More Like this

1. The ⁴¹ Ar(n,y) ⁴² Ar reaction

   https://doi.org/10.1051/epjconf/202328401037  

   Sahoo, R. N.; Paul, M.; Köster, U.; Scott, R.; Tessler, M.; Zylstra, A.; Avila, M. L.; Dickerson, C.; Jayatissa, H.; Kohen, M.S.; et al (January 2023, EPJ Web of Conferences)

   Mattoon, C.M.; Vogt, R.; Escher, J.; Thompson, I. (Ed.)

   The cross-section of the thermal neutron capture⁴¹Ar(n,γ)⁴²Ar(t_1/2=32.9 y) reaction was measured by irradiating a⁴⁰Ar sample at the high-flux reactor of Institut Laue-Langevin (ILL) Grenoble, France. The signature of the two-neutron capture has been observed by measuring the growth curve and identifying the 1524.6 keV γ-lines of the shorter-lived⁴²K(12.4 h) β⁻daughter of⁴²Ar. Our preliminary value of the⁴¹Ar(n,γ)⁴²Ar thermal cross section is 240(80) mb at 25.3 meV. For the first time, direct counting of⁴²Ar was performed using the ultra-high sensitivity technique of noble gas accelerator mass spectrometry (NOGAMS) at Argonne National Laboratory, USA. 

   more » « less
2. A technique for studying (n,p) reactions of astrophysical interest using radioactive beams with SECAR

   https://doi.org/10.1051/epjconf/202327913005  

   Tsintari, Pelagia; Berg, Georg P.; Blackmon, Jeff; Chipps, Kelly; Couder, Manoel; Deibel, Catherine; Dimitrakopoulos, Nikolaos; Garg, Ruchi; Greife, Uwe; Hermansen, Kirby; et al (January 2023, EPJ Web of Conferences)

   Freeman, S.; Lederer-Woods, C.; Manna, A.; Mengoni, A. (Ed.)

   The formation of nuclei in slightly proton-rich regions of the neutrino-driven wind of core-collapse supernovae could be attributed to the neutrino-p process (νp-process). As it proceeds via a sequence of (p,γ) and (n,p) reactions, it may produce elements in the range of Ni and Sn, considering adequate conditions. Recent studies identify a number of decisive (n,p) reactions that control the efficiency of the νp-process. The study of one such (n,p) reaction via the measurement of the reverse (p,n) in inverse kinematics was performed with SECAR at NSCL/FRIB. Proton-induced reaction measurements, especially at the mass region of interest, are notably difficult since the recoils have nearly identical masses as the unreacted projectiles. Such measurements are feasible with the adequate separation level achieved with SECAR, and the in-coincidence neutron detection. Adjustments of the SECAR system for the first (p,n) reaction measurement included the development of new ion beam optics, and the installation of the neutron detection system. The aforementioned developments along with a discussion on the preliminary results of the p( 58 Fe,n) 58 Co reaction measurement are presented. 

   more » « less
3. Regulated NiCu Cycles with the New ⁵⁷ Cu(p, γ ) ⁵⁸ Zn Reaction Rate and the Influence on Type-I X-Ray Bursts: GS 1826–24 Clocked Burster

   https://doi.org/10.1051/epjconf/202226011023  

   Lam, Yi Hua; Lu, Ning; Heger, Alexander; Jacobs, Adam Michael; Smirnova, Nadezda A.; Nieto, Teresa Kurtukian; Johnston, Zac; Kubono, Shigeru (January 2022, EPJ Web of Conferences)

   Liu, W.; Wang, Y.; Guo, B.; Tang, X.; Zeng, S. (Ed.)

   In Type-I X-ray bursts (XRBs), the rapid-proton capture (rp-) process passes through the NiCu and ZnGa cycles before reaching the region above Ge and Se isotopes that hydrogen burning actively powers the XRBs. The sensitivity study performed by Cyburt et al . [1] shows that the 57 Cu(p, γ ) 58 Zn reaction in the NiCu cycles is the fifth most important rp-reaction influencing the burst light curves. Langer et al . [2] precisely measured some low-lying energy levels of 58 Zn to deduce the 57 Cu(p, γ ) 58 Zn reaction rate. Nevertheless, the order of the 1 + 1 and 2 + 3 resonance states that dominate at 0:2 ≲ T (GK) ≲ 0:8 is not confirmed. The 1 + 2 resonance state, which dominates at the XRB sensitive temperature regime 0:8 ≲ T (GK) ≲ 2 was not detected. Using isobaric-multipletmass equation (IMME), we estimate the order of the 1 + 1 and 2 + 3 resonance states and estimate the lower limit of the 1 + 2 resonance energy. We then determine the 57 Cu(p, γ ) 58 Zn reaction rate using the full pf -model space shell model calculations. The new rate is up to a factor of four lower than the Forstner et al . [3] rate recommended by JINA REACLIBv2.2. Using the present 57 Cu(p, γ ) 58 Zn, the latest 56 Ni(p, γ ) 57 Cu and 55 Ni(p, γ ) 56 Cu reaction rates, and 1D implicit hydrodynamic K epler code, we model the thermonuclear XRBs of the clocked burster GS 1826–24. We find that the new rates regulate the reaction flow in the NiCu cycles and strongly influence the burst-ash composition. The 59 Cu(p, γ ) 56 Ni and 59 Cu(p, α ) 60 Zn reactions suppress the influence of the 57 Cu(p, γ ) 58 Zn reaction. They strongly diminish the impact of the nuclear reaction flow that bypasses the 56 Ni waiting point induced by the 55 Ni(p, γ ) 56 Cu reaction on burst light curve. 

   more » « less
4. Prospects for Surrogate Neutron Capture Measurements with Radioactive Ion Beams and GODDESS

   https://doi.org/10.1007/978-3-030-58082-7  

   Jolie A. Cizewski, Andrew Ratkiewicz (February 2021, Compound-Nuclear Reactions, Springer Proceedings in Physics 254)

   null (Ed.)

   Neutron capture reactions are responsible for the synthesis of almost all of the elements heavier than iron through the slow s-process, that proceeds close to the line of stability, and the rapid r-process, with very neutron-rich waiting points. Uncertainties in (n,γ) rates in neutron rich nuclei, especially near closed neu- tron shells, can have significant impact [1] on the predictions of final abundances for different astrophysical scenarios for the r process. Understanding (n,γ) rates on neutron-rich fission fragments is also important for nuclear forensics and stockpile stewardship science. Ratkiewicz et al. [2 and references therein] has recently demonstrated that the (d,pγ) reaction is a valid surrogate for (n,γ), where the formation of the compound nu- cleus from the breakup of the deuteron has been calculated in a reaction model and the subsequent measured gamma-decay probabilities are reproduced with standard level density and strength functions in a Bayesian approach. In parallel to the surrogate validation efforts, we have demonstrated that the (d,pγ) reaction can be measured in inverse kinematics with Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies (GODDESS) [3] where the Gammasphere array of Compton-suppressed HPGe detectors is coupled to the Oak Ridge Rutgers University Barrel Array of position-sensitive silicon strip detectors. During the commis- sioning campaign we measured the (d,pγ) reaction with 134Xe and 95Mo beams, the latter to demonstrate the surrogate method in inverse kinematics. The present talk will present preliminary results from this campaign including γ-decay probabilities and prospects for surrogate (n,γ) measurements with 143Ba fission-fragment beams. 

   more » « less
5. First application of a liquid argon time projection chamber for the search for intranuclear neutron-antineutron transitions and annihilation in ⁴⁰ Ar using the MicroBooNE detector

   https://doi.org/10.1088/1748-0221/19/07/P07032  

   Abratenko, P; Alterkait, O; Andrade_Aldana, D; Arellano, L; Asaadi, J; Ashkenazi, A; Balasubramanian, S; Baller, B; Barr, G; Barrow, D; et al (July 2024, Journal of Instrumentation)

   Abstract We present a novel methodology to search for intranuclear neutron-antineutron transition (n⟶n̅) followed byn̅-nucleon annihilation within an⁴⁰Ar nucleus, using the MicroBooNE liquid argon time projection chamber (LArTPC) detector. A discovery of n⟶n̅transition or a new best limit on the lifetime of this process would either constitute physics beyond the Standard Model or greatly constrain theories of baryogenesis, respectively. The approach presented in this paper makes use of deep learning methods to select n⟶n̅events based on their unique features and differentiate them from cosmogenic backgrounds. The achieved signal and background efficiencies are (70.22 ± 6.04)% and (0.0020 ± 0.0003)%, respectively. A demonstration of a search is performed with a data set corresponding to an exposure of 3.32 ×10²⁶neutron-years, and where the background rate is constrained through direct measurement, assuming the presence of a negligible signal. With this approach, no excess of events over the background prediction is observed, setting a demonstrative lower bound on the n⟶n̅lifetime in⁴⁰Ar of τ_m≳ 1.1×10²⁶years, and on the free n⟶n̅transition time of τ_n⟶n̅≳ 2.6×10⁵s, each at the 90% confidence level. This analysis represents a first-ever proof-of-principle demonstration of the ability to search for this rare process in LArTPCs with high efficiency and low background. 

   more » « less