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 KK: Mini-Symposium: Nuclear Pademonium: How Total Absorption Spectrometry Informs Outstanding Issues in Nuclear Physics II |
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Chair: Bertis Rasco, ORNL Room: Hyatt Regency Hotel Imperial 5AB |
Saturday, October 29, 2022 10:30AM - 10:42AM |
KK.00001: β-decay strength distributions of 66,68Co Stephanie M Lyons, Artemis Spyrou, Darren L Bleuel, Katherine L Childers, Benjamin P Crider, Alexander C Dombos, Erin C Good, Caley Harris, Ann Cecilia Larsen, Rebecca Lewis, Sean Liddick, Alicia Palmisano, Debra Richman, Nickolas Scielzo, Anna Simon, Hannah C Berg, Mallory Smith, Adriana Sweet, Remco Zegers, Magne S Guttormsen, Jacob Davis Approximately half of the elements heavier than iron are thought to be produced in the rapid-neutron capture process. Recent insights into the astrophysical site of this critical process highlight the need for experimental data on short-lived neutron-rich nuclei. R-process nucleosynthesis sensitivity studies show that the final abundance distributions of r-process nuclei are greatly impacted by β-decay properties, such as half-lives and β-delayed neutron-emission probabilities. The β-decay strengths for 66,68Co have been measured using the technique of total absorption spectroscopy with the Summing NaI (SuN) detector at the National Superconducting Cyclotron Laboratory and results for both nuclei will be presented. Highlighted is the resultant ground-state spin of 66Co confirmed to be Jp=1+, making a ground-state to ground-state transition an allowed transition. The resultant β-decay intensities and deduced Gamow-Teller strengths are compared to theoretical calculations used in r-process models. |
Saturday, October 29, 2022 10:42AM - 10:54AM |
KK.00002: Implantation detectors for first decay studies with FDSi Ian C Cox, Robert Grzywacz, Donnie Hoskins, Keith Vaigneur, Thomas T King, James Allmond, Heather L Crawford, Noritaka Kitamura, Gary Hollenhead, Wei Jia Ong, Thomas J Ruland, Kevin Siegl, Zhengyu Xu, Rin Yokoyama With the recent opening of the Facility for Rare Isotope Beams (FRIB) at Michigan State University, commissioning experiments have been underway for the FRIB Decay Station Initiator (FDSi) [1]. Implantation detectors serve as a vital part of the experimental setup, as they can stop the high-energy radioactive beam and then measure its subsequent decays. For FDSi, multiple position-sensitive detectors have been developed for implantation in both the discrete array and within the Modular Total Absorption Spectrometer (MTAS) [2]. The discrete array of FDSi uses a segmented inorganic scintillator coupled to a multi-anode photomultiplier tube, providing good timing resolution for neutron time of flight measurements [3]. To fit within MTAS, a brand-new smaller detector has been developed with a scintillator coupled to an array of silicon photomultipliers for millimeter position resolution at both implant and decay energies. The high position resolution allows for better correlation between beta decays and ion implantation events, and a reduction of background in measurements. |
Saturday, October 29, 2022 10:54AM - 11:06AM |
KK.00003: β-decay properties of the 72,74Co isotopes Hannah C. C Berg, Artemis Spyrou, Erin C Good, Darren L Bleuel, Katherine L Childers, Benjamin P Crider, Alexander C Dombos, Caley M Harris, Ann-Cecilie Larsen, Rebecca Lewis, Sean Liddick, Stephanie M Lyons, Alicia Palmisano, Debra Richman, Nicholas D Scielzo, Anna Simon, Mallory Smith, Adriana Sweet, Remco Zegers It is known that the majority of the heavy elements (Z>26) are formed in neutron capture processes, and the rapid neutron capture (r-) process is responsible for producing approximately half. To fully understand heavy-element nucleosynthesis through the r process, accurate knowledge of nuclear properties is needed. Frequently, nuclear input is not well constrained, and in lieu of data, extrapolations and theoretical models have to be used. Predictions can diverge over orders of magnitude for basic properties far from stability. One of the most important inputs to the r process is β-decay properties. Theory relies on data to constrain their models and make more reliable predictions for experimentally inaccessible nuclei. Measuring β-decay strength functions is a sensitive benchmark to such theoretical models. I will discuss preliminary results on the total absorption spectroscopy of the neutron-rich 72,74Co isotopes, which is compared to theoretical calculations for the Gamow-Teller strength, B(GT). The measurements were performed at the National Superconducting Cyclotron Laboratory using the SuN detector. |
Saturday, October 29, 2022 11:06AM - 11:18AM |
KK.00004: β Decay of 104Nb Verified with Total Absorption Spectroscopy Alexander M Laminack, Bertis C Rasco, Krzysztof Piotr P Rykaczewski, Toby King, Thomas J Ruland The Modular Total Absorption Spectrometer was used to measure the β decay of 104Nb produced at the CAlifornium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory. We report an updated half life of 5.9(3) s in disagreement with the previous measurements. Additionally, we provide evidence that the tentative, low spin assignment for the long-lived 104Nb is inaccurate. The absence of ground-state-to-ground-state feeding suggests that long-lived 104Nb is more likely high spin (≥2). The deduced β-strength pattern shows preferential feeding to high-lying states consistent with the Pandemonium effect and the aforementioned higher ground-state spin assignment. The newly measured β-feeding intensity increases the excess of reactor anti-neutrinos observed by Daya Bay in the 8 to 8.5 MeV anti-neutrino energy region from 24.4% to 28.5%. |
Saturday, October 29, 2022 11:18AM - 11:30AM |
KK.00005: β-feeding Intensity Distribution of 73Co From Total Absorption Spectroscopy Mejdi J Mogannam, Sean Liddick, Rebecca Lewis, Andrea L Richard, Stephanie M Lyons, Artemis Spyrou, Darren L Bleuel, Aaron Chester, Kathrine Childers, Benjamin P Crider, Alexander C Dombos, Magne Guttormsen, Caley Harris, Ann-Cecilie Larsen, Alicia Palmisano, Debra Richman, Nicholas D Scielzo, Anna Simon, Mallory K Smith, Adriana Sweet, Remco G Zegers The β-decay properties of isotopes far from stability are necessary for improving astrophysical r-process abundance calculations and validating nuclear structure models. Nuclei far from stability tend to have large β-decay Q-values, often leading to decay schemes with many weak β-decay branches and multiple deexcitation pathways to the ground state. These weak branches are difficult to detect with high efficiency detectors. These issues may be overcome using a large volume, high efficiency g-ray detector that can simultaneously measure all g-rays emitted following a β-decay event allowing for reconstruction of the initial excited state populated in the β-decay. In this work, the β-decay of 73Co was studied at the NSCL using the Summing NaI(Tl) (SuN) detector [1]. Implanted ions and subsequent β-decay electrons were detected using a DSSD while β-delayed g-rays were measured in SuN. The resulting feeding intensities are used to calculate the Gamow-Teller strength distribution (B(GT)) for the β decay of 73Co. The β-decay properties of neighboring isotopes have been completed previously using the same experimental setup and will be compared with the results of this analysis [2-3]. |
Saturday, October 29, 2022 11:30AM - 11:42AM |
KK.00006: Impact of Improved Beta-Decay Feedings of 105Mo on Reactor Decay Heat Thomas J Ruland, Jeff C Blackmon, Bertis C Rasco Reactor decay heat results from the β decay of fission products back to stability and produces 100% of the power after reactor shutdown. Proper understanding of reactor decay heat is vital to the safe operation of nuclear reactors, and this requires precise and accurate β-feeding intensities for the β decay of fission products. Historical measurements of β-feeding intensities using high-resolution detectors are often troubled by low γ-ray efficiencies, which can result in incomplete β- feeding intensities that generally over-predict low-energy level β feedings and under-predict β feeding to higher energy levels. This can be corrected using high-efficiency total absorption detectors such as the Modular Total Absorption Spectrometer (MTAS). We measured the β-feeding intensity of 105Mo using MTAS at Argonne National Laboratory. We find substantial discrepancies from previous results for β feedings and average γ-ray energy in 105Mo. Results and the impact on reactor decay heat will be presented. |
Saturday, October 29, 2022 11:42AM - 11:54AM |
KK.00007: Preliminary results for constraining i-process reaction rates Caley M Harris, Stephanie M Lyons, Artemis Spyrou, Andrea L Richard, Mallory K Smith, Jason A Clark, Paul A Deyoung, Alexander C Dombos, Beau Greaves, Rebeka Kelmar, Ann-Cecilie Larsen, Dennis Muecher, Alicia Palmisano, Daniel Santiago-Gonzalez, Guy Savard The majority of elements heavier than iron are produced via neutron capture processes, primarily the s process and the r process. However, certain astrophysical observations, such as Sakurai’s object and several CEMP stars that show enhancement of s- and r-elements, cannot be described by either process or a combination of the two. The intermediate i process was proposed as a neutron capture process that proceeds at neutron densities between those of the s and r processes, in a region several neutrons away from stability. Models to determine the final abundance pattern of astrophysical environments depend on nuclear physics input, including β-decay rates, nuclear masses, and neutron capture rates. Denissenkov et al. performed a sensitivity study on the neutron capture rates of 52 unstable isotopes and determined eight reactions that had the largest impact on the final abundance pattern of an i process model. Measurements of the neutron capture rates on 85-86Br, 87-89Kr, 89Rb, and 89,92Sr, would significantly reduce the uncertainties. The preliminary results of an experiment performed at Argonne National Lab using the SuN detector, its associated tape station (SuNTAN), and beams from the CARIBU facility will be presented for the indirect study of 87-89Kr(n,γ)88-90Kr. |
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