Scientists recreate the conditions of a star in a laboratory: how this breakthrough could change the future of energy.

Scientists have achieved observation, at the femtosecond (billionth of a second) scale, of the transformation of a metal into plasma by laser (Illustrative Image Infobae). An international team of scientists, led by researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), recorded, with femtosecond precision, the process by which a laser transforms metal into plasma, a state of matter comparable to that of stars. This observation paves the way for refining research in laser fusion, considered a long-term option for obtaining clean energy, according to the Science Daily science news portal. The significance of the experiment, published in the scientific journal Nature Communications, lies in the ability of these researchers to observe the formation and dissolution of highly charged copper ions in time intervals of up to ten picoseconds, that is, ten billionths of a second. No one had previously managed to analyze with such precision the mechanisms of laser-induced ionization under such extreme conditions, said Tom Cowan, former director of the Radiation Physics Institute at HZDR. The experiment combined two advanced lasers—a high-intensity optical laser (ReLaX) and an X-ray free-electron laser—at the HED-HiBEF station of the European XFEL, the European free-electron X-ray facility located in Schenefeld. An initial pulse struck a copper wire only one-seventh the thickness of a human hair, instantly vaporizing it and raising its temperature to several million degrees, with an intensity of 250 trillion megawatts per square centimeter for a tiny fraction of time, conditions equivalent to those that exist near neutron stars or during gamma-ray bursts. The experiment recreates in the laboratory conditions similar to those of neutron stars and gamma-ray bursts, raising the copper to millions of degrees (Illustrative Image Infobae). The physical process begins when the electrons closest to the atomic nucleus are displaced by the impact of the laser. These high-energy electrons behave like a wave capable of expelling more electrons from adjacent atoms. Then, this effect decreases: the free electrons lose energy, and upon being recaptured, the atoms gradually return to their neutral state. The research measured the temporal evolution of copper ions that lost up to 22 electrons (Cu²²⁺). After the initial flash that generated the plasma, a second pulse from the XFEL in the form of hard X-rays served as a diagnostic probe. The energy of the photons, 8.2 kiloelectronvolts, was tuned to coincide with a specific electronic transition in the Cu²²⁺, a process called resonant absorption. This methodology made it possible to capture a sequence of images of the internal dynamics of the plasma, explained Lingen Huang, head of the experimentation area in the High Energy Density division of HZDR. The results showed that the highly charged ions appear immediately after the laser impact, reach their maximum after about 2.5 picoseconds, and disappear through recombination in a total time of approximately ten picoseconds. The experiment combines a high-intensity optical laser and an X-ray free-electron laser at the European XFEL to study the copper plasma (Illustrative Image Infobae). Huang specified: "In our pump-probe experiment, we measured exactly the temporal development of this stimulated X-ray emission, because it reveals how many Cu²²⁺ ions are present in the plasma at each specific moment." The technique proved crucial for documenting, for the first time, the complete chronology of the ionization and recombination cycle with picosecond temporal resolution. Before this work, simulation models lacked direct experimental data on this time scale in high-density energy plasmas. Potential applications include refining diagnostic tools for fusing atomic nuclei using lasers, a methodology considered essential in the development of future fusion reactors. Ulf Zastrau, head of the HED-HiBEF experiment at the European XFEL, stated that "the experiment demonstrates the power of our lasers and paves the way for future laser fusion facilities," since fusion requires plasmas at extreme temperatures, heated by lasers and high-energy electrons. The new information collected will allow for the construction of more accurate simulations of these processes, a fundamental piece for designing more efficient and reliable laser fusion reactors, explained Zastrau.