Physics student honored for research related to neutrino mass project

Tuesday, Jul 16, 2024 • Greg Pederson :

A physics student at The University of Texas at Arlington studying ways to measure the mass of tiny particles called neutrinos has earned a prestigious award for her research.

Kara Stogsdill, who will be a senior this fall, received the Outstanding Undergraduate Research Award from the Society of Physics Students (SPS), an organization of the American Institute of Physics (AIP). The award is given to students based on exceptional research achievement in any physics-related field.

Stogsdill’s research is part of the Project 8 Neutrino Mass Experiment, which includes faculty and students from UTA and 13 other universities and national laboratories in the United States and Europe. Project 8’s goal is to measure the mass of the neutrino, which is a fundamental particle — one of the building blocks of the universe. Ben Jones, UTA associate professor of physics and Stogsdill’s faculty mentor, is a principal investigator for the project.

Neutrinos are extremely light, weighing at least one million times less than electrons, the next lightest particle. Measuring neutrino mass is difficult, so physicists are looking for innovative ways to do so. The Project 8 team’s method is to take a radioactive source that undergoes beta decay, releasing an electron and an electron antineutrino. The energy of the electron, which is easier to measure, can be used to infer the mass of the neutrino. Tritium, a radioactive isotope of hydrogen, undergoes beta decay; the project’s aim is to measure the absolute neutrino mass using tritium beta decays.

The Project 8 collaboration has developed a novel method of electron spectroscopy, called Cyclotron Radiation Emission Spectroscopy (CRES), for direct measurements of beta decay electrons. CRES is a method to measure the energy of an electron trapped in an externally applied magnetic field.

Stogsdill is building a Zeeman slower, an instrument that is used to slow and cool a beam of hot atoms to speeds of several meters per second and temperatures of 5-10K. Cooling and slowing atoms make it easier for scientists to study their properties. Tritium atoms will be used in the final experiment, but for prototype testing, lithium-6 will be used. Lithium-6 is the stable isotope of lithium with a relative atomic mass of 6.

“Lithium-6 is a lot cheaper and more readily available than tritium, and it acts close enough to tritium and has a close enough atomic mass to test our methods,” Stogsdill said. “The Zeeman slower works by shining a laser in the opposite direction from the beam of lithium atoms. As the lithium absorbs and releases the photons from the laser, it slows down and cools. At the end of the slower, the lithium atoms will be only 10-15 kelvin. At these cold, slow speeds, we can measure the properties of the atom.

“The next part of the experiment is called the Magnetic Evaporative Cooling Beamline (MECB), which cools the atoms from 10K to millikelvin. We need the Zeeman slower to cool the lithium down to the temperature we would expect the tritium to be, so that it is a good substitute to test the MECB.”

The MECB will be built at UTA in the next year. Its purpose is to slow the tritium atoms down enough for them to enter CRES, Stogsdill said.

“Kara is an outstanding researcher who has made major contributions to UTA’s work on cold atomic tritium beams for Project 8,” Jones said. “She has played a central role on our team, working with UTA scientists, undergraduates and graduate students to realize a new method of cooling large fluxes of atoms to millikelvin temperatures. She has led development of the Zeeman slower system in collaboration with magnet system engineers at Pacific Northwest National Laboratory.”

Stogsdill, who grew up in Waco, said she developed an early fascination with physics as well as chemistry, mathematics, and science in general. She came to UTA and chose to major in engineering because she thought the job prospects would be better, she said.

“It wasn’t until I started talking to my physics professors that I realized that being a physicist was a very realistic career goal,” she said. “I asked my PHYS 1441/1442 professor, Dr. [Barry] Spurlock, questions after class every day. Eventually he asked if I would like to see a lab, maybe get a job, and then he introduced me to Dr. Jones. I was brought down to see the lab, and I was hooked. I’ve now worked with the group for two years and love it all!”

Stogsdill said Jones has given her confidence to grow as an undergraduate researcher. She started out with no research experience and is now a seasoned member of the lab group.

“As a mentor, Dr. Jones is infectiously and intensely fascinated with experimental particle physics and invested in my research project, but he is also very respectful and flexible when it comes to what I need as a student,” she said.

The award will enable Stogsdill to present her research at either the American Physical Society (APS) Division of Nuclear Physics meeting in October or the next APS annual meeting in March 2025. It will also provide funds for the UTA chapter of SPS, which Stogsdill restarted last year after a period of dormancy.

After graduating next spring, Stogsdill said she plans to apply for an internship at a national laboratory and then enter graduate school to work on a doctoral degree.

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