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 DL: Mini-Symposium: Mass Measurements for Extreme Astrophysical Environments I |
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Chair: Kelly Chipps, ORNL Room: Hyatt Regency Hotel Imperial 5CD |
Friday, October 28, 2022 8:30AM - 9:06AM |
DL.00001: Reverse Engineering the r Process Invited Speaker: Rodney Orford A nuclear mass survey of rare-earth isotopes has been conducted with the Canadian Penning Trap mass spectrometer using the most neutron-rich nuclei thus far extracted from the CARIBU facility. With the phase-imaging ion-cyclotron-resonance measurement technique, several masses along Ce-Eu isotopic chains near N=100 have been measured with sub-10 keV/c2 precision for the first time. Independently, a detailed study exploring the role of nuclear masses in the formation of the r-process rare-earth abundance peak has been performed. Employing a Markov chain Monte Carlo (MCMC) technique, mass predictions of lanthanide isotopes have been made which uniquely reproduce the observed solar abundances near A = 164 under three distinct astrophysical outflow conditions. We compare our mass measurements to each of the predicted mass surface trends and find strong consistency with the ‘hot’ r-process environment where the rare-earth peak forms during an extended period of (n,γ) ↔ (γ,n) equilibrium. Here, I will give an overview of the mass measurement campaigns, briefly describe the MCMC calculations, and conclude with future measurement prospects at next-generation rare isotope beam facilities. |
Friday, October 28, 2022 9:06AM - 9:18AM |
DL.00002: Modeling masses with an artificial neural network Matthew R Mumpower, Trevor M Sprouse, Amy Lovell, Arvind Mohan We present a new model of masses based on an artificial neural network. Using a randomized fraction (~20%) of the Atomic Mass Evaluation we predict ~80% of measured masses to with an accuracy of approximately 300 keV. We employ a Mixture Density Network to produce probabilistic output. Thus our methodology also provides confidence intervals for each prediction. Addition of a physical constraint, here the Garvey-Kelson relations, greatly improves the predictive capabilities of this modeling. |
Friday, October 28, 2022 9:18AM - 9:30AM |
DL.00003: Microscopically-based energy density functionals and r-process nucleosynthesis Lauren Harewood, Rebecca Surman, Matthew R Mumpower, Rodrigo Navarro Perez, Nicolas Schunck, Trevor M Sprouse Masses are crucial inputs into calculations of r-process nucleosynthesis, the rapid neutron capture process responsible for about half of the elements heavier than iron in the solar system. Here we examine the nucleosynthetic impact of masses generated in a density functional theory approach, where the functional is microscopically constrained and based on local chiral potentials. This approach to nuclear masses has been found to outperform more phenomenological Skyrme functionals in reproducing known data. Here we test their performance for species far from stability in calculations of the r-process in a variety of astrophysical conditions. |
Friday, October 28, 2022 9:30AM - 9:42AM |
DL.00004: The Canadian Penning Trap at the N=126 Factory Adrian A Valverde, Maxime Brodeur, Jason A Clark, Biying Liu, Dwaipayan Ray, Guy Savard, Kumar S Sharma, Daniel P Burdette, Daniel E Hoff, Russell A Knaack, Kay Kolos, Gail C McLaughlin, Graeme Morgan, Matthew R Mumpower, Rodney Orford, William S Porter, Rebecca Surman, Louis Varriano, Nicole Vassh The Canadian Penning Trap (CPT) has been located at the CARIBU facility at Argonne National Laboratory's ATLAS accelerator for over a decade, where it has had a spectacularly successful mass spectrometry program, measuring over 200 nuclei produced through the spontaneous fission of 252Cf, recently focusing on masses of interest for the formation of the astrophysical r-process rare earth peak. The CPT will soon be relocating to the new N=126 Factory at ATLAS, where multi-nucleon transfer reactions between two heavy ions will offer a new method of producing heavy, neutron-rich nuclei that cannot be effectively accessed using traditional techniques. The CPT will make use of this facility to study new regions of the chart of the nuclei, like the neutron-rich nuclei near the N=126 shell closure critical for understanding the formation of the r-process A~195 abundance peak, as well as allowing further study of the rare earth peak farther than stability. The status of the N=126 Factory and the proposed measurement program will be presented. |
Friday, October 28, 2022 9:42AM - 9:54AM |
DL.00005: Mass measurements of r-process nuclei using the TITAN MR-ToF-MS Andrew Jacobs, Jens Dilling, Ania Kwiatkowski, Coulter Walls, Ali Mollaebrahimi, Chris Chambers Following the detection of the binary neutron-star merger GW170817, several key observations were made of the electromagnetic counterpart AT2017gfo. Namely, the early blue emission of the kilonova implied the production of elements in the first r-process peak, while the later red emission indicated the production of lanthanides. Additionally, Sr has been the only element specifically identified in the ejecta. To better predict isotopic production from these mergers using nucleosynthesis simulations, experimental nuclear inputs such as masses, half-lives, and decay channels are needed from neutron-rich nuclei in the r-process path. To this end, the Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-ToF-MS) at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) is an excellent device for performing the necessary mass measurements. This is due to its ability to perform high-precision measurements on short lived species with exceedingly high background contamination. The technique of mass-selective re-trapping has proven a useful tool for measurements near the r-process abundance peaks of A = 82 and 130. A series of experimental campaigns have been conducted in these regions, and a selection of the results will be discussed. |
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