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Livermore lab physicist to theorize on hydrogen’s equation of state in Jupiter
by Lawrence Livermore National Laboratory
Special thanks to Anne Stark, and Lawrence Livermore National Laboratory for making this article available.
Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy's National Nuclear Security Administration.
Laboratory news releases and photos are also available electronically on the World Wide Web of the Internet at URL http://www.llnl.gov/PAO and on UC Newswire.
Through laser experiments, Lawrence Livermore National Laboratory physicists determined that deuterium, an isotope of hydrogen, turns into a metal at a higher density than research performed at Sandia National Laboratory.
The behavior of hydrogen at extreme pressures provides crucial information on how Jupiter, made primarily of hydrogen, formed and evolved. LLNL Physicist Robert Caule will present the Livermore research Sunday, April 21, at a press conference titled "Extreme Hydrogen Physics" during a joint meeting of the American Physical Society and the High Energy Astrophysics Division of the American Astronomical Society in Albuquerque, N.M.
Cauble said the Livermore research shows that laser shocks compressing liquid deuterium at 300 kilobars of pressure - about 300,000 times more than the atmospheric pressure of Earth at sea level - turns the liquid to a metal.
"Hydrogen is all around the universe and a lot of it is at high pressure," Cauble said. "It’s important to know its equation of state (the relationship between pressure, density, and temperature)."
Hydrogen’s equation of state dictates at what pressures and densities hydrogen transforms into a metal and so determines the depth where Jupiter’s metallic hydrogen layer begins and the amount of metallic hydrogen it contains.
In the Livermore experiment, scientists used the now-decommissioned Nova laser to shock compress liquid deuterium and found it turned into a metal at a higher density than similar experiments conducted later by Sandia researchers. Using a different technique on Sandia’s Z Machine, Sandia scientists discovered that they also metallized deuterium but at densities lower than in the laser experiments. The two different equations of state implied by the disparate results affect how researchers view large planets like Jupiter.
Cauble and Marcus Knudson of Sandia will meet to discuss the experimental results as well as each group’s computer simulations of high-pressure hydrogen during Sunday’s press conference.
Cauble said it’s possible that the groups’ different results could both be right. It may depend on how the sample is shocked.
The research will be applied to inertial confinement fusion in which the hydrogen isotopes - deuterium and tritium - are used as fuel to attain fusion. Mega lasers, such as the National Ignition Facility, offer new opportunities for pursuing experimental science under extreme conditions of temperature and density
Cauble said Livermore scientists are conducting further research, using diamond anvil cells to probe the properties of matter under the relevant extreme conditions of pressure and compression found in the interiors of giant gas planets, such as Jupiter.
Special thanks to Anne Stark, and Lawrence Livermore National Laboratory for making this article available.
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