A series of experiments designed to recreate the most extreme conditions in the universe has found evidence that a theorized form of extra-hard diamond known as lonsdaleite actually does exist, according to research published recently in the journal Nature Communications.
The experiments, conducted at the SLAC National Accelerator Laboratory (a US Department of Energy facility located at Stanford University), were designed to simulate phenomena such as the violent impacts that can scar a planet’s surface and energy-generating reactions in bright stars.
As part of the research, Siegfried Glenzer, head of the laboratory’s High Energy Density Science Division, and his colleagues heated the surface of a soft form of carbon known as graphite with a powerful laser to determine if it would produce a shockwave similar to one produced by a meteor impact, and whether that would be powerful enough to produce lonsdaleite.
By using an optical laser pulse, they were able to produce the shockwave within the sample, and this is turn caused the graphite to rapidly compress, altering its atomic structure. They found that, at a pressure of 200 gigapascals (2 million times the atmospheric pressure at sea level), some of the samples formed lonsdaleite in just a fraction of a second
The study provides “compelling evidence” for the existence of lonsdaleite, Glenzer explained in a statement. Lead author Dominik Kraus, who was a postdoctoral researcher at the University of California, Berkeley when the study was completed, added that the results “strongly support the idea that violent impacts can synthesize this form of diamond, and that traces of it in the ground could help identify meteor impact sites.”
Studies also shed new light on liquid hydrogen, cosmic particle accelerators
In a second, related study that appears in the latest edition of Nature Communications, Glenzer’s team analyzed an unusual transformation believed to occur in gas giant planets such as Jupiter, a world that has an interior thought to be made of liquid hydrogen. When this substance is exposed to high temperatures and pressures, experts believe it changes state from a normal, insulating one to a metallic, conducting one.
While this phenomenon had been predicted decades ago, the authors explained that scientists had never actually been able to observe the atomic processes believed to be responsible. So, as a way to correct that, Glenzer’s conducted several experiments using the Lawrence Livermore National Laboratory’s powerful Janus laser to quickly heat and compress a heavy form of hydrogen called liquid deuterium and to create an X-ray burst to analyze structural changes in the sample.
What they found was that, above a pressure of 250,000 atmospheres and a temperature of 7,000 degrees Fahrenheit, deuterium did change from a neutral, insulating fluid to an ionized, metallic one. The discovery could aid not only planetary science, but could also improve energy research involving the use of deuterium as fuel for fusion reactions similar to those that occur in stars.
Finally, the researchers conducted a third experiment to learn more about how powerful cosmic particle accelerators, such as those found near supermassive black holes, can propel plasma into distant space. These streams produce a short-lived, intense gamma ray bursts which can even be detected on Earth, and the scientists believe that learning more about this process will shed new light on the universe and could lead to the creation of better particle accelerators.
As Frederico Fiúza from SLAC’s High Energy Density Science Division, lead investigator of a paper published last month in the journal Physical Review Letters, explained, he and his fellow researchers believe that a process known as magnetic reconnection, in which the magnetic field lines in plasma break apart and reattach in a different way, could be one of the forces that help drive these cosmic accelerators.
“Magnetic reconnection has been observed in the lab before, for instance in experiments with two colliding plasmas that were created with high-power lasers,” he said. “However, none of these laser experiments have seen non-thermal particle acceleration – an acceleration not just related to the heating of the plasma. But our work demonstrates that with the right design, current experiments should be able to see it.”
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Image credit: SLAC National Accelerator Laboratory
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