Surrogate 75Ga(d,pγ)76Ga measurement to inform i-process nucleosynthesis using GODDESS at FRIB

ORAL

Abstract

In a recent study of the metal-poor star HD94028, several anomalous high-Z isotopic abundance ratios (As/Ge, Se/As among others) that diverge from summed s- and r-process abundance distributions were reported [1]. A new neutron-capture driven process named the i-process has been proposed as an explanation, taking place at neutron densities intermediate to the s- and r-processes. A subsequent sensitivity study [2] using a one zone simulation to match the observed HD94028 abundances identified the 75Ga(n,γ)76Ga reaction rate to be the most significant when varied, showing a strong anti-correlation to the predicted As abundance. The GODDESS detector system was used in May 2024 at the Facility for Rare Isotope Beams (FRIB) to inform the 75Ga(n,γ)76Ga reaction rate using the 75Ga(d,pγ)76Ga reaction as a surrogate. Protons, heavy recoils, and gamma rays were detected in coincidence, permitting the use of both traditional surrogate analysis using discrete gamma spectroscopy, and a novel ‘no-gamma’ surrogate (NGS) reaction analysis that studies protons and heavy recoils in coincidence to arrive at the (n,γ) reaction rate as a function of excitation energy. Preliminary results from the experiment will be discussed.

[1] I. U. Roederer, et al. , Ap.J. 821, 37 (2016)

[2] J.E.McKay, et al. , MNRAS 491, 5179 (2019)

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Presenters

  • Sudarsan Balakrishnan

    Rutgers University, Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ, USA

Authors

  • Sudarsan Balakrishnan

    Rutgers University, Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ, USA

  • Steven D Pain

    Oak Ridge National Laboratory, Oak Ridge, TN, USA / Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA, Oak Ridge National Laboratory, University of Tennessee, Oak Ridge National Laboratory / University of Tennessee-Knoxville

  • Kelly A. Chipps

    Oak Ridge National Laboratory, Oak Ridge, TN, USA / Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA, Oak Ridge National Laboratory / University of Tennessee-Knoxville, Oak Ridge National Laboratory

  • Jolie Antonia Cizewski

    Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ, USA

  • Mara M Grinder

    Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ, USA, Rutgers University

  • Andrew Ratkiewicz

    Lawrence Livermore National Laboratory, Livermore, CA, USA, Lawrence Livermore National Laboratory

  • Timothy Gray

    Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA/Oak Ridge National Laboratory, Oak Ridge, TN, USA

  • Kate L Jones

    Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA, University of Tennessee, Knoxville

  • Alan B McIntosh

    Cyclotron Institution, Texas A&M, Texas A&M University, Cyclotron Institute, Texas A&M University, College Station, Texas, USA, Cyclotron Institution, Texas A&M University Cyclotron Institute