Progress in low energy nuclear reaction measurements
August Gula
Physics Graduate Student
University of Notre Dame

Ever since the discovery of nuclear fusion in stars, the need for high fidelity low energy nuclear reaction data has been apparent. At the Institute for Structure and Nuclear Astrophysics, an intensive effort to study these reactions is ongoing despite lockdowns. Using the 5U Pelletron, studies of the nuclear reactions ¹⁰B(a,pg), ¹⁰B(a,d), and ¹¹B(a,p) have been furthered and near completion. Narrow resonant structures in the energy range of 0.6-2 MeV were characterized by investigations into the ¹¹B(a,p) reaction. Additionally, current results for ¹⁰B+a show a strong resonant contribution at E_Lab=273 keV corresponding to the 11.807MeV state in the compound system of ¹⁴N. Both datasets were put through R-matrix analysis and preliminary fits will be presented at this talk.

Measurement of the ²⁵Mg(α, n) ²⁸Si reaction cross-section at low energy
Shahina¹
Physics Graduate Student
University of Notre Dame

(M. Wiescher ¹ , R.J. deBoer ¹ , K.T. Macon ¹ , A. Boeltzig ¹ , M. Febbraro ² , R. Toomey ²

1 Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
2 Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA)

There is uncertainty regarding the available neutron flux for the weak s-process in massive stars. In order to correctly model the s-process nucleosynthesis, one key ingredient is the rate of neutron producing reactions. The ²²Ne(α, n) ²⁵Mg is the main neutron source, but other reactions also contribute. In the present work we study one such reaction, namely ²⁵Mg(α, n) ²⁸Si, which acts as a potential neutron source for weak s-process and destroys the strongest neutron poison ²⁵Mg. Previous measurements for this reaction suffered from two shortcomings: they were not performed at low enough energies relevant for weak s-process in massive stars and measurements using neutron counters were hindered by the contamination of targets with lower Z material. In this work, we used two different setups consisting of deuterated liquid scintillator detectors for neutrons and LaBr₃ for γ-rays in order to measure the ²⁵Mg(α, n) ²⁸Si cross- section in the Gamow range 1.4-2.6 MeV. The neutron spectroscopy was performed via neutron spectrum unfolding technique which allows for a clear separation of the signal and the background. Preliminary results, including cross-sections determined from gamma-ray and neutron spectroscopy will be presented.

Hosted by Prof. Wiescher