Breakthrough in antimatter production

Summary

A new cooling technique means that the ALPHA experiment at CERN’s Antimatter Factory can produce antihydrogen atoms eight times faster than before In a paper published today in Nature Communications, researchers at the ALPHA experiment at CERN’s Antimatter Factory report a new technique that allows them to produce over 15 000 antihydrogen atoms – the simplest form of atomic antimatter – in a matter of hours. “These numbers would have been considered science fiction 10 years ago,” said Jeffrey Hangst, spokesperson for the ALPHA experiment. “With larger numbers of antihydrogen atoms now more readily available, we can investigate atomic antimatter in greater detail and at a faster pace than before.” To create atomic antihydrogen (a positron orbiting an antiproton), the ALPHA collaboration must produce and trap clouds of antiprotons and positrons separately, then cool them down and merge them so that antihydrogen atoms can form. This process has been refined and steadily improved over many years. But now, using a pioneering technique to cool the positrons, the ALPHA team has increased the rate of production of antihydrogen atoms eightfold. This spectacular advance in the production rate is all down to how the positrons are prepared. First, the positrons are collected from a radioactive form of sodium and contained in what is known as a Penning trap, where fine-tuned electromagnetic fields hold the antiparticles in place. However, they do not remain still. Like a tiger in a zoo, the positrons circle their cage, causing them to lose energy. This cools the cloud of positrons, but not enough for them to efficiently merge with the antiprotons to form antihydrogen atoms. So, the ALPHA team recently tried a new approach, which was to add a cloud of laser-cooled beryllium ions to the trap so that the positrons would lose energy in a process called sympathetic cooling. This got the positron cloud down to a temperature of around -266 °C, making it much more likely to form antihyd...