The study of the nucleosynthesis of elements found on Earth and, more broadly, in the universe, is a fundamental area of research aimed at understanding the production mechanisms of various elements. This includes both the lighter elements (hydrogen, deuterium, helium, lithium) created during Big Bang Nucleosynthesis, and the heavier ones, synthesized within stellar cores or during specific phases of stellar evolution. This line of research focuses on studying and measuring the nuclear processes involved in element formation within astrophysical contexts. It aims to extend cross-section measurements of relevant nuclear processes—which have so far been measured primarily in laboratories using neutral elements—to a plasma environment, where these elements exist in their ionized form. This latter scenario more accurately reproduces the stellar environment where these processes naturally occur, allowing for a more realistic estimation of the parameters of interest.

The elements present on Earth and their relative abundances constitute a significant observable in fundamental physics. The nuclei of the elements populating the periodic table were produced in different phases: the lighter ones (hydrogen, deuterium, helium, lithium) during the so-called Big Bang Nucleosynthesis, which took place within a few minutes of the Big Bang. In a process of expansion and cooling, this phase led to the transition from elementary degrees of freedom—quarks and gluons—to more complex ones, such as nucleons, and, by combining the latter, to light nuclei.

The subsequent synthesis phase, which produced elements up to iron, takes place instead within stellar cores, where thermodynamic conditions allow for densities and energies high enough to overcome the Coulomb barrier and trigger the fusion process. The latter is energetically favored up to iron; beyond this element, the binding energy tends to decrease with the atomic number, meaning the fusion process is no longer spontaneous. The synthesis of elements beyond iron therefore occurs through different processes based on neutron capture by heavy nuclei. Indeed, adding a neutron to an atomic nucleus leads to two different possible outcomes: if the beta decay of the produced nucleus is less probable than a further neutron capture, the element will tend to form a heavier isotope by capturing another neutron while keeping its electromagnetic properties unchanged. Conversely, if the nucleus undergoes beta decay, one of the neutrons transforms into a proton, increasing the atomic number and turning the initial element into the next one on the periodic table.

Nuclear physics thus plays a key role in studying the relative abundances of elements in the universe: accurate measurements of cross-sections for fusion and neutron capture processes, as well as beta-decay half-lives, are strategic for evaluating the competition between possible processes and estimating which one will occur.

To date, measurements of cross-sections and half-lives have been carried out using neutral elements. However, in stellar environments, elements exist in an ionized form, and to build realistic models of the phenomena occurring in stars, it is necessary to account for the element’s ionization state. Therefore, the project aims to define and execute an experimental campaign dedicated to measuring fusion processes and beta-decay half-lives in an ionized environment. This environment can be generated using a high-intensity laser that, upon striking a target composed of the isotope under analysis, induces immediate ionization, resulting in the formation of a plasma. The characteristics of this plasma can be controlled by appropriately calibrating the laser intensity and target properties in order to reproduce the stellar environment as accurately as possible. Given the innovative nature of this approach, preliminary work is required to identify the relevant observables—also in relation to available theoretical models—for characterizing the nuclear processes. Furthermore, it is necessary to design an appropriate measurement apparatus capable of operating in environments with high electromagnetic pulses (such as those generated by the laser) and to optimize the detection system, which must feature suitable efficiency and response times to effectively reconstruct the final state of the processes.