Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session 2WJA: Surrogate Techniques for Neutron-induced Reactions on Radioactive Nuclei for Fundamental and Applied Nuclear Science I |
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Chair: Jolie Cizewski, Rutgers Univesity Room: Hilton Kona 5 |
Tuesday, October 23, 2018 2:00PM - 2:30PM |
2WJA.00001: Neutron capture rates for neutron-rich nucleosynthesis Invited Speaker: Matthew Mumpower Radiative neutron capture is an important nuclear reaction whose theoretical description is needed for many applications ranging from nuclear technology to nuclear astrophysics. This process relies on the use of Hauser-Feshbach theory which requires the nuclear optical potential, level density, and gamma-strength function as model inputs. I discuss the details of theoretical neutron capture rate calculations and their role in the formation of the heavy elements during neutron-rich nucleosynthesis known as the rapid neutron capture process (r-process). Neutron capture rates of individual nuclei, for instance, may become important during the decay back to stability and also control the exact placement of abundance peaks. The impact on the final abundances of a collective M1 scissors mode operating in highly deformed nuclei is also explored. |
Tuesday, October 23, 2018 2:30PM - 3:00PM |
2WJA.00002: An outlook for fission cross-section theory and experiments on radioactive nuclei Invited Speaker: Walid Younes Understanding fission remains one of the most challenging problems in nuclear physics for both theorists and experimentalists. Surrogate reactions on radioactive nuclei present a unique opportunity to probe the effect of initial conditions, such as excitation energy, angular momentum, and parity, on fission probabilities and fission-fragment properties. These measurements provide in turn a critical testbed for dynamical theories of fission. In this talk, we will discuss some useful fission observables that surrogate reactions can provide, and we will review some of the theoretical approaches available to model the data. We will focus on the discrete-basis approach to scission dynamics we have been developing as a tool to interpret data from fission measurements on radioactive nuclei. |
Tuesday, October 23, 2018 3:00PM - 3:30PM |
2WJA.00003: Demonstrating the (d,p) Reaction as a Surrogate for (n,γ) Invited Speaker: Andrew Ratkiewicz Neutron-capture reactions are important to stellar nucleosynthesis and for societal applications. However, direct measurements of the (n,γ) reaction cross section on these exotic nuclei are very challenging or impossible. The difficulty in directly determining the (n,γ) reaction cross section has motivated the development of several indirect techniques for constraining it, one of which is the Surrogate Reactions Method. This method indirectly determines the AZ(n,γ)A+1Z cross section by measuring the decay of the compound nucleus formed in the X(a,c)A+1Z reaction. However, the accuracy of previous attempts to extracting an (n,γ) cross section from surrogate measurements have been limited by their inability to account for differences in the entry spin distribution between the surrogate and desired reactions. The (d,p) reaction is a promising candidate for an (n,γ) surrogate reaction from a theoretical and an experimental perspective. Recently, a new description of the d+A reaction has been developed [1] which enables the determination of the entry spin-parity distribution of the compound nucleus formed in a (d,p) reaction as a function of excitation energy. This description of the (d,p) reaction was used with a new method for constraining the parameters of a Hauser-Feshbach calculation through fits to experimental data [2]. The method has been used to describe the 95Mo(n,γ) reaction; the extracted cross sections are in excellent agreement with data. I will summarize these efforts and show results. [1] G. Potel, F. M. Nunes, and I. J. Thompson Phys. Rev. C 92, 034611 (2015) [2] J. E. Escher et al. EPJ Web of Conf. 122, 12001 (2016) [3] A.R. De L. Musgrove, B. Allen, J. Boldeman, and R. Macklin Nucl. Phys. A 270, 108 (1976) |
Tuesday, October 23, 2018 3:30PM - 4:00PM |
2WJA.00004: COFFEE BREAK
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