Becoming a nuclear scientist: LLNL traineeship inspires SJSU students

Historically, most undergraduate students in STEM are limited in their exposure to the field of nuclear science. This is especially true at minority-serving institutions, which often do not have the infrastructure, resources and technical support needed to maintain such courses.

To broaden the nuclear science pipeline and establish an equitable and inclusive workforce that reflects the broader U.S. population, Lawrence Livermore National Laboratory (LLNL) and San José State University (SJSU) joined forces to form the Multidisciplinary Training Experience in Nuclear Science (Mt. ENS, pronounced “mountains”) program. Mt. ENS is a hands-on student internship conducted at LLNL’s Center for Accelerator Mass Spectrometry (CAMS). At CAMS, researchers can accelerate particles to the high energies needed to study a nuclear reaction, making it the ideal place to train the next generation of nuclear scientists.

Funded by the Department of Energy Office of Science through the Reaching a New Energy Sciences Workforce initiative, this partnership takes advantage of LLNL’s and SJSU’s close proximity to bring new education and research opportunities to participating SJSU students, many of whom are from underrepresented groups in STEM.

A unique training experience

Over the spring semester, before starting their 10-week summer internship at Livermore, students took part in an introductory nuclear science course taught by SJSU professor Nicholas Esker. This course wasn’t just any regular nuclear science class. Rather, it was specifically designed to contextualize current research efforts and capabilities at LLNL and thus give students a sneak peek into what their internship would entail.

To further ease the transition between their coursework and internship, students were given five tours of LLNL and its facilities throughout the semester.

“We used the LLNL tours as signposts, crafting each lesson around the facilities and research they would encounter onsite as an intern,” Esker said. “Our in-class discussions and onsite visits got the students thinking about the areas of nuclear science that interested them the most.”

Once at Livermore, the students worked together under a common nuclear science project, carrying out their research alongside LLNL mentors Maria Anastasiou, John Wilkinson, Nicholas Scielzo, Jennifer Shusterman and Scott Tumey.

“This program is a true partnership between San José State and Livermore,” Wilkinson said. “In preparation for their internship, Dr. Esker put a lot of effort into giving the students a theoretical and topical discussion and background for nuclear science.”

All about cobalt

At CAMS, the interns learned about isotope production — an isotope is a variation of an element that has the same number of protons but different numbers of neutrons. For their project, the students researched different reaction pathways for producing cobalt-57 and cobalt-58 — radioactive isotopes of cobalt used in nuclear medicine and radiation detector calibration. The accelerator at CAMS utilizes electric fields to accelerate intense, high-energy ion beams into a target material, inducing the necessary nuclear reactions to yield highly excited cobalt-59 nuclei, which can decay to cobalt-58 and cobalt-57.

To find the most effective isotope production method, students were assigned different reaction pathways for creating cobalt-59, combining a starting isotope (targets made of manganese-55, natural iron, chromium-52, or natural titanium) and an ion beam (using alpha particles, deuterons, lithium-7, protons, or boron-11).

Since cobalt-59 has 27 protons and 32 neutrons, the starting isotope and ion beam were specifically chosen so that when they collide, a cobalt-59 nucleus is produced. For example, when manganese-55, which has 25 protons and 30 neutrons, is irradiated with alpha particles (two protons and two neutrons), the reaction produces the desired cobalt-59. The students studied these various combinations using a mix of theoretical modeling and experimental validation.

Aside from the irradiation step, there are a lot of other key phases that take place throughout the experimental process — from target preparation to post-irradiation analysis. To show students the complete experimental lifecycle, each intern was given a different focus of the broader experiment to develop their expertise.

This research structure helped introduce the students to different flavors of nuclear science, while also getting them used to the interdisciplinary nature of working in this field.

“We thought this would show them all the different components, people, and expertise that are needed to conduct research at an accelerator facility such as CAMS,” Anastasiou said, Mt. ENS principal investigator and LLNL staff scientist.

The complete lifecycle

At the forefront of any nuclear science experiment is radiation safety. With an interest in how policy connects with science, physics student Emily Foreman was in charge of performing calculations prior to an experiment to verify that the amount of radiation being produced remained well below the limit. Foreman said, “When performing these calculations, I am looking at variables like the beam intensity, time irradiated, or thickness and density of the target.”

Cross-section calculations, performed by Sofia Malmhall, a materials engineering major, were used to predict and estimate the amount of cobalt-57 and cobalt-58 being produced from the different reactions. A cross section is the probability that a certain reaction will occur between two particles for a given set of parameters.

“When modeling these cross sections, I input various parameters regarding the beam and target into a modeling software,” Malmhall said. “This helps us to predict what, for example, an experiment with a natural titanium target and a boron-11 beam would look like and how much cobalt we’ll make.”

Chemical engineering student Lamija Kovacevic focused on target preparation and post-irradiation radiochemistry analyses, which involve liquid chromatography separation techniques to separate the cobalt from other target material and reaction byproducts and measure the cobalt-58 and cobalt-57 production yields.

“I would argue that target prep is one of the most important parts of achieving a nuclear reaction because we have to make sure the targets are perfect in order for the reaction to go smoothly,” said Kovacevic. That is, each target must be prepared based on their chemical form. “For example, while iron targets are essentially just a bunch of little stacks of foil that sit together, manganese targets must be precisely mixed, as they are half-manganese and half-aluminum, and then carefully pressed into a pellet.”  

To ensure optimal beam properties for their experiments, Simar Singh Randhawa, a materials engineering student, worked to adjust the beam parameters. Randhawa explains, “We use a Toroidal Volume Ion Source, or ‘TORVIS,’ to create ions by making a plasma [an ionized gas made up of ions and electrons]. We can then take these ions and send them down the beamline into the target chamber, using magnets to manipulate and focus the beam in the direction we need it to go.” 

Following irradiation, the isotopes that were produced emit radiation in the form of gamma rays. With each isotope emitting distinct gamma rays, a radiation detector can be used to identify a “fingerprint” of the isotopes that were made. To confirm the detector is functioning properly, manufacturing and engineering major Cleophus Latimer worked on detector energy and efficiency calibrations. Latimer explains, “Because each isotope has a specific decay pattern, we can cross-reference the energy readings on the detector with the National Nuclear Data Center.”

With a well-calibrated detector, the data from an experiment can then be used to determine which radioisotopes were produced, as well as how much of each is present in the sample.

At the end of the project, the students worked together to interpret the results of the different target and beam combinations, analyzing the pros and cons of each method.

Shaping science identity

By having the interns work on different tasks of the same experiment, each student built expertise and confidence in their assigned area of research while also seeing all the different steps that go into a complete nuclear data measurement. This format gave the students the opportunity to leverage their technical strengths and take pride in their individual contributions to the team effort.

This was huge for the student’s science identity development. Kiera Wright, a science education master’s student at SJSU and an integral part of the Mt. ENS leadership team, worked with the interns throughout the entire program to evaluate how, and to what extent, this experience shifted how they saw themselves as scientists.

“My role is to provide a science education lens to the program and evaluate its efficacy, as well as identify how the students’ experiences throughout the internship have shaped their science identity and dismantle their preconceptions about what it means to be a scientist,” Wright said. “At the beginning, the students struggled to see themselves as scientists, but as the internship progressed, the students started to shift their mindset to: ‘I am a nuclear scientist. Anyone can be a nuclear scientist.’”

—Shelby Conn