Validating and Understanding Hydrodynamic Conditions of Recent Ignition Implosions at the National Ignition Facility*

Indirect drive capsule implosions at the National Ignition Facility (NIF) using High Density Carbon (HDC) ablators filled with a cryogenic layered deuterium-tritium (DT) fuel have achieved ignition by Lawson criterion [1] and target gain greater than unity for N221204.  To assess the compression shock timing, inflight implosion trajectory and capsule mass remaining, as well as implosion symmetry swings of these ignition implosions, a campaign of keyholes and convergent ablators (2DConA) [2] experiments were conducted.  We also studied the dependence of these parameters on the HDC capsule material (nano-crystalline vs micro-crystalline), laser pulse inners vs outers power ratio history (aka “cone fraction”).  The data recorded constrains modeling of these implosions in hydrodynamic simulations and allows for optimizations of target, capsule and fuel, as well as of the laser pulse that can significantly increase the fusion yields of future fuel layered DT implosions.  This work uncovered differences in the measured vs calculated shock symmetry and lower ablator mass remaining, which were key aspects factored into the design of N221204 following N210808.  We also found that the sensitivity of implosion shape to inner-to-outer laser power balance in the rise to peak power is less than predicted with simulations but resulted in a reduced symmetry swing.

 

[1] H. Abu-Shawareb et al., Phys. Rev. Lett. 129, 075001 (2022).

[2] J.R. Rygg, O.S. Jones, J.E. Field, M.A. Barrios, L.R. Benedetti, G.W. Collins, D.C. Eder, M.J. Edwards, J.J. Kroll, O.L. Landen et al, Phys. Rev. Lett. 112, 195001 (2014).