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idw - Informationsdienst
Wissenschaft
An international research team has achieved an important milestone for astrophysics at GSI/FAIR in Darmstadt: In the CRYRING@ESR storage ring, scientists were able to measure nuclear reactions at extremely low energies for the first time, mirroring the conditions inside stars. This novel experimental approach lays the foundation for decoding the formation of elements in the universe with even greater precision in the future.
In the extreme environments of stars, nuclear processes often occur at very low energies. These so-called "sub-MeV energies" (below one megaelectronvolt) are difficult to replicate in the laboratory because the probability of atomic nuclei interacting at such low speeds is exceptionally small. In the FAIR storage ring CRYRING@ESR, researchers were able to lower the energy available for the nuclear reaction in the center-of-mass frame of the two particles down to 403 kiloelectronvolts. This marks a new record: It is the lowest energy at which a nuclear reaction has ever been measured in a heavy-ion storage ring. The new findings were recently published in the journal The European Physical Journal A.
“The biggest challenge in achieving nuclear reactions at such low energies in storage rings is the very low beam lifetime,” explains Jordan Marsh, University of Edinburgh, first author of the paper. “At lower energies, ions are far more likely to be lost through atomic processes such as electron stripping, leaving fewer particles available for the reactions we want to study. Overcoming this demands both extreme-high vacuum conditions and the skill of beam operators, who create tightly focused, electron-cooled ion beams.”
In their experiment, the international team investigated reactions of nitrogen ions colliding with protons, among other processes. To achieve this, an ion beam was injected into CRYRING@ESR, brought to the desired energy, and aligned with extreme precision using a so-called electron cooler. Inside the ring, the beam then intersected a cryogenic hydrogen gas target. The high-resolution measurement system CARME (CRYRING Array for Reaction Measurements) was used to detect the reaction products generated during this process. The collected data aligns perfectly with theoretical predictions, proving that the experimental method works exceptionally well.
This success, part of the FAIR Phase-0 research program, opens the door for a multitude of future experiments. Going forward, exotic atomic nuclei that play a central role in stars will also be used at CRYRING@ESR. Since CRYRING@ESR has its own ion source, further experiments will take place there later this year. The combination of high-precision storage rings and state-of-the-art detector technology will help to solve lingering mysteries in nuclear astrophysics. “I am particularly excited about applications to Big Bang Nucleosynthesis (BBN), the process by which the light elements were formed in the first minutes after the Big Bang,” says Marsh. “At the CRYRING@ESR, we plan to study nuclear reactions involving deuterium, a key isotope in BBN which will hopefully enable us to better understand the conditions of the early Universe.”
https://link.springer.com/article/10.1140/epja/s10050-025-01783-3
Experiment setup CARME
Copyright: C. Bruno, GSI/FAIR
First author Jordan Marsh, University of Edinburgh
Copyright: G. Duwald, GSI/FAIR
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