Nuclear Two-Photon Decay with GRIFFIN

Theoretical models predicting neutron star properties require rigorous bench-marking of calculated properties which are experimentally observable; for example the electric polarizability of nuclear matter and the difference in electric polarizability for excited nuclear matter. One possible way of extracting this quantity is through the second order electromagnetic process of nuclear two-photon decay between low-lying $0^+$ states where single photon emission is forbidden. The first excited state of $^{90}$Zr satisfies these conditions and has been observed to undergo two-photon decay. The GRIFFIN spectrometer at TRIUMF-ISAC is a powerful set-up for decay studies that has the angular sensitivity, energy resolution, and electronics required to make a precision measurement of $^{90}$Zr decay using a high-activity $^{90}$Sr source. Preliminary data has been taken using a $^{90}$Sr source to test GRIFFIN's sensitivity to $2\gamma$ decay and the findings of these investigations will be discussed; along with ongoing GEANT4 simulation work to understand the effects of source position, event filtering, and polarization response to $2\gamma$ decay in the GRIFFIN array.