Couple 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, the plasmas under these extreme conditions are known as relativistic plasmas of electron-positron pairs, because they comprise a collection of electrons and positrons – all of which are flying around at nearly the speed of light.

Although such plasmas are ubiquitous in deep space conditions, producing them in a laboratory environment 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 high-density relativistic electron-positron pair plasma beams by producing two to three orders of magnitude more pairs than previously reported . The team’s findings appear in Nature communication.

The breakthrough opens the doors for follow-up experiments that could yield fundamental discoveries about how the universe works.

“The laboratory generation of plasma fireballs, consisting of matter, antimatter and photons, is a research goal at the forefront of high-energy density science,” said lead author Charles Arrowsmith, a physicist from the University of Oxford who joins LLE. in the fall.

“But the experimental difficulty of producing electron-positron pairs in large enough numbers has so far 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, worked with Arrowsmith and other scientists to design a new experiment 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 pairs using more than 100 billion protons from the SPS accelerator. Each proton has a kinetic energy 440 times greater than its rest energy. Because of such great momentum, when the proton destroys 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 laboratory contained enough particles to behave like a real astrophysical plasma.

“This opens up 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 has also developed techniques to modify pair-beam emissions, making it possible to conduct 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 until now we could only rely on numerical simulations. Our laboratory work will allow us to test and improve the predictions obtained from highly sophisticated calculations. to validate how cosmic fireballs are affected.” through the rarefied interstellar plasma,” says co-author Gianluca Gregori, professor of physics at the University of Oxford.

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

In addition to LLE, the University of Oxford and CERN, collaborating institutions for this research include the Science and Technology Facilities Council Rutherford Appleton Laboratory (STFC RAL), the University of Strathclyde, the United Kingdom Atomic Weapons Establishment, the 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 come from ongoing efforts to advance plasma science by colliding ultra-high intensity lasers, a research direction that will be explored using the NSF OPAL Facility.