Nuclear Structure 2024 Conference, held at Argonne National Laboratory in Lemont, Illinois

Rin YOKOYAMA
Project assistant professor
Center for Nuclear Study, the University of Tokyo

August 3, 2024
FUTI Travel Award Report

The primary objective of this travel was to attend the Nuclear Structure 2024 Conference, held at Argonne National Laboratory in Lemont, Illinois, from July 22 to 26. This conference is part of a biennial series on nuclear structure organized by North American national laboratories. The last meeting was held at Lawrence Berkeley National Laboratory in 2022. The conference regularly attracts attendees from all over the world. This year marked the 75th anniversary of the nuclear shell model by Hans Jensen and Maria Goeppert Mayer, and there were symposiums and plenary talks to celebrate its success. I presented a poster on my recent publication [R. Yokoyama et al., Phys. Rev. C 108, 064307 (2023)] at the conference. My main research subject is neutron emission after beta-decays from very neutron-rich atomic nuclei. This neutron- emission process plays an important role in nucleosynthesis in the universe, especially in what we call the “r-process,” which occurs in supernovae or neutron-star mergers. In my work, I applied results from the shell model calculation to the statistical model calculation, which is widely used to simulate the r-process. Our new calculation reproduces some of the experimental neutron-emission probabilities more accurately. It was an excellent opportunity to present my work to an international audience, especially those from the nuclear structure field.

From July 12 to 20, I visited Prof. Robert Grzywacz’s group at the Department of Physics and Astronomy, University of Tennessee, Knoxville, where I worked as a postdoc from 2017 to 2021. I met many new Ph.D./undergraduate students and postdocs at his lab. We had a productive week of working together and exchanging information about our recent works. I gave lectures to the students on the theoretical models I use to calculate neutron-emission probabilities. Additionally, I learned about some of their recent experimental results from various facilities. The group is actively performing experiments at nuclear physics facilities around the globe, such as FRIB at Michigan State University, ISOLDE at CERN, and RIBF at RIKEN, Japan. This visit helped me update my understanding of the global research in my field. I also met Krzysztof Rykaczewski and Bertis Rasco at Oak Ridge National Laboratory to discuss data analysis. Oak Ridge is about 30 miles away from the University of Tennessee. We worked together at RIKEN, Japan, in 2017-2018. After our discussion, we agreed to pursue a new publication through additional analysis of old data. My stay in Knoxville was fulfilling as I developed a solid plan for data analysis and new publications.

Additionally, I visited FRIB (Facility for Rare Isotope Beams) at Michigan State University from July 29 to 31. FRIB is one of the largest nuclear physics facilities in the US and the world, having started operations in 2022. This facility is poised to be a future hub for nuclear physics experiments worldwide. I visited Prof. Hendrik Schatz, who studies nuclear astrophysics, and took a tour of the facility. Thanks to Mathias Steiner and David Kahl at FRIB, I saw their vertical preseparator, which is usually not open to visitors. I learned about their detectors, data acquisition systems, and analysis techniques. I also visited FDSi (FRIB Decay Station Initiator) (https://fds.ornl.gov/). Notably, they have employed a YSO detector as an implant detector, which I developed during my postdoc at the University of Tennessee [R. Yokoyama et al., Nucl. Instrum. Methods Phys. Res. A937, 93-97 (2019)].

During one of the weekends, I visited a friend from the university who works at Amazon Web Services. This visit was unexpectedly meaningful, as I learned about their modern big data analysis tools, which I believe could be applied to nuclear physics experimental data. Overall, this travel provided me with opportunities to meet many people and have fruitful discussions that could lead to future international collaborations in the field. I am deeply grateful to Friends of UTokyo and their supporters for making this travel possible.

Me presenting my poster (left), and the group photo of the conference (right)
Ayres Hall at University of Tennessee (left), at FRIB (right)