Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - DoRES (Direct measurements of key nuclear Reactions for the creation of Elements in Stars)
Teaser
The chemical elements from carbon onwards have all been produced in stars. The elemental abundances we observe in our solar system, meteorites and distant stars provide us with clues of how these elements were produced in a variety of astrophysical sites and processes...
Summary
The chemical elements from carbon onwards have all been produced in stars. The elemental abundances we observe in our solar system, meteorites and distant stars provide us with clues of how these elements were produced in a variety of astrophysical sites and processes. However, many open questions remain, and a key to finding the answers is to study the nuclear reactions occuring in stars and stellar explosions which are responsible for element formation. These reactions often involve unstable nuclei which do not naturally occur on earth - this provides a challenge to make these nuclei accessible experimentally. This ERC project addresses major open questions in the field, related to the origin of elements heavier than iron, the origin of cosmic gamma ray emitters, and the source of neutrons in low mass stars. We aim to directly measure key nuclear reactions involving unstable particles, using upgraded and new world-leading international accelerator facilites, combined with advanced, sensitive detection systems, which are purpose-built within the ERC project.
Work performed
High precision measurements of neutron capture reactions have been performed on intermediate mass nuclei (germanium, selenium and zinc) at the neutron time-of-flight facility n_TOF at CERN. First results provide important clues about the production of the heavy elements in massive stars, which at the end of their lives explode as a core-collapse supernova. We have studied key neutron destruction reactions of the cosmic gamma ray emitter 26Al, an important tracer of nucleosynthesis in our galaxy, using the new ultra-high flux beamline EAR-2 at n_TOF. For this experiment, we designed and built an advanced silicon strip detection system to detect the particles produced in the reaction of 26Al with neutrons. We expect that this experiment will resolve long-standing discrepancies in previous experimental results, allowing a better understanding of 26Al production in massive stars. We have used the same detection system to investiagte reactions important for the neutron balance in stars, which has impact on the stellar structure and neutron capture nucleosynthesis in low mass stars. In addition, we have measured a key nuclear reaction of importance to the origin of certain proton rich isotopes, which are much more abundant in our solar system than can currently be explained by stellar models. This experiment was possible by combining a high intensity radioactive ion beam produced at the upgraded HIE-ISOLDE facility at CERN with an innovative detection system, allowing to minimise background.
Final results
New detection systems are combined with advanced accelerator facilities to study nuclear reactions of key importance for elemental synthesis in stars and stellar explosions. This project allowed to address several open questions by directly measuring certain key reactions for the first time, which will provide important information on nucleosynthesis processes and help to unravel the mysteries of element formation in the cosmos.