Seminars

Wednesday, Jan 22 at 4:10 PM
1300 FRIB Laboratory
Andrew Rogers, University of Massachusetts Lowell
Cracking the glass of nuclear mirror symmetry

Abstract:  Symmetries and conservation laws lie at the foundation of the physical sciences and manifest themselves throughout the natural world. Within the atomic nucleus, an underlying symmetry exists due to the similarity between protons and neutrons. The strong short-range nuclear force that binds these particles together is found to be nearly independent of their electric charge. From the relative invariance of the nuclear interaction, a striking symmetry emerges in the quantum states of mirror nuclei whose proton and neutron numbers are exchanged. This fundamental property is an important predictor of nuclear structure and is described within the formalism of isobaric-spin symmetry, which has proved remarkably accurate since its inception in the early 1930's. Recently, we performed an experiment that has revealed, for the first time, a unique violation of mirror symmetry between the ground states of two mirror nuclei, 73Sr and 73Br. The experiment was conducted at the National Superconducting Cyclotron Laboratory (NSCL) and utilized the Beta-Counting Station (BCS) coupled to the Radio-Frequency Fragment Separator (RFFS) to investigate beta-delayed proton emission along the N=Z line. In this talk I will briefly review the concept of mirror symmetry in nuclei and discuss some of its consequences within nuclear physics. I will then describe details of our recent measurement and discuss our observation of ground-state mirror-symmetry breaking in atomic nuclei. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-FG02-94ER40848 (UML).

Thursday, Jan 23 at 11:00 AM
1200 FRIB Laboratory
Chi-En Teh, Michigan State University
Neutron detection with Large Area Neutron Array (LANA) at NSCL
Monday, Jan 27 at 2:00 PM
1400 Biomedical and Physical Sciences Building
Nabin Rijal and Michael Pajkos, NSCL
JINA-CEE Science Cafe

Abstract:  "Vital Nuclear Processes in Core-collapse Supernovae" and "Measurements of alpha-processes relevant for the weak r-process", respectively

Tuesday, Jan 28 at 11:00 AM
1200 FRIB Laboratory
Carla Frohlich, North Carolina State University
Neutrinos, nuclei and compact remnants from supernovae

Abstract:  Core-collapse supernovae originate from the gravitational collapse of massive stars. These events are a source of neutrinos and a site of elements synthesis. They also play an important role in the evolution of galaxies. Despite being studied for decades, the explosion mechanism is still uncertain. This is in itself an important question, but it also affects the outcome (successful explosion or collapse to a black hole), the remnant left behind, and the detailed conditions under which explosive nucleosynthesis happens. In this talk, I will discuss the recent progress of my group in core-collapse supernova modeling.

Wednesday, Jan 29 at 4:10 PM
1200 FRIB Laboratory
Thomas Schenkel, Lawrence Berkeley National Laboratory
Fusion, beams, and qubits

Abstract:  In this talk I will present results from high energy density science and applied physics studies in the ATAP Division at Berkeley Lab (http://atap.lbl.gov/). We have recently expanded science at the BELLA petawatt laser from a focus on electron acceleration to include now also experiments on ion acceleration and laser-matter interactions with solid targets [1]. Here, a unique opportunity is warranted by the 1 Hz repetition rate of BELLA, which allows parametric explorations with thousands of shots. One example are nuclear reactions in plasmas and moderately hot targets where unreasonably high values of apparent electron screening potentials have been observed in studies of light ion fusion that can now be investigated with higher precision [2]. Pulsed ion beams provide access to the time domain of ion-solid interactions and they have been used to drive materials very far from equilibrium. I will report on our efforts to develop intense ion beams and on studies of color center qubit formation and damage accumulation in semiconductor devises with intense, pulsed ion beams [3, 4]. References: [1] J.-H. Bin, et al., Rev. Sci. Instr. 90, 053301 (2019) [2] T. Schenkel, et al., J. Appl. Phys. 126, 203302 (2019); C. P. Berlinguette, et al., Nature 570, 45 (2019) [3] J. Schwartz, et al., J. Appl. Phys. 116, 214107 (2014); J. J. Barnard, T. Schenkel, J. Appl. Phys. 122, 195901 (2017) [4] T Schenkel, et al., LLNL-CONF-758685; B. A. Ludewigt, et al., JRERE 36, 96 (2018) Acknowledgments: This work was supported by the Director, Office of Science, Offices of High Energy Physics and Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, by ARPA-E, and in part also by LDRD funding at Berkeley Lab, by Sandia National Laboratory, and by Google LLC under CRADA between LBNL and Google LLC.

Monday, Feb 10 at 12:30 PM
1400 Biomedical and Physical Sciences Building
Reto Trappitsch, Lawrence Livermore National Lab
Understanding stellar nucleosynthesis, its sites, and galactic chemical evolution by analyzing stardust grains

Abstract:  Stardust grains, which are micrometer-sized particles found in meteorites, formed in the death throes of dying stars and recorded their parent stars nucleosynthetic fingerprint. Analyzing these bona fide stellar condensates allows us to obtain these fingerprints for various stellar events and - in combination with experimental physics, observations, and modeling - allows us to better constrain stellar nucleosynthesis and galactic chemical evolution. In this talk I will present recent isotopic measurements of stardust that inform our understanding of the origin of the elements that formed the solar system, and discuss recent advances and possibilities on exploring galactic chemical evolution. I will also discuss ongoing efforts to experimentally study determine the stellar sites of actinide nucleosynthesis, i.e., the rapid neutron capture process.