From carbon to uranium, and from oxygen to iron, chemical elements are the building blocks of the world around us and the wider universe. Now, physicists hope to glimpse their unprecedented origins, with the opening of a new facility that will create thousands of strange and unstable versions of atoms that have never been recorded on Earth.
By studying these versions, known as isotopes, they hope to gain new insights into the interactions they create Elements in a supernova, as well as testing the theory of the “strong force” – one of the four fundamental forces in nature, which binds protons and neutrons together in atomic nuclei. The facility can also produce new isotopes for medical use.
Atoms consist of protons, neutrons and electrons. The number of protons determines the chemical behavior of an atom and which element it is – for example, carbon always has six protons, gold 79 – whereas atoms of the same element with different numbers of neutrons are called isotopes.
Because many isotopes are unstable and decay rapidly—sometimes within a millisecond—scientists study only a fraction of the isotopes thought to exist.
“There are 285 isotopes of the element found on Earth, but we think there may be 10,000 isotopes of the element even uranium,” said Professor Bradley Sherrill, scientific director of the Rare Isotope Ray Facility (FRIB) at Michigan State. The university officially opened on May 2. “FRIB’s goal is to provide as much access to this vast landscape as possible from any other technology-enabled peers.”
Some of these “rare isotopes” can cause reactions important for the formation of the elements, so by studying them, physicists hope to gain a better understanding of the chemical history of the universe — including how we got here.
Most elements are thought to have originated in supernovae, but “in most cases we don’t know which star created which element, because these interactions involve unstable isotopes – things we can’t get around easily,” said Professor Gavin Lotay, University of Surrey nuclear physicists, who plan to use the new facility to investigate common explosions called X-ray bursts inside neutron stars.
Another goal is to understand atomic nuclei well enough to develop comprehensive models of them, which could provide new insight into the role they play in generating energy for stars, or the reactions that occur inside nuclear power plants.
The facility can also produce medically useful analogues. Doctors already use radioisotopes in pet examinations and some types of radiotherapy, but finding more isotopes could help improve diagnostic imaging or provide new ways to find and destroy tumors.
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To produce this isotope, FRIB would accelerate a beam of atomic nuclei to half the speed of light and send it down a 450-meter tube, before crushing it into a target that splits several atoms into smaller clusters of protons and neutrons. A series of magnets will then filter out the desired isotope and direct it to the experimental chamber for further study.
“In a millionth of a second, we can pick a particular isotope and send it to an experiment where— [scientists] “We might catch it and watch its radioactive decay, or we might use it to induce another nuclear reaction and use the products of that reaction to tell us something about the structure of the isotope,” Sherrill said.
The first experiments will involve manufacturing the heaviest isotopes of fluorine, aluminum, magnesium and neon, and comparing radioactive decay rates to those predicted by current models. “It would be surprising if our observations were consistent with what we expected,” Cheryl said. “They probably won’t agree, and then we’ll use that disagreement to improve our model.”
About a month later, FRIB researchers plan to measure the radioactive decay of isotopes believed to be in neutron stars — some of the densest objects in the universe, which form when a massive star runs out of fuel and collapses — to better understand their behavior.
“Finally, we have the tools to enable people to do the research they’ve been waiting for 30 years,” Cheryl said. “It’s like having a new, bigger telescope that can look into the universe more than ever before – only we’re going to be looking further into the nuclear landscape than we were able to see before. Whenever you have a new instrument like that, there is potential for discovery.”
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