NIF Conceptual Design Studies of Bang Time Diagnostics Using d-t Fusion Gamma Rays*

Bang time and reaction history measurements are essential components of diagnosing failure-modes for ICF implosions on the National Ignition Facility (NIF). Fusion gamma rays are the preferred observable, as they offer the most direct link to deuterium-tritium (d-t ) burn. NIF requirements dictate time resolution and timing accuracy of $<$10 ps and $<$50 ps, respectively. Current approaches use Gas Cherenkov Detectors (GCDs) that convert d-t fusion gamma rays to optical Cherenkov photons, which are collected and recorded by an appropriately fast system. GCD systems, based on ultra-fast photomultiplier tubes and streak cameras, have been developed and fielded successfully at the Omega laser facility. A comparative study of streak-camera-based designs, using optical transport and light pipes, are presented. Trade-off analyses are provided based on achievable throughput and bandwidth. Related studies are also described that attempt to optimize the most advantageous aspects of the case studies.