Reaction-in-Flight Measurements using the National Ignition Facility (NIF) Neutron Time-of-Flight detectors

The deuterium-tritium (D-T) reaction is utilized for high yield Inertial Confinement Fusion (ICF) at the National Ignition Facility (NIF). The primary products of this reaction, neutrons and alpha particles, can elastically scatter with deuterons and tritons to produce up-scattered ions, which in turn can undergo fusion reactions. The resulting high energy reaction-in-flight (RIF) neutron spectrum is highly sensitive to stopping power losses, and therefore can act as a probe for key parameters of the ICF hot spot and fuel shell, such as mix fraction, quantum degeneracy of the cold fuel, and the fuel adiabat. The NIF neutron time-of-flight (nToF) spectrometer suite consists of five different lines-of-sight, each with multiple detectors located at ~20 m from the chamber center. These spectrometers can span over six orders of magnitude in dynamic range, allowing them to measure both the primary D-T and RIF spectra. This work will cover recent advancements in nToF-based RIF measurements, using improved diagnostic configurations, hardware, and analysis, and the understanding that can be gained for implosion performance at the NIF.