Cryogenic shock augmented implosion experiments on OMEGA

Shock ignition (SI) [Betti, R., et al. Physical review letters 98.15 (2007)] offers a promising path for inertial confinement fusion with a reduced energy threshold for ignition and enhanced robustness against hydrodynamic instabilities, relative to conventional hot-spot ignition. In this scheme, a cryogenic shell is first imploded at low velocity and low adiabat to assemble the fuel, followed by ignition triggered by a strong shock driven by a high-intensity laser spike. However, delivering a long-duration compression pulse and the extreme laser intensities (~6×10¹⁵ W/cm²) needed to launch the ignitor shock is beyond the capabilities of current laser facilities. Shock-augmented ignition (SAI) [Scott, R. H. H., et al. Physical Review Letters 129.19 (2022)] has been proposed as a viable alternative that preserves the advantages of SI while relaxing the peak intensity requirements. In SAI, the formation of the ignitor shock is facilitated by a temporary drop in laser power, allowing target decompression prior to a rapid ramp-up to peak intensity (~1.5×10¹⁵ W/cm² in this work). We present results from a series of cryogenic implosion experiments designed to investigate the key parameters governing SAI performance. Trends related to hydrodynamic stability, target diameter, and ignitor shock timing are examined, and results are compared to radiation-hydrodynamic simulations and statistical predictions.