Antimatter is extremely unstable: If it comes into contact with normal matter, they both annihilate each other, releasing energy. So far it has been impossible to transport antiparticles over long distances. But now such antimatter transport has been successful for the first time. A truck drove a cloud of suspended antiprotons across the grounds of the CERN research center near Geneva. This world premiere was made possible by a special container developed at CERN in which superconducting magnets enclose the antiparticles in a mobile vacuum chamber without contact. This transport is an important breakthrough because it is the only way samples can be taken from the antimatter factory at CERN to specialized laboratories in Germany and elsewhere in Europe.
It is one of the great mysteries of physics: our universe is now dominated by matter, even though just as much antimatter as matter must have been created in the Big Bang. Physicists suspect the cause lies in subtle differences in the characteristics or behavior of both forms of matter. Accordingly, they search intensively for evidence of such an asymmetry. But research into antimatter can also reveal more about the fundamental forces of physics and the Standard Model. But the antimatter required for this can only be produced and stored with great effort. If an antiparticle comes into contact with normal matter, both cancel each other out. Special traps are therefore necessary to keep the antiparticles in suspension without contact using magnetic fields.
Why antiprotons have to travel
The world’s only “antimatter factory” capable of producing low-energy antiprotons suitable for measurements and storage is located at the CERN research center near Geneva. There, accelerators produce the necessary antimatter and two other systems slow down the antiprotons to such an extent that they can be captured, stored and combined with positrons to form antihydrogen. The BASE collaboration at CERN has already succeeded in storing antimatter for months. The problem, however, is that CERN is unsuitable for particularly precise measurements of antiparticles. “The accelerators and systems at the antimatter factory generate magnetic field fluctuations that limit the accuracy of our measurements,” explains BASE spokesman Stefan Ulmer from the Heinrich Heine University in Düsseldorf. Although these fluctuations are less than a billionth of a Tesla, they are enough to influence the measurement results on the basic characteristics of the antiprotons.
That’s why the antimatter has to be taken somewhere else for high-precision measurements – for example to special laboratories at Düsseldorf University. But this is only possible if the antiparticles are cooled and kept in suspension throughout the transport. “That’s why we started designing a transportable trap about ten years ago,” reports Ulmer. This transport box, called BASE-STEP, contains a cooled down vacuum chamber in which the antiprotons are kept in suspension by superconducting magnets. The magnetic trap is designed to prevent the antimatter from coming into contact with the wall despite the shocks of road transport. The entire container weighs around 850 kilograms and fits in a truck.
Practical test on the CERN site
Now a first practical test proves that the antimatter transport box actually works. To do this, the BASE-STEP container was filled with a cooled cloud of almost 100 antiprotons and loaded onto a truck. This then drove all over the CERN site before the antiprotons were brought back to the laboratory. As CERN reports, the antimatter survived the trip unscathed and could then be used for experiments. This is the first time that physicists have succeeded in transporting antimatter through the area – a world first. “This is a huge leap towards our goal,” says Christian Smorra, head of the STEP project. The test proves that it is technically possible to bring antiprotons from CERN to other European laboratories. This represents an important step towards more precise measurements with these antiparticles.
The next destination for the antiprotons is a special laboratory at the University of Düsseldorf, around 700 kilometers from CERN. However, this still requires an upgrade of the BASE-STEP box: “So far we have stored antiprotons in BASE-STEP for two weeks without loss, and we can transport the trap autonomously for four hours,” explains Smorra. “But we need at least ten hours to reach our laboratory at HHU.” In order for the superconducting magnets to stay cold for such a long time, an electrically powered cryocooler must actively keep the liquid helium used as a coolant cool during this time. The truck must therefore also have a power generator. “The transport of antimatter is a milestone. We are at the beginning of an exciting scientific journey of discovery that will further deepen our understanding of antimatter,” says CERN Research Director Gautier Hamel de Monchenault.
Source: CERN, Heinrich Heine University Düsseldorf, Leibniz University Hannover