Evidence of non-Maxwellian ion velocity distributions in spherical shock-driven implosions
Owen Mannion, William Taitano, Brian Appelbe, Aidan Crilly, C. J. Forrest, V. Yu. Glebov, J. P. Knauer, P. W. McKenty, Z. L. Mohamed, C. Stöeckl, Brett Keenan, J. P. Chittenden, P. J. Adrian, J. A. Frenje, N. V. Kabadi, M. Gatu Johnson, S. P. Regan
Abstract
The ion velocity distribution functions of thermonuclear plasmas generated by spherical laser direct drive implosions are studied using deuterium-tritium (DT) and deuterium-deuterium (DD) fusion neutron energy spectrum measurements. A hydrodynamic Maxwellian plasma model accurately describes measurements made from lower temperature (<10 keV), hydrodynamiclike plasmas, but is insufficient to describe measurements made from higher temperature more kineticlike plasmas. The high temperature measurements are more consistent with Vlasov-Fokker-Planck (VFP) simulation results which predict the presence of a bimodal plasma ion velocity distribution near peak neutron production. These measurements provide direct experimental evidence of non-Maxwellian ion velocity distributions in spherical shock driven implosions and provide useful data for benchmarking kinetic VFP simulations.