The First GRIFFIN Experiment: An investigation of the $s$-process yields in the Cd-In-Sn region from $^{115}$Cd

In the $s$-process, it is assumed that He-shell flashes give rise to neutron bursts at two different thermal energies $(kT\sim10$ keV and $kT\sim25$ keV). The contribution to the isotopic abundance of $^{116}$Cd from the higher temperature neutron bursts are calculated assuming thermal equilibrium between the ground state and the long-lived isomeric state of $^{115}$Cd. However, it is unknown if the equilibrium between these states is present at the low temperature of the first burst, which would significantly decrease the calculated $s$-process yields of $^{116}$Cd. To answer this question, we are searching for gateway levels at slightly higher excitation energy than the isomer in $^{115}$Cd that could be populated from the isomeric state via $(\gamma,\gamma^\prime)$ reactions within stars. In November 2014, the GRIFFIN spectrometer was commissioned at TRIUMF's Isotope Separator and Accelerator. GRIFFIN is a state-of-the-art array consisting of 16 HPGe clovers, with a large $\gamma$-ray efficiency of roughly 17\% at 1 MeV. In this first experiment, a beam of $^{115}$Ag was delivered to GRIFFIN in order to search for transitions between gateway levels following the $\beta$ decay of $^{115}$Ag. In this talk, results from this first GRIFFIN experiment will be presented.