Fusion gamma-ray diagnosis with a gas Cherenkov detector on the 100-kJ laser facility

Fusion yield and burn history are critical metrics for evaluating implosion performance in inertial confinement fusion (ICF) experiments. Fusion gamma-rays provide a more precise burn history than neutrons in high areal-density implosions, and they can be distinguished from substantial neutron-induced interference by a gas Cherenkov detector utilizing its intrinsic threshold effect. This study presents a Geant4 simulation of gamma-ray spectra from deuterium-tritium (DT) and proton-deuteron (pD) implosions on the 100-kJ laser facility. The forward predicted DT gamma profiles are presented and validated against experimental signals from a gas Cherenkov detector. The measured gamma and neutron bang times show agreement within a standard deviation of 20 ps in low areal-density direct-drive implosions, demonstrating the capability of the gas Cherenkov detector for precise gamma bang time measurements. For pD implosions, a bimodal fitting algorithm successfully extracts the pure gamma signal from the precursor background, achieving a signal-to-noise ratio (SNR) of ~4:1. These results are helpful for characterizing DT implosion performance and advancing the understanding of laser-driven pD reactions.