Inside the world’s first antimatter delivery service

Located at the heart of CERN’s antimatter factory, surrounded by intensely powerful magnetic fields and within a vacuum sparser than interstellar space, is some of the most sensitive material on Earth. Inside a box the size of a filing cabinet, weighing a few hundred kilograms less than a Ford Focus, are a handful of antiprotons that have been sitting for weeks in extraordinary silence. Most other particles produced in this building can expect to be probed and propelled, but these antiprotons have only one job: to sit tight and wait for their ride.

These hundred or so antimatter particles will soon be transported on the back of a truck around a four-kilometre road around the CERN campus, which will be the first demonstration of a future antimatter delivery service that will one day see antimatter transported to laboratories around Europe.

I’ve arrived at CERN’s campus, near Geneva, Switzerland, to see the experiment, called Symmetry Tests in Experiments with Portable antiprotons (STEP), in its final preparations before the big day, as project manager Christian Smorra shows me around the facility. “It’s groundbreaking for antimatter science,” he says. “The idea of ​​transporting antiprotons has existed in principle since the time this facility started, and now is the first time it has become possible to actually do it.”

We have known since the 1920s that many particles have an almost identical counterpart, except for an opposite charge, called antimatter. But it took nearly half a century before scientists were able to produce and store the simplest antimatter—an antiproton—in significant quantities because of its propensity to annihilate and disappear when it encounters its matter counterpart, the abundant proton.

The first experiments to confine antiprotons were carried out at CERN in the 1980s, where they were produced by smashing protons into metal targets. Today, CERN’s Antimatter Decelerator hall, known as the antimatter factory, is the only place in the world that can produce millions of antiprotons on demand and store them for further study. It is home to seven different antimatter experiments, including the Baryon Antibaryon Symmetry Experiment (BASE), of which STEP is a part.

All of these experiments test antimatter’s fundamental properties to extreme precision to see how it might differ from ordinary matter. Any differences may shed light on why we seem to live in a matter-dominated universe, with an almost total absence of antimatter.

But to really probe down to the extraordinary precision required, it is necessary to filter out noisy radiation that can interfere with measurements, which is a problem for the antimatter factory. When antiprotons enter the hall, they travel at nearly the speed of light and must be slowed down by powerful magnetic fields, which are impossible to block completely.

In 2018, Smorra and his team realized they needed to move antimatter away from the factory to a quieter location – and hatched an escape plan. “We had seen the impact of the magnetic field fluctuations, so it was clear that eventually we would need to continue our precision measurements (elsewhere),” says Smorra.

This was no easy task. Containing antimatter usually requires powerful magnetic fields produced by superconducting magnets, which must be kept at almost absolute zero, and requires enormous amounts of power. Smorra and his team designed STEP to use only a 30-gallon tank of liquid helium to keep the magnets cool, allowing the electronics to run on a simple diesel generator instead. However, for the upcoming test run, it will only use battery power.

The magnet must also be designed to cope with the stop-start accelerations that occur during driving, as well as a bespoke vacuum system to ensure that the absence of problematic regular material can be maintained while the antiprotons are loaded and unloaded from the trap.

In 2024, Smorra and his team demonstrated that STEP works for ordinary protons by driving their equipment around the CERN campus on a truck. Now Smorra and his team are about to try the real thing.

The preparations so far have been relatively straightforward. About a week before I arrived, about 100 antiprotons were slowed down and entered the complex system of vacuum and electromagnetic fields that will hold them.

Since then, they have sat there inert in the middle of a tangle of wires and liquid helium tubes. Smorra and his team can check the antimatter’s vital signs by using a small oscilloscope screen attached to the machine, where the characteristic frequency at which the antiprotons vibrate takes the form of two humps. They have lovingly affixed two googly eyes above each peak.

Early on Tuesday morning, a crane will lift the entire 850kg trap onto the back of a lorry, driven by someone who will be specially trained to drive around CERN’s sensitive equipment, making sure they don’t accelerate or stop too suddenly.

The truck will then make a 4-kilometer loop around the CERN campus, arriving back at the antimatter factory where it started.

If their test is successful, the ultimate goal for Smorra and his team will be to drive their antimatter capsule on roads outside of CERN, delivering it to labs across Europe. Such a facility is currently under construction at Heinrich Heine University in Düsseldorf, Germany, where antimatter will be studied in the absence of almost all external magnetic fields. However, this goal could take several years, as CERN will largely shut down in July to upgrade the Large Hadron Collider to operate at higher powers. That upgrade won’t be completed until late 2028.

But when the antimatter delivery service is up and running, you could be driving down a Swiss or German highway and find yourself next to a truck full of antimatter. It will look just like a regular truck, but its contents will be anything but normal. This may sound like a worrying proposition, given antimatter’s tendency to annihilate when it encounters ordinary matter, but people should not be afraid, says Smorra.

“There is nothing dangerous about transporting antibodies, because the amount we transport is so small,” says Smorra. “If you transport 1,000 antiprotons and it’s lost, you won’t even notice.”