This powerful new accelerator looks for keys to the center of atoms
Nuclear physicists trying to piece together how atoms are built are about to get a powerful new tool.
Why it matters: When the Facility for Rare Isotope Beams begins experiments later this spring, physicists from around the world will use the particle accelerator to better understand the inner workings of atoms that make up all the matter that can be seen in the universe.
- In the more than 13.7 billion years since the Big Bang, all of the elements in the universe lighter than iron have been forged in nuclear reactions, mostly within stars. Heavier elements are suspected to form in the mergers of stars or supernova, explosive scenarios that FRIB will mimic to try to understand the elements' origins in the universe.
- On Earth, modeling how protons and neutrons bind to form nuclei could help to improve medical diagnostics and treatments that use isotopes — different forms of an element.
- "[The facility] gives us the most exotic isotopes that can be made anywhere on the planet and opens the door to a whole new slew of studies that could not be done without FRIB," says Ani Aprahamian, a professor of physics at the University of Notre Dame who chairs the science advisory committee at FRIB.
The big picture: More than 30 years in the making, the $730 million FRIB is operated by Michigan State University and funded by the Department of Energy.
- It will complement the Relativistic Heavy Ion Collider and planned Electron-Ion Collider at Brookhaven National Laboratory and the Continuous Electron Beam Accelerator Facility at the Jefferson Lab.
- Those accelerators smash electrons, protons, heavy ions or nuclei together to dislodge and study quarks, which make up protons and neutrons, and gluons, which carry the force that holds the quarks themselves together.
- "The manifestation of those fundamental forces is the atomic nucleus," says Brad Sherrill, a professor of physics at Michigan State University and the scientific director of FRIB.
- But nuclei can have different sizes, densities and shapes — resembling pears, footballs and pancakes — depending on the ratio of protons and neutrons in them. Coming up with a model to describe the many configurations of nuclei is one of physics' toughest, most fundamental problems.
That's where FRIB comes in.
- It accelerates a beam of a naturally occurring isotope to about 60% of the speed of light and strikes it against a target, stripping neutrons and protons from the nuclei of atoms in the beam to create rare isotopes.
- The isotope of interest is filtered out by magnets so physicists can study its properties and the reactions that form it.
- FRIB's powerful beam can take any of the roughly 90 naturally occurring elements on Earth and create isotopes of them — many of which vanish almost immediately. These rare isotopes represent the range of possible configurations of the nucleus and give scientists a sketch of nuclear limits, including how many neutrons can be added or subtracted before a nucleus falls apart.
- The goal is to produce about 80% of all theoretically possible isotopes for elements up to and including uranium.
The latest: Last month, physicists reported using FRIB's predecessor — the National Superconducting Cyclotron Laboratory — to make the lightest isotope of magnesium ever seen.
- FRIB will build on that research when it switches to operation mode in early February and starts experiments in late May or early June.
- The first experiments will focus on testing existing models of the nucleus to see if they hold for extreme isotopes with many or few neutrons, Sherrill says.
- Early in its operation, it will also look at rates of nuclear reactions at extremely high temperatures, like those in supernovas.
The intrigue: The mass of an atom is less than the sum of the masses of the individual protons and neutrons that make up the nucleus. The missing mass is energy lost when protons and neutrons interact and bind together.
- Physicists hope to piece together how that happens by combining findings about protons and neutrons from FRIB with data from other accelerators focused on quarks and gluons.
What to watch: Federal budget constraints could affect Department of Energy funding of the field's next flagship programs.
Far on the horizon, findings from these experiments might help to make nuclear isotope production for medicine and other applications more efficient, says Christine Aidala, a professor of physics at the University of Michigan who works on the planned Electron-Ion Collider and isn't involved with FRIB.
- Decades from now, accelerator technology might even be miniaturized to the point where tabletop nuclear printers could make isotopes on demand, she says.
Editor's note: This story was originally published on Jan. 20.