Improved Gamma Imaging at NIF Using the Ceramic Scintillator GYGAG

We have recently demonstrated significant improvements to the resolution and sensitivity of the NIF gamma imaging system by replacing the existing EJ262 plastic scintillator with the Ce-doped gadolinium garnet transparent ceramic scintillator GYGAG. Penumbral imaging of inelastic gammas emitted during inertial confinement fusion (ICF) experiments at NIF can be used to recover the time integrated spatial distribution of the remaining shell during the fusion burn, the technique is therefore a critical diagnostic for understanding the failure modes and quality of NIF implosions. In this work we discuss GEANT4 calculations of the relative sensitivities of GYGAG and EJ262 as well as rolled edge measurements made on NIF shot N221204 in December 2022, for the purpose of directly comparing the spatial resolution of each scintillator in-situ.