Britannica Sources used in this answer

Why does inertial confinement fusion require much denser fuel than magnetic confinement fusion?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

laser-activated fusion — nuclear fusion Interior of the U.S. Department of Energy's National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory, Livermore, California. The NIF target chamber uses a high-energy laser to heat fusion fuel to temperatures sufficient for thermonuclear ignition. The facility is used for basic science, fusion energy research, and nuclear weapons testing.

In inertial confinement fusion (ICF), the fuel must be compressed to extreme densities—typically 1,000 to 10,000 times that of normal solids—because of the fundamental difference in how the plasma is confined compared to magnetic confinement fusion.1

In magnetic confinement, a low-density plasma is held in place by magnetic fields for relatively long periods, often a second or more, allowing for continuous operation. Conversely, ICF does not attempt to hold the plasma in place; instead, it relies entirely on the fuel's own inertia to maintain its shape during the brief moment of fusion. Because the plasma disassembles almost instantly—typically within nanoseconds—the reaction must occur extremely rapidly.123

To achieve a practical energy yield within this incredibly short "burn time," the probability of fusion reactions must be significantly increased. Since the rate of fusion power production is proportional to the square of the ion density, compressing the fuel to massive densities is necessary to ensure that enough fusion occurs before the pellet expands and blows apart.132