Diamond melting mystery solved in new fusion energy study

A new discovery in high-pressure physics may help shape the future of clean energy and deepen our understanding of the solar system.

Scientists at Lawrence Livermore National Laboratory (LLNL) have observed diamond melting under pressures about three times greater than those found at Earth’s core.

The results, published in Nature Physics, settle a scientific debate that has lasted for twenty years. Until now, computer models and laboratory experiments disagreed by about 20 percent on the temperature at which diamond melts.

The team used the Omega Laser Facility at the University of Rochester to subject tiny diamond samples to laser-driven shock waves, reaching temperatures exceeding those on the Sun’s surface.

 Since these conditions lasted only a billionth of a second, researchers used advanced X-ray techniques to observe how the diamond’s atomic structure changed.

The data showed that solid diamond floats in liquid carbon, similar to how ice floats in water.

This finding could help advance inertial confinement fusion, a process used at facilities such as the National Ignition Facility, where diamond capsules hold fusion fuel. 

The new results show that a slower initial laser shock wave can still melt the diamond capsule, making the fuel inside more compressible. This approach could increase fusion energy yield by up to 3 times without increasing laser power.

The research also offers important insights for astronomers. Knowing how carbon behaves under extreme pressure will help scientists create more precise models of ice giant planets such as Neptune and Uranus, where high pressures are thought to produce diamond rain.