Toward a burning plasma state using high density carbon ablator inertially confined fusion implosions on the National Ignition Facility*

In indirect-drive Inertial Confinement Fusion (ICF), a spherical shell of cryogenic deuterium- tritium (DT) fuel surrounded by a low Z ablator is imploded at high velocity. The kinetic energy of the shell (fuel + unablated material) is converted at stagnation to internal energy of a central hot-spot. Recent experiments on the National Ignition Facility (NIF) using High Density Carbon ablators generated 54 kJ of fusion output, exceeding for the first time the peak kinetic energy of the shell by more than a factor of 2. Implosions have achieved hot spot areal densities rR » 0.3 g/cm3 and stagnation pressures P = 360 Gbar, higher than at the center of the sun. The fraction of alpha particles stopped in the hot spot » 85 % is enough to sustain self-heating once the number of D-T reactions is sufficient. Current experiments are investigating hot spot physics in the high alpha regime, including sensitivity to velocity, symmetry, and shock-timing. The results of current experiments with 980 μm outer radius capsules will inform future implosions using larger HDC capsules at similar adiabat and peak velocity.