Fusion Energy Output Greater than the Kinetic Energy of an Imploding Shell at the National Ignition Facility

Abstract

A series of cryogenic, layered deuterium-tritium (DT) implosions have produced, for the first time, fusion energy output twice the peak kinetic energy of the imploding shell. These experiments at the National Ignition Facility utilized high density carbon ablators with a three-shock laser pulse (1.5 MJ in 7.5 ns) to irradiate low gas-filled (0.3 mg/cc of helium) bare depleted uranium hohlraums, resulting in a peak hohlraum radiative temperature ∼290 eV. The imploding shell, composed of the nonablated high density carbon and the DT cryogenic layer, is, thus, driven to velocity on the order of 380 km/s resulting in a peak kinetic energy of ∼21 kJ, which once stagnated produced a total DT neutron yield of 1.9×10^{16} (shot N170827) corresponding to an output fusion energy of 54 kJ. Time dependent low mode asymmetries that limited further progress of implosions have now been controlled, leading to an increased compression of the hot spot. It resulted in hot spot areal density (ρr∼0.3 g/cm^{2}) and stagnation pressure (∼360 Gbar) never before achieved in a laboratory experiment.

Nuclear probes of an out-of-equilibrium plasma at the highest compression

“…(4) vs T from eq.(1). Omega and NIF data are derived from the experiments [25], using the Down Scatter Ratio [23,21]. Our results using the DSR method (N 4 /N 3 ) are given by the open triangle symbols in good agreement with the N 3 /N 2 ratios.…”

“…Careful methods might be devised to keep the system as close as possible to equilibrium for instance using several laser beams to compress and heat a target [21]. Nevertheless, important out of equilibrium effects might still be present [22,23,24] and prevent the optimization of nuclear fusion reactions towards a prototype of a nuclear reactor. Stimulated by these considerations we decided not to fight non-equilibrium effects but rather enhance them, i.e.…”

Burn regimes in the hydrodynamic scaling of perturbed inertial confinement fusion hotspots

“…While implosion symmetry in recent years has improved remarkably, allowing yields to reach 2×10 16 [11], some level of perturbation persists.…”

“…Their impacts have been reduced through a combination of improved laser drive symmetry control and different ablator materials [17]. Currently, the gas fill-tube is the most damaging perturbation source on the HDC implosions [11]. Methods for addressing the impact of the fill-tube [11,18] have produced the highest yield implosions to date, with neutron yields of ∼ 2×10 16 .…”

Petapascal Pressure Driven by Fast Isochoric Heating with a Multipicosecond Intense Laser Pulse

“…The fast isochoric laser heating of imploded plasma is one of the scheme to create ultra-high-energy-density (UHED) state, which is equivalent to the state at the center of the sun, for the inertial confinement fusion (ICF) science.In conventional implosion, kinetic energy of the imploded shell is converted to the internal energy of the compressed matter at the maximum compression. A UHED state with 36 Peta-Pascal (PPa) was achieved on the National Ignition Facility with 1.8 MJ of laser energy by the indirect X-ray driven implosion [7]. The OMEGA laser facility with 30 kJ of laser energy produced 5.6 PPa of UHED by the direct laser-driven implosion [8].…”