Long-awaited accelerator ready to explore origins of elements

[NNadir]

This is a news item in Nature; it should be open sourced.

Long-awaited accelerator ready to explore origins of elements

Subtitle:

The Facility for Rare Isotope Beams will be the first to produce and analyse hundreds of isotopes crucial to physics.

Some excerpts:

One of nuclear physicists’ top wishes is about to come true. After a decades-long wait, a US$942 million accelerator in Michigan is officially inaugurating on 2 May. Its experiments will chart unexplored regions of the landscape of exotic atomic nuclei and shed light on how stars and supernova explosions create most of the elements in the Universe.

“This project has been the realization of a dream of the whole community in nuclear physics,” says Ani Aprahamian, an experimental nuclear physicist at the University of Notre Dame in Indiana. Kate Jones, who studies nuclear physics at the University of Tennessee in Knoxville, agrees. “This is the long-awaited facility for us,” she says.

The Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) in East Lansing had a budget of $730 million, most of it funded by the US Department of Energy, with a $94.5 million contribution from the state of Michigan. MSU contributed an additional $212 million in various ways, including the land. It replaces an earlier National Science Foundation accelerator, called the National Superconducting Cyclotron Laboratory (NSCL), at the same site. Construction of FRIB started in 2014 and was completed late last year, “five months early and on budget”, says nuclear physicist Bradley Sherrill, who is FRIB’s science director...

All FRIB experiments will start in the facility’s basement. Atoms of a specific element, typically uranium, will be ionized and sent into a 450-metre-long accelerator that bends like a paper clip to fit inside the 150-metre-long hall. At the end of the pipe, the beam of ions will hit a graphite wheel that spins continuously to avoid overheating any particular spot. Most of the nuclei will pass through the graphite, but a fraction will collide with its carbon nuclei. This causes the uranium nuclei to break up into smaller combinations of protons and neutrons, each a nucleus of a different element and isotope.

This beam of assorted nuclei will then be directed up to a ‘fragment separator’ at ground level. The separator consists of a series of magnets that deflect each nucleus towards the right, each at an angle that depends on its mass and charge. By fine-tuning this process, the FRIB operators will be able to produce a beam consisting entirely of one isotope for each particular experiment...

...Researchers have therefore concocted a variety of simplified models that predict some features of a certain range of nuclei, but might fail or give only approximate estimates outside that range. This applies even to basic questions, such as how fast an isotope decays — its half-life — or whether it can form at all, says Nazarewicz. “If you ask me how many tin isotopes exist, or lead, the answer will be given with a large error bar,” he says. FRIB will be able to synthesize hundreds of previously unobserved isotopes (see ‘Unexplored nuclei’), and by measuring their properties, it will begin to put many nuclear models to the test...

In my private studies, I've often perused the table of nuclides - I've always liked the Kaeri site for its simplicity, and ease for finding general things quickly; I use BNL when I want to go deeper - and this graphic is a cool representation of it pointing to the possible rather than the known:

...Jones and others will be especially keen to study isotopes that have ‘magic’ numbers of protons and neutrons — such as 2, 8, 20, 28 or 50 — that make the structure of the nucleus especially stable because they form complete energy levels (known as shells). Magic isotopes are particularly important because they provide the cleanest tests for the theoretical models. For many years, Jones and her group have studied tin isotopes with progressively fewer neutrons, edging towards tin-100, which has magic numbers of both neutrons and protons.

Theoretical uncertainties also mean that researchers do not yet have a detailed explanation for how all the elements in the periodic table formed. The Big Bang produced essentially only hydrogen and helium; the other chemical elements in the table up to iron and nickel formed mostly through nuclear fusion inside stars. But heavier elements cannot form by fusion. They were forged by other means...

The article states that a similar facility is being built in Germany and was scheduled for completion in 2027; however completion is in doubt because Russian scientists were partners in it and Russian participation has been frozen because an insane government in that country.

[xocetaceans]

1. That is cool.

I'll have to read up on this. Thanks for the very interesting post.