CERN’s faster antihydrogen production enables particle physics insights

Four experiments at the CERN Antiproton Decelerator presently use nonneutral traps to produce antihydrogen, aiming to understand the differences between antimatter and matter in the universe and explain the observed excess of matter over antimatter. Researchers create antihydrogen by slowly merging antiprotons and positrons. However, producing large quantities of antihydrogen in the stable ground state is difficult because antiprotons and positrons tend to form excited states of antihydrogen during the recombination process.

Hunter et al. developed key improvements that enabled slow-merge methods to work with about 30 times more antiprotons than previously possible. By boosting the supply of antiprotons, the researchers dramatically increased antihydrogen production, generating more than 2 million antihydrogen atoms in a 15-minute run — 20 times the previous record.

The total antihydrogen yield and the number of atoms escaping the trap as a beam are greatest when the positron temperature is lowest and when antiprotons enter the positron plasma at the smallest radius. The researchers maximized this yield by controlling the rate of variation of the electrostatic barrier between the antiproton and positron plasmas during the merge.

“Others are already putting this knowledge to use,” said author Eric Hunter, pointing out that antihydrogen experiments at CERN have relied on the refined method ever since it was first circulated internally.

The researchers plan to use their produced antihydrogen to measure ground state hyperfine antihydrogen splitting.

“Prior to the advances we report, the beam intensity was far too low to envisage such a measurement,” Hunter said. “Now we hope to see our first signal by August.”

However, further optimizing antimatter production and extraction for such studies remains an open challenge.

“Although our work is an important step, the dynamics of slow extraction remain largely unexplained,” Hunter said.

Source: “Optimizing antihydrogen production via slow plasma merging,” by E. D. Hunter, M. Bumbar, C. Amsler, M. Bayo, H. Breuker, M. Cerwenka, G. Costantini, R. Ferragut, M. Giammarchi, A. Gligorova, G. Gosta, M. Hori, C. Killian, V. Kraxberger, N. Kuroda, A. Lanz, M. Leali, G. Maero, C. Malbrunot, V. Mascagna, Y. Matsuda, S. Migliorati, D. J. Murtagh, M. Rome, R. E. Sheldon, M. C. Simon, M. Tajima, V. Toso, S. Ulmer, L. Venturelli, A. Weiser, and E. Widmann, Physics of Plasmas (2026). The article can be accessed at https://doi.org/10.1063/5.0311707 .