High pressure research

Researchers at

have developed a technique that could squeeze materials to pressures 100 to 1,000 times greater than possible today, reproducing conditions expected in the cores of supergiant planets.

Until now, these pressures have only been available experimentally next to underground nuclear explosions.

The researchers have achieved pressures near 10 million atmospheres using the 30 kilojoule ultraviolet Omega laser at the University of Rochester's Laboratory for Laser Energetics in New York. They hope eventually to use the 2 megajoule laser of Lawrence Livermore National Laboratory’s National Ignition Facility to achieve more than a billion atmospheres of pressure.

Diamond anvil cells squeeze liquids and solids to pressures of 4 to 5 million atmospheres, slightly higher than the pressure at the centre of the Earth. With diamond anvils, the temperature as well as pressure can be varied, and scientists can study the compressed samples for long periods.

Laser-induced shock waves can produce tens of millions of atmospheres, but only for a split-second and at very high temperatures. This technique also requires lasers the size of a building.

Combining the two gives higher pressures and much higher densities than either of the methods alone, allowing scientists to study what happens as you bring atoms really close together, and compare the observations to quantum mechanical calculations.

The combined methods also allow physicists to tune the temperature over a wide range independent of density, something almost impossible to do with laser-induced shock waves alone.

When materials are squeezed to a million atmospheres of pressure, the chemistry is changed dramatically. Materials go from being insulators to becoming metallic or even superconducting.

According to the scientists, there is reason to expect that when pressure reaches the billion atmosphere range, there will be further huge changes in chemical bonding and material properties.