Dependence of Shock Timing on Coronal Parameters for OMEGA Direct-Drive Implosions

Accurate shock timing is essential to produce the desired isentrope or adiabat $\alpha $, of an inertial confinement fusion implosion. However, plasma formation and its effects on shock timing are not fully understood, leaving an area of interest for improving shock-timing predictive capability. This study examines the shock-timing sensitivity of two key coronal feature parameters that can be potentially inferred experimentally: conduction-zone length $D_{\mbox{c}} $ and coronal temperature $T_{\mbox{c}} .$ The former includes the plasma formation rate and influences the time between laser incidence and shock formation at the ablation surface, while the latter can influence shock strength. A two-picket implosion was simulated that had plasma profiles developing differing $D_{\mbox{c}} $ and $T_{\mbox{c}} $ after the end of the first picket (the profiles were otherwise identical). After launching the 2nd picket, correlations between the subsequent shock-merger time and main shock speeds (i.e., the observables with the VISAR diagnostic) to $D_{\mbox{c}} $ and $T_{\mbox{c}} $ are then calculated and in future experiments will be validated to improve code-predictive capability. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.