Undergraduate interns explore nuclear physics research at LLNL

Scientists at Lawrence Livermore National Laboratory (LLNL) recently helped launch a new internship program aimed at connecting with undergraduate students at two nearby California State University (CSU) campuses and inspiring them to consider a science-focused research career. The new program, which started in early 2025, involves multiple staff and postdocs from the Lab’s Nuclear and Chemical Sciences (NACS) Division, who are collaborating with faculty and students at the two participating universities to help develop, deploy and refine the multi-year program.

The program’s name — Nuclear Physics California Connection to Train Undergraduate Students (NP-CACTUS) — reflects its focus on experimental and computational research in nuclear physics. Initial funding was provided by the Office of Science at the Department of Energy (DOE), and the two collaborating universities are CSU East Bay (CSUEB) and CSU Sacramento.

According to Erika Holmbeck, an astrophysicist with NACS who coordinates the program at LLNL, the initiative is much broader than a typical summer internship experience. Its aim is to provide multifaceted support for undergraduate students, before and after their summer spent onsite at LLNL. In addition, it provides LLNL postdocs with opportunities to gain experience leading lectures and lab class sessions for undergrads.

The program includes focused learning activities for students in the spring, a 10-week onsite experience at LLNL during the summer, and follow-up activities in the fall. For example, in the fall, while interns continue working on their LLNL research project, they also give talks describing their research to peers at their home institutions. In addition, they start functioning as peer mentors, connecting with other undergrads and helping to spark interest in pursuing research-oriented careers.

“We want to provide undergraduate students with opportunities to conduct research on a topic that interests them, working side-by-side with scientists, and seeing what the work environment is like at a national lab,” said Holmbeck. “We hope this experience will help students better understand what it’s like to have a job focused on science research. We also want them to feel more confident that this type of career is something they could pursue in the future, either at a research institution or in academia.”

CACTUS in action: From math student to nuclear data analyst

The only intern in the first cohort who wasn’t majoring in physics was Oscar Thompson, a math major from CSUEB who had no experience with experimental work before starting his internship. According to Becca Toomey, an LLNL postdoc who served as Thompson’s mentor, he may have been a bit apprehensive before starting his internship, but it turned out to be a fantastic experience, for both Toomey and Thompson.

“I carefully considered which project to give to Oscar,” said Toomey, whose research focuses on novel neutron spectroscopy techniques that support nuclear safeguarding activities. “I wanted to give Oscar a project that would be meaningful to him and tap into his math knowledge, while recognizing that he had never taken a nuclear physics course.”

During the initial part of his internship, Thompson focused on hands-on experimental work testing gamma-ray detectors. But as his internship progressed, his focus shifted to designing new methods to analyze data generated during experiments that probe neutron energy spectra. As part of that effort, Thompson developed a new technique that improves the precision of measurements collected using neutron spectrometers by identifying and removing systematic uncertainties.

CSUEB faculty member Jesús Oliver, a mathematical physics expert, served as Thompson’s faculty mentor. He helped Thompson sort through possible routes to create the new technique, providing insight regarding how Thompson could approach the problem from a mathematical perspective. Thompson is currently preparing a manuscript that describes this work, which he will submit to a peer-reviewed journal. He also plans to present the results at an upcoming national conference.

“For someone who previously had no research experience in nuclear physics, I think this accomplishment is amazing,” said Toomey. “It was an outstanding meshing of two different fields (math and physics) to create an elegant solution, showing the magic of multidisciplinary research.”

According to Oliver, the structure of the internship program enabled Thompson to be successful, with its focus on learning from a range of mentors at CSUEB and LLNL. “I reminded Oscar and the other interns that when they felt stuck, they should ask a mentor for advice,” said Oliver, “including their mentors at LLNL.”

CACTUS transitions: From intern to peer mentor and outreach champion

LLNL physicist Sofia Quaglioni, who also played a key role creating the new internship program, is mentoring Sabria Hinton, a CSUEB undergraduate student majoring in physics. During her summer at LLNL, and through follow-on work this fall, Hinton is helping Quaglioni develop new techniques that will improve predictive descriptions of helium–oxygen nuclear reactions, which scientists study in order to better understand radiation risks related to deep-space travel, as well as how heavy elements are formed in stars.

According to Hinton, her favorite part of the research experience so far has been using LLNL’s supercomputers to conduct the reaction modeling. Over the summer, Hinton used ab initio (first principle) calculations and a mathematical concept known as a Schur complement to develop accurate models of how neutrons interact with alpha particles from cosmic rays and solar flares. This fall, she’s building on this work by combining the interaction potentials with ab initio calculations of the neutron spatial distribution in oxygen to construct alpha–oxygen interaction models and improve predictions of alpha–oxygen reactions.

When Hinton started working on the project, she was a bit apprehensive due to her lack of knowledge regarding coding. However, as the internship progressed, she said that Quaglioni helped her confidence increase, reassuring her that she was capable of writing code.

In addition to the research experience Hinton is gaining as an intern, she also valued the opportunity to attend talks by scientists during her time onsite at LLNL. She was inspired by presenters who share her passion for space science research. In fact, the aim of Hinton’s research for LLNL connects well with this passion, as it focuses on ways to shield astronauts and their spacecrafts from harmful cosmic rays during long-duration space travel.

Hinton also valued the opportunity to meet other interns at LLNL. “The Lab hosted multiple events for summer interns, and I learned a lot through these interactions,” said Hinton. “It helped me feel more confident in my own journey to a future research career.”

Hinton is already transitioning from intern to mentor, per the CACTUS program’s design, through her involvement in outreach to CSUEB students. For example, she recently gave a talk at CSUEB describing the research she’s conducting for LLNL. In addition, she’s involved in multiple outreach efforts on campus, aiming to help other students consider majoring in a STEM field or working as a teacher or researcher after graduation.

“I want to make sure that other first-generation college students know that this career path is something they should consider,” said Hinton.

Quantum CACTUS: Studying superconducting mater

Over the summer, intern Jack Slavin from CSU Sacramento (CSUS) explored the performance and thermal behavior of superconducting quantum sensors at extremely low temperatures. Working with his supervisor at LLNL, physicist Geon-Bo Kim, he supported a research team that develops ultra-sensitive radiation detectors based on quantum magnetometry.

For example, Slavin collected experimental data and compared two data sets, before and after a thermalization wire was linked to a sensor in the detector’s heat bath, enabling heat transfer by conducting electrons. As a result of this comparison, he identified a key measurement that helps explain the heat transfer at varying temperatures.

This fall, he is continuing to analyze these results and hopes to present his findings at an American Physical Society meeting in the spring.

Program launch: Creating a community that inspires future scientists

During a previous collaborative effort involving LLNL and CSUEB, Quaglioni and Oliver started discussing the possibility of designing a more defined, wide-ranging internship program that connects CSU undergrads with scientists at a national lab. They explored program components that would make the most impact on students, bringing faculty from CSUS into the discussions, including Michael Ray, Christopher Hodges and Rodolfo Barniol-Duran, who ultimately became CACTUS program principal investigators.

According to Oliver, one of the program’s key features is its focus on building community.

“It’s the foundation that makes the program successful,” he said. The interns become part of a community that includes postdocs, internship supervisors and peer mentors who previously completed an internship at LLNL. Even after their summer experience at LLNL ends, they continue to engage with this community when they are back at their home institution.

“The dual mentoring approach is another important program component,” said Oliver. Each intern has two primary mentors: one who is a CSU faculty member and one who is an LLNL scientist. This approach enables students to receive feedback from two perspectives (academia and national lab) as they tackle their research projects and explore opportunities to earn a graduate degree.

According to Holmbeck, during early discussions regarding the scope of the CACTUS program, it also became clear that it would be highly beneficial to include LLNL postdocs as mentors. “Having postdocs involved in the project provides opportunities for the undergrads to connect with an early-career scientist who can describe their own educational journey,” said Holmbeck.

Postdoc involvement also supports another key aim of the CACTUS program: preparing interns to engage in nuclear physics research. Postdocs involved in CACTUS gain teaching experience as they lead undergrad classes. In addition, CACTUS is helping spark curriculum development. For example, Hodges developed a new undergraduate course at CSUS on nuclear and particle physics, with the needs of CACTUS interns and other undergraduate students in mind.

“It has been exciting to watch the program take shape and get underway,” said Holmbeck. “I appreciate all of the time and energy that went into program planning, as well as ongoing participation by faculty from CSUEB and CSUS. We’re looking forward to recruiting the next intern cohort soon, while continuing to engage with the first group as they move forward on their research journey.”

— Lisa Valdez