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 C09: Nuclear Astrophysics I |
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Chair: Artemis Spyrou, Michigan State University Room: Hilton Waikoloa Village Kohala 2 |
Tuesday, November 28, 2023 7:00PM - 7:15PM |
C09.00001: Absolute normalization of the 12C(p,γ)13N and 13C(p,γ0)14N cross sections Carl R Brune, Colton Feathers, Brittney Kenady, David C Ingram, Richard J deBoer The 12C(p,γ)13N and 13C(p,γ0)14N reactions play a critical role in the Carbon-Nitrogen (CN) cycle. Surprisingly, the absolute normalization of the reaction rates for both reactions are quite uncertain. Both reactions have strong and broad resonances a few 100~keV above the proton threshold. We report here new measurements of the absolute 12C(p,γ)13N and 13C(p,γ0)14N cross sections at the peaks of these resonances. The measurements were conducted by bombarding enriched 12C or 13C targets with proton beams and detecting the emitted γ rays with high-purity Ge detectors. The thicknesses of the carbon targets, which are essential for determining the absolute cross sections, were determined by deuteron energy loss and elastic α scattering measurements. The implications for the reaction rates of proton capture on carbon isotopes in the CN cycle will be discussed. |
Tuesday, November 28, 2023 7:15PM - 7:30PM |
C09.00002: The 13C(α, n)16O differential cross section Richard J deBoer, Michael T Febbraro, Dan W Bardayan, Chevelle Boomershine, Kristyn H Brandenburg, Carl R Brune, Sydney D Coil, Manoel Couder, Joseph A Derkin, Stefania Dede, Ruoyu Fang, Adam L Fritsch, August Gula, Gy. Gyurky, Brennan T Hackett, Gulakhshan M Hamad, Yenuel Jones-Alberty, Rebeka Kelmar, Khachatur Manukyan, Miriam Matney, John P McDonaugh, Zachary P Meisel, Shane Moylan, Jason Nattress, Daniel M Odell, Patrick O'Malley, Mark W Paris, Daniel Robertson, Shahina Shahina, N. Singh, Karl Smith, Michael S Smith, Edward Stech, Wanpeng Tan, Michael C F Wiescher Neutron production for the slow neutron capture process (s-process) is dominated by (α,n) reactions on light nuclei during stellar helium burning. Chief among these is the 13C(α,n)16O reaction, whose low energy cross section is enhanced by the presence of broad resonances and subthreshold states. Experimental measurements have been reported recently at both the LUNA and JUNA underground facilities, reaching to unprecedentedly low energies. These measurements have verified R-matrix extrapolations, constrained by transfer reaction determinations of the dominant subthreshold resonance strength, that the cross section is lower than previous above ground measurements indicated. To further reduce the uncertainty, we report measurements of the differential cross section of the 13C(α,n)16O reaction, which extend from laboratory α-particle energies of 0.8 to 6.5 MeV in approximately 10 keV energy steps at 18 angles between 0 and 160◦, resulting in over 700 distinct angular distributions. These measurements are the first accurate differential cross section measurements of this reaction below 1 MeV. We use these differential data to augment the previous state-of-the-art R-matrix fit of the low energy 13C(α,n)16O reaction and use Bayesian uncertainty estimation to demonstrate that the differential data decreases the uncertainty by a factor of two, from ≈10% to ≈5% over the energy region of astrophysical interest. |
Tuesday, November 28, 2023 7:30PM - 7:45PM |
C09.00003: Narrow resonance measurements of the 17O compound nucleus Joseph A Derkin, Carl R Brune, Thomas N Massey, Yenuel Jones-Alberty, Justin Warren, Bikash Chauhan, Nisha Singh, Michael Jeswald The 13C(α, n)16O reaction is the primary source of neutrons fueling the slow neutron capture process (s-process) to produce increasingly heavier isotopes along the nuclear chart. Using both direct and indirect methods, many efforts within the nuclear astrophysics community have been made to further constrain this reaction rate. An intermediate state can be formed during the 13C(α, n)16O reaction, causing a resonance to appear as an excitation in the 17O compound nucleus. Further measurements are therefore required to refine the 16O total neutron cross section database, leading to a more accurate evaluation of the 13C(α, n)16O reaction rate. We have identified a number of narrow resonances in the 16O + n entrance channel to be studied using neutron transmission and scattering measurements. Our measurements utilize the newly-installed Fixed Angle Short Trajectory (FAST) reaction-based collimated neutron source at the Edwards Accelerator Laboratory at Ohio University. The FAST neutron station is also equipped with a newly designed time-varying voltage ramp supply, which provides a unique approach for performing narrow resonance scanning techniques. This presentation includes an explanation of the experimental apparatus, a Monte Carlo simulation design of the FAST neutron source and preliminary data from its commissioning experiments. |
Tuesday, November 28, 2023 7:45PM - 8:00PM |
C09.00004: Measurement of the γ-Decay Probability of the Hoyle State Kosuke sakanashi, Takahiro Kawabata, Tatsuya Furuno, Atsushi Tamii, Shintaro Okamoto, Satoshi Adachi, Masatoshi Itoh, Hidetoshi Akimune, Yohei Matsuda, Soichiro Aogaki, P-A Söderström, Shigeru Kubono The triple alpha (3α) reaction is one of the most important processes in the nucleosynthesis. In this reaction, α particle is captured by the 2α resonance of 8Be, and form a 3α cluster state. Most of the 3α resonance states decay to three α particles, but a tiny fraction of them decays to the ground state in 12C via radiative processes of γ decay or e+e--pair emission. Therefore, the γ-decay probability is an important parameter that directly determines the amount of 12C produced in the nucleosynthesis. Many γ-decay probability measurements were performed by 1976 and radiative-decay probability γrad/γ = 4.16(10) × 10-4 [1] from the Hoyle state has been widely accepted. |
Tuesday, November 28, 2023 8:00PM - 8:15PM |
C09.00005: Precision Elastic Scattering Measurement Using the St. George Recoil Mass Separator Adam T Sanchez, Ruoyu Fang, Shane Moylan, Joachim Goerres, Jerry D Hinnefeld, Chloe Jones, John P McDonaugh, Ruchi Rathod, Daniel Robertson, Edward Stech, Manoel Couder Helium radiative capture plays a key role in most stellar environments beyond their hydrogen burning phase. The cross section of these reactions, for the most part, are dominated by resonances. The strength of these resonances are in turn partially dominated by the alpha partial width. Recoil mass separators, such as St. George at the University of Notre Dame, are designed to study these low energy radiative capture reactions in inverse kinematics. |
Tuesday, November 28, 2023 8:15PM - 8:30PM |
C09.00006: Measurements of the energies, strengths and partial widths for the Ec.m. = 1323 and 1487 keV resonances in the 15N(α, γ)19F reaction Ruoyu Fang, Joachim Gorres, Shane Moylan, Adam T Sanchez, Khachatur Manukyan, Thomas L Bailey, Scott R Carmichael, Richard J deBoer, Jes Koros, Kevin Lee, Miriam Matney, John P McDonaugh, Daniel Robertson, Javier Rufino, Edward Stech, Manoel Couder For many years, the production site of fluorine has been debated. Observational evidence has confirmed that Asymptotic Giant Branch (AGB) stars can produce 19F via the 15N(α, γ)19F reaction, making this environment at least one likely production site. Recent measurements of the resonances at Ecm = 1323 and 1487 keV have indicated discrepancies in resonance energies, strengths, and partial widths that may affect the 19F production rate in AGB stars. To investigate these discrepancies, a gamma spectroscopy measurement was performed at the Nuclear Science Laboratory at the University of Notre Dame. The measurement results and their impacts will be discussed in this talk. |
Tuesday, November 28, 2023 8:30PM - 8:45PM |
C09.00007: Cascade transitions versus cascade transitions in 15N(p,γ)16O at the stellar energy range Nataliya A Burkova, Sergey B Dubovichenko, Roman Y Kezerashvili, Alessya S Tkachenko The reaction 15N(p,γ)16O is a branch point in the CNO cycle. Consideration of broad resonances Jπ=1-, 2-,3- in 16O are key points for description of the S-factor and reaction rate for radiative p15N capture at the stellar energy T9<10. We report results for astrophysical low-energy S−factor that includes contributions of the 3S1 resonances due to the E1 transitions and the contribution of M1 transition via 3P1 scattering wave in p + 15N channel [1]. The extrapolated S(0) turned out to be within 34.7 − 40.4 keV·b depending on an asymptotic constant. We estimate the contribution of cascade transitions to the reaction rate based on the exclusive experimental data for the cascade transitions 15N(p,γ(6.050))16O, 15N(p,γ(6.130))16O, 15N(p,γ(7.117))16O. The reaction rate enhancement due to these cascade transitions is observed from T9 > 0.3 and reaches the maximum factor ∼ 1.3 at 1.3T9. Our results obtained based on the experimental partial S-factors contradict to a peculiar enhancement behavior of the ratio reported in NACRE II at 0.4< T9 < 10. The latter calls for a careful theoretical investigation of contributions two interfering resonances 2- at 12.530 MeV and 12.9686 MeV and two interfering resonances 3- at 13.142 MeV and 13.265 MeV.
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Tuesday, November 28, 2023 8:45PM - 9:00PM |
C09.00008: Nuclear astrophysics activities at CENS Kevin I Hahn The IBS Center for Exotic Nuclear Studies (CENS) in Korea was launched in 2019 to carry out experiments with both radioactive isotope and stable beams, develop state-of-the-art detector and target systems as well as robust theories. The radioactive ion (RI) beam accelerator facility called RAON is under construction in Korea. It will produce RI beams by the ISOL and In-flight methods. An experimental facility called KoBRA with 20-30 MeV/u beams from the low energy superconducting linac (SCL3) is expected to carry out nuclear astrophysics in the early phase of RAON. We are developing several major instruments such as an active target TPC detector, silicon detector system, and cryogenic gas target system mainly for nuclear astrophysics experiments. Current research activities and plan for nuclear astrophysics experiments will be presented. |
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