Diamond has been subjected to the wrath of the world's largest laser, which compressed the stone to greater pressures than it has ever experienced on Earth. The results hint at the mysterious conditions deep inside giant planets.
The dense atmospheres of gas giants Jupiter and Saturn contain carbon. Chemical modelling suggests pressure deep inside the planets would crush it into a rain of diamond chips and perhaps create chunks of diamond large enough to impress even the Kardashians. But until now, no one had been able to replicate such pressures on Earth and test the notion.
"Our experiment provides the first actual data of diamonds under such high pressure," says Ray Smith at the Lawrence Livermore National Laboratory in California.
Using the National Ignition Facility (NIF) at Livermore, Smith's team bombarded tiny targets with 176 laser beams to put the squeeze on diamond. The trick was to compress the stone as slowly as possible, says Smith.
"If you compress it too fast, it gets very hot and melts, and you'd just have liquid carbon," he says. To avoid this, the team used a technique called ramp compression, which NIF engineers originally designed to implode fuel capsules for research into nuclear fusion power.
The team fixed a diamond inside a hole cut in a small gold cylinder, and then precisely timed laser pulses to strike the cylinder's interior walls. This caused the gold to emit an avalanche of X-rays that bombarded the stone, triggering powerful compression waves inside it.
From start to finish, each run of the experiment lasted only about 20 nanoseconds – much faster than the blink of an eye, but slow enough not to melt the stone. During that short time, the team was able to squeeze diamond to pressures of up to 5 terapascals – about 50 million times the atmospheric pressure on Earth's surface. The team's data can now be used to improve models of gas giants and the suspected diamond in their depths.
Dave Stevenson at the California Institute of Technology in Pasadena called the experiment an impressive achievement. "These findings contribute to an ongoing effort to put together an understanding of the cores of giant planets," says Stevenson.
Nikku Madhusudhan at the University of Cambridge says the results can also aid our understanding of the insides of "diamond planets". These exoplanets are rocky like Earth but are rich in carbon rather than silica, and may contain large layers of diamond. His team reported on models of such a world, dubbed 55 Cancri e, in October 2012.
"The present result is extremely valuable, because we can now use direct experimental data to model the deep interiors of carbon-rich planets," says Madhusudhan.
Journal reference: Nature, DOI: 10.1038/nature13526
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