The new Pulse Dilation – Photomultiplier Tube for gamma reaction history measurements at the National Ignition Facility*

Gas Cherenkov Detectors (GCD) have been successfully in use in diagnostics like the Gamma Reaction History (GRH) at the National Ignition Facility (NIF) for several years. The Cherenkov process is inherently fast, but the temporal resolution has been limited to ~100ps by state-of-the-art photomultiplier tube (PMT) technology. The new Pulse Dilation – Photomultiplier Tube (PD-PMT) at NIF will allow for temporal resolutions comparable to that of the gas cell, or ~10ps. Enhanced resolution will contribute to the quest for ignition in a crucial way through high precision reaction history measurements and better constrained models. First measurements at NIF might reveal features in the burn history such as onset of alpha heating, shock reverberations, and burn truncation due to dynamically evolving failure modes. The PD-PMT is well characterized by test measurements performed at AWE. GCD-3 - a Gas Cherenkov Detector fielded in a Well-DIM at NIF - serves as a test bed for the PD-PMT. The lessons learned by fielding PD-PMT on GCD-3 will contribute to the design of the next generation Gas Cherenkov Detector.