Inertial confinement
Crushing a small pellet of fuel with powerful lasers or similar drivers, so that fusion happens in the tiny interval before the fuel flies apart.
In 1972 John Nuckolls and colleagues at Livermore published calculations showing that lasers could compress fuel to about ten thousand times the density of the liquid, enough to ignite fusion[1].
Nothing holds the fuel in place except its own inertia — the fact that mass cannot start moving instantly. Confinement lasts only about a tenth of a nanosecond, and is compensated by extreme density. It is the opposite strategy to magnetic confinement.
In December 2022 the US National Ignition Facility (NIF) used this approach to release more fusion energy than the laser energy delivered to the target[2].
To generate electricity, though, pellets would have to be fired many times a second and the lasers themselves would need to become far more efficient. NIF fires only a few shots a day.
Related terms
- IgnitionThe state in which a plasma keeps burning on the heat of its own fusion products — the helium nuclei — without any outside heating.
- Q valueFusion energy released divided by the energy put in from outside to heat the plasma. Q = 1 is breakeven; Q becoming infinite corresponds to ignition.
- Magnetic confinementHolding a hot plasma away from the vessel walls in a cage of magnetic field, using the fact that charged particles spiral along magnetic field lines.
On the timeline
Sources
- J. Nuckolls, L. Wood, A. Thiessen, G. Zimmerman, “Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) Applications,” Nature 239, 139–142 (1972).
- H. Abu-Shawareb, et al. (Indirect Drive ICF Collaboration), “Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment,” Phys. Rev. Lett. 132, 065102 (2024).