Marius Millot, the LLNL physicist who led the work, said in the lab’s announcement<\/a> that the team got its samples “hotter than the surface of the sun” and still measured temperature, density, atomic structure, and reflectivity before each one came apart. LLNL puts the pressure at roughly three times what you’d find at the center of the Earth. Every reading had to land inside a billionth of a second, because that’s how long the squeezed state held.<\/p>\n Not with an oven, that’s for sure.<\/p>\n The experiments ran on the OMEGA laser at the University of Rochester’s Laboratory for Laser Energetics<\/a>, which fires 60 ultraviolet beams into a target chamber 10.8 feet (3.3 meters) across. The beams start out as infrared light and get frequency-tripled to 351 nanometers on the way in. Together they can drop up to 30 kilojoules on a target in pulses lasting anywhere from 100 picoseconds to 4 nanoseconds. And it’s the machine the US fusion community leans on as its workhorse, running experiments for national labs and universities from all over.<\/p>\n The beams flash-vaporize the surface of the target, and the material blasting off kicks a shock wave into the diamond underneath, the same way a rocket gets shoved forward by everything leaving out the back. Most of the diamond never sees laser light directly; it doesn’t need to. That one wave squeezes and heats the sample in a single hit. A billionth of a second later, the whole thing comes apart.<\/p>\n You may be wondering how anyone reads atomic structure in a window that short. The answer is more lasers. A separate set of beams makes a flash of X-rays timed to go off while the shock is still moving through the diamond, and the way those X-rays scatter off the sample tells you whether the atoms are still holding a crystal pattern or they’ve let go of each other. Optical instruments grab the temperature and the shock speed in the same instant.<\/p>\n Millot said this was the first time shock-compressed diamond had been watched with X-ray diffraction all the way up to melting, and the reason nobody managed it earlier is that carbon is a small, light atom that scatters very few X-rays, so the signal isn’t much to work with.<\/p>\n The samples stayed diamond right up to the moment they melted, even at 145 million psi. Theory says carbon should switch into a denser crystal called BC8 somewhere around that pressure, and earlier shots on Sandia National Laboratories’ Z machine had picked up hints of exactly that. These shots didn’t find a trace of it. Millot’s read is that a single shock doesn’t leave the atoms time to rearrange, so the crystal stays trapped in the diamond structure until it turns liquid.<\/p>\n Frankly, the stranger result to me is how it melts. The team pinned the melt near 12,680 \u00b0F and watched the melting temperature drop slightly as the pressure climbed. When squeezing something harder makes it melt a little easier, that’s the signature of a liquid that packs tighter than its own solid. Most materials do the opposite. Water pulls pretty much the same trick as diamond here, and that’s why ice cubes float in your drink. Run that logic at 145 million psi and you get a sentence I didn’t expect to type: a chunk of solid diamond floats on molten carbon.<\/p>\n Jon Eggert, the LLNL scientist whose experiments first pointed at that floating behavior about 20 years ago, has now watched it get confirmed directly by the diffraction data, along with the less flattering news that his original temperature measurement missed by more than 1,000 degrees. He called the correction exciting anyway, which strikes me as a pretty healthy way to take it.<\/p>\n Planetary scientists walk away with something too. Models suggest carbon can crystallize deep inside Neptune and Uranus and sink toward the core as diamond rain, and you can’t exactly fly a probe down there to check. These experiments reached pressures beyond what those interiors hold, so the people modeling ice-giant planets now have measured numbers to anchor their math instead of extrapolations.<\/p>\n Here’s where it loops back to energy. At the National Ignition Facility (NIF), the world’s largest laser, the fuel for its fusion shots rides inside a capsule made of diamond, and the implosion’s first shock has to melt that shell into a smooth fluid. Any leftover solid lumps grow into flaws that can make the reaction fizzle. To make sure the shell melts, the lab’s been hitting its capsules with a fairly strong first shock.<\/p>\n The new numbers say a gentler first shock would melt the shell just as completely. A gentler shock leaves the fuel more compressible, and more compression squeezes more energy out of the same laser. LLNL’s simulations suggest the change could as much as triple the energy gain, though the lab hangs a condition on it: every other way an implosion can degrade has to stay under control first. That’s a best-case number in my book, and fusion predictions have a pretty long history of taking their time.<\/p>\n There’s a lot of motion around that machine right now anyway. A US startup says it can grow the smooth hydrogen fuel layer inside those capsules in two to three hours, a job NIF’s own process spends days and sometimes a week on<\/a>, and a New Jersey shop just ran a flat fusion magnet to 6 tesla<\/a> chasing a completely different route to the same goal.<\/p>\n LLNL says the next round of diamond experiments runs on NIF itself, to watch how the capsule material behaves under a train of several shocks instead of one, and the lab hasn’t put a date on any of it. Millot and his colleagues published the melting study in Nature Physics on August 13.<\/p>\n","protected":false},"excerpt":{"rendered":" Diamond has spent the better part of a century marketing itself as the toughest thing on Earth. Jewelers sell it … <\/p>\nSo how do you actually melt a diamond?<\/h2>\n
![\"OMEGA](\"https:\/\/www.autonocion.com\/us\/wp-content\/uploads\/2026\/09\/OMEGA-laser-target-chamber--1024x576.jpg\")
Diamond floats on its own melt<\/h2>\n
The fusion crowd has been waiting on this<\/h2>\n