Inside the world’s first antimatter delivery service

Nestled in the heart of CERN’s antimatter factory, surrounded by intensely powerful magnetic fields and in a vacuum sparser than interstellar space, lies one of the most sensitive materials on Earth. Inside a box the size of a filing cabinet, which weighs a few hundred pounds less than a Ford Focus, are a handful of antiprotons that have sat for weeks in extraordinary stillness. Most other particles produced in this building might expect to be probed and prodded, but these antiprotons have just one job: sit and wait for their journey.

These hundred antimatter particles will soon be transported on the back of a truck on a 4-kilometer road loop around the CERN campus, in what will be the first demonstration of a future antimatter delivery service that will one day see antimatter transported to laboratories across Europe.

I’ve come to the CERN campus near Geneva, Switzerland, to see the experiment, called Symmetry Tests in Portable Antiproton Experiments (STEP), in its final preparations before the big day, as project leader Christian Smorra shows me around the facility. “This is revolutionary for antimatter science,” he says. “The idea of ​​transporting antiprotons existed, in principle, from the beginning of this facility, and now is the first time it has become possible to do so.”

We have known since the 1920s that many particles have an almost identical counterpart, except for an opposite charge, called antimatter. But it took almost half a century for scientists to be 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 capable of producing millions of antiprotons on demand and storing them for later studies. It houses seven different antimatter experiments, including the Baryon Antibaryon Symmetry Experiment (BASE), of which STEP is a part.

All of these experiments test the fundamental properties of antimatter with extreme precision to see how it might deviate from ordinary matter. Any differences could explain why we seem to live in a matter-dominated universe, with a near-total absence of antimatter.

But to truly achieve the extraordinary precision required, it is necessary to filter out noisy radiation that could interfere with the measurements, which poses a problem for the antimatter factory. When the antiprotons enter the room, they travel at almost the speed of light and must be slowed down using powerful magnetic fields, which are impossible to completely block.

In 2018, Smorra and his team realized they would need to move the factory’s antimatter to a quieter location – and came up with an evacuation plan. “We had noted the impact of fluctuations in the magnetic field. It was therefore clear that we eventually needed to continue our precision measurements. [elsewhere]”, says Smorra.

It was not an easy task. Containing antimatter typically requires powerful magnetic fields produced by superconducting magnets, which must be maintained at a near absolute level, requiring enormous amounts of energy. Smorra and his team designed STEP to use only a 30-liter tank of liquid helium to keep the magnets cool, so the electronics could run with a simple diesel generator. However, for the next test, it will only use battery power.

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

In 2024, Smorra and his team demonstrated that STEP works with regular protons by driving their machine onto the CERN campus in a truck. Now, Smorra and his team are about to try the real thing.

So far, the preparations have been relatively simple. About a week before my arrival, about a hundred antiprotons were slowed down and entered the complex system of voids and electromagnetic fields that will trap them.

Since then, they have remained there, arms crossed, in the center of a tangle of wires and liquid helium pipes. Smorra and his team can check the vital signs of their antimatter using a small oscilloscope screen attached to the machine, where the characteristic frequency at which the antiprotons vibrate takes the shape of two bumps. They lovingly pinned two googly eyes above each peak.

In the early hours of Tuesday morning, a crane will lift the entire 850-kilogram trap onto the back of a truck, driven by someone who will have specialized training in operating CERN’s sensitive equipment, ensuring it does not accelerate or stop too suddenly.

The truck will then travel a 4 kilometer loop around the CERN campus back to the antimatter factory where it started.

If their test is successful, Smorra and his team’s ultimate goal will be to take their antimatter capsule on routes beyond CERN, to deliver it to laboratories across Europe. One such facility is currently under construction at Heinrich Heine University in Düsseldorf, Germany, where antimatter will be studied in the absence of almost any external magnetic field. However, this goal could take several years, as CERN will be largely closed in July to upgrade the Large Hadron Collider to operate at higher powers. This upgrade will not be completed until the end of 2028.

But once the antimatter delivery service is up and running, you could find yourself on a Swiss or German highway next to a truck full of antimatter. It will look like a normal truck, but its contents will be anything but normal. That might sound worrying, given antimatter’s tendency to annihilate when it encounters ordinary matter, but people shouldn’t be afraid, Smorra says.

“Transporting antimatter is not dangerous, because the amount we transport is very small,” says Smorra. “If you carry 1,000 antiprotons and they get lost, you won’t even notice.”