From carbon to uranium, from oxygen to iron, chemical elements are the building blocks of the world around us and of the universe at large. Now physicists hope to gain unprecedented insight into their origins, with the opening of a new facility that will create thousands of peculiar, unstable versions of atoms never before recorded on Earth.
By studying these versions, known as isotopes, they hope to gain new knowledge about the reactions that created the elements in exploding stars, as well as test theories about the “strong force” – one of four fundamental forces of nature, which binds protons and neutrons together in the nucleus of an atom. The facility could also produce new isotopes for medical use.
Atoms are made up of protons, neutrons and electrons. The number of protons dictates the chemical behavior of an atom and which element it is – for example, carbon always has six protons and gold 79 – whereas atoms of the same element contain different numbers of neutrons are called isotopes.
Since many isotopes are unstable and decay rapidly – sometimes within fractions of a second – scientists have studied only a small proportion of those thought to exist.
“There are 285 isotopes of elements that exist on Earth, but we think there are potentially 10,000 isotopes for elements up to uranium,” said Professor Bradley Sherrill, scientific director of the Facility for Rare Isotope Beams (FRIB) at Michigan State. University, which officially opened on May 2. “FRIB’s goal is to provide as wide access to this vast landscape of other isotopes as technology permits.”
Some of these “rare isotopes” can lead to reactions that are crucial for the formation of elements. So by studying them, physicists hope to better understand the chemical history of the universe, including how we got here.
The vast majority of elements are thought to have been created in exploding stars, but “in many cases we don’t know which stars created which elements because these reactions involve unstable isotopes – things we couldn’t not easily get their hands on”. said Professor Gavin Lotay, a nuclear physicist at the University of Surrey, who plans to use the new facility to investigate common explosions called X-ray bursts in neutron stars.
Another goal is to understand atomic nuclei well enough to develop a comprehensive model of them, which could provide new insights into the role they play in creating energy for stars or the reactions occurring in nuclear power plants. .
The facility could also produce medically useful isotopes. Already, doctors are using radioactive isotopes, for example in Pet scans and some types of radiation therapy, but the discovery of new isotopes could help improve diagnostic imaging or provide new ways to find and destroy tumors.
To generate these isotopes, FRIB will accelerate a beam of atomic nuclei to half the speed of light and send them down a 450-meter pipe, before smashing them into a target which will cause some atoms to fragment into smaller combinations of protons and neutrons. A series of magnets will then filter out the desired isotopes and direct them to experimental chambers for further study.
“In a millionth of a second, we can select a particular isotope and deliver it to an experiment where [scientists] can catch it and watch its radioactive decay, or we can use it to induce another nuclear reaction and use those reaction products to tell us something about the structure of the isotope,” Sherrill said.
The first experiments will consist of making the heaviest possible isotopes of fluorine, aluminum, magnesium and neon, and comparing their radioactive decay rates with those predicted by existing models. “The surprise will be if our observations agree with what we expected,” Sherrill said. “They probably won’t agree, and then we’ll use that disagreement to refine our models.”
About a month later, FRIB researchers plan to measure the radioactive decay of isotopes believed to exist in neutron stars – some of the densest objects in the universe, formed when a massive star runs out of fuel and decays. collapses – to better understand their behavior.
“Finally, we have the tools to allow people to do the research they’ve been waiting for 30 years,” Sherrill said. “It’s like having a new, bigger telescope that can see further into the universe than ever before – only we’ll see further into the nuclear landscape than we’ve ever been able to look before. Every time you have a new tool like this, there is potential for discovery.