An accessible guide to inertial confinement fusion — how the world’s most powerful lasers compress tiny fuel capsules to stellar conditions in billionths of a second.
Laser fusion (inertial confinement fusion, or ICF) takes the opposite approach to tokamaks. Instead of holding a thin plasma in a magnetic bottle for seconds, ICF compresses a tiny pellet of fusion fuel to extreme density in a few billionths of a second. The fuel’s own inertia holds it together long enough for fusion reactions to occur — hence “inertial” confinement.[1]
Step 1 — The laser pulse: At the National Ignition Facility, 192 laser beams deliver about 2 million joules of ultraviolet light in a 20-nanosecond pulse. The beams enter a gold cylinder (hohlraum) that converts the laser light to X-rays.[2]
Step 2 — Implosion: The X-rays uniformly irradiate a spherical fuel capsule (about 2 mm in diameter) inside the hohlraum. The outer shell ablates (blows off) outward, and by Newton’s third law the remaining fuel is driven inward at velocities exceeding 400 km/s.
Step 3 — Ignition: At peak compression, the fuel reaches temperatures above 100 million degrees and densities exceeding 1,000 g/cm³. A central hot spot (about 50 micrometres across) triggers a thermonuclear burn wave that propagates outward through the compressed fuel.
The main obstacle to laser fusion energy is repetition rate: NIF fires about one shot per day, but a power plant would need 10–15 shots per second. This requires new laser technologies (diode-pumped solid-state or excimer lasers), mass-manufactured targets, and a reactor chamber that can withstand repeated micro-explosions.[3]