Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session L09: Nuclear Astrophysics V |
Hide Abstracts |
Chair: Stephanie Lyons, Pacific Northwest National Laboratory Room: Hilton Waikoloa Village Kohala 2 |
Friday, December 1, 2023 9:00AM - 9:15AM |
L09.00001: Using proton-inelastic scattering and transfer reactions to constrain neutron-induced cross sections with the Surrogate Method Andrew Ratkiewicz Neutron-induced reactions on unstable nuclei are of interest for applications as well as nuclear astrophysics. However, due to the short-lived nature of all the participants such reactions can be very difficult or impossible to measure directly. Because of the importance of these reactions several indirect methods have been developed to constrain them. One such technique is called the Surrogate Reaction Method (SRM). In the SRM an experimentally-tractable reaction is chosen that forms the "same" compound nucleus as would be created in the desired reaction. The decay of this compound nucleus is measured, and the measurements are used to constrain calculations of the desired reaction. |
Friday, December 1, 2023 9:15AM - 9:30AM |
L09.00002: Mass Measurements of 119g,mCd and 119g,mAg Astromers with the Canadian Penning Trap Fabio Rivero, Maxime Brodeur, Jason A Clark, Aaron T Gallant, Daniel E Hoff, Kay Kolos, Filip G Kondev, Biying Liu, G. Wendell Misch, G. E Morgan, Matthew R Mumpower, Rodney Orford, William S Porter, Dwaipayan Ray, Daniel Santiago-Gonzalez, Guy Savard, Kumar S Sharma, Adrian A Valverde, Louis Varriano
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Friday, December 1, 2023 9:30AM - 9:45AM |
L09.00003: Total Absorption Spectroscopy of Ground and Isomeric States in 70Cu Eleanor K Ronning, Sean N Liddick, Andrea Richard, Artemis Spyrou, Isaac T Yandow, Ryan Ringle, B A Brown, Aaron Chester, Katherine L Childers, Paul A Deyoung, Jordan Owens-Fryar, Alec S Hamaker, Caley Harris, Rebecca Lewis, Kasey R Lund, Stephanie M Lyons, Alicia R Kyle, Daniel Puentes, Rachel Sandler, Chandana S Sumithrarachchi, Mathis Wiedeking, Yongchi Xiao Theoretical models studying the origin of elements in the universe and stellar nucleosynthesis processes such the rapid neutron capture process (r-process), require physics information about beta-decay properties and neutron-capture reaction rates [1]. Currently quasiparticle random phase approximation (QRPA) calculations are used across the nuclear landscape to predict β-decay properties in astrophysical simulations [2]. QRPA calculations are typically bench-marked against known half-lives and β-delayed neutron emission probabilities, instead of comparing against the full distribution of β-decay feeding intensities (Iβ) as a function of excitation energy. Nuclei with larger β-decay Q-values have decay schemes with many weak de-excitation pathways to the ground state and β-decay branches, which are difficult to measure without high efficiency detectors. Here, we use the method of total absorption spectroscopy to investigate the β-decay of 70Cu which has three β-decaying spin-parity states (6− ground state, and two isomeric states: 3−, and 1+) and is thought to be produced in the weak r-process [3, 4]. In an experiment performed at the National Superconducting Cyclotron Laboratory 70Cu was produced, sent to the Low Energy Beam and Ion Trap (LEBIT) [5], and delivered to the Summing NaI (SuN) Total Absorption Spectrometer [6]. Spectra from the β-decay of each spin-parity state were isolated using different beam on/off periods. Iβ values from total absorption spectroscopy following the β-decay of each of the three β-decaying spin-parity states will be presented and compared to Shell Model and QRPA calculations. |
Friday, December 1, 2023 9:45AM - 10:00AM |
L09.00004: Investigating the Impact of the Strontium Neutron-Capture Reaction Rates on i-Process Nucleosynthesis Lauren Harewood, Andrea Richard, Richard O Hughes, Pavel Denissenkov, Emma Mcginness, Rebecca A Surman, Jutta E Escher, Gregorio Aguilar Potel, Falk Herwig The origin of elements in the universe is a longstanding open question in nuclear astrophysics. It is well known that most of the heavy elements greater than iron are synthesized via the traditional neutron-capture processes such as the slow (s) and rapid (r) processes. Recently a third process has come into the picture and is known as the intermediate (i) process. The i-process is less well known as compared to the two traditional neutron-capture processes. Some possible astrophysical sites containing conditions consistent with the i-process include CEMP stars, low metallicity, low mass super AGB or post AGB stars. Studies of neutron-capture reaction rates and their impact on i-process nucleosynthesis have been investigated and sensitivity studies have been performed. Recent advances in radioactive beam facilities have enabled researchers to experimentally constrain reaction rates such as the 93Sr(n,g)94Sr, which is important for the i-process. Here we use Hauser Feshbach formalism to calculate the 93Sr(n,g)94Sr reaction rate and implement it in a one-zone i-process simulation to investigate its significance for the i-process. |
Friday, December 1, 2023 10:00AM - 10:15AM |
L09.00005: Neutron capture reactions on 44Ti relevant for core-collapse supernovae Heshani Jayatissa, Sean A Kuvin, Hye Young Lee, Veronika Mocko, Christiaan E Vermeulen, Hyeong Il Kim Signatures of short-lived radioisotopes such as 44Ti (T1/2 = 60 years) originating in explosive stellar environments such as core-collapse supernovae (CCSNe) have been observed using satellite-based gamma-ray observatories. In order to improve theoretical CCSN models, nuclear physics inputs such as nuclear reaction rates need to be constrained. This includes characterizing the reactions that both produce and destroy 44Ti at the relevant temperatures, in which the neutron-induced destruction paths can be measured directly using radioactive targets at facilities that can produce sufficiently high quality neutron beams. Using a radioactive target of 44Ti and an intense neutron beam covering a broad range of fast neutron energies at the Los Alamos Neutron Science Center (LANSCE) facility at Los Alamos National Laboratory, 44Ti(n,p) reaction cross sections have been measured. Preliminary reaction cross sections, along with proposed improvements for future measurements will be presented. This includes some highlights of the development of a solenoid spectrometer at LANSCE for further optimized measurements using radioactive targets. |
Friday, December 1, 2023 10:15AM - 10:30AM |
L09.00006: Impact of the Experimentally Constrained 93Sr(n,γ)94Sr Reaction for the Astrophysical i-Process Andrea Richard, Richard O Hughes, Daniel Yates, Greg Hackman, Jutta E Escher, Gregory Potel, Reiner Krucken Neutron-capture cross sections play a vital role in our understanding of heavy element nucleosynthesis. In astrophysical processes such as the intermediate neutron-capture process, or i-process, element formation occurs in neutron-rich environments and involves short-lived isotopes for which capture cross sections cannot be measured via direct techniques. Instead reaction rates in these regions rely on calculations that have uncertainties up to a few orders of magnitude. Recent measurements of the β-decay of 94Rb, which compared the neutron-to gamma-ray-branching ratio of state decays above the neutron separation energy in 94Sr, suggest an enhanced γ-ray branch which would in turn lead to an unexpectedly large 93Sr(n,γ) cross section. If confirmed, such an enhancement could have a strong impact on our understanding of i-process nucleosynthesis involving nuclei in this region. In order to investigate this potential enhancement of the 93Sr(n,γ) cross section and its impact on the i-process, an experiment was performed at TRIUMF using an 8 MeV/u 93Sr beam impinging on a CD2 target. The (d,pγ) coincidence data was measured using the SHARC and TIGRESS arrays. Experimental details from the measurement of 93Sr(d,pγ)94Sr and interpretation of the 93Sr(n,γ)94Sr cross section using the Surrogate Reaction Method will be presented along with preliminary i-process calculations. |
Friday, December 1, 2023 10:30AM - 10:45AM |
L09.00007: Measuring the 88Sr(α, n)91Zr reaction cross section with Accelerator Mass Spectrometry Maria Anastasiou, Wei Jia Ong, John Wilkinson, Scott Tumey, Kay Kolos McCubbin Supernovae, the explosive conclusion to nuclear burning in massive stars, dominate contributions to the early galactic abundance of the elements. Different astrophysical scenarios, under which supernovae seed the early galaxy with elements heavier than iron, are still being investigated. Of particular interest are the lighter heavy elements from Sr to Ag with their origin being placed in the neutrino-driven ejecta in core-collapse supernovae. While the s- and r- process have been perceived for years as the dominant mechanisms for the formation of heavier elements, more recent studies support that in particular the elements from Sr to Ag are synthesized via (α, n)-reactions or the so-called “weak” r-process. Sensitivity studies have shown that (α, n) reaction rates of these lighter heavy nuclei indeed play a crucial role in predicting their abundances, suggesting the need of experimental data to constrain the uncertainties on those rates and thus the abundance predictions. The 88Sr(α, n)91Zr reaction has been identified among the key processes that impact these abundances with no experimental data currently available. At the Center for Accelerator Mass Spectrometry of Lawrence Livermore National Laboratory, we measure this reaction using a combination of target irradiation and Accelerator Mass Spectrometry (AMS). This talk focuses on the development of the experimental methods and the preliminary data obtained. |
Friday, December 1, 2023 10:45AM - 11:00AM |
L09.00008: Extraction of Nuclear Level Densities and gamma-ray strength functions for the 85Rb compound nucleus relevant to the p- process Konstantinos Bosmpotinis, Alicia Palmisano, Artemis Spyrou, Artemis Tsantiri, Hannah Berg, Paul A Deyoung, Alexander C Dombos, Panagiotis Gastis, Orlando Gomez, Erin C Good, Caley Harris, Sean N Liddick, Stephanie M Lyons, Jorge Pereira, Andrea Richard, Anna Simon, Mallory K Smith, Remco G Zegers There are 35 proton-rich stable isotopes, known as p-nuclei. Their existence is attributed to the p-process, which primarily consists of a network of photodisintegration reactions on s- and r-process seed nuclei. The abundances of p-nuclei can be obtained based on simulations of this network, with most of the isotopes involved being radioactive. For this reason, direct measurements of these reactions are challenging, thus reaction rates are often obtained via theoretical models. Here we focus, not only on reaction cross section measurements of specific reactions, but also on extracting statistical properties such as the nuclear level density (NLD) and the gamma-ray strength function (gSF). Measurement of the 84Kr(p,γ)85Rb proton capture reaction has been performed with the SuN detector at the NSCL at MSU. A stable 84Kr beam was impinged on to a hydrogen gas target in the energy range 2.7 MeV/u to 3.7 MeV/u. In the present work, a systematic investigation was performed to obtain the NLD and gSF for the 85Rb compound nucleus. The RAINIER code was implemented to simulate the statistical de-excitation of the 85Rb compound nucleus using various combinations of NLD and gSF. The resulting simulated spectra were compared to the experimental data to identify suitable combinations of NLD and gSF. |
Friday, December 1, 2023 11:00AM - 11:15AM |
L09.00009: 58Ni(3He,t)58Cu*(γ) Measurements with GODDESS to Constrain Astrophysical Rate of 57Ni(p,γ)58Cu Scott R Carmichael, Dan W Bardayan, Patrick O'Malley, Steven D Pain, Claus Muller-Gatermann, Marco Siciliano, Jolie A Cizewski, Kelly A Chipps, Andrew Ratkiewicz, Kate Jones Nucleosynthesis models of core-collapse supernovae are validated by comparing radioisotope abundances predicted by models to abundances inferred from the observation of gamma rays emitted in supernovae remnants. One such radioisotope, 44Ti, is especially sensitive to the reaction rate of 57Ni(p,γ)58Cu. To effectively validate these models, it is therefore crucial to precisely determine this rate. Despite this importance, no experimental rates exist for this reaction. To experimentally constrain this rate, GODDESS (GRETINA ORRUBA Dual Detectors for Experimental Structure Studies) was used to measure structure properties of 58Cu via the 58Ni(3He,t)58Cu*(γ) reaction at Argonne National Laboratory’s ATLAS facility. The coupling of these two highly efficient arrays allows for the precise determination of 58Cu level energies via the detection of gamma rays in coincidence with charged particles. Because the reaction rate depends exponentially on these level energies, this precision is critical. Preliminary results of the experimental data analysis will be presented. |
Friday, December 1, 2023 11:15AM - 11:30AM |
L09.00010: Sn Target Development and First Results From Measurements of Capture Reactions for the γ-Process Using HECTOR John P McDonaugh, Anna Simon, Khachatur Manukyan, Miriam Matney, Jes Koros, Chloe R Jones The formation of p-nuclei and their abundances are an important and ongoing study in nuclear astrophysical measurements. To understand and constrain theoretical models on the abundances of p-nuclei, further measurements of important branching points of the γ-process are needed. For this purpose the cross sections of (p,γ) and (α,γ) reactions on 112,114,116Sn and 108Pd(p,γ)109Ag over a combined energy range of Ep=2-5MeV and Eα=5-11.5MeV will be investigated. To cover this wide range of energies in the Gamow Window for these reactions, thin targets around 200-400 μg/cm2 are required. The development and characterization of these thin targets for the various Sn isotopes will be discussed in detail. The measurements utilizing these targets will be performed using both the 5U and the FN accelerators at the Nuclear Science Laboratory at the University of Notre Dame. First experimental results obtained using the new targets will be presented. |
Friday, December 1, 2023 11:30AM - 11:45AM |
L09.00011: Constraining the Astrophysical γ Process: Cross Section Measurements of (p,γ) Reactions in Inverse Kinematics Artemis Tsantiri, Artemis Spyrou, Alicia R Kyle, Hannah Berg, Konstantinos Bosmpotinis, Paul A Deyoung, Erin C Good, Caley Harris, Sean N Liddick, Stephanie M Lyons, Gerard J Owens-Fryar, Jorge Pereira, Andrea Richard, Amal Sebastian, Mallory K Smith, Sivahami Uthayakumaar, Remco G Zegers One of the most fundamental queries in nuclear astrophysics is understanding the mechanisms through which the elements are forged in the stars. For the vast majority of the elements heavier than iron, stellar nucleosynthesis is largely governed by the slow and rapid neutron capture processes. However, a relatively small group of naturally occurring, neutron-deficient isotopes, located in the region between 74Se and 196Hg, the so called p nuclei, cannot be formed by either of those processes. These ~30 stable nuclei are believed to be formed in the so called γ process from the "burning" of preexisting r and s process seeds at stellar environments of sufficiently high temperature, where a sequence of photodisintegration reactions can occur. |
Friday, December 1, 2023 11:45AM - 12:00PM |
L09.00012: The Plasma Window as a Vacuum-Atmosphere Interface for Measurements of Stellar Neutron-Induced Reaction Cross Sections Ophir M Ruimi Neutrons play a dominant role in the stellar nucleosynthesis of heavy elements. We review a scheme for the experimental determinations of neutron-induced reaction cross sections using a high-intensity neutron source based on the 18O(p,n)18F reaction with an 18O-water target at SARAF's upcoming Phase II. The quasi-Maxwellian neutron spectrum with effective thermal energy kT ≈ 5 keV, characteristic of the target (p,n) yield at proton energy Ep ≈ 2.6 MeV close to its neutron threshold, is well suited for laboratory measurements of MACS of neutron-capture reactions, based on activation of targets of astrophysical interest along the s-process path. 18O-water's vapour pressure requires a separation in between the accelerator vacuum and the target chamber. The high-intensity proton beam (in the mA range) of SARAF is incompatible with a solid window in the beam's path. Our suggested solution is the use of a Plasma Window, which is a device that utilizes ionized gas as an interface between vacuum and atmosphere, and is useful for a plethora of applications in science, engineering and medicine. The high-power dissipation (few kW) at the target is expected to result in one of the most intense sources of neutrons available at stellar-like energies. Preliminary results concerning proton beam energy loss and heat deposition profiles for target characteristics and design, a new full-scale 3-dimensional computer-aided design model of the Plasma Window (as well as its operation principles) and the planned experimental scheme, will be reviewed. |
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