Pair plasmas found in deep space can now be generated in the lab

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. In and around these extreme astrophysical environments exists plasma, the fourth fundamental state of matter besides solids, liquids, and gases. Specifically, plasmas under these extreme conditions are known as relativistic electron-positron pair plasmas because they contain a collection of electrons and positrons—all traveling at nearly the speed of light.

While such plasmas are ubiquitous in deep space conditions, their production under laboratory conditions has proven challenging.

Now, an international team of scientists, including researchers from the University of Rochester’s Laboratory for Laser Energetics (LLE), has experimentally generated relativistic beams of electron-positron pair-plasma with high production densities of two to three orders of magnitude. more pairs than previously reported. The team’s findings appear in The nature of communication.

The breakthrough opens the door to follow-up experiments that could yield 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, a physicist at the University of Oxford who joins LLE. autumn.

“But experimental difficulties in producing electron-positron pairs in high enough numbers have limited our understanding to purely theoretical studies.”

Rochester researchers Dustin Froula, director of the Division of Plasma and Ultrafast Laser Sciences and Engineering at LLE, and Daniel Haberberger, associate scientist at LLE, collaborated with Arrowsmith and other scientists to design a new experiment using the HiRadMat facility at the Super Proton Synchrotron (SPS) in Europe Organization for Nuclear Research (CERN) in Geneva, Switzerland.

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

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

“This opens up a whole new frontier in laboratory astrophysics by allowing the microphysics of gamma-ray bursts or blazar jets to be investigated experimentally,” says Arrowsmith.

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

“Satellite and ground-based telescopes are unable to see the smallest details of these distant objects, and so far we have only been able to rely on numerical simulations. Our laboratory work will allow us to test these predictions obtained from very sophisticated calculations and verify how cosmic fireballs are affected.” thin interstellar plasma,” says co-author Gianluca Gregori, professor of physics at the University of Oxford.

Additionally, he adds, “This achievement underscores the importance of exchange and collaboration between experimental facilities around the world, especially as they break into new areas of access to increasingly extreme regimes of physics.”

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

The team’s findings come amid ongoing efforts to advance plasma science by colliding ultrahigh lasers, a research avenue that will be explored with the NSF OPAL Facility.