Department of Physics
Physics Department Colloquia & Seminars
Archives (2005-present)
Fall 2025
Fission Product Yield Measurements of 235U, 238U, and 239Pu from 2 MeV Neutron Irradiation
Speaker: MAJ. Drake Brewster
Date: Friday, September 5, 2025
Time: 3:00 P.M. Central Standard Time
Location: Currens Hall 205
Abstract: We report new experimental results of cumulative fission product yields (FPY) from neutron-induced fission of 235U, 238U, and 239Pu using quasi-monoenergetic neu- trons at 2 MeV. Experiments were performed at the Triangle Universities Nuclear Labor- atory (TUNL) employing a dual-fission chamber, with thin (10-100 渭g/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center be- tween the two chambers. This method allows for the accurate determination of the num- ber of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Fission products in the thick activation target were identified and quantified via high-resolution 纬-ray spectroscopy using shielded 60% HPGe detectors at TUNL. Yields were measured for over 30 fission products per acti- nide, with uncertainties typically less than 10%. These data offer a new benchmark for fission modeling and validation of evaluated nuclear data libraries (e.g., ENDF/B-VIII.0), particularly in an energy region where experimental FPY data are sparse. Comparisons to theoretical model predictions and existing evaluations reveal notable discrepancies in the asymmetric peak and rare earth regions. Recent FPY data has practical importance with implications for nuclear energy applications, nonproliferation, and nuclear forensics.
About the speaker: Drake Brewster is an alumnus of 香蕉视频, where he graduated Magna Cum Laude in Physics in the year 2009, and earned his commission through the ROTC program. He went on to serve as an Infantry and Intelligence Officer in the U.S. Army before completing an M.S. in Physics with distinction at the Naval Postgraduate School. MAJ Brewster later served as an Assistant Professor of Physics and Nuclear Engineering at the United States Military Academy at West Point and as an intelligence analyst with the Defense Intelligence Agency, where he authored assessments on nuclear issues for senior policymakers. He is now a Ph.D. candidate in Nuclear Engineering at the University of California, Berkeley, having completed all coursework and begun analysis of initial results for his dissertation on fission product yield measurements.
Fall 2023 and Spring 2024
Synthesis and Characterization of Novel 2D Dirac/Weyl Materials
Speaker: Dr. Chunhui Chen
Date: Thursday, November 30, 2023
Time:听3:00 P.M. Central Standard Time
窜辞辞尘:听
Abstract: The discovery of graphene has stimulated enormous interest in two-dimensional (2D) electron gas with linear band structure. 2D Dirac materials possess many intriguing physical properties such as high carrier mobility and zero-energy Landau level for the relativistic dispersion and chiral spin/pseudospin texture. In this talk, we will discuss three new variants of 2D Dirac materials including (1) unpinned 2D Dirac semimetals in 伪-antimonene1,2, (2) Rashba spin-split 2D Weyl semimetals in 伪- bismuthene3, and (3) interacting Dirac states in graphene heterostructures4. The results offer new insights to the relativistic behavior of electrons in reduced dimensions. We will review the emergent properties and device applications of relativistic electrons in those 2D Dirac/Weyl semimetals, especially, cloning of Dirac fermions, Moir茅 flat bands, and spin/valley separators.
Reference:
[1] Lu et al., Nat. Commun. 13:4603 (2022)
[2] Kowalczyk et al., ACS Nano 14, 1888 (2020)
[3] Lu et al., arXiv:2303.02971(2023)
[4] Lu et al., Advanced Materials 2200625 (2022)
About the speaker: Guang Bian is an associate professor at the department of physics and astronomy, University of Missouri, Columbia. After receiving his Ph.D. at University of Illinois at Urbana- Champaign in 2013, he was a postdoctoral fellow at Princeton University and he joined University of Missouri as an assistant professor in 2016. Dr. Bian has extensive experience in molecular beam epitaxy (MBE) fabrication and spectroscopic characterization of low-dimensional quantum systems and novel topological/functional materials. Dr. Bian鈥檚 research work has been recognized by 鈥淧resident's Early Career Award鈥�, University of Missouri (2019), 鈥淎laddin Lamp Award鈥�, Synchrotron Radiation Center, Wisconsin (2010), and 鈥淕ordon and Betty Moore Foundation Experimental Physics Investigator鈥� (2023).
听
The Mystery of the Matter and Antimatter Asymmetry
Speaker: Dr. Chunhui Chen
Date: Thursday, November 9, 2023
Time: 4:00 P.M. Central Standard Time
Location: Currens Hall 205
Abstract: In modern physics, every type of particle (matter) is accompanied by an antiparticle (antimatter) of equal mass but possessing opposite electric charge, parity, and time properties. Both matter and antimatter were generated in equal quantities during the Big Bang, which marked the birth of our Universe. However, while matter is abundant in the cosmos today, antimatter has become exceedingly elusive. The profound enigma of how antimatter disappeared during the Universe's evolution, known as the Matter and Antimatter Asymmetry problem, has perplexed scientists for years. To address this mystery, physicists are employing SuperKEKB, the world's brightest particle collider, located at The High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan. This facility enables physicists to create a controlled physical system with an equal quantity of matter and antimatter, facilitating the study of their properties and interactions. This research aims to elucidate CP violation, a fundamental principle that may offer insights into the disappearance of antimatter in our Universe. In this presentation, I will provide an overview of the historical context, the physics involved, and the latest findings pertaining to the Matter and Antimatter Asymmetry, as discovered through our experiments. The talk will be tailored to a general audience and will avoid delving into excessive technical details, ensuring that the content remains accessible to undergraduate physics students.
About the speaker: Professor Chunhui Chen is an experimental particle physicist affiliated with Iowa State University. Throughout his career, he has conduct research at large international experiments at Fermilab, the Stanford Linear Accelerator Center, the European Organization for Nuclear Research (CERN), and The High Energy Accelerator Research Organization (KEK). At present, Professor Chen is actively engaged in the Belle II experiment, located at KEK in Tsukuba, Japan. His current research is primarily focused on unraveling the mystery surrounding the asymmetry between matter and antimatter. More information about Professor Chen鈥檚 research can be found at:
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