Inside the world’s first antimatter delivery service

Within the core of CERN’s antimatter facility, amidst powerful magnetic forces and a vacuum more sparse than space itself, lies some of the Earth’s most sensitive material. Encased in a box about the size of a filing cabinet and lighter than a Ford Focus, several antiprotons have been resting in exceptional stillness for weeks. While most particles in this building undergo various tests, these antiprotons have one simple task: remain in place until they’re ready to be transported.

Soon, these approximately 100 antimatter particles will embark on a journey around a 4-kilometre loop on the CERN campus, marking the first step towards a future service that will eventually deliver antimatter across Europe to various laboratories.

I visited CERN near Geneva, Switzerland, to witness the final preparations of the Symmetry Tests in Experiments with Portable antiprotons (STEP) project. Project leader Christian Smorra explained, “It’s groundbreaking for antimatter science. The idea of transporting antiprotons has been around since this facility started, but now it’s finally becoming a reality.”

Since the 1920s, we have known that many particles have an antimatter counterpart with an opposite charge. However, it took almost 50 years for scientists to produce and store significant amounts of antiprotons, due to their tendency to annihilate on contact with protons, their matter counterparts.

The initial efforts to trap antiprotons started at CERN in the 1980s, where they were generated by colliding protons with metal targets. Today, CERN’s Antimatter Decelerator hall, known as the antimatter factory, is the sole global facility capable of producing millions of antiprotons on demand and storing them for research. It hosts seven antimatter experiments, including the Baryon Antibaryon Symmetry Experiment (BASE), which STEP is a part of.

All these experiments are meticulously analyzing the fundamental properties of antimatter to identify any differences from regular matter. Such findings could help explain why the universe is predominantly composed of matter, with antimatter being nearly absent.

For achieving the high precision necessary in these studies, it is crucial to eliminate any disruptive radiation that could skew measurements. This presents a challenge in the antimatter factory, where antiprotons enter at near-light speeds and require slowing by powerful magnetic fields that cannot be completely shielded.

In 2018, Smorra and his team recognized the need to relocate antimatter to a quieter environment and devised a plan to do so. “We noticed the effects of magnetic field fluctuations and understood that we needed to continue our precision measurements elsewhere,” Smorra stated.

This task was not straightforward. Typically, containing antimatter involves using superconducting magnets that need to be maintained at near-absolute zero, which demands significant power. Smorra’s team developed STEP to utilize a 30-litre tank of liquid helium for cooling, allowing the electronics to run on a simple diesel generator. For the upcoming test run, however, only battery power will be used.

The magnet must also be designed to withstand the start-stop motions of driving, and a custom vacuum system is essential to keep regular matter at bay while loading and unloading antiprotons from the trap.

In 2024, Smorra’s team successfully demonstrated STEP with regular protons by transporting them around the CERN campus via truck. Now, they are ready to attempt the same with antiprotons.

The preparations have been relatively straightforward. About a week before my visit, approximately 100 antiprotons were decelerated and placed into a complex system of vacuums and electromagnetic fields.

Since then, the antiprotons have remained stationary, surrounded by wires and liquid helium pipes. Smorra’s team monitors their condition using a small oscilloscope attached to the machine, where the vibration frequency of the antiprotons appears as two peaks. They have humorously added googly eyes above each peak.

In the early hours of Tuesday, a crane will load the 850-kilogram trap onto a truck, which will be driven by someone specially trained to handle CERN’s sensitive equipment. The driver will ensure smooth transport without sudden stops or accelerations.

The truck will complete a 4-kilometre circuit around the CERN campus, returning to the antimatter factory where it began.

If this trial succeeds, Smorra and his team aim to transport their antimatter capsule beyond CERN to various labs across Europe. One such lab is being built at Heinrich Heine University Düsseldorf in Germany, where antimatter will be examined in a nearly magnetic-field-free environment. However, this goal may take years, as CERN is set to undergo significant upgrades starting in July, with completion expected in late 2028.

Once operational, you might find yourself on a Swiss or German highway alongside a truck carrying antimatter. Though it might look like an ordinary truck, its contents are far from ordinary. Despite antimatter’s reputation for annihilating when it meets regular matter, there is no cause for alarm, assures Smorra.

“Transporting antimatter is safe because the quantity is so minuscule,” Smorra explains. “If 1000 antiprotons were lost, you wouldn’t even notice.”