Researchers at Helmholtz-Zentrum Dresden-Rossendorf have filmed copper atoms losing and regaining electrons in femtoseconds using dual lasers. The experiment creates superheated plasma mimicking extreme cosmic conditions. Findings could advance laser fusion research.
Scientists used two advanced lasers at the HED-HiBEF station of the European XFEL in Schenefeld near Hamburg to observe plasma formation. An intense optical laser pulse from ReLaX struck a thin copper wire, vaporizing it into plasma reaching millions of degrees. A subsequent X-ray free-electron laser probe captured the process in snapshots, tracking highly charged Cu²²⁺ ions via resonant absorption at 8.2 kiloelectronvolts, as detailed in Nature Communications published in 2026. The energy density hit 250 trillion megawatts per square centimeter over femtosecond pulses of 25 to 30 duration. Dr. Lingen Huang, head of experimentation in HZDR's Division of High-Energy Density, explained: 'These are exactly the conditions provided by the two lasers that have pulse durations of just 25 and 30 femtoseconds -- that is, trillionths of a second.' Measurements showed Cu²²⁺ ions peaking after 2.5 picoseconds before recombining within 10 picoseconds. Prof. Tom Cowan, former director of HZDR's Institute of Radiation Physics, noted: 'No one has ever looked at this type of ionization so precisely before.' Computer simulations revealed electron waves driving further ionization as freed electrons knocked out more from neighboring atoms. Dr. Ulf Zastrau, responsible for the HED-HiBEF station, said: 'This experiment demonstrates how powerful our lasers are and paves the way for future laser fusion facilities.' The work refines simulations for laser-heated plasmas essential to fusion reactors.