Conveners
Nuclear Astrophysics
- Sergio Cristallo (Istituto Nazionale di Fisica Nucleare)
Nuclear Astrophysics
- Sergio Cristallo (Istituto Nazionale di Fisica Nucleare)
Nuclear Astrophysics
- There are no conveners in this block
Nuclear Astrophysics
- There are no conveners in this block
Based on an idea by Carlo Rubbia, the n_TOF facility at CERN has been built and has been operating for over 20 years. It is a neutron spallation source, driven by the 20 GeV/c proton beam from the CERN PS accelerator. Neutrons in a very wide energy range (from GeV, down to sub-eV kinetic energy) are generated by a massive Lead spallation target feeding two experimental areas. EAR1, horizonal...
Molybdenum neutron cross section, especially capture cross section, has a role in many scientific fields from nuclear astrophysics to nuclear power plant safety. It is found as a pollutant in pre-solar silicon carbide grains, and it is important for the stellar nucleosynthesis of heavy elements in AGB stars. Moreover, molybdenum is present inside nuclear power plants as a fission product, and...
To calculate the reaction rate in the neutron capture processes it is common to work with the Maxwellian Average Cross Section (MACS), defined as the reaction rate scaled by the most probable neutron velocity of the Maxwell- Boltzmann distribution. For the s-process mainly, the MACS directly describes the reaction rate inside the stars, for a given temperature and neutron density. Hence, the...
Among the nucleosynthesis mechanism involving the heavy nuclei, the so-called slow (s-)process is responsible of about half of the element heavier than iron. Being one of the better known, many models were built in order to describe the process and the final element abundances.
The main component of the s-process take place in the outer layer of the AGB stars, where the heavy elements are...
The high-intensity quasi-Maxwellian neutron source based on the Soreq Applied Research Accelerator Facility (SARAF) [1] and the Liquid-Lithium Target (LiLiT) [2,3] were used to investigate neutron capture reactions in the weak and main $s-$process regimes. Experimental determinations of these reactions are important for helping to disentangle the different $s-, r-, p-$processes of...
The slow neutron capture processes (”main” and ”weak”) build up elements heavier
than iron through sequential neutron captures and β-decays, following the valley
of stability from seed nuclei in the iron region. The neutron sources for these processes
are the two reactions 13C(α,n)16O and 22Ne(α,n)25Mg. Their measurement is
quite difficult due to the astrophysically relevant energy ranges...
We discuss our novel theoretical and computational method for calculating beta-decay rates of radioisotopes in astrophysical scenarios, which takes into account both nuclear end electronic degrees of freedom at the same level of theory. Within this framework, we analyze the 134Cs —-> 134Ba and 135Cs ——> 135Ba beta decays, which are crucial production channels for Ba isotopes in Asymptotic...
In this presentation we introduce the theoretical methods and relevant computational approaches to calculate the electronic and nuclear structures within the mean-field approximation of the Dirac equation for many-particle systems. This model includes nuclear and electromagnetic correlations and the self-consistent numerical solutions are obtained by using either radial mesh or Gaussian basis...
Nuclear and atomic parameters both play a crucial role in constraining reaction rates of processes involved in several astrophysics domains. Reactions relevant for the s-process nucleosynthesis largely request for assessing yet open uncertainties on neutron capture cross sections and weak-interaction rates, for specific nuclear reactions, which branching ratio highly impacts on the final...
Lifetimes of radioactive nuclei are known to be affected by the level configurations of their respective atomic shells. Immersing such isotopes in environments composed of energetic charged particles like stellar plasmas can result in $\beta$-decay rates orders of magnitude different from those measured terrestrially. Accurate knowledge of the relation between plasma parameters and nuclear...
For more than two decades, the ERNA Collaboration has investigated nuclear processes of astrophysical interest through the direct measurement of cross sections or the identification of the nucleosynthesis effects. Measurements of cross-section of radiative capture reactions have been mainly conducted using the ERNA Recoil Mass Separator, and more recently with an array of charged particle...
Asymptotic Giant Branch (AGB) stars play a major role in determining the galactic chemical evolution being the production site of almost 50% of elements heavier than iron through the slow neutron capture process (the so-called s-process) [1,2].
From a pure nuclear point of view, several processes take part during this peculiar stage of stellar evolution thus requiring detailed experimental...
${\rm ^{19}F}$ has been clearly observed in AGB stars, and its abundance is strongly related to the physical conditions of stars. This element in fact can be destroyed via ${\rm ^{19}F(}n,\gamma{\rm)^{20}F}$, ${\rm ^{19}F(}p,\alpha{\rm )^{16}O}$, and ${\rm ^{19}F(}\alpha,p{\rm )^{22}Ne}$, with $\alpha$ capture that is expected to dominate in the He-intershell region. Direct measurements for...
The study of Asymptotic Giant Branch star (AGB) nucleosynthesis is fundamental to understand the Galaxy chemical evolution. At the energies of interest for AGB stars direct measurements of the nuclear cross sections are challenging because of the extremely low count rate. A breakthrough in experimental nuclear astrophysics is represented by the Laboratory for Underground Nuclear Astrophysics...
The synthesis of Ne, Na, Mg, and Al isotopes is connected to the NeNa-MgAl cycles of stellar burning. The entire cycle speed is controlled by the $\mathrm{^{20}Ne(p, \gamma)^{21}Na}$ ($Q=2431.68$ keV) reaction, which is the first and slowest reaction of the whole NeNa cycle. At the state of the art, the uncertainty on the $\mathrm{^{20}Ne(p, \gamma)^{21}Na}$ reaction rate affects the...
The s-process path involves unstable isotopes for each element.
After the discovery of live Tc-99 in the Red Giant RCor Bor star by Paul
Merrill in 1952, several have been found alive in meteorites, or through their extinct daughters trapped in microscopic Silicon Carbide grains.
We will dwell on the short-live Ca-41, Nb-92, Pd-107, Hf-182.
Then we will the origin of the stable isotope...
