Speaker
Description
In this talk, I will present results on the first $(\alpha,n)$ cross-section measurements on beams of $^{86}$Kr and $^{94}$Sr. Both reactions are influential for the weak r-process in neutrino-driven winds of type-II supernovae and neutron star mergers. The measurement of $^{94}$Sr$(\alpha,n)$ constitutes the first weak r-process reaction measured with a radioactive beam. This work was enabled by novel nanostructured Si:He targets, demonstrating their suitability for measurements of astrophysical reactions for the first time. Reactions were identified by recoil-$\gamma$ coincidences using the EMMA mass spectrometer combined with the TIGRESS HPGe array at TRIUMF. The obtained cross-sections are compared with predictions from Hauser-Feshbach theory, from which we also compute a new recommended reaction rate at temperatures characteristic of the weak r-process.
