Pair plasma generated in laboratory experiments at CERN

An international team of scientists has developed a novel way to experimentally produce pair plasma ‘fireballs’ on Earth, opening a new frontier in laboratory astrophysics.

Almost the entire visible universe exists in a plasma state, the fourth fundamental state of matter alongside solids, liquids, and gases. While the plasma composition in the interstellar medium typically consists of electrons, ionized hydrogen, and other nuclei, in close proximity to certain astrophysical compact objects, such as black holes and neutron stars, the plasma composition is known to be quite different. Here, the electromagnetic fields are intense enough to create copious amounts of electrons and positrons, the anti-particle of the electron. These ‘pair plasmas’ have unique properties, owing to the mass-symmetry of the two species.

While pair plasmas are common in astrophysical systems, producing them in a laboratory setting has proved challenging.
Now, for the first time, an international team of scientists, including researchers from MPIK, 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 Communications.

The breakthrough opens the doors to follow-up experiments that could yield fundamental discoveries about how the universe works.
“The 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 from the University of Oxford. “But the experimental difficulty of producing electron-positron pairs in sufficiently high numbers has, to this point, limited our understanding to purely theoretical studies.”

MPIK scientists Brian Reville and Thibault Vieu collaborated with Arrowsmith and other scientists to design a novel experiment harnessing 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 of 440 Giga-electronvolts. When a proton with such high energy collides with another nucleus, it induces a cascade that produces vast quantities of secondary products, including pions, muons and crucially copious amounts of electrons and positrons.
In other words, the beam they generated in the lab had enough particles to start behaving like a true astrophysical plasma.

“These experiments explore plasma regimes where understanding depends heavily on numerical simulations.”  says co-author Brian Reville of MPIK.  “These simulations are computationally demanding, and are limited in the range of scales they can access. Experimental studies thus open up exciting directions in the novel field of relativistic laboratory astrophysics.”
“Our laboratory work will enable us to test predictions obtained from very sophisticated calculations and validate how cosmic fireballs are affected by the tenuous interstellar plasma,” says co-author Gianluca Gregori, also at the University of Oxford.

In addition to MPIK, 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 UK, the Lawrence Livermore National Laboratory, The University of Rochester’s Laboratory for Laser Energetics (LLE), the University of Iceland, and the Instituto Superior Técnico in Portugal.

This project has received funding from the European Union’s Horizon Europe Research and Innovation program under Grant Agreement No 101057511 (EURO-LABS).

Original publication:

Laboratory realization of relativistic pair-plasma beams
C. D. Arrowsmith, P. Simon, P. J. Bilbao, A. F. A. Bott, S. Burger, H. Chen, F. D. Cruz, T. Davenne, I. Efthymiopoulos, D. H. Froula, A. Goillot, J. T. Gudmundsson, D. Haberberger, J. W. D. Halliday, T. Hodge, B. T. Huffman, S. Iaquinta, F. Miniati, B. Reville, S. Sarkar, A. A. Schekochihin, L. O. Silva, R. Simpson, V. Stergiou, R. M. G. M. Trines, T. Vieu, N. Charitonidis, R. Bingham & G. Gregori
Nature Communications 15, 5029 (2024). DOI: 10.1038/s41467-024-49346-2


Research group "Astrophysical Plasma Theory" (APT) at MPIK

HiRadMat (High-Radiation to Materials) at CERN


Dr. Thibault Vieu
MPI für Kernphysik
Phone: +496221 516-584

Charles Arrowsmith
High-Energy Density Laboratory Astrophysics (LAP)
University of Oxford

Dr. Brian Reville
MPI für Kernphysik
Phone: +49 6221 516-589

Presse- und Öffentlichkeitsarbeit

Dr. Renate Hubele / PD Dr. Bernold Feuerstein
Tel.: +49 6221 516-651 / +49 6221 516-281

How it works: A proton (far left) from the Super Proton Synchrotron (SPS) accelerator at CERN impinges on carbon nuclei (small gray spheres). This produces a shower of various elementary particles, including a large number of neutral pions (orange spheres). As the unstable neutral pions decay, they emit two high-energy gamma rays (yellow squiggly arrows). These gamma rays then interact with the electric field of Tantalum nuclei (large gray spheres), generating electron and positron pairs and resulting in the novel electron-positron fireball plasma. Because of these cascade effects, a single proton can generate many electrons and positrons, making this process of pair plasma production extremely efficient. Credit: University of Rochester Laboratory for Laser Energetics illustration / Heather Palmer.