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 KH: Nuclear Reactions: Heavy-Ions/Rare isotope Beams II |
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Chair: Sergio Almaraz-Calderon, Florida State University Room: Hyatt Regency Hotel Celestin H |
Saturday, October 29, 2022 10:30AM - 10:42AM |
KH.00001: A technique for the study of (n,p) reactions of astrophysical interest with SECAR Pelagia Tsintari, Georgios Perdikakis, Fernando Montes, Nikolaos Dimitrakopoulos, Ruchi Garg, Hendrik Schatz, Caleb A Marshall, Manoel Couder, Georg P Berg, Remco G Zegers, Jorge Pereira, Cavan A Maher, Zachary P Meisel, Jeff C Blackmon, Michael S Smith, Kelly A Chipps, Catherine M Deibel, Uwe Greife, Ashley A Hood, Rahul Jain, Sara Miskovich, Thomas J Ruland, Kiana Setoodehnia, Louis Wagner Neutron-induced reactions are essential for the advancement of nucleosynthesis for elements heavier than iron. Recent studies show that key (n,p) reactions starting from $^{56}$Ni accelerate the so-called neutrino-p process, enabling the synthesis of heavy elements in type II Supernovae. The $\nu$p-process occurs in slightly proton-rich regions in the neutrino-driven wind of core-collapse supernovae, via a sequence of (p,$\gamma$) and (n,p) reactions, where a small abundance of neutrons originates from anti-neutrino captures on free protons. The study of such (n,p) reactions is achievable via the measurement of the reverse (p,n) reactions. The challenge in studying such reactions is that the recoils and the unreacted projectiles have nearly identical masses. An appropriate separation level is achievable with the SEparator for CApture Reactions at FRIB. The first direct measurement of the p($^{58}$Fe,n)$^{58}$Co reaction was possible by the in-coincidence detection of the $^{58}$Co at the end of SECAR and the emitted neutrons. With this reaction measurement, we pave the path for (p,n) reaction studies of significant astrophysical interest with SECAR using radioactive beams provided by FRIB. In this talk, preliminary results of the aforementioned measurement along with the development of the experimental method will be discussed. |
Saturday, October 29, 2022 10:42AM - 10:54AM |
KH.00002: Multi-step abrasion reactions in the search for the drip line Oleg Tarasov A major objective of rare isotope beam facilities is to study isotopes far from stability with extreme proton-to-neutron ratios. Such isotopes are produced with very low probability offset by high beam power accelerator. Identification of the optimal production mechanisms is an ongoing challenge. A multi-step reaction scheme is shown to be a way to explore the neutron rich region based on experimental results [1,2]. The fact that isotopes close to the drip-lines nuclides have short half-lives, requires a fast in-flight production technique at least for the last step. Assuming Abrasion-Fission of a primary 238U beam to be a first production step to reach neutron rich nuclei in region 25 ≤ Z ≤ 70, the Initial Fissile Nucleus utility developed in the LISE++ package can be used to generate initial cross section tables. Use of empirical parameterizations based on data with stable beams for next production steps can lead to large variations, though with the Abrasion-Ablation (AA) model use it is possible to select a mass model which better describe exotic nuclei experimental cross-sections. Difficulties and how to overcome know issues when using the AA model for the multi-step reactions will be discussed. |
Saturday, October 29, 2022 10:54AM - 11:06AM |
KH.00003: Comparing Fission-product Yields from Photon-induced Fission of 240Pu and Neutron-induced Fission of 239Pu as a Function of Incident Energy Jack A Silano, Anthony Paul D Ramirez, Ronald C Malone, Anton P Tonchev, Mark A Stoyer, Roger Henderson, Nicolas Schunck, Werner Tornow, Calvin R Howell, FNU Krishichayan, Sean W Finch, Matthew E Gooden The Bohr Hypothesis, one of the most fundamental assumptions in nuclear fission theory, states that the decay of a compound nucleus with a given excitation energy, spin and parity is independent of its formation. Using fission product yields (FPYs) as a sensitive probe, we have performed novel high-precision test of the combined effects of the entrance channel, spin and parity on the fission process. Two different reactions were used in a self-consistent manner to produce a compound 240Pu nucleus with the same excitation energy: neutron induced fission of 239Pu and photon-induced fission of 240Pu. The FPYs from these two reactions were measured using quasimonoenergetic neutron beams from the TUNL’s FN tandem Van de Graaff accelerator [1] and quasimonenergetic photon beams from the HIGS facility. An updated comparison of the FPYs from 239Pu(n,f) at En=1.5 and 4.6 MeV with those from 240Pu(γ,f) at Eγ=8 and 11.2 MeV will be presented. |
Saturday, October 29, 2022 11:06AM - 11:18AM |
KH.00004: Abstract Withdrawn
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Saturday, October 29, 2022 11:18AM - 11:30AM |
KH.00005: Elastic and neutron breakup cross sections of 11Be on 12C with BlueSTEAl to test the ratio method Shuya Ota, Gregory Christian, Kris Hagel, Emily Harris, Zifeng Luo, Elizabeth McCutchan, Chris Morse, Brian T Roeder, Michael J Roosa, Antti Saastamoinen, Dustin P Scriven A new method to constrain the properties of neutron-halo nuclei, the ratio method, was experimentally studied. The ratio method theoretically predicts that it is possible to constrain the single-particle state and the binding energy of a neutron-halo nucleus from the ratios of neutron breakup and elastic cross sections. We, therefore, tested the method to verify the predictions using a well-studied halo nucleus, 11Be, and explored the possibility of further extending the method to more exotic halo nuclei in the future. We measured angular differential elastic and neutron breakup cross sections of 11Be on 12C at 22 MeV/u at the Texas A&M University K500 cyclotron. The 12C target was bombarded with a 11Be beam produced at MARS (Momentum Achromat Recoil Separator). Elastic 11Be and neutron breakup 10Be were detected with the BlueSTEAl Si detector array that we developed recently. We will present preliminary results from our experiment. |
Saturday, October 29, 2022 11:30AM - 11:42AM |
KH.00006: Deblurring decay energy spectrum from invariant mass measurement Pierre Nzabahimana, Thomas Redpath, Pawel Danielewicz, Thomas Baumann, Pablo Giuliani, Paul Gueye The measured decay energy spectra from invariant mass spectroscopy can give insights into the shell structure of particle-unbound systems. However, it is challenging to extract the underlying physics from the measured spectrum due to detector resolution and acceptance effects. The traditional approaches rely on fitting methods such as the chi-square that require the number of resonance peaks in the spectrum to be known a priori, information that is not always accessible. Another common technique used is the inverse problem method, but it may suffer from a singularity during matrix inversion. We introduce a deblurring method that utilizes the Richardson-Lucy algorithm, which has proven to be successful in optics. The method does not require any prior knowledge about the resonance states in the observed spectrum, and it circumvents the singularity issue by iteratively adjusting a positive definite distribution. The only inputs are the observed energy spectrum and the detector's response matrix also referred to as the Transfer Matrix (TM). We tested the method’s performance on a simulated spectrum generated using the in-house simulation package for the MoNA-LISA-Sweeper setup and the associated TM. Finally, the approach is applied to the energy spectrum of the 26O system decaying into 24O + n +n, from an experiment conducted at NSCL by the MoNA Collaboration. We demonstrate its successful performance in restoring the resonance states in the decaying systems from decay energy measurement. |
Saturday, October 29, 2022 11:42AM - 11:54AM |
KH.00007: Relative temperatures of neutron-rich and neutron-poor compound nuclei Alan B McIntosh, Kris Hagel, Lauren McIntosh, Roy Wada, Jerome Gauthier, Sherry J Yennello How the nuclear caloric curve, a key facet of the nuclear equation of state, depends on neutron excess remains an open question. We have extracted temperatures of compound nuclei produced in fusion evaporation reactions of 78K+C and 86Kr+C @ 15, 25, and 35 MeV/u from the evaporated charged particles. The excitation energy is deduced from the measured velocity of the heavy residues. We explore the systematic differences between the T vs E*/A correlation for the neutron-rich and neutron-poor systems. The systematic differences observed, within the limits of the systematic uncertainties, offer constraint on the asymmetry dependence of the nuclear caloric curve within theoretical models. |
Saturday, October 29, 2022 11:54AM - 12:06PM |
KH.00008: Constraining (n,γ) Cross Sections via Surrogate Measurements With Hyperion Jes Koros, Anna Simon, Philip Adsley, Barbara S Wang, Orlando Gomez, Jason T Harke, Richard O Hughes, Brenden R Longfellow, Miriam Matney, Lauren McIntosh, Craig S Reingold, Antti Saastamoinen, Aaron S Tamashiro Indirect measurements are necessary to constrain cross sections and reaction rates of nuclear reactions inaccessible for direct measurement. The surrogate method is an indirect technique which uses an alternate reaction channel to populate a short-lived compound nucleus of interest to obtain its γ-decay probabilities. The surrogate analysis uses the experimental γ-decay probabilities in statistical Hauser-Feshbach calculations, which model the desired and surrogate reactions using nuclear level densities, optical model potentials, and γ-strength functions (γSF). Experimental γ-decay probabilities may be used to constrain the γSF models and resulting cross sections. This project involves the surrogate analysis of data taken with Hyperion, a particle-γ detector array. The reactions measured were 64,70Zn(p,p’), 64,70Zn(p,d), and 64,70Zn(p,t) as surrogates for 61,62,63,68,69,70Zn(n,γ). The experiment was performed in fall 2021 at Texas A&M University’s Cyclotron Institute with a proton beam from the K150 cyclotron. Preliminary results presented are the extracted γ-decay probabilities; further analysis is under way to use these results in constraining (n,γ) cross sections. |
Saturday, October 29, 2022 12:06PM - 12:18PM |
KH.00009: Measuring neutron scattering cross sections for actinides Richard O Hughes, Ching-Yen Wu, Stanimir P Kisyov, Darren L Bleuel, Werner Tornow, Calvin R Howell, Sean W Finch, Collin R Malone, Forrest Q Friesen, Thomas N Massey Cross sections and emission spectra of fast neutron interactions with actinides are crucial data inputs to models relevant to applications like nuclear energy and stockpile stewardship. Actinide elastic/inelastic neutron scattering cross sections are historically poorly constrained due to limited experimental data for these very challenging measurements that generally require neutron detection in high neutron background environments and large mass, radioactive actinide targets. A program of measurements tackling this need is underway at Triangle Universities Nuclear Laboratory (TUNL). The experiments utilize pulsed, monoenergetic neutron beams generated via the p(t,n)3He reaction and time of flight neutron detection with PSD scintillators. Results from initial test measurements on 238U and outlook for upcoming work will be presented. |
Saturday, October 29, 2022 12:18PM - 12:30PM |
KH.00010: Neutron resonance parameters of 191Ir and 193Ir Gencho Y Rusev, Evelyn M Bond, Todd A Bredeweg, Aaron J Couture, Brad J DiGiovine, Cathleen E Fry, Paul E Koehler, Shea Mosby, Christopher J Prokop, Athanasios Stamatopoulos, John L Ullmann, Marian Jandel Neutron capture and neutron transmission measurements with isotopically enriched 191Ir and 193Ir samples were carried out at the Los Alamos Neutron Sciences Center with the DANCE and DICER instruments, respectively. Combining the neutron capture and transmission data sets and performing R-matrix analysis enables us to determine the neutron width and the total width of the resonances. The spins of the resonances were assigned using the gamma-ray multiplicity distribution. We will describe the experiments, data analysis, and report the obtained resonance parameters of 191Ir and 193Ir. |
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