From carbon to uranium, and from oxygen to iron, the chemical elements are the building blocks of the world around us and the wider universe. Now, physicists hope to get an unprecedented glimpse into their origins, with the opening of a new facility that will create thousands of strange and unstable versions of atoms that have never before been recorded on Earth.
By studying these versions, known as isotopes, they hope to gain new insights into the interactions that created Elements inside supernovae, as well as testing theories about the “strong force” – one of the four fundamental forces in nature, which bind protons and neutrons together in the nucleus of an atom. The facility can also produce new analogues for medical use.
Atoms are made up of protons, neutrons, and electrons. The number of protons determines the chemical behavior of an atom and which element it is – eg carbon always has six protons, gold 79 – while atoms of the same element with different numbers of neutrons are called isotopes.
Because many isotopes are unstable and decay rapidly—sometimes in milliseconds—scientists have only studied a small percentage of those isotopes thought to exist.
“There are 285 isotopes of elements found on Earth, but we think there are likely 10,000 isotopes of elements even uranium,” said Professor Bradley Sherrill, scientific director of the Rare Isotope Rays Facility (FRIB) at Michigan State. The university officially opened on May 2. “The goal of FRIB is to provide as much access to this vast landscape from other peers as technology allows.”
Some of these “rare isotopes” may lead to reactions crucial to 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.
The vast majority of the elements are thought to have formed inside exploding stars, but “in many cases we don’t know which stars created which elements, because these interactions involve unstable isotopes – things we can’t easily obtain,” said Professor Gavin Lotay, a nuclear physicist. The University of Surrey, who plans 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 a comprehensive model of them, which could provide new insights into the role they play in the generation of energy for stars, or the reactions that occur within nuclear power plants.
The facility can also produce medically useful analogs. Doctors already use radioisotopes in pet exams and some types of radiotherapy, but discovering more isotopes could help improve diagnostic imaging or provide new ways to find and destroy tumors.
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To generate these isotopes, FRIB will accelerate a beam of atomic nuclei to half the speed of light and send it down a 450-meter tube, before smashing it into a target that breaks some of the atoms apart into smaller groups of protons and neutrons. A series of magnets will then filter out the desired isotopes and direct them to experimental rooms for further study.
“Within a millionth of a second, we can select a specific isotope and submit it to an experiment where [scientists] “We might capture it and watch its radioactive decay, or we might 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 involve making the heaviest possible isotopes of fluorine, aluminum, magnesium and neon, and comparing radioactive decay rates to those predicted by current models. “It would be a surprise 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 models.”
About a month later, FRIB researchers plan to measure the radioactive decay of isotopes believed to exist within neutron stars — some of the densest objects in the universe, which form when a massive star ran out of fuel and collapsed — to better understand their behavior.
“Finally, we have the tools to enable people to do the research they’ve waited 30 years to do,” Cheryl said. “It’s like having a new, larger telescope that can see into the universe more than ever before – only we’ll see farther into the nuclear landscape than we were able to look before. Whenever you have a new instrument like that, there is potential for discovery.”