Ion temperature measurements at MJ yields using the National Ignition Facility (NIF) Neutron Time-of-Flight detectors

With the advent of ignition and MJ yields at the National Ignition Facility (NIF), DT ion temperatures above 15 keV are routinely being measured by the suite of neutron time-of-flight (nToF) spectrometers. This is a new regime for Inertial Confinement Fusion (ICF) implosions, and understanding these measurements is crucial to evaluating performance and refining experimental designs to push to higher yields. Each nToF has both scintillator and Cherenkov-based detectors, which have different sensitivities and responses. As yields at the NIF have increased, discrepancies between the two detection methods have grown. This work will present efforts to resolve these discrepancies: on-shot detectors tests, alternate detection methods, and calibration data collected from neutron sources. Conclusions of these tests will be presented.

*This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-866218.