Observation of "suprathermal" ion kinetic energy in Inertial Confinement Fusion (ICF) implosions at the National Ignition Facility (NIF).*

Recent experiments conducted on the NIF have achieved burning plasmas, plasmas for which the dominant energy evolves from fusion itself. Neutron time-of-flight measurements of the plasma flow burn-averaged velocities developed for the ICF program at NIF provide a part per 10,000 measurement precision of the collective plasma motion, as well as a 2 keV precision of the mean neutron kinetic energy. This new diagnostic capability reveals that “high performing” ICF implosions depart from the “hydrodynamic” expectation relating the neutron mean energy to the ion temperature. This departure is a signature of an ion kinetic energy population increase over the Maxwellian behavior of a hydrodynamic plasma.