Improved Performance of High Areal Density Indirect Drive Implosions at the National Ignition Facility using a Four-Shock Adiabat Shaped Drive

Abstract

Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth leading to a 3 to 10 times higher yield with fuel ρR > 1 g=cm 2 . This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition.

A strategy for reducing stagnation phase hydrodynamic instability growth in inertial confinement fusion implosions

“…A subsequent deuterium-tritium (DT) implosion experiment demonstrated a three-to ten-fold increase in neutron yield compared to low foot counterparts but at nearly the same fuel compression. 10,11 This result conclusively demonstrated the importance of ablation front instabilities in degrading the yield of the high compression, low foot implosions fired during the NIC.…”

Rayleigh–Taylor instabilities in high-energy density settings on the National Ignition Facility

“…In the deceleration phase of implosions, RT growth from low-mode asymmetries and high-mode perturbations was measured near peak compression with X-ray and nuclear techniques. In one technique, the self-emission from the hot spot was enhanced with 1% argon dopant to “self-backlight” the shell in flight (40), and “adiabat-shaping” techniques were developed (49) to control hot-spot mix in cryogenic layered DT implosions (36, 50, 51).…”

The high velocity, high adiabat, “Bigfoot” campaign and tests of indirect-drive implosion scaling

“…Experimental performance during the NIC did not follow this scaling with velocity and adiabat suggesting that strong 2D and 3D effects were dominating 1D behavior, which was later confirmed experimentally. 6,8,12,13 The Bigfoot approach is to trade off high convergence and areal-density, for conditions that are favorable for controlling hohlraum symmetry and hydrodynamic instabilities. The aim is improving predictability, while leveraging high velocity, potentially enabling high yields at high adiabat (a $ 4-5).…”