Increased compression in HDC-based ablator implosions using modified drive profile

Abstract

Compression is an essential component of achieving high gain in inertial confinement fusion. However, increasing compression with crystalline ablator-based implosions had not succeeded up to now, attributed to increased hydrodynamic instability growth. We present experimental results demonstrating record high compression of stagnated fuel in indirectly driven implosions that use a high-density carbon ablator at the National Ignition Facility (NIF) [Spaeth et al., Fusion Sci. Technol. 69, 25 (2016)]1536-105510.13182/FST15-144 by the use of a modified drive pulse (and capsule design). Specifically, the SQ-n design [Clark et al., Phys. Plasmas 29, 052710 (2022)1070-664X10.1063/5.0087052] replaces the second and the third shock phase with a more gently ramped rise designed to reduce in-flight fuel adiabat and instability growth at both the ablation front and the ablator-DT fuel interface and hence promote increased compression. Comparing the results from a large set of experiments, we show that SQ-n achieves ≈15%–30% higher compression than prior designs, a finding that may chart a path toward increased compression and higher gain at the NIF [Abu-Shawareb et al., Phys. Rev. Lett. 129, 075001 (2022)0031-900710.1103/PhysRevLett.129.075001.].