Senior physics major Rebekah Roundey said she likes to joke that she practiced alchemy during her summer research project since the focus of her research involved transmuting elements.
Instead of attempting to turn lead into gold, however, Roundey’s research involved the production of radioactive nickel isotopes, or different forms of nickel with varying amounts of neutrons in the atom’s nucleus, using state-of-the-art instrumentation at Texas A&M University. She was able to synthesize nickel-51, a type of nickel that had not been made before using Texas A&M’s instruments.
“Our goal was to determine what isotopes in the area of nickel-51 on the drip line can be produced at the available energies,” Roundey said. “We then wanted to calculate the production rates of those isotopes.”
Roundey wanted to determine whether adjusting the method for producing these radioactive isotopes would help researchers to make the isotopes more efficiently. She presented her research at a poster presentation for the Division of Nuclear Physics, and also presented her work at Hillsdale last semester on Dec. 7.
She focused on a special group of proton-rich elements with many more protons than neutrons in their atomic nucleus.
“There are different ways to transmute elements,” Roundey said. “Radioactive or unstable nuclei decay naturally using either alpha, beta, or gamma decay, or you can fuse extra neutrons onto a nucleus to make a different isotope. You could add a proton or a neutron, or you could shave them off of a nucleus.”
Changing the number of neutrons results in different forms, or isotopes, of the same element, while changing the number of protons causes the atom to become a different element altogether. At a certain point, however, some atoms can’t accept any more protons.
“For some, there isn’t another isotope there because if you try to add a proton, it’s so unstable that the proton just drips off,” Roundey said. “So that’s why this line, the line where you can’t add another proton, is called the drip line.”
Understanding the properties and behavior of isotopes along the proton drip line is important for nuclear astrophysics, Roundey said.
“Inside stars, nuclei are fusing, creating new isotopes, and if they’re going through rapid proton capture, they’re adding protons repeatedly,” Roundey said. “But if you reach one of these points where you can’t add another proton, they still want to keep adding protons, but first, it has to decay before it can start adding more protons.”
Since researchers can’t get up close enough to observe the inner workings of stars firsthand, they instead create the radioactive isotopes in the lab using a cyclotron, an instrument that accelerates particles to high speeds. Roundey used the cyclotron to create beams of nickel ions.
“Cyclotrons are great if you want a beam of a stable isotope, but radioactive beams are important, so you have to find a way to produce radioactive beams from these stable beams,” Roundey said.
To make the radioactive beams, Roundey used the MARS spectrometer, a particular spectrometer that runs the stable beam into a thick target, creating a variety of particles during the collision. The products of the collision are then sorted out based on their response to electromagnetic fields, and detected based on their energy levels when they exit the instrument.
To determine how to create more of the radioactive nickel particles, Roundey tried different types of targets and a piece of carbon foil meant to serve as a filter. She found that the foil actually reduced yields, most likely because it prevented some of the nickel atoms from entering the instrument — a result she said was unexpected.
She then analyzed the data from the instrument and confirmed the identities of the different isotopes that were detected.
Her work at Texas A&M’s cyclotron institute used some of the same equipment used by NASA, the Jet Propulsion Lab, and by national defense organizations and businesses, according to Henry Clark, facility supervisor of the cyclotron institute and an accelerator physicist. Other work at the cyclotron institute relates to supernova explosions and ultra-precise measurements of the half-life of different radioactive isotopes. Roundey said the cyclotron institute is the only place that allows outside organizations to purchase time to use the cyclotron.
The cyclotron institute is internationally recognized for its research contributions to the fundamental understanding of nuclear particles, according to its website.
Chairman of the Physics Department Kenneth Hayes said Roundey was one of two Hillsdale students to conduct research at other colleges over the summer through a national program that provides undergraduate students with an opportunity to conduct research.
“We encourage all of our physics majors to apply for summer REU positions,” Hayes said in an email. “REU’s are very helpful for the students as they get to experience what graduate-level research is like at a research university. Also, having done an REU greatly strengthens a student’s application to graduate school … Hillsdale College physics majors have been quite successful in obtaining REU positions.”
Roundey said working at Texas A&M was exciting, even though she has decided not to pursue a career in research.
“We can sit in the control room adjusting how the beam is being focused and tuned and see in the target chamber, how the beam is changing shape,” Roundey said. “It was really exciting and made me feel powerful to be fiddling with these ancient knobs and watching a whole bunch of radioactive particles moving around.”