Diagnosing Spatial Ion Temperature of ICF Implosions Using Multiplexed PMTs

Neutron imaging of inertial confinement fusion (ICF) implosions measures the spatial fusion
emission from the thermonuclear hotspot. Following the achievement of ignition on the NIF, high yield neutron imaging capabilities are being designed to explore previously unreachable physics, including the spatially resolved ion temperature distribution. The technique spatially resolves the neutron time-of-arrival at the detector to infer the ion thermal distribution from each corresponding region at the source plane. A 1D imager has been demonstrated in spherical implosions on the OMEGA laser, and a full 2D system is being developed for ignition-class shots on the NIF. A quasi-2D proof-of-concept is also being designed for application at sub-ignition yields using the temporally multiplexed neutron time-of-flight technique. Upcoming experiments on OMEGA aim to measure the 1D ion temperature using fiber-multiplexed PMTs to improve dynamic range and diagnostic scalability to facilitate 2D imaging. Results are constrained by a collinear OMEGA nTOF detector and will be used to validate forward models of the quasi-2D ion temperature imager. (LA-UR-26-22436)