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George Zimba and Alfredo Estrada discuss the experiment.

Seeking keys to the universe

CMU team runs experiment at superconducting cyclotron to help solve nuclear puzzle

Contact: Gary H. Piatek

​When two neutron stars collided in 2017 in a never-before-seen event, astronomers and astrophysicists were in seventh heaven, so to speak.

Nuclear reactions from the exploding stars rained cosmic debris thought to be the source of gold, silver, platinum and uranium ­­­— heavy elements that astrophysicists say have enhanced the chemical composition of the universe.

"My wedding band emerged from a neutron star merger," ScienceNews quoted Harvard theoretical astrophysicist Avi Loeb at the time.

Understanding the conditions that create chemical elements is the goal of physics instructors such as Central Michigan University assistant professor Alfredo Estrade. But reproducing on Earth how these and other elements are created in the nuclear reaction of a stellar explosion is impossible — unless each step in the chain is studied separately, he said.

To do that, a team of CMU faculty and students recently ran its experiment at one of the world's flagship nuclear science research facilities — the National Superconducting Cyclotron Laboratory on the campus of Michigan State University.

The NSCL is used by researchers from around the world to produce and study rare isotopes, which are the lighter and heavier — and short-lived — versions of the nuclei of commonly known elements. Understanding them will not only add to the understanding of our world but hold untold applications for society, such as developing new medical diagnostics and treatments of diseases, Estrade said.

The NSCL will soon have a partner for researchers in the nearly completed Facility for Rare Isotope Beams. The FRIB will enable scientists to study the rarest of isotopes through the world's most powerful beam of rare isotopes.

Seeking universe-size answers

The CMU team studied the mass of particular atoms to determine what type of nuclear reactions are possible — or how much energy they could release and how fast is each reaction — to produce heavy elements like gold and uranium in a stellar explosion.

"We are tackling one of the big open questions in astrophysics: How did all the chemical elements that surround us, and that we're made of, come to be? We need better nuclear physics data," Estrade said.

The final results of their experiment, which won't be known for a year, will be applied in computer simulations that Estrade's collaborators will use to test the different theories of how all the chemical elements have been formed.

On the CMU team were Tom Chapman, a sophomore physics major from Lawton, Michigan; graduate students George Zima from Zambia and Neerajan Nepal from Nepal; and Kailong Wang, a postdoctoral student from the Institute of Modern Physics in China. The team will spend this year doing the data analysis. Joining Estrade in leading the team was Western Michigan University faculty member Mike Famiano.

Former CMU master's student Shree Neupane, who graduated and now is a Ph.D. student at the University of Knoxville, Tennessee, last year led a CMU team that created the timing system used for this year's experiment. It enabled the team to measure time differences of 50 picoseconds, just one trillionth of a second. Such precision is essential to measure the mass for the atoms zooming at a third of the speed of light through the accelerated beam of the NSCL.

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