Antiprotons from CERN antimatter factory make their first road trip

The team filled the trap with antiprotons at CERN's antimatter factory, then disconnected it from the facility, and loaded it onto a truck. The experiment shows that antiprotons can be transported safely and reliably.

'This is a remarkable achievement, given that antimatter is very difficult to preserve and it annihilates upon contact with matter,' explains Christian Smorra, the leader of the STEP project and ERC grantee. 'Our aim is to confine antiprotons and deliver them to our laboratories at Heinrich Heine University in Düsseldorf, Germany, where we can perform high-precision antimatter measurements.'

In recent years, scientists at the Baryon Antibaryon Symmetry Experiment (BASE) at CERN have pushed their measurements to such high precision that they can no longer improve them at CERN's antimatter facility. The machines and equipment at CERN's 'antimatter factory' cause magnetic field fluctuations that restrict the precision of antiproton measurements. That is why the researchers developed the transportable antiproton trap "BASE-STEP": an apparatus designed to store and transport antimatter.

'We have validated the feasibility of transporting our trap with protons earlier, but what we achieved today with antiprotons, which requires much more challenging vacuum environment than protons, is a huge leap forward towards our objective.'

Antimatter is nearly identical to ordinary matter, but with opposite charges and magnetic properties. The Big Bang should have produced equal amounts of both, which would have annihilated each other. Yet the Universe is dominated by matter, a long-standing puzzle. Physicists suspect hidden differences that allowed matter to survive. The researchers the Baryon Antibaryon Symmetry Experiment (BASE) compare the magnetic moments of protons and antiprotons to look for differences between matter and antimatter.

BASE-STEP is small enough to be loaded onto a truck and fit through standard laboratory doors, and it can withstand the bumps and vibrations during transport. The current apparatus - which includes a superconducting magnet, liquid helium cryogenic cooling, power reserves, and a vacuum chamber that traps the antiparticles using magnetic and electric fields - weighs 850 kilograms: much more compact than BASE or any existing system used to study antimatter.

The scientists tested that BASE-STEP can keep the antiprotons stored for two weeks with no losses. They can also transport the trap for four hours which allows us to move antiprotons to other laboratories at CERN and its vicinity. However, to conduct other crucial experiments - for example at the dedicated precision laboratory in Düsseldorf it would take them at least 12 hours.

This means the trap's superconducting magnet would need to be kept at extremely low temperatures, below 8.2 K for the entire journey. Instead of relying on liquid helium, which can run out, this would require a generator to power a cryocooler on the truck. Researchers are now working to implement this approach.

The next challenge is to transfer the antiprotons into local precision experiments after transport. Work is under way to develop the necessary techniques.