Motivation
The search for our cosmic origins has been a driving force in mankind’s cultural evolution through-out the centuries involving branches from the domain of the natural and exact sciences to the humanities. Scientific research carried out in the last 80 years has shown that man and universe have a common cosmic legacy, i.e. the chemical elements from which human bodies as well as galaxies are made of.
Nuclear Astrophysics, where the project described in the present proposal belongs, was first established as a research field in 1957, when Margaret Burbidge, Geoffrey Burbidge, Willy Fowler and Fred Hoyle published their famous B2FH paper [1] in which they reviewed all of what was known about nuclosynthesis in stars. Nowadays, Nuclear Astrophysics is a vastly interdisciplinary field dealing with different problems requiring input from many different disciplines such as nuclear physics, astronomy, astrophysics, nuclear chemistry and meteoritics.
The interplay between Nuclear Physics and Astrophysics is known: stars shine and evolve because nuclear reactions take place in their interiors and the primary nuclear physics quantity interconnecting these fields is the nuclear reaction cross section σ, which quantifies the probability that a nuclear reaction takes place in a stellar environment of temperature T. Both quantities, T and σ, enter following equation:
This equation plays a prominent role in Nuclear Astrophysics. It defines the quantity <συ>, known as reaction rate, which is of paramount importance in stellar evolution and nucleosynthesis studies; <συ> provides the number of reactions between a pair of non-identical nuclides per time per volume. μ and E in Eq. 1 are, respectively, the reduced mass and the center-of-mass energy of the interacting particles and k is the Boltzmann’s constant.
Eq. 1 justifies why cross section measurements are by far the major task in nuclear astrophysics and why low-energy ion-beam accelerators, like the 5.5MV TANDEM operating at the Institute of Nuclear and Particle Physics (INPP) of the National Center for Scientific Research “Demokritos” (NCSRD), have been used for decades for this purpose in an on-going scientific challenge to search for our cosmic origins.
Using the TANDEM accelerator of “Demokritos” as the main experimental tool, a research program related to stellar nucleosynthesis was launched in the early nineties and a vibrant nuclear astrophysics (NA) group has gradually been formed. Since then, the NA group has carried out numerous measurements at the in-house TANDEM as well as abroad, in collaboration with various well-established nuclear astrophysics groups and, to date, the NA group of INPP plays a worldwide leading role in stellar nucleosynthesis studies focusing, mainly on nuclear reactions related to the understanding of the p process [2], i.e., the nucleosynthetic mechanism of certain nuclei heavier than iron, that takes place in explosive stellar sites, such as supernovae.
To date, the TANDEM accelerator laboratory (TAL) of “Demokritos” is recognized by the international scientific community as a laboratory of international stature. This status has been strongly enhanced by an EC FP7 Grant through which the project with the acronym LIBRA was funded with ≈1.5 million Euros. Thanks to LIBRA, we could acquire state-of-the art instruments and upgrade key accelerator components.
A natural follow-up of LIBRA was the establishment of a national research infrastructure. Indeed, after a long-lasting evaluation procedure our proposal for a “Cluster of Accelerator Laboratories for Ion-Beam Research and Applications”, in short CALIBRA [3], has been included in the 19 research infrastructures of the first National Roadmap of Research Infrastructures. As a result, CALIBRA was funded with ≈3.5 million Euros by the currently running Partnership Agreement for the Development Framework (ΕΣΠΑ 2014-2020) [4], which is co-financed by Greece and the European Union through the European Regional Development Fund (ERDF). CALIBRA is expected to complete in a year from now, when approximately the ARENA project is expected to be launched, in case of a positive evaluation of this proposal and subsequent grant award.
Motivated by the on-going scientific challenges related to the open question how chemical species were created in cosmos, we propose herewith a project of key importance for a deeper understanding of the nucleosynthesis of trans-iron elements in stars under explosive conditions. ARENA is also the result of our long-term research experience and worldwide prominent role in the addressed scientific field. The available state-of-the art, partly unique, facilities and experimental setups at the TANDEM accelerator laboratory of “Demokritos” make the project absolutely feasible.
