April 23, 2019 | 61° F

Physicists talk hunt for ‘super-heavy elements’ at lecture

Photo by Daphne Alva |

Sabrina Strauss, a graduate student at the University of Notre Dame, discusses her research on super-heavy elements last Thursday at the Physics Lecture Hall on Busch campus.

The hunt for super-heavy elements is a very active field, said Sabrina Strauss, a graduate student at the University of Notre Dame.

Strauss, a Rutgers alumna, discussed her work with super-heavy elements last Thursday with the Rutgers Society of Physics Students in the Physics Lecture Hall on Busch campus.

She also came to discuss the University of Notre Dame’s outreach and graduate programs, said Aditya Parikh, vice president of SPS and a School of Arts and Sciences junior. 

The SPS hosts similar talks every two weeks, said Alexandra DeMaio, president of the club and a School of Arts and Sciences senior.

Strauss began researching super-heavy elements while at the Lawrence Livermore National Laboratory in California. Super-heavy elements, also called transuranium elements, are generally defined as anything heavier than uranium or anything heavier than the actinide group on the periodic table.

“They’re all artificial — they don’t exist in nature,” she said. “They’re all man-made.”

Many of the super-heavy elements on the periodic table were discovered in the past 15 years, she said.  

Strauss said she chose to study flerovium, element 114, because it could be more easily detected using plutonium. The goal of the experiment is to find a stable isotope — a form of the atom that does not immediately break down into different atoms.

“Normally, when you’re doing these experiments, you’re relegated to whatever isotopes you can get,” she said. “We could get lighter isotopes of plutonium that were fairly pure to make the targets out of.” 

The experiments involved firing a particle at a rotating target, she said. The particle was accelerated to 10 percent of the speed of light through a cyclotron, which uses a magnetic field to spin particles before it was fired at the target. 

Researchers used a rotating target to prevent the particle from melting through it, she said. For these experiments, they used calcium-48, a neutron-rich and stable form of calcium, as the initial particles.

The purpose of the experiment is to find flerovium-284, she said. So far, the experiment has focused on creating flerovium-285, an isotope with one more neutron.

“We were looking at the flerovium-285 as a benchmark to go, ‘OK, everything is working,’” she said. “Now, we can go look for that flerovium-284, and if we see what we saw before, we know what we saw is correct. If we don’t, that sends up a bunch of red flags.”

The particles created may split apart unpredictably in a process known as spontaneous fission, she said. Otherwise, they might lose protons and electrons through alpha and beta particle decay.

Lighter particles — those with fewer neutrons — are better for the experiment, she said.

“If we continue to go lighter, instead of heavier, we go more and more into stable things we can actually look at,” she said. “We can look at alpha decays instead of spontaneous fissions.”

Initial results are compared with expected characteristics to determine if the right element was formed, she said. Energy loss and when the particle appears during the process are both important factors.

Different types of events may occur, each with its own set of defining characteristics, she said.

“If [the result] matches the characteristics of what we’re looking for, we can say we actually found what we’re looking for,” she said. “If it doesn’t, either the theory is wrong, which is possible, or we’re not looking at what we think we are.”

The researchers use various detectors in the experiment, she said. These include silicon detectors, which take the most measurements, and side detectors, which see if any particles escape the chamber. 

The experiment in Dubna, Russia, had two successful results, Strauss said. They created two “chains” over the last year, both of which existed for fractions of a second. 

One of the chains was found in both analog and digital data, she said. The other existed only in the digital data, and it did not exist long enough to register in the analog data. 

The experiment will now shift toward creating flerovium-284, she said. They plan to compare the results from this experiment to flerovium-285. If the results are the same, the team can proceed with their analysis, but if they are not, the previous data will need to be revisited.

Not many groups are working on studying super-heavy elements, she said.

“The lab we were working with in Russia [is] one of three labs that does this in the world,” she said. “The others are in Germany and Berkeley, California, so it’s one of those things that you don’t have as many people working on as you’d like.”

Nikhilesh De

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