A dual ion beam facility, which enables two ion beams from different accelerators to be combined simultaneously, has been inaugurated in Zagreb, strengthening Croatia’s fusion research and expanding the global supply of facilities with such cutting-edge capabilities. Installed with IAEA support, the Ruđer Bošković Institute’s He Ion Source & DiFU Dual-Beam Facility will help scientists test and develop new structural materials indispensable for fusion energy to become a reality. Only very few facilities of this kind exist worldwide.
Fusion researchers and engineers work to develop methods to harness the power generated by the fusion of light nuclei, a process comparable to the energy production of stars. It holds the promise of abundant, safe and carbon free energy.
However, fusion reactions generate highly energetic neutrons and alpha particles which, after some time of exposure, can damage reactor walls. Ion beam technology like the dual-beam facility in Croatia can simulate these extreme conditions and help to develop new materials sturdy enough to sustain them.
“Installation of the He ion source at the smaller 1.0 MV tandem accelerator was the last missing component at the RBI accelerator facility, which is now capable of performing the most realistic simulation of the fusion environment,” said Milko Jasic, Senior Scientist at the Ruđer Bošković Institute’s Laboratory for Ion Beam Interactions. “This investment will also enable increased use of ion beam analysis techniques for a wide range of other applications.”
“It will allow researchers and engineers to test that materials are robust enough to contain a fusion reaction, among other things,” added Danas Ridikas, Head of the Physics Section at the IAEA. “The facility is good news for Europe and for IAEA Member States in other regions too.”
The Ruđer Bošković Institute has been working with the IAEA through a collaborative agreement signed in 1997. The IAEA has provided the Institute with equipment and assisted through a capacity building programme. The IAEA recently launched a new coordinated research project to facilitate experiments at ion beam facilities worldwide. Interested scientists from other IAEA Member States also have access to the Institute, including this new dual ion beam facility.
Advancing fusion research
In a fusion device, the nuclei are heated to extremely high temperatures to cause them to fuse and release energy. Researchers worldwide have made impressive progress in fusion and plasma physics lately, Ridikas said. Controlled nuclear fusion and plasma physics research is currently carried out in more than 50 countries to prove the scientific feasibility of fusion as an energy source.
“Complex experiments and initiatives are taking place around the world on plasma physics,” Ridikas said. “But important questions are still open. For example: how can we know that materials will be strong enough to withstand a fusion reaction after years and years of exposure?”
Technology like the dual-beam ion facility in Croatia can simulate similar circumstances — including the transmutation products and damage produced by high-energy neutrons and alpha particles that come from fusion — that a material would be exposed to in a fusion reactor.
“With the right measurements, right temperature control, and two simultaneous ion beams — hence, dual beam — hitting the material, we are creating a simulated reality where we can get an indication of how the structural material will react to the force of fusion,” Ridikas said. “This way, we can test which material holds up and for how long.”
The two beams are directed at a steel sample — the material typically used for fusion reactors due to its robustness — to simulate how fusion plasma could interact with and modify this material. This nuclear interaction, in addition to possibly damaging the crystal structure of the material, creates transmutation gas products such as helium and hydrogen. This might lead to the formation of bubbles inside the steel, which can cause the material to swell. Knowing how and when these reactions occur, scientists can adapt the material to counteract these unwanted effects.
Last month, the IAEA and the ITER International Fusion Energy Organization have agreed to strengthen their cooperation in nuclear fusion research and related activities with the long-term goal of realizing fusion energy production on an industrial, power-plant scale. ITER is an international experimental reactor under construction in France, and one of the most advanced and largest fusion experiments in the world. In parallel, dual-beam facilities like the one installed at the Ruđer Bošković Institute, or the new EU-led DONES initiative in Spain, a fusion-dedicated neutron source, will advance research in materials testing.