energies close to the Coulomb barrier. We focus ...on a series of experiments that have been carried out to study the nucleon-nucleon correlations for closed shell and superfluid systems. They are discussed together with the newest results concerning the proton transfer channels above and below the Coulomb barrier. The second set of the experiments was performed to study the production mechanism of heavy neutron-rich nuclei and the related effects of secondary processes.
58Ni +64Ni is the first case where the influence of positive Q-value transfer channels on sub-barrier fusion was evidenced, in a very well known experiment by Beckerman et al., by comparing with the ...two systems 58Ni +58Ni and 64Ni +64Ni. Subsequent measurements on 64Ni +64Ni showed that fusion hindrance is clearly present in this case. On the other hand, no indication of hindrance can be observed for 58Ni +64Ni down to the measured level of 0.1 mb. In the present experiment the excitation function has been extended by two orders of magnitude downward. The cross sections for 58Ni + 64Ni continue decreasing very smoothly below the barrier, down to ≃1 μb. The logarithmic slope of the excitation function increases slowly, showing a tendency to saturate at the lowest energies. No maximum of the astrophysical S-factor is observed. Coupled-channels (CC) calculations using a Woods-Saxon potential and including inelastic excitations only, underestimate the sub-barrier cross sections by a large amount. Good agreement is found by adding two-neutron transfer couplings to a schematical level. This behaviour is quite different from what already observed for 64Ni+64Ni (no positive Q-value transfer channels available), where a clear low-energy maximum of the S-factor appears, and whose excitation function is overestimated by a standard Woods-Saxon CC calculation. No hindrance effect is observed in 58Ni+64Ni in the measured energy range. This trend at deep sub-barrier energies reinforces the recent suggestion that the availability of several states following transfer with Q >0, effectively counterbalances the Pauli repulsion that, in general, is predicted to reduce tunneling probability inside the Coulomb barrier.
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The response function of the magnetic spectrometer PRISMA is studied via a Monte Carlo simulation that employs a ray tracing code to determine the trajectories of individual rays through the ...electromagnetic fields. The calculated response is tested on angular and energy distributions provided by theoretical calculations for the
48
Ca +
64
Ni multinucleon transfer reaction and applied to the corresponding experimental data.
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