The pair 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. In and around these extreme astrophysical environments exist plasmas, the fourth fundamental state of matter along with solids, liquids, and gases. Specifically, plasmas under these extreme conditions are known as relativistic electron-positron pair plasmas, because they involve a collection of electrons and positrons—all flying around at nearly the speed of light.

While such plasmas are ubiquitous in the conditions of deep space, their production in a laboratory environment has proven challenging.

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

The discovery 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 is LLE joins. in autumn.

“But the experimental difficulty of producing electron-positron pairs in sufficiently high numbers has, until this point, 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, a staff scientist at LLE, collaborated with Arrowsmith and other scientists to design an experiment new using the HiRadMat facility at the Super Proton Synchrotron. SPS) accelerator at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland.

That 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 a large momentum, when the proton smashes into an atom, it has enough energy to release its internal components – 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 had enough particles to start behaving like a true astrophysical plasma.

“This opens up a whole new frontier in laboratory astrophysics by making possible the experimental investigation of the microphysics of gamma-ray bursts or blazar jets,” says Arrowsmith.

The team has also developed techniques to modify the emission of even beams, making it possible to perform controlled studies of plasma interactions in scaled analogues of astrophysical systems.

“Satellite and ground-based telescopes are not able to see the smallest details of those distant objects, and so far we can only rely on numerical simulations. Our laboratory work will enable us to test those predictions obtained from very detailed calculations. sophisticated and prove how cosmic fireballs are affected by weak interstellar plasma,” says co-author Gianluca Gregori, a professor of physics at the University of Oxford.

Furthermore, he adds, “The achievement highlights the importance of exchange and collaboration between experimental facilities around the world, especially as they break new ground in accessing increasingly extreme physical regimes.”

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

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