Paired plasmas found in deep space can now be generated in the laboratory

An international team of scientists has developed a new way to experimentally produce plasma “fireballs” on Earth.

Black holes and neutron stars are among the densest known objects in the universe. Within and around these extreme astrophysical environments exist plasmas, the fourth fundamental state of matter alongside solids, liquids and gases. Specifically, plasmas in these extreme conditions are known as relativistic electron-positron pair plasmas, because they include an array of electrons and positrons, all flying at close to the speed of light.

Although such plasmas are ubiquitous in deep space, producing them in the laboratory has proven challenging.

Now, for the first time, an international team of scientists, including researchers at the University of Rochester’s Laser Energy Laboratory (LLE), has experimentally generated relativistic electron-positron pair plasma beams at high density producing two to three orders of magnitude. more pairs than previously reported. The team’s findings appear in Natural communications.

This breakthrough opens the door to follow-up experiments that could lead to fundamental discoveries about how the universe works.

“Laboratory generation of plasma ‘fireballs’ composed of matter, antimatter, and photons is a research goal at the forefront of high-energy-density science,” says lead author Charles Arrowsmith, physicist from the University of Oxford who joins the LLE. in autumn.

“But the experimental difficulty of producing electron-positron pairs in sufficiently high numbers has, until now, limited our understanding to purely theoretical studies.”

Rochester researchers Dustin Froula, division director for plasma and ultrafast laser science and engineering at LLE, and Daniel Haberberger, LLE research scientist, collaborated with Arrowsmith and other scientists to design a new experiment leveraging the HiRadMat facility at the European Organization for Nuclear Research’s (CERN) Super Proton Synchrotron (SPS) in Geneva, Switzerland.

This experiment generated extremely high yields of near-neutral electron-positron pair beams using more than 100 billion protons from the SPS accelerator. Each proton carries a kinetic energy 440 times greater than its rest energy. Because of this large momentum, when the proton crushes an atom, it has enough energy to release its internal constituents – quarks and gluons – which then immediately recombine to produce a shower that eventually decays into electrons and positrons.

In other words, the beam they generated in the lab contained enough particles to start behaving like a real astrophysical plasma.

“This opens a whole new frontier in laboratory astrophysics by making it possible to experimentally probe the microphysics of gamma-ray bursts or Blazar jets,” says Arrowsmith.

The team also developed techniques to modify the emittance of pair beams, enabling controlled studies of plasma interactions in analogues at the scale of astrophysical systems.

“Satellite and terrestrial telescopes are not capable of seeing the smallest details of these distant objects and until now we could only rely on numerical simulations. Our laboratory work will allow us to test the predictions obtained from calculations very sophisticated and to validate the impact of cosmic fireballs by tenuous interstellar plasma,” explains co-author Gianluca Gregori, professor of physics at the University of Oxford.

Furthermore, he adds, “this achievement highlights the importance of exchange and collaboration between experimental facilities around the world, particularly as they innovate in access to physical regimes of more and more extreme.”

In addition to LLE, the University of Oxford and CERN, institutions collaborating on this research include the Science and Technology Facilities Council’s Rutherford Appleton Laboratory (STFC RAL), the University of Strathclyde, the Atomic Weapons establishment in the Kingdom -United, Lawrence Livermore National Laboratory. , the Max Planck Institute for Nuclear Physics, the University of Iceland and the Instituto Superior Técnico in Portugal.

The team’s findings are part of ongoing efforts to advance plasma science by colliding ultra-high intensity lasers, a research avenue that will be explored using the facility NSF OPAL.