Proton transport from the antimatter factory of CERN

Published on 4 June 2025

The BASE international research collaboration, which is located at CERN who were a partner in the AVA project, have successfully demonstrated the transport of a cloud of trapped protons from the Antimatter Factory (AMF) using a revolutionary, portable Penning-trap system. This pioneering achievement, published in Nature, marks a crucial step towards being able to relocate antiprotons to specialized, low-noise laboratories worldwide, promising unprecedented precision in the search for subtle differences between matter and antimatter.

The experiment, conducted by the Baryon-Antibaryon Symmetry Experiment (BASE) collaboration, utilized a device called BASE-STEP (Symmetry Tests in Experiments with Portable Antiprotons). While the initial test involved ordinary protons, the success of this dress rehearsal strongly indicates the feasibility of transporting antiprotons, the antimatter counterparts of protons, which are produced at CERN's Antimatter Decelerator (AD).

Experiments at CERN's AMF, such as BASE, are designed to test fundamental charge-parity-time (CPT) invariance by precisely comparing the properties of protons and antiprotons, including their magnetic moments and charge-to-mass ratios. However, the precision of these measurements has been limited by magnetic field fluctuations caused by the very accelerators that produce the antiprotons. Professor Dr Stefan Ulmer, founder and spokesperson of the BASE collaboration, explains: “We need an extremely high level of measuring accuracy to be able to identify possible differences in the magnetic moment or charge-to-mass ratio. It is virtually impossible to achieve this close to CERN’s accelerators, though, as the magnetic disturbance that the accelerators there generate is simply too high. Accordingly, we want to bring antiprotons produced at CERN to [Heinrich Heine Universität] Düsseldorf to measure them here in a new, extremely well shielded laboratory.”

The BASE-STEP system is a transportable, superconducting, autonomous, and open Penning-trap system. During the test, a cloud of trapped protons was transferred from the experimental area at the AMF onto a truck and transported across CERN's Meyrin site. Marcel Leonhardt , a master’s student of Professor Ulmer at Heinrich Heine Universität Düsseldorf and lead author of the publication said: “We were able to demonstrate the loss-free relocation of protons, sustain autonomous operation without external power for four hours and continue to operate the trap loss-free afterwards. An important step that shows that particles can thus be relocated over longer distances in normal road traffic.”

This successful proton transport confirms that the intricate electromagnetic confinement required for charged particles can be maintained outside laboratory environments. Now that the transport system’s functionality has been proven with protons, the next step is to tackle the relocation of antiprotons. Dr Christian Smorra, BASE-STEP Project Leader and senior scientist in BASE adds: “If we also manage this, then it will mark the potential rise of a new era in antimatter precision research. We could then perform antiproton spectroscopy in the most suitable laboratories”

The ultimate goal remains the lossless relocation of antiprotons, which would not only alleviate the need for duplicating expensive antimatter facilities but also enable unprecedented measurement accuracies, pushing the boundaries of our understanding of the universe's fundamental symmetries.

This article is based partly on an original article on the GSI website and also on the paper in published in Nature

 

* Feature Image:

1. The route for the first transport demonstration through the AMF hall. Point 1 is the experiment zone from which an overhead crane moved the transport frame to point 2; at point 2, the transport frame was loaded onto a trailer and moved to point 3, where it then got picked up by the second overhead crane. Point 4 is the loading bay with the truck.
2. Road map of the Meyrin site of CERN and the GPS position data recorded during transportation. Map reproduced from https://www.openstreetmaps.org.
3. Magnet temperature
4. total acceleration
5. liquid helium level measured during transport.

Image credit: M.Leonhardt et al, Nature 641, 871–875 (2025)