Constraining Neutron Capture Cross Sections via Surrogate Measurements With Hyperion

Indirect measurements are necessary to constrain the cross sections and reaction rates of nuclear reactions that are inaccessible for direct measurement. One such indirect technique is the surrogate method. This method uses an alternate reaction channel to populate a nucleus of interest, and in-beam γ-ray spectroscopy enables measurement of γ-decay probabilities for very short-lived nuclei. Experimental results are used together with nuclear data as constraints in Hauser-Feshbach calculations. These are statistical nuclear models of the desired and surrogate reactions which use nuclear level densities, optical model potentials, and γ-strength functions (γSF) to predict reaction cross sections. Experimental γ-decay probabilities may be used to constrain the γSF models, and therefore the resulting neutron capture cross section.

This project involves the surrogate analysis of data taken with Hyperion, a particle-γ coincidence detector array utilizing in-beam γ-ray spectroscopy. The reactions measured were ^64,70Zn(p,d) and ^64,70Zn(p,t) as surrogates for ^61,62,67,68Zn(n,γ). The experiment was performed in fall 2021 at Texas A&M University’s Cyclotron Institute with a 27-MeV proton beam from the K150 cyclotron. Preliminary results presented are the extracted γ-decay probabilities; further analysis is under way using these results in constraining (n,γ) cross sections.