123 research outputs found
Laboratory for Underground Nuclear Astrophysics
No full textNuclear reactions shape the life and death of stars and they produce most of the chemical elements in the Universe. The cross section, at the energy of the Gamow peak, is a crucial ingredient to improve our knowledge on stellar and Universe chemical evolution. Its low value at stellar energies prevent direct measurements in earth-based laboratories. In recent years low energy data significantly improved thanks to underground facilities, pioneered by the Laboratory for Underground Nuclear Astrophysycs (LUNA). LUNA started its activity in 1991 with a 50 kV electrostatic accelerator installed under Gran Sasso, which is a natural shield against cosmic rays ensuring a ultra low background environment. LUNA early activity was dedicated to reactions relevant to the Sun, and then, thanks to the installation of a new accelerator (LUNA400), it focused on the study of the Big Bang Nucleosynthesis (BBN) and of the CNO, NeNa and MgAl cycles. LUNA is now facing the next steps, helium and carbon burning, thanks to the new 3.5MV accelerator, which has just started its activity at the Bellotti Facility of LNGS. The accelerator provides hydrogen, helium and carbon beams, allowing to study the reactions that shape both the evolution of massive stars to their final fate and the synthesis of most of the elements in the Universe
Aristocracy and Literary Production in the Tenth Century
No full textTaking as its starting point the figure and work of John Geometra, a poet active in 10th-century Constantinople, the article examines two interrelated phenomena. On the one hand, the author questions whether a literary production of aristocratic and provincial inspiration existed in Byzantium during the period under examination, and proposes to identify traces of it in the Byzantine literature that has come down to us. On the other hand, the research intends to reconstruct how the Constantinopolitan cultural elite active at the Macedonian court was able to translate the ambitions and traditions of this rising social group, expressing them in the language of the 'high' classicizing literature
The long-standing connection of BBN and Indirect measurements: The
No full textNuclear reactions play a key role in the framework of the Big Bang Nucleosynthesis. A network of 12 principal reactions has been identified as the main path which drives the elemental nucleosynthesis in the first twenty minutes of the history of the Universe. Among them an important role is played by neutron-induced reactions, which, from an experimental point of view, are usually a hard task to be measured directly. Nevertheless big efforts in the last decades have led to a better understanding of their role in the primordial nucleosynthesis network. In this work we apply the Trojan Horse Method to extract the cross section at astrophysical energies for the 3He(n,p)3H reaction after a detailed study of the 2H(3He,pt)H three–body process. The experiment was performed using the 3He beam, delivered at a total kinetic energy of 9 MeV by the Tandem at the Physics and Astronomy Department of the University of Notre Dame. Data extracted from the present measurement are compared with other published sets available in literature. Astrophysical applications will also be discussed in details
The Trojan Horse Method as a tool for investigating astrophysically relevant fusion reactions
No full textThe Trojan Horse Method (THM) has been largely adopted for investigating astrophysically relevant charged-particle induced reactions at Gamow energies. Indeed, THM allows one to by pass extrapolation procedures, thus overcoming this source of uncertainty. Here, the recent THM results and their impact in astrophysics are going to be discussed
High-precision mass measurements for the rp-process at JYFLTRAP
No full textThe double Penning trap JYFLTRAP at the University of Jyvaskyla has been successfully used to achieve high-precision mass measurements of nuclei involved in the rapid proton-capture (rp) process. A precise mass measurement of 31Cl is essential to estimate the waiting point condition of 30S in the rp-process occurring in type I x-ray bursts (XRBs). The mass-excess of 31Cl measured at JYFLTRAP, -7034.7(3.4) keV, is 15 more precise than the value given in the Atomic Mass Evaluation 2012. The proton separation energy Sp determined from the new mass-excess value confirmed that 30S is a waiting point, with a lowertemperature limit of 0.44 GK. The mass of 52Co effects both 51Fe(p,γ)52Co and 52Co(p,γ)53Ni reactions. The mass-excess value measured, - 34 331.6(6.6) keV is 30 times more precise than the value given in AME2012. The Q values for the 51Fe(p,γ)52Co and 52Co(p,γ)53Ni reactions are now known with a high precision, 1418(11) keV and 2588(26) keV respectively. The results show that 52Co is more proton bound and 53Ni less proton bound than what was expected from the extrapolated value.peerReviewe
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