Stability properties of the laser direct drive designs for broadband, megajoule-class laser facilities

Recently proposed laser direct drive target designs¹ for future ICF and IFE laser facilities use a broadband laser to mitigate LPI, wetted foam to improve stability, laser zooming to increase energy coupling and achieve upward of 100 megajoule yield. In this work we study the sensitivity of the designs to the laser imprint and methods of its mitigation: 2D Smoothing by Spectral Dispersion, Induced Spatial Incoherence and FLUX laser based broadband laser smoothing which is currently being developed at LLE. We use 3-D rad-hydro code HYDRA and realistic on target laser intensity distribution that take into account the distributed phase plate, smoothing system time-dependent phase, and beam phase aberrations to assess the impact of the laser seeded non-uniformities on the target performance and identify main sources of its degradation. In particularly, the studies show the designs are robust with respect to high imprint modes, but require control of the low (l<20) laser modes.

¹W. Trickey et al., Phys. Plasmas 31, 012702 (2024).



This material is based upon work supported by the Department of Energy [National Nuclear Security Administration] University of Rochester “National Inertial Confinement Fusion Program” under Award Number(s) DE-NA0004144 and Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.