Please drive carefully: scientists plan to transport volatile antimatter for first time | Cern

WAs the truck pulls away from the building at Cern, Europe’s particle physics laboratory near Geneva, all eyes will be on its precious cargo, a one-ton contraption containing some of the most exotic materials on the planet.

The 20-minute test around campus, scheduled for later this month, will mark the world’s first attempt to transport antimatter, a substance so delicate that when it meets normal matter, both are consumed in a burst of pure energy.

It took years to get to this moment. But if the test goes well – that is, the truck returns with the antimatter intact – it will open the way for Cern to transport the material to other laboratories. At these facilities, researchers will make precision measurements in hopes of understanding why our universe is built from matter and not these strange mirror particles.

“A central question we want to understand is where matter comes from. And then, if you know about antimatter, it’s natural to ask why that isn’t the case here? The process is not understood and we are looking for clues as to why this happened,” says Dr Christian Smorra, physicist of the baryon-antibaryon symmetry experiment (basic) at Cern.

Antimatter, a name that implies an almost ideological opposition to the basis of our existence, is warmly embraced in science fiction. In Star Trek, it powers the Enterprise’s warp drive and photon torpedoes. In Angels and Demons by Dan Brown, a cartridge containing a quarter of a gram of antimatter is stolen from Cern as part of a plot to blow up the Vatican.

The reality is reassuring and banal. Antimatter emitters are readily available in supermarkets in the form of bananas, which emit antiparticles by radioactive decay of potassium. Unfortunately, their value for understanding the universe is limited. The device on the Cern truck will carry around 1,000 antimatter particles, weighing around a billionth of a trillionth of a gram. If containment failed and antimatter came into contact with normal matter, the resulting pulse of energy would be so small that the charge would not even warrant a radioactive label.

Antimatter was first predicted in 1928 when physicist Paul Dirac married quantum theory, which describes the behavior of subatomic particles, with special relativity, with Einstein’s theory of space and time. This work earned Dirac a Nobel Prize and described a universe in which each particle has a corresponding antiparticle, identical but oppositely charged.

The first antimatter was detected four years later. Carl Anderson of the California Institute of Technology spotted what turned out to be an antielectron, or positron, tearing apart an instrument that captured showers of particles triggered by cosmic rays. He also received a Nobel Prize for his work.

Scientists have since confirmed the full range of antiparticles. Antimatter versions of electrons, protons and neutrons can assemble into antiatoms and antimolecules. In a different universe, anti-planets could be warmed by anti-suns in shimmering anti-galaxies.

“If we were all made of antimatter and lived in a universe made entirely of antimatter, we wouldn’t notice any difference,” says Dr Jack Devlin, a Royal Society research fellow at Imperial College London. “The strange thing is that the laws of physics allow for the existence of this substance that appears to behave in the same way as normal matter.”

According to modern models of the universe, equal amounts of matter and antimatter were created during the big bang. But what happened next? When matter and antimatter meet, the particles are transformed directly into energy. So why isn’t the cosmos a vast expanse of energy?

“It seems that we have found ourselves in a universe completely submerged in ordinary matter and containing almost no antimatter, and that is the heart of the mystery,” says Devlin.

Subtle differences between matter and antimatter, which are already emerging, should explain how matter came to dominate, but discovering them requires extremely precise comparisons of particle properties. It also requires a reliable supply of materials.

Enter the CERN antimatter factory, which lives up to its name. Researchers at the facility smash high-energy protons, the nuclei of hydrogen atoms, into a dense metal target, creating showers of secondary particles. Among them are antiprotons, which are directed towards a decelerator, slowed down and finally captured in an antimatter trap.

But even though the factory can produce antimatter, it’s not the best place to make precision measurements. The decelerator that slows the antiprotons to about a tenth the speed of light uses powerful fields that make it impossible to make sensitive measurements at close range. Other labs could measure antimatter with 100 times greater precision, the researchers say.

To carry out such experiments, Smorra and his colleague Stefan Ulmer are building an antiproton receiving device at the Heinrich Heine University in Düsseldorf. To survive the trip from Cern, the antimatter would have to be confined for more than 10 hours: two for loading and unloading the trap and the rest for the 500-mile drive.

The trap itself is a feat of engineering. It must contain the antimatter so that it never comes into contact with normal matter. To do this, the chamber is kept under ultra-high vacuum, comparable to the vacuum of interstellar space. It is cooled to -269°C, which causes stray gases to freeze on the chamber walls. Strong magnetic and electric fields are then used to keep the antiprotons in the center of the cryogenic chamber.

The fields are strong enough to hold the antimatter in place if the truck hits bumps or brakes suddenly during transport. Perhaps the biggest threat to equipment is getting stuck in traffic and losing power. For the test at Cern, the trap will be powered by batteries lasting around four hours. Longer trips will require a dedicated generator on board.

“If we ever want to do antiproton experiments elsewhere, we need to get this going and that’s what we’re trying to do,” says Smorra. “First of all, we need to show that we can move antimatter and that’s an important step for us.”