Evolution Of The Neutron Imaging Aperture

Neutron imagers based on thick apertures have become important diagnostics for the shape and size of the burning and cold fuel regions of inertial confinement fusion sources for high-energy density physics. Over time, the designs of these apertures have changed to meet the requirements of newer sources and taken advantage of improvements in manufacturing and alignment technology. In this paper, we discuss the evolution of thick apertures for neutron imaging at laser-driven ICF facilities. We describe the parameters that define the apertures and the apertures that have been fabricated and fielded. We also discuss the lessons learned with each iteration. We also discuss the impact that added features such as collinear or near-collinear gamma-ray and x-ray imaging systems have had on the designs of the aperture arrays.