Hot electron preheat in hydrodynamically scaled direct-drive inertial confinement fusion implosions on the NIF and OMEGA

Hot electron preheat has been quantified in warm, directly driven inertial confinement fusion implosions on OMEGA and the National Ignition Facility (NIF), to support hydrodynamic scaling studies. These CH-shell experiments were designed be hydrodynamically equivalent, spanning a factor of 40 laser energy 3.4 spatial temporal scales, while preserving incident intensity 1015 W/cm2. Experiments with similarly low levels beam smoothing NIF show similar fraction (∼0.2%) deposited as hot unablated shell both per mass (∼2 kJ/mg), despite generating three more electrons (∼1.5% energy) than (∼0.5% energy). This is plausibly explained by absorption ablated CH plasma due larger areal density, well smaller solid angle imploding viewed from region being produced at standoff distance lower-density regions stimulated Raman scattering, contrast higher-density two-plasmon decay OMEGA. The results indicate that for warm intensities around W/cm2, equivalence not violated preheat, though cryogenic implosions, reduced attenuation deuterium–tritium will have considered.