Imaging a cosmic plasma instability in the laboratory
Many of the most energetic phenomena in the universe, from exploding stars to powerful cosmic particle accelerators, are governed by the complex behaviour of plasmas under extreme conditions. In these environments, plasmas can develop instabilities that shape magnetic fields, drive particle acceleration, and influence how energy is transported across vast distances. One such process, known as current filamentation, plays a key role in both astrophysical plasmas and laboratory experiments. Understanding how this instability forms and evolves is essential not only for interpreting observations of distant cosmic events, but also for advancing controlled fusion research, where similar plasma conditions arise.
Now, for the first time, a multinational team jointly led by researchers at IPFN and at the U.S. Department of Energy’s SLAC National Accelerator Laboratory imaged how the current filamentation instability evolves in real-time in high-density plasma. Their work, reported in Nature Communications, demonstrates a new way to study instabilities in plasmas using SLAC’s Linac Coherent Light Source (LCLS) X-ray laser.
“I’m truly thrilled by this experimental breakthrough,” said Frederico Fiúza, IPFN researcher and Professor in the Department of Physics at IST, who originally proposed the concept and has led the effort over the past eight years. “For the first time, we can directly observe the real-time evolution of this phenomenon in relativistic and high-energy-density plasmas, which is key to understanding fundamental processes in extreme astrophysical environments as well as in laboratory plasmas. Turning this initial idea into a working experiment required years of persistence, technical development, and close collaboration using theory, simulations and experiments, and it is immensely satisfying to finally see it come to fruition.”
“This is the most detailed description of this instability yet,” said Christopher Schoenwaelder, project scientist at SLAC and first author of the paper. “We actually image the evolution of the instability and then combine that with state-of-the-art simulations to try to make constraints on existing theoretical models of it.”
Energetic X-rays yield unprecedented resolution
In the current filamentation instability, a laser accelerates electrons in a plasma to very high energies, producing a current of hot electrons. This current interacts with a return current of cold electrons streaming in the opposite direction, which gives rise to the filament-shaped instability.
While this instability has been imaged in low-density plasmas, it is far more challenging to study in the high-energy-density regimes that are relevant to many astrophysical environments, such as supernova, gamma-ray bursts, and other high-energy cosmic plasmas, where strong currents and magnetic fields naturally arise. High-energy-density plasma conditions are also found in inertial fusion experiments, making them of broad interest across plasma physics. Conventional imaging methods cannot penetrate such dense plasmas, but the high-intensity X-rays from the LCLS carry enough energy to pass through them and directly image the instability as it forms.
In the experiment, the team induced the instability using a powerful laser at the Matter in Extreme Conditions (MEC) instrument. The resultant images showed the formation of the micrometer-scale filamentary structures over a tiny fraction of a second, providing unprecedented spatial and temporal resolution of this instability.
“Every 500 femtoseconds [quadrillionths of a second], we took snapshots to get a true image of what was happening at that moment in time, showing details like never before,” said co-author Siegfried Glenzer, High Energy Density Division director and professor for photon science at SLAC,
A new way to study plasma instabilities
The analysis also showed that, during the experiment, the instability produced a 1,000-Tesla magnetic field, which is about 100,000 times stronger than that of a typical refrigerator magnet. In plasmas in astrophysical phenomena, such as exploding stars, this strong magnetic field amplification is thought to enable the acceleration of high-energy particles known as cosmic rays. Eventually, a better understanding of this instability could allow scientists to use plasma experiments in the lab to learn about events happening light-years away.
The platform developed in this work could also be extended to study other types of plasma instabilities, including those that take energy away from fusion reactions.
Schoenwaelder and Maxence Gauthier, associate staff scientist at SLAC, spearheaded the experimental aspects of this work. Frederico Fiúza, who leads the Group of Astrophysical Plasmas at IPFN and is a visiting professor of photon science at SLAC, and Alexis Marret, research associate at SLAC, focused on the simulation and theory side. By comparing cutting-edge simulations of the experiment with the data and theory, they identified mechanisms that shape the evolution of this instability.
The international research team also included members from Stanford University; University of Alberta, Canada; University of Erlangen-Nuremberg, Helmholtz Center Dresden-Rossendorf, Technical University Dresden, European XFEL, and Technical University Darmstadt, all in Germany. Part of this work was funded by the European Research Council Consolidator Grant XPACE.
To know more & image credit:
C. Schoenwaelder et al., Time-resolved X-ray imaging of the current filamentation instability in solid-density plasmas. Nature Communications, 9 January 2026.
