Swansea physicists drive antihydrogen breakthrough at CERN with record trapping technique

Physicists from Swansea University have played the leading role in a scientific breakthrough at CERN, developing an innovative technique that increases the antihydrogen trapping rate by a factor of ten.

The advancement, achieved as part of the international Antihydrogen Laser Physics Apparatus (ALPHA) collaboration, has been published in Nature Communications and could help answer one of the biggest questions in physics: why is there such a large imbalance between matter and antimatter? According to the Big Bang theory, equal amounts were created at the beginning of the Universe, so why is the world around us made almost entirely of matter?

Antihydrogen is the “mirror version” of hydrogen, made from an antiproton and a positron. Trapping and studying it helps scientists explore how antimatter behaves, and whether it follows the same rules as matter.

Producing and trapping antihydrogen is an extremely complicated process. Previous methods took 24 hours to trap just 2,000 atoms, limiting the scope of experiments at ALPHA. The Swansea-led team has changed that.

Using laser-cooled beryllium ions, the team has demonstrated that it is possible to cool positrons to less than 10 Kelvin (below –263°C), significantly colder than the previous threshold of about 15 Kelvin. These cooler positrons dramatically boost the efficiency of antihydrogen production and trapping—allowing a record 15,000 atoms to be trapped in under seven hours.

This marks a new era at ALPHA, expanding the range of possible experiments and enabling more precise tests of fundamental physics, including how antimatter responds to gravity and whether it obeys the same symmetries as matter.

Professor Niels Madsen from the School of Biosciences, Geography and Physics, lead author of the study and Deputy Spokesperson for ALPHA, said: “It’s more than a decade since I first realised that this was the way forward, so it’s incredibly gratifying to see the spectacular outcome that will lead to many new exciting measurements on antihydrogen.”

Maria Gonçalves, a leading PhD student on the project, added: “This result was the culmination of many years of hard work. The first successful attempt instantly improved the previous method by a factor of two, giving us 36 antihydrogen atoms—my new favourite number! It was a very exciting project to be a part of, and I’m looking forward to seeing what pioneering measurements this technique has made possible.”

Dr Kurt Thompson, a leading researcher on the project, said: “This fantastic achievement was accomplished by the dedication and collaborative efforts of many Swansea graduate students, summer students and researchers over the past decade. It represents a major paradigm shift in the capabilities of antihydrogen research. Experiments that used to take months can now be performed in a single day.”

Read the full study.