The Antimatter Van: How CERN Moved Particles That Vanish on Contact
When Stefan Ulmer watched the monitor on his phone during the drive, he was tracking the vital signs of something that should not exist: ninety-two antiprotons, bouncing inside a trap bolted to a flatbed truck rumbling down a public road.
Everything about antimatter defies intuition. When it touches ordinary matter, both vanish in a flash of energy. Yet on Tuesday, scientists at CERN successfully completed the world's first road transport of antiprotons—a ten-kilometer journey around the laboratory's Geneva campus that Ulmer called "the starting point to a new era."
The particles returned, so this was a success. The relief was audible in his voice.
Why This Matters
The achievement breaks a fundamental constraint that has limited antimatter research for decades. CERN's antimatter factory, the only place on Earth where antiprotons can be produced and studied, sits embedded within the same accelerator complex that generates them.
Those machines create constant electromagnetic noise—subtle but enough to muddy the most precise measurements scientists can take.
Ulmer's team, working on an experiment called BASE that probes why the universe contains more matter than antimatter, had hit a wall. They want to understand something about the fundamental symmetries of nature, and they know that if these experiments are conducted outside of the accelerator facility, they can measure 100 to 1,000 times better.
The Container
The solution required building a container sophisticated enough to keep antiprotons alive long enough to survive a truck ride.
The team loaded their cargo—chilled to 8.2 Kelvin, just above absolute zero—into an 850-kilogram cryogenic Penning trap. A powerful vacuum inside the trap ensures the particles never collide with residual gas molecules, which would trigger instant annihilation.
The whole assembly looked, as one journalist noted, like a large filing cabinet.
Dozens of scientists in hard hats gathered to watch a ceiling crane lift the trap onto the truck. They had rehearsed this. What they hadn't rehearsed was the next step: actually driving away.
The most critical part is on the road, because there you have additional vibrations, said Marcus Jankowski, who oversaw safety for the transfer. The truck bore a simple slogan on its sides: Antimatter in Motion.
Flanked by escort vehicles with flashing lights, it crept through the campus while Ulmer followed in his car, eyes fixed on his phone.
The monitor displayed the antiprotons as two peaks—an M-shape representing their characteristic vibrational frequency. A single peak would mean the particles had been lost.
During the drive, the trace wobbled slightly, and for a moment the tension in the convoy must have been palpable. But it was only the detector's own resonant frequency shifting by a few hertz. The particles are still at the same position, Ulmer announced. Everything went smoothly. It's a very big success.
It's fantastic! This opens up so many possibilities, Francois Butin, the technical coordinator of the antimatter factory, told AFP.
The Road Ahead
The ultimate goal stretches far beyond a campus drive. CERN plans eventually to ship antiprotons to partner laboratories across Europe, beginning with a dedicated precision facility in Düsseldorf—roughly eight hours away in Germany.
Keeping the trap cold enough for that duration presents the next engineering challenge. But the harder moment, according to Christian Smorra, who leads the BASE-STEP experiment, will come at the destination: transferring the antiprotons into whatever apparatus awaits without losing a single one.
That problem is one for later. For now, physicists have demonstrated that antimatter can leave the lab—a capability that would have seemed like science fiction just years ago.
Based on: The Antimatter Van: How CERN Moved Particles That Vanish on Contact; Reuters; Phys.org / AFP, 2024.