Bulletin of the American Physical Society
Fall 2022 Meeting of the APS Division of Nuclear Physics
Volume 67, Number 17
Thursday–Sunday, October 27–30, 2022; Time Zone: Central Daylight Time, USA; New Orleans, Louisiana
Session EL: Mini-Symposium: Mass Measurements for Extreme Astrophysical Environments II |
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Chair: Rodney Orford, LBNL Room: Hyatt Regency Hotel Imperial 5CD |
Friday, October 28, 2022 10:30AM - 10:42AM |
EL.00001: Progress at the N=126 factory and its application to identify and characterize long-lived isomers Guy Savard, Miguel Bencomo, Maxime Brodeur, Daniel P Burdette, Jason A Clark, Aaron T Gallant, Daniel E Hoff, Kay Kolos, Filip G Kondev, Biying Liu, G. Wendell Misch, Matthew R Mumpower, Wei Jia Ong, Rodney Orford, Nicholas D Scielzo, Dwaipayan Ray, Adrian A Valverde The N=126 factory, currently under construction at the ATLAS facility at ANL, will provide access to heavy neutron-rich isotopes of interest to astrophysics and nuclear structure studies. This will allow measurements on isotopes and long-lived isomers in the so-far unexplored region around the N=126 line. The CPT Penning trap mass spectrometer, currently being used at CARIBU to measure masses and identify long-lived isomers, will be moved to the N=126 factory to extend these measurements to heavier nuclei. The N=126 factory and the technique developed to characterize isomers with the CPT spectrometer will be described. Recent results at CARIBU will be presented together with the expected reach of the system when installed at the N=126 factory, with particular focus on potential “astromers”, isomers that influence the astrophysical nucleosynthesis processes. |
Friday, October 28, 2022 10:42AM - 10:54AM |
EL.00002: The TITAN Penning trap; an upgrade for high precision mass measurements of low-lying isomers Eleni Marina Lykiardopoulou, Ivana Belosevic, Sakshi Kakkar, Alexander Ridley, Jens Dilling, Ania Kwiatkowski A detailed study of the r-process path requires knowledge of nuclear isomers and their excitation energy. Mass measurements have proven to be an excellent way of discovering new isomers and determining their excitation energy. However, small excitation energies can be challenging due to the mass spectrometer's resolution and due to low statistics. |
Friday, October 28, 2022 10:54AM - 11:06AM |
EL.00003: Recent Results of the Time-of-Flight Magnetic-Rigidity (TOF-Bρ) Mass Measurements Chowdhury Irin Sultana, Kailong Wang, Alfredo Estradé, Michael A Famiano, Matt Amthor, Thomas J Baumann, Daniel Bazin, Khushi Bhatt, Thomas Chapman, Nikolaos Dimitrakopoulos, Joseph Dopfer, Benjamin W Famiano, Michael Giles, Tom Ginter, Rahul Jain, Jared R jenkin, Shilun Jin, Levi Klankowski, Sean Liddick, Zach Meisel, Wolfgang Mittig, Neerajan Nepal, Jorge Pereira, Nabin Rijal, Andrew Rogers, Elizabeth Rubino, Sithira Samaranayake, Hendrik Schatz, Oleg Tarasov, Pelagia Tsintari, George Zimba Nuclear masses are crucial to understand both nuclear structure and nuclear astrophysics. In particular masses around A=40 are essential for the nuclear processes occurring in the crust of an accreting neutron star and the evolution of nuclear shell closures towards the neutron drip-line. Furthermore, masses of heavy isotopes beyond the N=50 shell closure are valuable input for the r-process models. One of the techniques available to access these short-lived exotic nuclei is the TOF-Bρ technique. In the last TOF-Bρ experiment at the National Superconducting Cyclotron Laboratory (NSCL), we measured the masses near the 42Si region using the fragmentation of 48Ca. A previous TOF-Bρ experiment at NSCL measured the masses near the N=70 region from Zr to Ru using the fragmentation of 124Sn. I will present the status and results of these experiments. In addition, with the Facility for Rare Isotope Beams (FRIB), we can expect to expand the current reach for measurements of the nuclear mass surface. I will discuss the future plans of the TOF-Bρ collaborations at FRIB. |
Friday, October 28, 2022 11:06AM - 11:18AM |
EL.00004: High-precision mass measurement of 24Si and a refined determination of the rp process at the A=22 waiting point Daniel Puentes, Zachary P Meisel, Georg Bollen, Alec S Hamaker, Christoph Langer, Erich Leistenschneider, Catherine R Nicoloff, Wei Jia Ong, Matthew Redshaw, Ryan Ringle, Chandana Sumithrarachchi, Jason Surbrook, Adrian A Valverde, Isaac T Yandow Type I x-ray bursts occur at astrophysical sites where a neutron star accretes H/He-rich matter from a companion star, leading to nuclear burning on the neutron star surface. The only observable is the x-ray burst light curve, which is used as a unique diagnostic of the outer layers of accreting neutron stars such as the accretion rate and fuel composition. In addition to the astrophysical conditions, the main determinant of the shape of the light curve is the nuclear physics involved. Variations within the uncertainty of the 23Al(p,γ)24Si reaction rate lead to significant shifts in simulated x-ray light curves, where the ground state mass of 24Si is currently the dominant source of the reaction rate uncertainty (19 keV). A high-precision mass measurement of 24Si was performed with the LEBIT facility at the National Superconducting Cyclotron Laboratory. The atomic mass excess, 10 753.8(37) keV, is a factor of 5 more precise than previous results. This substantially reduces the uncertainty of the 23Al(p,γ)24Si reaction rate, which is a key part of the rapid proton capture (rp) process powering type I x-ray bursts. The updated rate constrains the onset temperature of the (α,p) process at the 22Mg waiting point to a precision of 9%. |
Friday, October 28, 2022 11:18AM - 11:30AM |
EL.00005: Nuclear mass measurements of palladium and ruthenium isotopes at the CPT William S Porter, Maxime Brodeur, Jason A Clark, Biying Liu, Matthew R Mumpower, Dwaipayan Ray, Guy Savard, Kumar S Sharma, Adrian A Valverde Nuclear mass measurements are critical in furthering our understanding of the production of heavy elements in extreme astrophysical processes, both through direct input into simulations and through benchmarking and guiding nuclear mass models, which aim to predict masses well beyond current experimentally achievable bounds. The Canadian Penning Trap (CPT) has a long history of success in measuring nuclear masses while located at the CARIBU facility at Argonne National Laboratory, which produces many isotopes relevant to the astrophysical r-process through the spontaneous fission of a 252Cf source. The CPT was used in the measurement of ruthenium and palladium isotopes around A ~ 110. The masses of 108Ru, 110Ru and 116Pd were measured using the Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique, which has been reliably established at the CPT and achieves relative mass precisions less than 10-7. These mass measurement results will be discussed and compared to current state-of-the-art mass models typically used for r-process abundance calculations. |
Friday, October 28, 2022 11:30AM - 11:42AM |
EL.00006: Mass measurements of neutron-rich Rh isotopes using the Canadian Penning Trap Biying Liu, Maxime Brodeur, Daniel P Burdette, Nathan Callahan, Jason A Clark, Daniel E Hoff, Kay Kolos, Graeme Morgan, Rodney Orford, William S Porter, Dwaipayan Ray, Fabio Rivero, Guy Savard, Kumar S Sharma, Adrian A Valverde, Louis Varriano The Canadian Penning Trap (CPT) has been at the Argonne National Laboratory's CARIBU facility for over a decade, where it measured the masses of over 300 nuclei produced from the spontaneous fission of CARIBU’s 252Cf source. The current phase-imaging ion-cyclotron-resonance technique adopted by the CPT provides a typical precision of 1-10 keV/c2. With such precision, not only atomic masses can be measured to high precision, but also the energy difference between the nuclear ground state and certain nuclear isomer. Recently, a series of mass measurement campaigns were carried out using the CPT to measure the masses of importance for understanding the astrophysical rapid neutron capture process (r process), to improve precision on certain nuclear masses which largely depend on beta end point measurements, or to probe the ground state and the isomer(s) mass for the purpose of nuclear structure or nuclear astrophysics study. These measurements include neutron-rich odd-odd 108,110,112,114,116Rh isotopes, which were known to present long-lived isomeric states (of unknown energy) based on lifetime measurements. We will present the most precise measurements to date, done at sufficient precision to resolve some of the isomers for the first time as well as unveil possible unknown isomers. |
Friday, October 28, 2022 11:42AM - 11:54AM |
EL.00007: The Mass of 128Sb and its Role as an Astromer Daniel E Hoff, Kay Kolos, Biying Liu, Dwaipayan Ray, Adrian A Valverde, Maxime Brodeur, Daniel P Burdette, Nathan Callahan, Jason A Clark, Aaron T Gallant, Filip G Kondev, G. Wendell Misch, Graeme Morgan, Matthew R Mumpower, Rodney Orford, William S Porter, Fabio Rivero, Guy Savard, Nicholas D Scielzo, Kumar S Sharma, Kamila Sieja, Trevor M Sprouse, Louis Varriano Recently it was shown that nuclear isomers play a significant role in nucleosynthetic pathways, in particular the rapid neutron-capture process. These astrophysically metastable isomers, otherwise known as ``astromers", influence the population of unstable nuclei and hence can impact the heating and light output. We have recently performed the first direct mass measurements of one such astromer 128Sb and of the ground state 128Sb using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. We find an excitation energy of this astromer that differs significantly from the previous upper limit, changing its thermalization temperature. Our measurement provides the first step in understanding the role of 128Sb in the rapid neutron-capture process, and we will discuss some of the implications. |
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